WO2024081561A2

WO2024081561A2 - Acridinium compounds with fused heterocycles

Info

Publication number: WO2024081561A2
Application number: PCT/US2023/076242
Authority: WO
Inventors: Eswarreddy BHIMIREDDY; David Sharpe; Robert Owens; Qingping Jiang
Original assignee: Siemens Healthcare Diagnostics Inc.
Priority date: 2022-10-13
Filing date: 2023-10-06
Publication date: 2024-04-18
Also published as: WO2024081561A3

Abstract

Chemiluminescent acridinium conjugates and compounds capable of forming conjugates are disclosed. These chemiluminescent acridinium conjugates may be used as chemiluminescent tracers in immunoassays for the quantification and identification of certain analytes.

Description

ACRIDINIUM COMPOUNDS WITH FUSED HETEROCYCLES FIELD OF DISCLOSURE [0001] The present disclosure relates to a group of chemiluminescent acridinium compounds containing one or more heterocyclyls such as 2,3-cyclic alkylenedioxy fused to the acridinium ring system. These substitutions result in high quantum yields and significantly increased chemiluminescence stability. Structural features of acridinium compounds necessary for high quantum yield with increased chemiluminescence stability are disclosed herein. BACKGROUND [0002] The chemiluminescence of acridinium systems has led to their use in immunoassays of analytes in samples. By conjugation of an acridinium system to a ligand or a binding partner thereof, the chemiluminescence can be correlated with the presence or concentration of an analyte. [0003] An early generation of stable acridinium was the acridinium ester (AE) referred to as DMAE (dimethyl acridinium ester) as shown in U.S. Pat. Nos. 4,918,192 and 5,110,932 are hereby incorporated by reference in their entirety and particularly in relation to the acridinium esters disclosed therein such as DMAE. DMAE contains two methyl groups on a phenyl moiety which flank the acridinium ester ring and stabilize the ester linkage therebetween until, for example, chemiluminescence is induced. By conjugation to a reactive functional group such as N-hydroxysuccinimide (NHS) ester capable of covalently binding to an analyte or binding partner thereof, the DMAE-NHS label can be used to form conjugates capable of use in an immunoassay. DMAE-NHS has the structure:

6 7

DMAE-NHS where the numbering of the acridinium ring system is indicated as used herein, as well as the presence of an A- counterion. [0004] Modifications of these acridinium compounds have resulted in alterations to characteristics of the compounds. For example, U.S. Patent No. 5,656,426, which is hereby incorporated by reference in its entirety, includes hydrophilic modifications of DMAE (termed NSP-DMAE-NHS) where the N-methyl group in DMAE is replaced with an N-sulfopropyl (NSP) group to form a zwitterionic compound. Zwitterion contains separated positive and negative charges within the same molecules where the net charge is zero. NSP-DMAE-NHS has the structure:

[0005] Similarly, U.S. Pat. Nos.8,778,624 and 9,575,062, which are hereby incorporated by reference in their entirety, include AE labels that contain zwitterion group in one and more sites of the molecule and other modifications to the acridinium ring system. Three labels of this group of AEs have been termed ZAE, ISOZAE and ISODIZAE, the structures of which are:

[0006] U.S. Pat. No. 6,664,043, which is hereby incorporated by reference in its entirety, provides hydrophilic acridinium ester such as HEGAE (1) where a polyethylene glycol (PEG) moiety is introduced into the leaving group as a linker to a ligand or binding partner for detection of an analyte. PEG incorporation increases hydrophilicity of the label. HEGAE (1) has the structure:

[0007] U.S. Pat. No. 11,332,445, which is hereby incorporated by reference in its entirety, includes AEs that contain a branched PEG structure covalently attached to the acridinium ring system. The structural features of this group of molecules are given below.

[0008] U.S. Patent Nos. 7,309,615 and 7,785,904, which are hereby incorporated by reference in their entirety, each detail acridinium compounds containing hydrophilic alkoxy groups at C2 and/or C7 of the acridinium ring wherein two oxygen atoms that modify the chemiluminescent output. The hydrophilic groups appended to the two oxygens also increase water solubility. In particular, the most useful labels, HQYAE (2) and TSPAE (3), have requisite parameters exceeding those of most other acridiniums in an immunoassay. HQYAE contains two hydrophilic polyethylene glycol substitutions. TSPAE contains two hydrophilic, negatively charged N-sulfopropyl groups at specific positions on the acridinium ring system. As a result, TSPAE is a water soluble label conferring hydrophilicity to its conjugates and is capable of lowering the isoelectric point (pI) value of the labeled conjugates. TSPAE and HQYAE are increasingly used acridinium labels in commercially available immunoassays that require high sensitivity. The structures of these compounds are:

[0009] Although HQYAE and TSPAE have been used increasingly in assays that require high sensitivity, they suffer stability issues. These labels need to be formulated in slightly acidic pH buffer in order for them to maintain adequate chemiluminescence stability for long term storage. [0010] There is a continuing need for chemiluminescent compounds that can provide high sensitivity for analyte detection while also being stable. SUMMARY [0011] In accordance with the foregoing objectives and others, the present disclosure includes acridiniums that can be used in the chemiluminescent assays. As shown herein, fusing heterocyclic groups (e.g., from five to 10 membered heterocyclic groups) to the acridinium ring system can affect the functionality of the compound and, in some cases, increase the stability and/or reaction kinetics and/or the light output as compared to an otherwise identical compound having hydrogens at the fused positions (e.g., C2 and C3) or a compound having hydrogen and/or an electron donating group at the fused positions. The chemiluminescent acridinium compounds of the present disclosure typically contain 2,3-cyclic alkylenedioxy (or dioxolo) substitutions resulting in high quantum yields and significantly increased chemiluminescence stability. These compounds are useful in assays because of high quantum yield and increased chemiluminescence stability. [0012] For example, compounds are provided (e.g., a detectable conjugate of an analyte or a binding partner for an analyte (e.g., ligand that binds to an analyte) having the structure of formula (I):

wherein A is an analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “j” is 1, 2, 3, 4, 5, or 6; R1 is hydrogen, –R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z, or R₂ and R₃ together form a 5-10 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure: ; where “q” and “l” are indepe

“r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, – C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1- ₃–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2– NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, – (CH₂)_1-3–S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH– (CH2)1-4–, –N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1- ₁₀–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl), optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms, with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl); or a salt thereof (e.g., a halide salt such as a chloride salt). In some embodiments, R3 is hydrogen. In various implementations, R₂ is alkoxy optionally substituted at one or more (e.g., one, two, three) positions with one or more independently selected substituents (e.g., –X such as –S(=O)1- ₂–R*, –O–S(=O)₂–R*, –S(=O)₂–OR*, –O–SO₃, –O–S(=O)₂–OR*, –O–S(=O)–OR*, –O– S(=O)–R*, –S(=O)–OR*, or –S(=O)–R*, where R* is H or a C1-10 hydrocarbon). [0013] Compounds for forming the conjugates are also provided. For example, the compound (e.g., a compound for conjugating with an analyte or binding partner of an analyte such as a peptide, a protein, or a macromolecule including an antibody) may have the structure of formula (IV):

wherein RFG is a reactive functional group for conjugating to the analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “

R1 is hydrogen, –R, –X, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z, or R2 and R3 together form a 5-10 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure:

; where “q” and “l” are independently 0 or 1; “r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, – C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, – (CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2–NH–, – (CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or – (CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl), optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms, with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl); or a salt thereof. In particular embodiments, R1 is –R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z. [0014] In various implementations, the compound for forming a conjugate is selected from:

[0015] Methods for forming a conjugate are provided. In some embodiments, the method may comprise reacting the compound for forming a conjugate with an analyte or binding partner for an analyte (e.g., an antibody) to form a conjugate. [0016] In another aspect of the invention, a reagent is provided for the detection of an analyte comprising a detectable conjugate having a chemiluminescent acridinium with a heterocycle fused to the acridinium ring structure. The detectable conjugate may comprise one or more (e.g., one, two) zwitterionic functional groups. The concentration of the reagent may be chosen in relation to the sensitivity of the assay such that assays requiring higher sensitivity may have a high concentration. For example, the sample may have a concentration of detectable analyte of less than 10^-3 M. In some embodiments the sample may have a concentration of detectable conjugate from 10^-15 M to 10^-3 M. In various implementations, the reagent may have a concentration of detectable conjugate of less than 10^-3 M. In some embodiments, the reagent may have a concentration of detectable conjugate from 10^-15 to 10^-3 M. [0017] In a further aspect of the invention, an assay for the detection or quantification of an analyte in a sample is provided comprising: (a) providing a detectable conjugate having the structure of formula (I); (b) providing a solid support having immobilized thereon a molecule capable of forming a binding complex with said analyte and capable of forming a binding complex with said detectable conjugate; (c) mixing said compound, said solid support, and said sample; (d) separating said solid support from said mixture; (e) triggering chemiluminescence of any acridinium label complexed to said solid phase; (f) measuring the amount of light emission with a luminometer; and (g) detecting the presence or calculating the concentration of said analyte by comparing the amount of light emitted with a standard dose response curve which relates the amount of light emitted to a known concentration of the analyte. In some embodiments, the sample is serum. [0018] These and other aspects of the invention will be better understood by reference to the following detailed description including the appended claims. BRIEF DESCRIPTION OF FIGURES [0019] FIG.1 (1A-1E) provide light emission spectrum as measured from several acridinium compounds described herein. FIG.1A is the Light Emission Spectrum of ADOAE A (5). FIG. 1B is the Light Emission Spectrum of ADOAE D (7) and ADOAE E (8). FIG.1C is the Light Emission Spectrum of ADOAE G (10). FIG.1D is the Light Emission Spectrum of ADOAE I (12). FIG.1E is the Light Emission Spectrum of ADOAE K (14). [0020] FIG.2 provides the light emission kinetics of acridinium esters HEGAE (1), HQYAE (2) and ADOAEs D to L (7-15). As can be seen, ADOAE F (9), ADOAE H (11), ADOAE J (13), and ADOAE L (15) each have faster chemiluminescent reaction kinetics than the other tested compounds. [0021] FIG. 3 (3A-3D) provides structures of comparative acridiniums (FIG. 3A) and exemplary ADOAEs (FIGS.3B-3D) described and used in the syntheses, measurements, and analyses provided herein. DETAILED DESCRIPTION [0022] For convenience, certain terms employed in the specification, including the examples and appended claims, are collected here. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. [0023] Unless otherwise explicitly defined, the following terms and phrases are intended to have the following meanings throughout this disclosure: [0024] All percentages given herein refer to the weight percentages of a particular component relative to the entire composition, including the carrier, unless otherwise indicated. It will be understood that the sum of all weight % of individual components within a composition will not exceed 100%. [0025] The terms “a” or “an,” as used in herein means one or more. As used herein, the term “consisting essentially of” is intended to limit the invention to the specified materials or steps and those that do not materially affect the basic and novel characteristics of the claimed invention, as understood from a reading of this specification. Recitations of “comprising” include “consisting essentially” and “consisting.” When a compound comprises an indicated chemical moiety, that chemical moiety will be a part of the compound and include any number of substitution at any position occupied by hydrogen in the indicated structure. For example, the compound comprising an indicated structure (e.g., the structure of formula (I), A, L, Ψ) may be independently substituted one or more times, for example, with a optionally substituted C1-C35 hydrocarbon. [0026] The following definitions of various groups or substituents are used, unless otherwise described. Specific and general values listed below for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for the radicals and substituents. Unless otherwise indicated, alkyl, alkenyl, alkynyl, alkoxy, and the like denote straight, branched, and cyclic groups, as well as any combination thereof. [0027] The term hydrocarbon may refer to a radical or group containing carbon and hydrogen atoms which may be bound at an indicated position (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R₄, R₅, R₆, R₇, R₈). Examples of hydrocarbon radicals include, without limitation, alkyl, alkenyl, alkynyl, aryl, aryl-alkyl, alkyl-aryl, and any combination thereof (e.g., alkyl-aryl- alkyl). As used herein, unless otherwise indicated, hydrocarbons may be monovalent or multivalent (e.g., divalent, trivalent) hydrocarbon radicals. A radical of the form –(CH2)n–, including a methylene radical, i.e., –CH₂–, is regarded as an alkyl radical if it does not have unsaturated bonds between carbon atoms. Unless otherwise specified, all hydrocarbon radicals (including substituted and unsubstituted alkyl, alkenyl, alkynyl, aryl, aryl-alkyl, alkyl-aryl) may have from 1-35 carbon atoms. In other embodiments, hydrocarbons will have from 1-20 or from 1-12 or from 1-8 or from 1-6 or from 1-3 carbon atoms, including for example, embodiments having one, two, three, four, five, six, seven, eight, nine, or ten carbon atoms. Hydrocarbons may have from 2 to 70 atoms or from 4 to 40 atoms or from 4 to 20 atoms. [0028] A substituted hydrocarbon may have as a substituent one or more hydrocarbon radicals, substituted hydrocarbon radicals, or may comprise one or more heteroatoms. Any hydrocarbon substituents disclosed herein (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R₆, R₇, R₈) may optionally include from 1-20 (e.g., 1-10, 1-5) heteroatoms. Examples of substituted hydrocarbon radicals include, without limitation, heterocycles, such as heteroaryls. Unless otherwise specified, a hydrocarbon substituted with one or more heteroatoms will comprise from 1-20 heteroatoms. In other embodiments, a hydrocarbon substituted with one or more heteroatoms will comprise from 1-12 or from 1-8 or from 1-6 or from 1-4 or from 1-3 or from 1-2 heteroatoms. Examples of heteroatoms include, but are not limited to, oxygen, nitrogen, sulfur, phosphorous, halogen (e.g., F, Cl, Br, I), boron, or silicon. In some embodiments, heteroatoms will be selected from the group consisting of oxygen, nitrogen, sulfur, phosphorous, and halogen (e.g., F, Cl, Br, I). In certain embodiments, the heteroatoms may be selected from O, N, or S. In some embodiments, a heteroatom or group may substitute a carbon. In some embodiments, a heteroatom or group may substitute a hydrogen. In some embodiments, a substituted hydrocarbon may comprise one or more heteroatoms in the backbone or chain of the molecule (e.g., interposed between two carbon atoms, as in “oxa”). In some embodiments, a substituted hydrocarbon may comprise one or more heteroatoms pendant from the backbone or chain of the molecule (e.g., covalently bound to a carbon atom in the chain or backbone, as in “oxo”). [0029] When an indicated group is substituted with an indicated substituent, the specified group may be substituted with one or more of any or all of the named substituents. For example, where a group, such as an alkyl or heteroaryl group, is “substituted with an unsubstituted C1- C₂₀ alkyl, or unsubstituted 2 to 20 membered heteroalkyl,” the group may contain one or more unsubstituted C1-C20 alkyls, and/or one or more unsubstituted 2 to 20 membered heteroalkyls. Moreover, where a moiety is substituted with an R substituent, the group may be referred to as “R-substituted.” Where a moiety is R-substituted, the moiety is substituted with at least one R substituent and each R substituent is optionally different. If an indicated group is used multiple times in chemical genus (e.g., R groups), it will be understood that each group is independently selected at each occurrence. [0030] Unless otherwise specified, any compound disclosed herein which has one or more chiral centers may be in the form of a racemic mixture with respect to each chiral center, or may exist as pure or substantially pure (e.g., great than 98% ee) R or S enantiomers with respect to each chiral center, or may exist as mixtures of R and S enantiomers with respect to each chiral center, wherein the mixture comprises an enantiomeric excess of one or the other configurations, for example an enantiomeric excess (of R or S) of more than 60% or more than 70% or more than 80% or more than 90%, or more than 95%, or more than 98%, or more than 99% enantiomeric excess. In some embodiments, any chiral center may be in the “S” or “R” configurations. [0031] It will be understood that the description of compounds herein is limited by principles of chemical bonding. Accordingly, where a group may be substituted by one or more of a number of substituents, such substitutions are selected so as to comply with principles of chemical bonding such as regard to valencies, and to give compounds which are not inherently unstable. For example, any carbon atom will be bonded to two, three, or four other atoms, consistent with the four valence electrons of carbon. [0032] Substituent (radical) prefix names may be derived from the parent hydride by either (i) replacing the “ane” or in the parent hydride with the suffixes “yl,” “diyl,” “triyl,” “tetrayl;” or (ii) replacing the “e” in the parent hydride with the suffixes “yl,” “diyl,” “triyl,” “tetrayl,” (here the atom(s) with the free valence, when specified, is (are) given numbers as low as is consistent with any established numbering of the parent hydride). Accepted contracted names, e.g., adamantyl, naphthyl, anthryl, phenanthryl, furyl, pyridyl, isoquinolyl, quinolyl, and piperidyl, and trivial names, e.g., vinyl, allyl, phenyl, and thienyl are also used herein throughout. [0033] Generally, the anionic group (X^a and/or X^b) may provide an anionic charge to counterbalance any cationic charge directly or indirectly covalently attached and in order to form a zwitterion. In some embodiments, X^a and X^b are independently at each occurrence carboxylate (–C(O)O-), sulfonate (–SO_ଷି ), sulfate (–OSO_ଷି ), phosphate (–OP(O)(OR^P)O-), or oxide (–O-), and R^P is hydrogen or C1-12 hydrocarbon optionally substituted with up to 10 heteroatoms. [0034] Alkyl groups typically refer to a saturated hydrocarbon chain that may be a straight chain or branched chain, containing the indicated number of carbon atoms. For example, C1- C6 alkyl indicates that the group may have from 1 to 6 (inclusive) carbon atoms in it. Any atom can be optionally substituted, e.g., by one or more substituents. Examples of alkyl groups include without limitation methyl, ethyl, n-propyl, isopropyl, and tert-butyl. Any alkyl group referenced herein (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) may have from 1-35 carbon atoms. In other embodiments, alkyl groups will have from 1-20 or from 1-12 or from 1-8 or from 1-6 or from 1-3 carbon atoms, including for example, embodiments having one, two, three, four, five, six, seven, eight, nine, or ten carbon atoms. Alkyl groups may be lower alkyl (e.g., C1-C4 alkyl). An alkyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heteroalkyl groups such as amino groups (e.g., alkylamino, dialkylamino), alkoxy groups, or haloalkyl groups). [0035] Haloalkyl groups are typically alkyl groups where at least one hydrogen atom is replaced by halo. In some embodiments, more than one hydrogen atom (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14) are replaced by halo. In these embodiments, the hydrogen atoms can each be replaced by the same halogen (e.g., fluoro) or the hydrogen atoms can be replaced by a combination of different halogens (e.g., fluoro and chloro). Haloalkyl may include alkyl moieties in which all hydrogens have been replaced by halo (sometimes referred to herein as perhaloalkyl, e.g., perfluoroalkyl, such as trifluoromethyl). Haloalkyl groups may be optionally substituted. [0036] Typically, alkoxy groups have the formula –O(alkyl). Alkoxy can be, for example, methoxy (–OCH3), ethoxy, propoxy, isopropoxy, butoxy, iso-butoxy, sec-butoxy, pentoxy, 2- pentoxy, 3-pentoxy, or hexyloxy. Likewise, the term “thioalkoxy” refers to a group of formula –S(alkyl). Finally, the terms “haloalkoxy” and “halothioalkoxy” refer to –O(haloalkyl) and – S(haloalkyl), respectively. The term “sulfhydryl” refers to –SH. As used herein, the term “hydroxyl,” employed alone or in combination with other terms, refers to a group of formula – OH. Any alkoxy, thioalkoxy, or haloalkoxy group referenced herein (e.g., R, R’, R”, L₁, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) may have from 1-35 carbon atoms. In other embodiments, alkoxy, thioalkoxy, or haloalkoxy groups will have from 1-20 or from 1-12 or from 1-8 or from 1-6 or from 1-3 carbon atoms, including for example, embodiments having one, two, three, four, five, six, seven, eight, nine, or ten carbon atoms. Alkoxy groups may be lower alkoxy (e.g., C₁-C₄ alkoxy). [0037] Aralkyl groups typically refers to groups where an alkyl moiety in which an alkyl hydrogen atom is replaced by an aryl group. One of the carbons of the alkyl moiety serves as the point of attachment of the aralkyl group to another moiety. Any ring or chain atom can be optionally substituted, e.g., by one or more substituents. Non-limiting examples of aralkyl include benzyl, 2-phenylethyl, and 3-phenylpropyl groups. An aralalkyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heteroarylalkyl groups such as amino groups (e.g., arylamino), aryloxy groups, or haloarylalkyl groups). [0038] The term “alkenyl” may refer to a straight or branched hydrocarbon chain containing the indicated number of carbon atoms and having one or more carbon-carbon double bonds. Any atom can be optionally substituted, e.g., by one or more substituents. Alkenyl groups can include, e.g., vinyl, allyl, 1-butenyl, and 2-hexenyl. One of the double bond carbons can optionally be the point of attachment of the alkenyl substituent. Any alkenyl group referenced herein (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) may have from 1-35 carbon atoms. In other embodiments, alkenyl groups will have from 1-20 or from 1-12 or from 1-8 or from 1-6 or from 1-3 carbon atoms, including for example, embodiments having one, two, three, four, five, six, seven, eight, nine, or ten carbon atoms. An alkenyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heteroalkenyl groups such as amino groups (e.g., alkenylamino, alkenylalkylamino), alkenyloxy groups, or haloalkenyl groups). [0039] The term alkynyl may refer to a straight or branched hydrocarbon chain containing the indicated number of carbon atoms and having one or more carbon-carbon triple bonds. Alkynyl groups (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) can be optionally substituted, e.g., by one or more substituents. Alkynyl groups can include, e.g., ethynyl, propargyl, and 3-hexynyl. One of the triple bond carbons can optionally be the point of attachment of the alkynyl substituent. An alkynyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heteroalkynyl groups such as amino groups (e.g., alkynylamino, alkenylalkylamino) alkynyloxy groups, or haloalkynyl groups. [0040] The term heterocyclyl typically refers to a fully saturated, partially saturated, or aromatic monocyclic, bicyclic, tricyclic, or other polycyclic ring system having one or more constituent heteroatom ring atoms independently selected from O, N (it is understood that one or two additional groups (e.g., R^N) may be present to complete the nitrogen valence and/or form a salt), or S. The present disclosure is partially premised on the installation of one or more fused heterocyclyl groups to an acridinium. The heteroatom or ring carbon can be the point of attachment of the heterocyclyl substituent to another moiety. Any atom can be optionally substituted, e.g., with one or more substituents (e.g. heteroatoms or groups X). Heterocyclyl groups can include, e.g., tetrahydrofuryl, tetrahydropyranyl, piperidyl (piperidino), piperazinyl, morpholinyl (morpholino), pyrrolinyl, and pyrrolidinyl. By way of example, the phrase “heterocyclic ring containing from 5-6 ring atoms, wherein from 1-2 of the ring atoms is independently selected from N, NH, N(C₁-C₆ alkyl), NC(O)(C₁-C₆ alkyl), O, and S; and wherein said heterocyclic ring is optionally substituted with from 1-3 independently selected R” would include (but not be limited to) tetrahydrofuryl, tetrahydropyranyl, piperidyl (piperidino), piperazinyl, morpholinyl (morpholino), pyrrolinyl, and pyrrolidinyl. [0041] The term heterocycloalkenyl typically refers to partially unsaturated monocyclic, bicyclic, tricyclic, or other polycyclic hydrocarbon groups having one or more (e.g., 1-4) heteroatom ring atoms independently selected from O, N (it is understood that one or two additional groups may be present to complete the nitrogen valence and/or form a salt), or S. A ring carbon (e.g., saturated or unsaturated) or heteroatom can be the point of attachment of the heterocycloalkenyl substituent. Any atom can be optionally substituted, e.g., by one or more substituents. Heterocycloalkenyl groups can include, e.g., dihydropyridyl, tetrahydropyridyl, dihydropyranyl, 4,5-dihydrooxazolyl, 4,5-dihydro-1H-imidazolyl, 1,2,5,6-tetrahydro- pyrimidinyl, and 5,6-dihydro-2H-[1,3]oxazinyl. [0042] Cycloalkyl groups may be fully saturated monocyclic, bicyclic, tricyclic, or other polycyclic hydrocarbon groups. Any atom can be optionally substituted, e.g., by one or more substituents. A ring carbon serves as the point of attachment of a cycloalkyl group to another moiety. Cycloalkyl moieties can include, e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbornyl (bicycle[2.2.1]heptyl). A cycloalkyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heterocycloalkyl groups such as oxiranyl, oxetanyl, azetidinyl, aziridinyl, furanyl, pyranyl, pyrrolidinyl, piperidinyl, thiiranyl, thietanyl, tetrahydrothiphenyl, thiopyranyl, or halocycloakyl. [0043] Cycloalkenyl groups may be partially unsaturated monocyclic, bicyclic, tricyclic, or other polycyclic hydrocarbon groups. A ring carbon (e.g., saturated or unsaturated) is the point of attachment of the cycloalkenyl substituent. Any atom can be optionally substituted, e.g., by one or more substituents. Cycloalkenyl moieties can include, e.g., cyclohexenyl, cyclohexadienyl, or norbornenyl. A cycloalkenyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heterocycloalkenyl groups such as oxiranyl, oxetanyl, azetidinyl, aziridinyl, furanyl, pyranyl, pyrrolidinyl, piperidinyl, thiiranyl, thietanyl, tetrahydrothiphenyl, thiopyranyl, or halocycloalkenyl. [0044] Aryl groups are often aromatic monocyclic, bicyclic (2 fused rings), or tricyclic (3 fused rings), or polycyclic (> 3 fused rings) hydrocarbon ring system. One or more ring atoms can be optionally substituted, e.g., by one or more substituents. Aryl moieties include, e.g., phenyl and naphthyl. A cycloalkenyl group substituted with one or more heteroatoms (e.g., N, O, halogen) may include heteroaryl groups or haloaryl groups. [0045] Heteroaryl groups typically are aromatic monocyclic, bicyclic (2 fused rings), tricyclic (3 fused rings), or polycyclic (> 3 fused rings) hydrocarbon groups having one or more heteroatom ring atoms independently selected from O, N (it is understood that one or two additional groups may be present to complete the nitrogen valence and/or form a salt), or S in the ring. One or more ring atoms can be optionally substituted, e.g., by one or more substituents. Examples of heteroaryl groups include, but are not limited to, 2H-pyrrolyl, 3H-indolyl, 4H- quinolizinyl, acridinyl, benzo[b]thienyl, benzothiazolyl, β-carbolinyl, carbazolyl, coumarinyl, chromenyl, cinnolinyl, dibenzo[b,d]furanyl, furazanyl, furyl, imidazolyl, imidizolyl, indazolyl, indolyl, isobenzofuranyl, isoindolyl, isoquinolyl, isothiazolyl, isoxazolyl, naphthyridinyl, oxazolyl, perimidinyl, phenanthridinyl, phenanthrolinyl, phenarsazinyl, phenazinyl, phenothiazinyl, phenoxathiinyl, phenoxazinyl, phthalazinyl, pteridinyl, purinyl, pyranyl, pyrazinyl, pyrazolyl, pyridazinyl, pyridyl, pyrimidinyl, pyrrolyl, quinazolinyl, quinolyl, quinoxalinyl, thiadiazolyl, thianthrenyl, thiazolyl, thienyl, triazolyl, and xanthenyl. [0046] In general, when a definition for a particular variable includes both hydrogen and non-hydrogen (halo, alkyl, aryl) possibilities, the term “substituent(s) other than hydrogen” refers collectively to the non-hydrogen possibilities for that particular variable, unless otherwise specified. [0047] In general, the limits (end points) of any range recited herein are within the scope of the invention and should be understood to be disclosed embodiments. Additionally, any half- integral value within that range is also contemplated. For example, a range of from 0 to 4 expressly discloses 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, and any subset within that range (e.g., from 1 to 2.5). [0048] The term “substituent” may refer to a group “substituted” on a hydrocarbon (e.g., an alkyl, haloalkyl, cycloalkyl, heterocyclyl, heterocycloalkenyl, cycloalkenyl, aryl, or heteroaryl group) at any atom of that group, replacing one or more atoms therein. In one aspect, the substituent(s) on a group (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) are independently any one single, or any combination of two or more of the permissible atoms or groups of atoms delineated for that substituent. In another aspect, a substituent may itself be substituted with any one of the above substituents. Further, as used herein, the phrase “optionally substituted” means unsubstituted (e.g., substituted with an H) or substituted. It is understood that substitution at a given atom is limited by valency. Common substituents include halo (e.g. F), C1-12 straight chain or branched chain alkyl, C2-12 alkenyl, C2-12 alkynyl, C3-12 cycloalkyl, C6-12 aryl, C3-12 heteroaryl, C3-12 heterocyclyl, C1-12 alkylsulfonyl, nitro, cyano, –COOR, –C(O)NRR’, –OR, –SR, –NRR’, and oxo, such as mono- or di- or tri-substitutions with moieties such as trifluoromethoxy, chlorine, bromine, fluorine, methyl, methoxy, pyridyl, furyl, triazyl, piperazinyl, pyrazoyl, imidazoyl, and the like, each optionally containing one or more heteroatoms such as halo, N, O, S, and P. R and R’ are independently hydrogen, C1-12 alkyl, C_1-12 haloalkyl, C_2-12 alkenyl, C_2-12 alkynyl, C_3-12 cycloalkyl, C_4-24 cycloalkylalkyl, C_6-12 aryl, C7-24 aralkyl, C3-12 heterocyclyl, C3-24 heterocyclylalkyl, C3-12 heteroaryl, or C4-24 heteroarylalkyl. Unless otherwise noted, all groups described herein optionally contain one or more common substituents, to the extent permitted by valency. Further, as used herein, the phrase “optionally substituted” means unsubstituted (e.g., substituted with an H) or substituted. As used herein, the term “substituted” means that a hydrogen and/or carbon atom is removed and replaced by a substituent (e.g., a common substituent). The use of a substituent (radical) prefix names such as alkyl without the modifier “optionally substituted” or “substituted” is understood to mean that the particular substituent is unsubstituted. However, the use of “haloalkyl” without the modifier “optionally substituted” or “substituted” is still understood to mean an alkyl group, in which at least one hydrogen atom is replaced by halo and any other associated substitutions as necessary. [0049] When a moiety of the compounds of the present disclosure are described as an analyte or a binding partner thereof, it will be understood that a covalent linkage is formed with an analyte or binding partner thereof (e.g., using the reactive functional groups which form covalent linkages), for example, by replacing a hydrogen on the unconjugated analyte or binding partner thereof with a covalent bond to the indicated moiety. The covalent linkage on the analyte or binding partner thereof may be formed, for example, at a group on the analyte, binding partner thereof, or derivatized version of the analyte containing a group for forming a linkage. The group may be, for example, an amine group, a thiol group, a carboxy group, a maleimidyl group, or a carbohydrate group. For example, if a covalent linkage is formed through a primary amine of the analyte or binding partner thereof, the compound may have the structure:

where the unconjugated analyte or binding partner A has the structure A’–NH2. In some embodiments, if a covalent linkage is formed through a thiol of the analyte or binding partner thereof, the compound may have the structure:

wherein the unconjugated analyte or binding partner A has the structure A’-SH. [0050] In some embodiments, any hydrocarbon or substituted hydrocarbon disclosed herein (e.g., R, R’, R”, L1, L^C, R^L, R^C, R1, R2, R3, R4, R5, R6, R7, R8) may be substituted with one or more (e.g., from 1-6 or from 1-4 or from 1-3 or one or two or three) substituents X, where X is independently selected at each occurrence from one or more (e.g., 1-20) heteroatoms or one or more (e.g., 1-10) heteroatom-containing groups, or X is independently selected at each occurrence from –F, –Cl, –Br, –I, –OH, –OR*, –NH2, –NHR*, –N(R*)2, –N(R*)3⁺, –N(R*)– OH, –N(→O)(R*)₂, –O–N(R*)₂, –N(R*)–O–R*, –N(R*)–N(R*)₂, –C=N–R*, –N=C(R*)₂, – C=N–N(R*)2, –C(=NR*)(–N(R*)2), –C(H)(=N–OH), –SH, –SR*, –CN, –NC, –CHF2, –CCl3, –CF₂Cl, –CFCl₂, –C(=O)–R*, –CHO, –CO₂H, –C(O)CH₃, –CO₂-, –CO₂R*, –C(=O)–S–R*, – O–(C=O)–H, –O–(C=O)–R*, –S–C(=O)–R*, –(C=O)–NH2, –C(=O)–N(R*)2, –C(=O)– NHNH₂, –O–C(=O)–NHNH₂, –C(=S)–NH₂, –(C=S)–N(R*)₂, –N(R*)–CHO, –N(R*)–C(=O)– R*, –C(=NR)–OR*, –O–C(=NR*)–R*, –SCN, –NCS, –NSO, –SSR*, –N(R*)–C(=O)–N(R*)2, –CH₃, –CH₂–CH₃, –CH₂–CH₂–CH₃, –C(H)(CH₂)_2, –C(CH₃)₃, –N(R*)–C(=S)–N(R*)₂, – S(=O)1-2–R*, –O–S(=O)2–R*, –S(=O)2–OR*, –N(R*)–S(=O)2–R*, –S(=O)2–N(R*)2, –O–SO3, –O–S(=O)2–OR*, –O–S(=O)–OR*, –O–S(=O)–R*, –S(=O)–OR*, –S(=O)–R*, –NO, –NO2, – NO₃, –O–NO, –O–NO₂, –N₃, –N₂–R*, –N(C₂H₄), –Si(R*)₃, –CF₃, –O–CF₃, –O–CHF₂, –O– CH3, –O–(CH2)1-6CH3, –OC(H)(CH2)2 –OC(CH3)3, –PR*2, –O–P(=O)(OR*)2, or – P(=O)(OR*)₂; where, independently at each occurrence, R* may be H or a C_1-10 or C_1-8 or C_1-6 or C1-4 hydrocarbon, including without limitation alkyl, alkenyl, alkynyl, aryl (e.g., phenyl), alkyl-aryl (e.g., benzyl), aryl-alkyl (e.g., tolyl) In some embodiments, X may comprise a C₁- C8 or C1-C6 or C2-C4 perfluoroalkyl. In some embodiments, X may be a C1-C8 or C2-C6 or C3- C₅ heterocycle (e.g., heteroaryl radical). The term “halo” or “halogen” refers to any radical of fluorine, chlorine, bromine or iodine. In some embodiments, X is independently selected at each occurrence from –OH, –SH, –NH₂, –N(R*)₂, –C(O)OR*, –C(O)NR*R*, –C(O)NR*R*, –C(O)OH, –C(O)NH2, F, or –Cl. In some embodiments, X is F. R and R* may be, independently at each occurrence, saturated or unsaturated alkyl (e.g., C₁-C₈ alkyl). In some embodiments, R and R* are independently selected from hydrogen, methyl, ethyl, propyl, or isopropyl. In some embodiments, R and R* are independently selected from hydrogen, methoxy, ethoxy, propoxy, or isopropoxy. In some embodiments, X is –CF3 or –O–CF3. [0051] Compounds are provided (e.g., a detectable conjugate of an analyte or a binding partner for an analyte) having the structure of formula (I): (^I) wherein A is an analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “j” is 1, 2, 3, 4, 5, or 6; R₁ is hydrogen, –R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z, or R2 and R3 together form a 5-10 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure:

where “q” and “l” are independently 0 or 1; “r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, – C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1- 3–, –(CH2)1-3–C(O)–N(R^N)–, –NH–S(O)1-2–, –N(R^N)–S(O)1-2–, –S(O)1-2–N(R^N)–, –S(O)1-2– NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, – (CH2)1-3–S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S–, –NH– (CH₂)_1-4–, –N(R^N)–(CH₂)_1-4–, –(CH₂)_1-4–N(R^N)–, –(OCH₂)_1-10–, –(CH₂O)_1-10–, –(OCH₂CH₂)_1- 10–, or –(CH2CH2O)1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon group (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents such as one or more groups –X); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) group, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-20 substituents such as one or more groups – X); R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl); or a salt thereof (e.g., a halide salt such as a chloride salt). In some embodiments, R3 is hydrogen. In various implementations, R₂ is alkoxy optionally substituted at one or more (e.g., one, two, three) positions with one or more independently selected substituents (e.g., –X such as –S(=O)1- 2–R*, –O–S(=O)2–R*, –S(=O)2–OR*, –O–SO3, –O–S(=O)2–OR*, –O–S(=O)–OR*, –O– S(=O)–R*, –S(=O)–OR*, or –S(=O)–R*, where R* is H or a C_1-10 hydrocarbon). In some embodiments, R1 is –R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z. [0052] The compound may have the structure of Formula (Ia):

wherein “

R1 is hydrogen, –R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z, or R₂ and R₃ together form a 5-10 membered fused heterocyclyl group; R4 is independently at each occurrence selected from hydrogen and –R (e.g., R’, R^N, lower alkyl such as C₁-C₄ alkyl); Ω is S, O, or N; Y is selected from –R, –L₁–R, –R^L–Z, –L₁–R^L–Z, or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L1–, –R^L–, –R^L–L1–, –L1–L1–, –L1– R^L–, –L1–R^L–L1, or –R^L–L1–R^L–; and Y’ comprises one or more linkages to L^C or Z^L; Z is a zwitterionic group having the structure: ;

“r” is independently an integer from 0 to 10; L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, –C(O)–O– , –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH₂)_1-3–, –(CH2)1-3–C(O)–N(R^N)–, –NH–S(O)1-2–, –N(R^N)–S(O)1-2–, –S(O)1-2–N(R^N)–, –S(O)1-2–NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S–, –NH–(CH2)1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or –(CH2CH2O)1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl, combinations thereof), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, aralkyl, combinations thereof) group, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl). Z is a zwitterionic group independently at each occurrence having the structure:

; where “q” and “l” are independently 0 or 1; “r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, – C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1- ₃–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2– NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, – (CH2)1-3–S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S–, –NH– (CH2)1-4–, –N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1- 10–, or –(CH2CH2O)1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents); R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl); or a salt thereof (e.g., a halide salt such as a chloride salt). In some embodiments, Ω is S, O, or N. In various implementations, R1 is–R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z. In certain aspects, R1 is–R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z and Ω is S, O, or N. For example, each of R4 in Formula (Ia) may be hydrogen. In some embodiments, “

” is 2 or 3. In various implementations, the compound has the structure of formula (II)

wherein Ω is S, O, or N; Y is selected from –R, –L1–R, –R^L–Z, –L1–R^L–Z or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L₁–, –R^L–, –R^L–L₁–, –L₁–L₁–, –L₁– R^L–, –L1–R^L–L1, or –R^L–L1–R^L–; and Y’ comprises one or more linkages to A or L (e.g., to L^C or Z^L); R₁ is hydrogen, –R, –X, –R^L–X, –L₁–R, –L₁–X, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z; Z is a zwitterionic group having the structure: ;

“r” is independently an integer from 0 to 10; L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, –C(O)–O– , –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH₂)_1-3–, –(CH2)1-3–C(O)–N(R^N)–, –NH–S(O)1-2–, –N(R^N)–S(O)1-2–, –S(O)1-2–N(R^N)–, –S(O)1-2–NH–, –(CH₂)_1-3–NH–S(O)_1-2–, –(CH₂)_1-3–N(R^N)–S(O)_1-2–, –(CH₂)_1-3–S(O)_1-2–N(R^N)–, –(CH₂)_1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, or heteroarylalkyl groups; with 1-10 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl). In particular embodiments, Ω is S, O, or N. In some embodiments, R1 is –R, – X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z. In certain aspects, Ψ has the structure of formula (IIa)

wherein “h” is 1, 23, 4, 5, or 6. In some embodiments, the compound has the structure of formula (IIb):

wherein R₅-R₈ are independently hydrogen or C_1-35 hydrocarbon radical (e.g., alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, amino; and wherein L1 is covalently bonded to A (e.g., L absent) optionally having one or more (e.g., 1-20 points of substitution) or L (e.g., to L^C or Z^L). L1 may be, for example, –NH–C(O)–, –C(O)–NH– or –C(O)–O– or –O–C(O)–. In particular embodiments, R5 and R6 are each lower alkyl (e.g., C1-C4 alkyl, methyl) and R7 and R8 are each hydrogen. [0053] In some embodiments, the compound may have the structure of formula (IIc):

wherein Y” is either absent or is –L1–, –R^L–, –L1– R^L–, or –R^L–L1–, where Y” is covalently attached to A (e.g., L is absent) or L (e.g., to L^C or Z^L). [0054] In some embodiments, the compound may have the structure of formula (IId):

wherein Y” is either absent or is –L1–, –R^L–, –L1– R^L–, or –R^L–L1–, where Y” is covalently attached to A (e.g., L is absent) or L (e.g., to L^C or Z^L). In some embodiments, R in formula (IId) is optionally substituted aryl (e.g., C6-C12 aryl, phenyl) which may be substituted with, for example, aryl. For example, the compound may have the structure of formula (IIe):

wherein Y” is either absent or is –L₁–, –R^L–, –L₁– R^L–, or –R^L–L₁–, where Y” is covalently attached to A (e.g., L is absent) or L (e.g., to L^C or Z^L). [0055] In some embodiments, L has the structure –L^C–(Z^L)z– where “z” is 0 or 1; L^C is a divalent C_1-35 alkyl, alkenyl, alkynyl, aryl, or arylalkyl radical, optionally substituted with 1 to 20 heteroatoms; and Z^L is a zwitterionic linker group having the structure:

; “m” is 0 (i.e. it is a bond) or 1; “n” and “p” are independently at each occurrence an integer from 0 (i.e. it is a bond) to 10; X^a is an anionic group; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., substituted with 1-10 heteroatoms, substituted with 1-10 substituents); and R’ is hydrogen or a C1-10 alkyl. L^C may have the structure: –(X1)0-1–(R^L)0-5–(X2)0-1– (R^L)0-5–(X3)0-1–(R^L)0-5–(X4)0-1–(R^L)0-5– wherein X1 is selected from =N–, –O–, –S–, or –NR^N–; X₂–X₄ are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)– NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from–(CH2)1-5–, –(CH2CH2O)1-5–, or – (OCH₂CH₂)_1-5–, or C₅-C₆ optionally substituted cycloalkylene (e.g., cyclopentylene, cyclohexylene). In various embodiments, L^C comprises at least one atom (or at least two atoms) in the chain between A and Ψ (or between A and Z^L). In some embodiments, L comprising a linking moiety associated with conjugation to thiols. For example, when the reactive functional group is a maleimide, X1 (or X₂-X₄) may be:

wherein indicates the point of attachment to either neighboring group. For example, the point of attachment marked with a “*” may be the linkage to a thiol on the analyte or binding partner thereof. In some embodiments, X^a and X^b may be, for example, independently at each occurrence carboxylate (–C(O)O-), sulfonate (–SO_ଷି ), sulfate (–OSO_ଷି ), phosphate (– OP(O)(OR^P)O-), or oxide (–O-), and R^P is hydrogen or C_1-12 hydrocarbon optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents). For example, R1 may comprise (or be) –R^L–SO_ଷି (e.g., sulfopropyl). In some embodiments, R₁ comprises (or is) sulfopropyl. In some embodiments, R₁ is –S(O)₂–NH–Z or –(CH2)1-3–S(O)2–NH–Z. In various implementations, R2 and R3 are independently at each occurrence hydrogen, alkyl, or alkoxy (e.g., lower alkoxy such as C₁-C₄ alkoxy, methoxy, ethoxy, propoxy, isopropoxy). In some embodiments, R2 and R3 are each hydrogen. In other embodiments, one of R₂ or R₃ is hydrogen and the other of R₂ or R₃ is alkoxy (e.g., lower alkoxy such as C1-C4 alkoxy, methoxy, ethoxy, propoxy, isopropoxy). In some embodiments, X^a is sulfonate ( m is 1, R^L is propyl, and n and p are each 3, such that Z^L has the structure:

. [0056] In particular embodiments, the compound has the structure of formula (IIIa) or (IIIb):

In particular embodiments, “j” is 2 or 3. [0057] The compounds may be used to detect for the presence of a material in a sample such as an analyte (e.g., a biomolecule). In some embodiments, the analyte is a thyroid hormone (e.g., a thyroid stimulating hormone and, for example, A is a binding partner therefor such as an anti-thyroid stimulating hormone monoclonal antibody (AntiTSH-mAb)), an androgen, a steroid hormone (e.g., androstenedione, testosterone), a troponin, thyroglobulin, anti-thyroid peroxidase antibody, triiodothyronine (T3) hormone, thyroxine (T4) hormone, thyroxine- binding globulin (TBG), neurofilament light chain (e.g., serum neurofilament light chain), a vitamin (e.g., vitamin-D such as 25-hydroxy-vitamin D), or an antibody for a virus (e.g., hepatitis). [0058] Compounds for forming the conjugates are also provided. For example, the compound (e.g., a compound for conjugating with an analyte or binding partner of an analyte such as a peptide, a protein, or a macromolecule including an antibody) may have the structure of formula (IV):

wherein “j” is 1, 2, 3, 4, 5, or 6; R₁ is hydrogen, –R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z, or R₂ and R₃ together form a 5-7 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure:

; where “q” and “l” are independently 0 or 1; “r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, – C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, – (CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2–NH–, – (CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or – (CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl; with 1-10 substituents, for example, hydrocarbons having 1-10 substituents selected from one or more groups –X); R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms, with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl). For example, the reactive functional group may be selected from:

COOH. The compound may have the structure of Formula (IVa):

wherein “j” is 1, 2, 34, 5, or 6; R₁ is hydrogen, –R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z, or R₂ and R₃ together form a 5-10 membered fused heterocyclyl group; R₄ is independently at each occurrence selected from hydrogen and –R (e.g., R’, R^N, lower alkyl such as C1-C4 alkyl); Ω is S, O, or N; Y is selected from –R, –L1–R, –R^L–Z, –L1–R^L–Z, or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L1–, –R^L–, –R^L–L1–, –L1–L1–, –L1– R^L–, –L₁–R^L–L₁, or –R^L–L₁–R^L–; and Y’ comprises one or more linkages to L^C or Z^L; Z is a zwitterionic group having the structure: ;

“r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)–O– , –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2–NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl, combinations thereof), optionally substituted with 1-10 heteroatoms and/or substituents; R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, aralkyl, combinations thereof) radical, optionally substituted with 1-20 heteroatoms and/or substituents; R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl). Z is a zwitterionic group independently at each occurrence having the structure: ;

“r” is independently an integer from 0 to 10; L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, – C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1- ₃–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2– NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, – (CH₂)_1-3–S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH– (CH2)1-4–, –N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1- ₁₀–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents); R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms, with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl); or a salt thereof (e.g., a halide salt such as a chloride salt). In some embodiments, Ω is S, O, or N. In various implementations, R₁ is–R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L1–R^L–Z. In certain aspects, R1 is–R, –X^b, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L₁–R^L–Z and Ω is S, O, or N. For example, each of R₄ in Formula (IVa) may be hydrogen. In some embodiments, “

” is 2 or 3. [0059] The compounds for forming the conjugates may have the relevant groups (e.g., Ω, Y, Y’, Y”, R, R’, R”, L₁, L^C, R^L, R^C, R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, X, X^a, X^b) as described herein. For example, the compound may have the structure of formula (V), (Va), (Vb), (Vc), (Vd), (Ve), (VIa), (VIb), (VIc), (VId), or (VIe):

. [0060] In various implementations, the compound is selected from:

[0061] In some embodiments, the compounds of the present disclosure may be zwitterionic and include one or more zwitterionic groups. For example, the R₁ group attached to the positively charged nitrogen of the acridinium may optionally substituted with up to 20 heteroatoms (e.g., N, O, S, P, Cl, Br, F) and therefore may in combination with the positively charged acridinium nitrogen atom, constitute a zwitterionic group. For example, a sulfopropyl or sulfobutyl group attached to the acridinium nitrogen may form a zwitterionic pair. The R₁ group may also be neutral (e.g., methyl) or by itself be zwitterionic (e.g., R1 is –Z, –R^L–Z, – L₈–Z, or –R^L–L₈–R^M–Z). In some embodiments, R₁ has the structure:

. When the compound is charged (e.g., R₁ has a net neutral charge), the compound may be in its salt form and optionally include a counterion to balance the positively charged nitrogen of the acridinium nucleus. The counterion may be selected from CH₃SO₄-, FSO₃-, CF₃SO4-, C₄F₉SO₄- , CH3C6H4SO3-, halide (e.g., Cl-, F-, Br-), CF3COO-, CH3COO-, or NO3-. In some embodiments, R1 is methyl, ethyl, propyl, or isopropyl. In some embodiments, the acridinium compound may be zwitterionic by via covalent attachment to an anion. For example, R1 may comprises –R^L– X and –X is sulfonate (–SO_ଷି ). In some embodiments, R₁ is –R^L–X and –X is sulfonate (–SO_ଷି ). In some embodiments, R1 is –R^L–X or –L8–Z. In some embodiments, L8 is –S(O)2–NH– or – (CH2)1-3–S(O)2–NH–. R1 may comprise a sulfopropyl group (–(CH2)3–SO_ଷି ). In a specific embodiment, R₁ is sulfopropyl. [0062] In some implementations, the chemiluminescent acridinium Ψ is an acridinium ester. For example, Ψ may have the structure:

wherein Ω is S, O, or N; Y is selected from –R, –L₁–R, –R^L–Z, –L₁–R^L–Z, or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L1–, –R^L–, –R^L–L1–, –L1–L1–, –L1– R^L–, –L₁–R^L–L₁, or –R^L–L₁–R^L–; and Y’ comprises one or more linkages to L^C or Z^L; R₁ is hydrogen, –R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z; Z is a zwitterionic group having the structure: ;

“r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)–O– , –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2–NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally substituted with 1-10 heteroatoms (e.g., hereoalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl) and/or substituents; R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally substituted with 1-20 heteroatoms (e.g., heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl) and/or substituents; R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl). In particular embodiments, Ω is S, O, or N and/or R1 is –R, –X^b, –R^L–X^b, –L1– R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z. In some embodiments, Ψ may be a chemiluminescent acridinium comprising the structure:

wherein “h” is 1, 2, 3, 4, 5, or 6. In some embodiments, Ψ is a chemiluminescent acridinium comprising the structure:

. [0063] The substituents on the chemiluminescent acridinium ester may be modified to vary the rate and yield of light emission, to reduce the non-specific binding, increase stability, or increase hydrophilicity. Typically, these modifications will have minimal interference substantially with the binding of the analyte and its binding partner. Examples of substituent variability are disclosed in Natrajan et al. in U.S. Pat No 7,309,615, hereby incorporated by reference herein, which describes high quantum yield acridinium compounds containing alkoxy groups (OR*) at C2 and/or C7, wherein R* is a group comprising a sulfopropyl moiety or ethylene glycol moieties or combinations thereof. In some embodiments, R2 and/or R3 may be alkoxy groups (e.g., OR and/or OR*.). Natrajan et al. in International Pub. No. WO2015/006174, hereby incorporated by reference in its entirety, also describes hydrophilic high quantum yield, chemiluminescent acridinium esters possessing certain electron-donating functional groups at the C2 and/or C7 positions as well. These electron donating groups at R1 and/or R₂ may have the structure:

wherein R₉-R₁₄ are independently selected at each occurrence a methyl group or a group – (CH2CH2O)aCH3, where a is an integer from 1 to 5. In some embodiments, R2 and R3 are independently at each occurrence hydrogen, alkyl (e.g., methyl, ethyl, propyl, isopropyl), or alkoxy (e.g., methoxy, ethoxy, propoxy, or isopropoxy). In some embodiments, R2 and R3 are each hydrogen. In other embodiments, R₂ or R₃ is hydrogen and the other of R₂ or R₃ is alkoxy or an electron donating group. [0064] The detectable conjugate or compound for forming a detectable conjugate may comprise a chemiluminescent acridinium sulfonamide. For example, Ψ in the conjugate or compound for forming a detectable conjugate may have the structure of formula (IIa), (IIb), (IIc), (IId), or (IIe):

wherein “h” is 1, 2, 3, 4, 5, or 6;

wherein R5-R8 are independently hydrogen or C1-35 alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, or amino; and wherein L₁ is covalently bonded to A (e.g., L absent) or L (e.g., to L^C or Z^L).

wherein Y” is either absent or is –L1–, –R^L–, –L1– R^L–, or –R^L–L1–, where Y” is covalently attached to L (e.g., to L^C or Z^L). In some embodiments, R^L is an optionally substituted five- or six-membered bivalent aromatic hydrocarbon. For example, any R^L may have the structure:

wherein R₁₅ is independently at each occurrence hydrogen, halogen, or R. In some embodiments, R^L has the structure:

wherein R₅-R₈ are independently C_1-35 alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, or amino. In some embodiments, R7 and R8 are each hydrogen and R5 and R6 are each methyl. In some embodiments, Ψ comprises two flanking methyl groups on a phenolic ester to stabilize the bond as disclosed in Law et al. Journal of Bioluminescence and Chemiluminescence 4: 88-89 (1989), hereby incorporated by reference in its entirety. In some embodiments Ψ has the structure:

. [0065] In some embodiments, A, L and Ψ are each covalently linked. Portions of the covalent linkage between A and Ψ may be formed from a reactive functional group for forming covalent linkages with a peptide, a protein, or a macromolecule, wherein the functional group comprises an electrophilic group, nucleophilic group, or a photoreactive group. The reactive functional group may an amine-reactive group, a thiol-reactive group, a carboxy-reactive group, a maleimide-reactive group, or a carbohydrate-reactive group. In some embodiments, the reactive functional group may react with a functional group of the analyte or binding partner therefore such as a primary amine. The reactive functional group may comprise (or be) an isothiocyanate, isocyantate, acyl azide, NHS ester, sulfonyl chloride, aldehyde, glyoxal, epoxide, oxirane, carbonate, aryl halide, maleimide, imidoester, carbodiimide, anhydride, fluorophenyl ester, or combinations thereof. In various implementations, the reactive functional group labels the analyte or binding partner therefor through acylation or alkylation. For example, the linkage may be formed from a reactive group selected from: 5

In some embodiments, the compound comprises a linker group having the structure –NH– C(O)– or –C(O)–NH–. In a preferred embodiment, the compound or moiety thereof (e.g., L^C, Ψ) comprises at least one –NH–C(O)– or –C(O)–NH– linker group. [0066] The covalent linkage between A and Ψ (e.g., L) or RFG and Ψ (e.g., L) may comprise (or be) a divalent C1-20 alkyl, alkenyl, alkynyl, aryl, or arylalkyl radical, optionally substituted with up to 20 heteroatoms (e.g., N, O, S, P, Cl, F, Br). In some embodiments L comprises a zwitterionic linker. L may have the structure –L^C–(Z^L)z–, wherein z is 0 or 1. L^C may have the structure –(X₁)_0-1–(R^L)_0-5–(X₂)_0-1– (R^L)_0-5–(X₃)_0-1–(R^L)_0-5–(X₄)_0-1–(R^L)_0-5– wherein X₁ is selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)–NR^N–, –O– C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–, =N–, –O–, or –S–; X₂–X₄ are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)– NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from ––(CH2)1-5–, –(CH2CH2O)1-5–, or – (OCH₂CH₂)_1-5–, or optionally substituted cycloalkylene (e.g., C₅-C₆ cycloalkylene) substituted at one or more positions with, for example, alkyl (e.g., C1-C5 alkyl), alkoxy (e.g., C1-C5 alkoxy) or halo (e.g., F), ; with, for example, the proviso that L^C comprises at least one atom (or at least two atoms) in the chain between A and Ψ (or between A and Z^L). [0067] In some embodiments, L and/or Ψ comprises –C(O)–NH–. In some embodiments, L^C has the structure:

,

[0068] The detectable label may comprise a dimethyl acridinium ester (DMAE) moiety and a zwitterionic linker comprising a zwitterionic linker or a polyethylene glycol derived linker to improve properties of the compound. Such properties as non-specific binding, hydrophilicity, or compound stability may be improved when Ψ comprises a zwitterionic linker or a polyethylene glycol derived linker or a dimethyl phenyl ester. In some embodiments, Z^L has the structure:

. In several embodiments, R’ is hydrogen or lower alkyl (e.g., methyl, ethyl, propyl). [0069] In some embodiments, the detectable conjugates may have the structure of formula (III):

wherein z is 0 (i.e., it is a bond) or 1. In some embodiments the compound for forming a conjugate may have the structure:

[0070] Exemplary compounds for forming the conjugates are disclosed in Table 1. In some embodiments, the detectable conjugate is formed by reacting a compound (e.g., a compound of Formula (IV), (Va), (Vb), (Vc), (Vd), (Ve), (VIa), (VIb), a compound from Table 1) with an analyte, binding partner thereof, or derivatized version of the foregoing capable of reacting with a reactive functional group. As used to describe the compounds, these are generally 2,3- cyclic alkylenedioxy (“ADO”) containing acridiniums. The compounds may be an acridinium ester (“AE”). The compounds designations may include “Z” which may refer to a zwitterionic linker, “CMO” which may refer to a carboxy methyl oxime linker, “CME” which may refer to a carboxy methyl ether linker, “CETE” which may refer to carboxy ethyl thioether, “ZAE” which may refer to a zwitterionic acridinium ester (which is typically an N-sulfopropyl dimethyl acridinium ester in the examples shown (“NSP-DMAE”)), “ISODIZAE” which may refer to an acridinium nucleus with an isopropoxy functional group attached thereto and a full zwitterionic group (comprising both N⁺ and X-) attached to the positive N of the acridinium. Table 1

[0071] In some embodiments, the detectable conjugate may have the structure of one or more of:

wherein z is independently at each occurrence 0 or 1; y is independently at each occurrence 0, 1, 2, 3, 4, or 5; and A’ is the analyte or binding partner thereof conjugated via a primary amine of an unconjugated analyte or binding partner thereof A; wherein X2–X4 are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)– NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from –(CH₂)_1-5–, –(CH₂CH₂O)_1-5–, or – (OCH2CH2)1-5–, or optionally substituted C5-C6 cycloalkylene. For example, the conjugate may have the formula:

. [0072] In various implementations, the compound has the structure:

wherein z is independently at each occurrence 0 or 1; y is independently at each occurrence 0, 1, 2, 3, 4, or 5; and A’ is the analyte or binding partner thereof conjugated via a thiol of an unconjugated analyte or binding partner thereof A; wherein X2–X4 are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, – C(O)–NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from –(CH2)1-5–, –(CH2CH2O)1-5–, or – (OCH₂CH₂)_1-5–, or optionally substituted C₅-C₈ cycloalkylene (e.g., cyclohexane). [0073] In various implementations a moiety of the linker may decrease the rate of hydrolysis of the reactive functional group as compared to an otherwise identical compound having, for example, an alkyl linkage proximal to the reactive functional group. For example, and particularly with embodiments comprising a maleimide reactive functional group, the linker may comprise a moiety such as an optionally saturated cycloalkyl group proximal to the reactive functional group. For example, the compound may have the structure:

. [0074] The compounds of the present disclosure may be characterized by their stability. For example, a compound may be considered stable if there is a minimal loss of chemiluminescent activity as measured by the loss of relative light units (“RLU”) when the compounds or conjugates are stored in an aqueous solution typically, in the pH range of 6-9. Compounds having increased instability as compared to another compound may have a greater loss of chemiluminescent activity. For example, the compounds of the present disclosure (e.g., compounds having the structure of formula (I)-(VI) may be characterized as having increased stabilities at pH 6 and/or 7 and/or 8) at 4°C (common reagent storage temperature) and/or 37°C (accelerated temperature) over 33 days. The compounds may have increased stability as compared to an otherwise identical compound not having fused heterocycles conjugated to the acridinium system. In some embodiments, the compounds may be characterized as having a change in chemiluminescent activity of less than (or from 1% to) 40% (e.g., less than 30%, less than 20%, from 10% to 40%, from 10% to 30%, from 10% to 20%) after 33 days of storage at 37°C and pH 7 and/or pH 8. [0075] Comparative chemiluminescence quantum yields may also be used to characterize the compounds of the present disclosure. Quantum yield can be determined as the amount of observable chemiluminescence for a defined mass of a compound. The increase in quantum yield from acridinium esters is one of several advantageous properties for the presently disclosed acridinium compounds which exhibit higher quantum yield relative to other acridinium compounds. Chemiluminescence may be measured in relative light units (RLU) on a luminometer. Quantum yields of acridinium may be measured as the amount of chemiluminescence (RLU) per mole of acridinium. An increase of quantum yield from an acridinium increases its likelihood of detection, even if low masses of acridinium ester are required for detection such as, with low doses of analyte in immunoassays. An increase in the quantum yield of acridinium ester might consequently increase the sensitivity of immunoassays employing a high quantum yield acridinium. Relative quantum yields may be calculated as the ratio with a compound of the disclosure as compared to HEGAE. Relative quantum yields with values greater than one indicate enhancement of quantum yield with respect to HEGAE. In some embodiments, the compound has a relative quantum yield with respect to HEGAE of more than (or up to 5) 1.0 (e.g., 1-6, 1-5, more than 1.5, 1.5-4, 1.7-3.8, more than 2, more than 3). In some embodiments, the compound has a relative quantum yield with respect to HQYAE of more than 1 (or up to 3) (e.g., 1.1-1.5). [0076] The compound may also be characterized by their wavelengths of chemiluminescent emission. For example, the compounds of the present disclosure may have an emission wavelength maxima (λmax) from 430 nm to 460 nm. [0077] In some embodiments, the compound may be characterized by the light emission kinetics. The compounds of the present disclosure generally complete emission within 5 seconds of chemiluminescent triggering. In some embodiments, the compounds of the present disclosure may have faster light emission kinetics as compared to other acridinium compounds such as emitting 90% of their light, measured over 5 seconds, within 2 seconds. [0078] Table 2 provides exemplary characterizations of the compounds for several of the measured species (the dashed double bond indicates the fusing to the acridinium ring) Table 2

[0079] The compounds may also be characterized by their light output or signal to noise ratio in a chemiluminescent assay. For example, the compound may be characterized by a thyroid stimulating hormone assay having a larger signal to noise ratio as compared to HQYAE or TSPAE, acridinium conjugates having the similar as shown in U.S. Pat. Nos. 7,309,615 and 7,785,904, which are each hereby incorporated by reference in their entirety and particularly in relation to quantum yields of TSPAE and HQYAE. In some embodiments, the compounds may be characterized as having a relative signal to noise ratio as compared to HQYAE or TSPAE (e.g., in a TSH assay) of more than 1 (e.g., from 1 to 2). Typically, a higher signal to noise ratio for the same amount of analyte is an indicator of better assay sensitivity. [0080] The compounds can be prepared from commercially available starting materials, compounds known in the literature, or readily prepared intermediates, by employing standard synthetic methods (in addition to those provided herein). Standard synthetic methods and procedures for the preparation of organic molecules and functional group transformations and manipulations can be readily obtained from the relevant scientific literature or from standard textbooks in the field. It will be appreciated that where typical or preferred process conditions (e.g., reaction temperatures, times, mole ratios of reactants, solvents, pressures) are given, other process conditions can also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvent used, but such conditions can be determined by one skilled in the art by routine optimization procedures. Those skilled in the art of organic synthesis will recognize that the nature and order of the synthetic steps presented may be varied for the purpose of optimizing the formation of the compounds described herein. [0081] Synthetic chemistry transformations (including protecting group methodologies) useful in synthesizing the compounds described herein are known in the art and include, for example, those such as described in R.C. Larock, Comprehensive Organic Transformations, 2d. Ed., Wiley-VCH Publishers (1999); P.G.M. Wuts and T.W. Greene, Protective Groups in Organic Synthesis, 4th Ed., John Wiley and Sons (2007); L. Fieser and M. Fieser, Fieser and Fieser's Reagents for Organic Synthesis, John Wiley and Sons (1994); and L. Paquette, ed., Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons (1995), and subsequent editions thereof, each of which are hereby incorporated by reference in their entirety. [0082] The processes described herein can be monitored according to any suitable method known in the art. For example, product formation can be monitored by spectroscopic means, such as nuclear magnetic resonance spectroscopy (e.g., ¹H

or ¹³C), infrared spectroscopy (FT- IR), spectrophotometry (e.g., UV-visible), or mass spectrometry (MS), or by chromatography such as high-pressure liquid chromatography (HPLC) or thin layer chromatography (TLC). [0083] Preparation of compounds can involve the protection and deprotection of various chemical groups. The need for protection and deprotection, and the selection of appropriate protecting groups can be readily determined by one skilled in the art. The chemistry of protecting groups can be found, for example, in Greene, et al., Protective Groups in Organic Synthesis, 2d. Ed., Wiley & Sons, 1991, which is incorporated herein by reference in its entirety. [0084] The reactions of the processes described herein can be carried out in suitable solvents which can be readily selected by one of skill in the art of organic synthesis. Suitable solvents can be substantially nonreactive with the starting materials (reactants), the intermediates, or products at the temperatures at which the reactions are carried out, i.e., temperatures which can range from the solvent’s freezing temperature to the solvent’s boiling temperature. A given reaction can be carried out in one solvent or a mixture of more than one solvent. Depending on the particular reaction step, suitable solvents for a particular reaction step can be selected. [0085] Resolution of racemic mixtures of compounds can be carried out by any of numerous methods known in the art. For example, the absolute configuration of the stereoisomers may be determined by 1D and 2D NMR techniques such as COSY, NOESY, HMBC and HSQC. Specific implementations of these NMR techniques may be found in Hauptmann, H et al., Bioconjugate Chem.11 (2000): 239-252 or Bowler, J. Steroids 54/1 (1989): 71-99, each hereby incorporated by reference in their entirety. Another example method includes preparation of the Mosher’s ester or amide derivative of the corresponding alcohol or amine, respectively. The absolute configuration of the ester or amide is then determined by proton and/or ¹⁹F NMR spectroscopy. An example method includes fractional recrystallization using a “chiral resolving acid” which is an optically active, salt-forming organic acid. Suitable resolving agents for fractional recrystallization methods are, for example, optically active acids, such as the D and L forms of tartaric acid, diacetyltartaric acid, dibenzoyltartaric acid, mandelic acid, malic acid, lactic acid, or the various optically active camphorsulfonic acids. Resolution of racemic mixtures can also be carried out by elution on a column packed with an optically active resolving agent (e.g., dinitrobenzoylphenylglycine). Suitable elution solvent compositions can be determined by one skilled in the art. [0086] Typically, zwitterionic acridinium esters (“ZAE”) comprising a reactive functional group for forming covalent linkages as described in U.S. Pat Nos.6,664,043 to Natrajan et al., 7,309,615 to Natrajan et al., 9,575,062 to Natrajan et al., or 9,487,480 to Natrajan, each hereby incorporated by reference in their entirety and in particular with respect to the zwitterionic acridinium esters described therein and their syntheses, may be used for synthesizing the compounds disclosed herein. For example, the zwitterionic acridinium ester starting materials may comprise an N-sulfopropyl (“NSP”) group in a zwitterionic moiety and/or comprise a charged nitrogen atom connected to the charged acridinium nucleus (“DIZAE”) and/or comprise a sterically stabilized dimethyl acridinium ester (“DMAE”) and/or comprise an isopropoxy functionalized acridinium nucleus (“ISO”) and/or comprise a zwitterionic (“Z”) and/or hexa(ethylene) glycol derived (“HEG”) and/or glutarate derived (e.g., –C(O)–(CH₂)₃– C(O)–) linking moieties between the acridinium ester and the reactive functional group. The reactive functional group may by NH₂, or N-hydroxysuccinimidyl ester (“NHS”), or maleimide derived. For example, the compound (e.g., a compound for conjugating with an analyte or binding partner of an analyte such as a peptide, a protein, or a macromolecule including an antibody) may have the structure of formula (IV): (^IV) wherein RFG is a reactive functional group for conjugating to the analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “

R₁ is hydrogen, –R, –X, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z, or R2 and R3 together form a 5-7 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure:

“r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, – C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, – (CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2–NH–, – (CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH–(CH₂)_1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or – (CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl groups; with 1-10 substituents); R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl groups; with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl). [0087] The chemiluminescent conjugates or compounds for forming the conjugates may also be synthesized through the use of acridinium sulfonamide reactants. For example, the acridinium sulfonamides disclosed in US Pat No 5,543,524 to Mattingly et al., hereby incorporated by reference in its entirety, are useful starting materials for the preparation of the chemiluminescent compounds disclosed herein. [0088] The chemiluminescent conjugates are useful as labels in assays for the determination or quantitation of certain analytes capable of competing for binding to a binding partner. [0089] The assay may be, for example, a competitive immunoassay which typically involves the detection of a large molecule, also referred to as macromolecular analyte, using binding molecules such as antibodies. The antibody is immobilized or attached to a solid phase such as a particle, bead, membrane, microtiter plate, or any other solid surface. Analytes that are typically measured in such assays are often substances of some clinical relevance and can span a wide range of molecules from large macromolecules such as proteins, nucleic acids, viruses bacteria, to small molecules such as valproate, vitamins, steroids, hormones, therapeutic drugs. [0090] The compounds of the present disclosure may be used in a sandwich immunoassay which typically involves the detection of a large molecule, also referred to as macromolecular analyte, using two binding molecules such as antibodies. One antibody is immobilized or attached to a solid phase such as a particle, bead, membrane, microtiter plate or any other solid surface. The compounds may be used in competitive assays as well. In an example of a competitive heterogeneous assay, a support having an antibody for an analyte (e.g., 3C3, 3H10, 4G8 bovine monoclonal antibodies) bound thereto is contacted with a medium containing a sample suspected of containing the analyte and the chemiluminescent conjugates (or “labeled analogs”) described herein. Analyte from the sample competes for binding to the analyte antibody with the labeled analog. After separating the support and the medium, the label activity of the support or the medium is determined by conventional techniques and is related to the amount of analyte in the sample. In a variation of the above competitive heterogeneous assay, the support comprises the analyte analog, which competes with analyte of the sample for binding to an antibody reagent in accordance with the principles described herein. The labeled analyte analog may be covalently attached with a chemiluminescent or fluorescent molecule often referred to as a label or tracer. [0091] When the solid phase with the immobilized antibody or other binder is mixed with a sample containing the analyte and the labeled analyte, a binding complex is typically formed between the analyte or the labeled analyte. The binder may be, for example, an antibody, antibody fragment, nucleic acid, peptide, binding protein or synthetic binding polymers. In some embodiments, the binder may be a protein such as Intrinsic Factor which binds to Vitamin B12 or the Folate-Binding protein which binds to folate. This type of assay is often called a heterogeneous assay because of the involvement of a solid phase. The chemiluminescent signal associated with the binding complex can then be measured and the presence or absence of the analyte in the sample can be inferred. Usually, the binding complex is separated from the rest of the binding reaction components such as excess, labeled analyte, prior to signal generation. For example, if the binding complex is associated with a magnetic bead, a magnet can be used to separate the binding complex associated with the bead from bulk solution. [0092] By using a series of ‘standards,’ that is, known concentrations of the analyte, a ‘dose- response’ curve can be generated for the known labeled analyte. Thus, the dose-response curve correlates a certain amount of measured signal with a specific concentration of analyte. In a competitive assay, as the concentration of the analyte increases, the amount of signal decreases if the chemiluminescence from the binding complex is measured. The concentration of the analyte in an unknown sample can then be calculated by comparing the signal generated by an unknown sample containing the macromolecular analyte, with the dose-response curve. [0093] The methodology of the attachment of binding molecules such as antibodies to solid phases typically involves a mixing of the requisite components to induce attachment. For example, an antibody can be covalently attached to a particle containing amines on its surface by using a cross-linking molecule such as glutaraldehyde. The attachment may also be non- covalent and may involve simple adsorption of the binding molecule to the surface of the solid phase, such as polystyrene beads and microtiter plate. Labeling of binding molecules such as antibodies and other binding proteins are also well known in the prior art and are commonly called conjugation reactions and the labeled antibody is often called a conjugate. Typically, an amine-reactive moiety on the label reacts with an amine on the antibody to form an amide linkage. Other linkages, such as thioether, ester, carbamate, and the like between the antibody and the label may also be used. [0094] In another aspect of the invention, a reagent may be provided for the detection of an analyte comprising a chemiluminescent acridinium compound bound the analyte or binding partner. The reagent may have a concentration of detectable conjugate of less than 10^-3 M. In some embodiments the reagent may have a concentration of less than 10^-3 M (e.g., 10^-15 M to 10^-3 M chemiluminescent acridinium compound. In some embodiments, the compound is provided in a reagent which further comprises a buffer. [0095] Typically, the assay for the detection or quantification of an analyte in a sample comprises: (a) providing a detectable conjugate; (b) providing a solid support having immobilized thereon a molecule capable of forming a binding complex with said analyte and capable of forming a binding complex with said detectable conjugate; (c) mixing said compound, said solid support, and said sample; (d) separating said solid support from said mixture; (e) triggering chemiluminescence of any acridinium label complexed to said solid phase; (f) measuring the amount of light emission with a luminometer; and (g) detecting the presence or calculating the concentration of said analyte by comparing the amount of light emitted with a standard dose response curve which relates the amount of light emitted to a known concentration of the analyte. [0096] In some embodiments, the sample derived from a mammal (e.g., human). In some embodiments, the sample comprises saliva and/or blood and/or serum. In some embodiments, the sample is saliva and/or blood and/or serum. [0097] In some assays, the sample to be analyzed is subjected to a pretreatment to release analyte from endogenous binding substances such as, for example, plasma or serum proteins that bind the analyte. The release of the analyte from endogenous binding substances may be carried out, for example, by addition of a digestion agent or a releasing agent or a combination of a digestion agent and a releasing agent used sequentially. The digestion agent is one that breaks down the endogenous binding substances so that they can no longer bind the analyte. [0098] The conditions for conducting an assay on a portion of a sample in accordance with the principles described herein may include carrying out the assay in an aqueous buffered medium at a moderate pH, generally that which provides optimum assay sensitivity. The aqueous medium may be solely water or may include from 0.1 to 40 % by volume of a cosolvent. The pH for the medium may be in the range of 4 to 11, or 5 to 10, or 6.5 to 9.5, or 7 to 8. Usually, the pH value of the solution will be a compromise between optimum binding of the binding members of any specific binding pairs, the pH optimum for other reagents of the assay such as members of the signal producing system, and so forth. Various buffers may be used to achieve the desired pH and maintain the pH during the assay. Illustrative buffers include borate, phosphate, carbonate, TRIS, barbital, PIPES, HEPES, MES, ACES, MOPS, and BICINE, for example. [0099] Various ancillary materials may be employed in the assay methods. For example, in addition to buffers, the medium may comprise stabilizers for the medium and for the reagents employed. In some embodiments, the medium may comprise proteins (e.g., albumins), organic solvents (e.g., formamide), quaternary ammonium salts, polyanions (e.g., dextran sulfate), binding enhancers (e.g., polyalkylene glycols), polysaccharides (e.g., dextran, trehalose), and combinations thereof. [0100] Triggering the chemiluminescence of the analogs may be performed by the addition chemiluminescent triggering reagents. The chemiluminescent triggering reagents may be acidic or basic. Multiple chemiluminescent triggering reagents may be added sequentially. For example, an acidic solution (e.g., an acidic solution comprising hydrogen peroxide) may first be added followed by a basic solution (e.g., an alkali hydroxide comprising surfactant). In some embodiments, the chemiluminescent triggering reagents comprise hydrogen peroxide, hydrogen peroxide salts, nitric acid, nitric acid salts, sodium hydroxide, ammonium salts, surfactant, or combinations thereof. EXAMPLES [0101] The following Examples illustrate the synthesis of a representative number of compounds, characterization of parameters implicated in assay development, and the use of these compounds in the measurement of samples in heterogeneous competitive assay. Accordingly, the Examples are intended to illustrate but not to limit the disclosure. Additional compounds not specifically exemplified may be synthesized using conventional methods in combination with the methods described herein. Example 1: Quantum Yield [0102] Comparative chemiluminescence quantum yields were measured for new structures of acridinium esters. The increase in quantum yield from acridinium esters is one of several advantageous properties for acridinium esters exhibiting higher quantum yields relative to those exhibiting lower quantum yields. Chemiluminescence was measured in relative light units (RLU) on a luminometer. Quantum yields of acridinium esters are measured as the amount of chemiluminescence (RLU) per mole of acridinium ester. Quantum yield is therefore the amount of observable chemiluminescence for a defined mass of acridinium ester. An increase of quantum yield from an acridinium ester increases its likelihood of detection particularly at diminishingly low masses of acridinium ester, for example, with low doses of analyte in immunoassays. An increase in the quantum yield of acridinium ester might consequently increase the sensitivity of immunoassays employing high quantum yield acridinium ester. Relative quantum yields were calculated as the ratio with that for HEGAE as the denominator. Relative quantum yields with values greater than one indicate enhancement of quantum yield with respect to HEGAE. [0103] Table 3 lists the relative quantum yields of novel ADO acridinium esters of the present invention, along with HEGAE and HQYAE for comparison. The quantum yields of the new ADOAEs measured, with the exception of ADOAE A (4), are significantly higher (1.7 to 3.8 times) than that of HEGAE. Table 3

[0104] Compounds ADOAE A (4) and ADOAE C (6) are structurally very similar. The only difference is that the former contains a five-membered ADO ring, and the latter has six- membered ADO ring at their respective 2- and 3- positions. However, the quantum yield of ADOAE A (4) is only 1/5 of that of ADOAE C (6). This demonstrates the finding that the ring size is implicated in the performance of the acridinium esters and does not abrogate chemiluminescence. Without wishing to be bound by theory, increasing ring size (e.g., six membered, seven membered) for the 2,3-cyclic substitution increases compound viability in an immunoassay.

Example 2: Light Emission Wavelength [0105] The light emission spectra of new compounds were measured using PR-740 FSSS Spectro camera, which is capable of measuring light emission intensity over a wavelength range of 380 – 780 nm. The emission wavelengths of HEGAE and HQYAE were measured for comparison. The emission wavelength maxima (λmax) of the new acridinium esters are found to be 440 – 450 nm, which is longer than that of HEGAE (425 nm) and shorter than that of HQYAE (475 nm). [0106] All acridinium compounds were diluted with DMF and prepared in a 1 mg/mL stock solution.20 μL of aliquot was placed in a glass tube and further diluted with 250 μL of DMF. Next, 300 μL of flash reagent 1 was added to the sample and the glass tube was placed in front of the PR-740 FSSS Spectro camera. The emission spectrums of all compounds were recorded after the addition of 300 μL of flash reagent 2 in a 5 second time window. Emission spectra are given in FIGS.1A-E. Table 4 provides the measured λmax for several acridinium esters of the present disclosure. Table 4

Example 3: Light Emission Kinetics [0107] Chemiluminescence emission kinetics of the new acridinium esters were measured using the Berthold Technologies’ AutoLumat Plus LB953 luminometer (LB953). HEGAE and HQYAE were included in the measurement for comparison. The ADOAEs and TSPAE aliquots were initially diluted with DMF and prepared 1 mg/ml concentration. The concentration was diluted 100 folds with DMF to 10^⁻2 mg/mL. Serial dilution of this solution in flash buffer from 10^⁻2-fold to 10^-8-fold was made using 100 μL solution for each dilution. The 10 μL of the diluted sample was used in measurement of chemiluminescence kinetics in a total time of 5 seconds with 50 data points on AutoLumat Plus LB953 where chemiluminescence values are acceptable for good linearity in the range of 10⁵ to 10⁶ RLU/10µL. [0108] The results of the measurements are displayed in FIG. 2. As can be seen, all tested acridinium esters completed light emission in 5 seconds. New compounds ADOAE F (9), ADOAE H (11), ADOAE J (13) and ADOAE L (15) emit ~90% light within 2 seconds, which is significantly faster than HEGAE and HQYAE. The property of fast light emission kinetics is suitable for a short cycle of light detection, which is desirable for high throughput instruments. Example 4: Thyroid Stimulating Hormone (TSH) assays [0109] AntiTSH-mAb conjugates of new acridinium esters 7-11 and 13-15 were prepared along with TSPAE (3) for comparison. TSPAE (3) is one of the best high quantum yield AEs used in assays having similar light output to HQYAE from U.S. Pat. Nos. 7,309,615 and 7,785,904, which are hereby incorporated by reference in their entirety and particularly in relation to the light output an immunoassay measurement of HQYAE. The concentrations of the conjugates were determined with a Micro BCA™ Protein assay. The acridinium ester incorporation onto the antiTSH mAb was measured through MALDI-TOF mass spectroscopy. [0110] The functionality in an immunoassay of the conjugates was evaluated using Siemens- Healthineers Centaur TSH3 UL assay on ADVIA Centaur XPT where the Lite reagent was replaced with the experiment antiTSH-mAb conjugate and all other test reagents remained to be the same. Relative light units for each tested compound were measured at 10 different standards—each having a known concentration of TSH. [0111] Briefly, the anti-TSH conjugates of several TSH conjugated AEs were diluted in TSH3-UL Lite reagent buffer to 0.3mg/mL. Commercially available TSH3-UL reagents (REF 06491072 lot 332) were used for the study. The anti-FITC solid phase and FITC ancillary reagent from lot 332 were recovered and paired with each TSH-AE Lite reagent. The reagents were then assayed on ADVIA Centaur XPT (Equipment ID: B1072). The system automatically performs the following actions: • Dispenses 100 µL of sample (standards) into a cuvette. • Dispenses 50 µL of Ancillary Reagent and 50 µL of Lite Reagent and incubates for 2.75 minutes at 37°C. • Dispenses 200 µL of Solid Phase and incubates for 5.5 minutes at 37°C. • Separates, aspirates, and washes the cuvettes with Wash 1. • Dispenses 300 µL each of Acid Reagent (flash reagent 1) and Base Reagent (flash reagent 2) to initiate the chemiluminescent reaction. • Internal TSH3-UL Master Curve Standards lot 19031 were used as sample and mean RLUs calculated. [0112] As shown in Tables 5 and 6, the tested conjugates showed the functionality in the assay. Table 5

Table 6

[0113] The signal to noise ratio of each compound at each test condition were also calculated based on the RLU values from Tables 5 and 6. Tables 7 and 8 provide the signal to noise ratios of the measured conjugates. Most conjugates had low background signal at the zero dose of the TSH standard. Compounds 7, 9, 11 and 15 had equivalent or higher signals at high dose end (e.g., S10) compared to TSPAE (3). Overall signal-to-noise ratios relative to zero dose of compounds 9, 13, and 15 are higher than those of TSPAE. The higher signal-to-noise ratios typically correlates with better assay sensitivity afforded by the compounds of the present of the disclosure. Table 7

Table 8

Example 5: Chemiluminescence Stability [0114] Excellent chemiluminescence stability (negligible instability) is one of several advantageous properties of acridinium esters used as labels in immunoassays, which ensures that assay-derived clinical data do not change and become invalid over the lifetime of test kits. For example, the main mechanism of chemiluminescence instability of acridinium esters in aqueous solution is hydrolysis of the phenolic ester by hydroxide anion and other nucleophiles. High quantum yield acridinium esters such as HQYAE and TSPAE contain two hydrophilic alkoxy groups at 2-and 7- positions and have been observed to be less stable than the un- substituted acridinium esters, due presumably to additional mechanisms of chemiluminescence instability. [0115] Comparative chemiluminescence stabilities were measured for new ADO acridinium esters conjugated to anti-hTSH monoclonal antibody through N-hydroxysuccinimide activation of the acridinium esters benzoic acid groups. The rate of chemiluminescence instability of acridinium esters was measured by the loss of chemiluminescence over a set period under conditions approximating the expected storage and handling conditions of assay test kits. [0116] Additionally, the separate heating of acridinium esters at temperatures in excess of recommended storage conditions is intended to give an estimate of long-term instability of product. Alongside the stability assessments of newly created acridinium ester conjugates, one control conjugate from TSPAE was also tested, representing a commercial high quantum acridinium ester. Incubation buffers were formulated to narrow the interpretation of results to those relating the loss of chemiluminescence due to temperature and pH only. Therefore, these buffers did not include complex biological components, nor a plethora of surfactants and other potentially stabilizing agents that might complicate the interpretation of results. [0117] The comparative chemiluminescence instabilities of acridinium esters were measured at two temperature ranges, 4°C (standard refrigeration) and 37°C (accelerative heating), and at the three pHs of 6.0, 7.0 and 8.0 at each of these two temperature ranges. The buffer in which the comparative chemiluminescence stabilities of acridinium ester-antibody conjugates were measured consisted of 0.10M sodium phosphate (pH buffering agent), 0.15M sodium chloride (ionic strength agent), 7.7mM sodium azide (antimicrobial preservative) and 0.1%(w/v) bovine serum albumin (protein-conjugate stabilization agent). Three volumes of this buffer were subsequently adjusted separately to the three stated pHs. Chemiluminescence is measured in relative light units (RLU) on luminometers. The measurements of the residual chemiluminescence for each of the acridinium ester-antibody conjugates were made using the ADVIA Centaur XPT, where the conjugates were initially diluted to a targeted chemiluminescence concentration of approximately 5×10⁶ RLU/25µL, as an appropriate dilution. This level of chemiluminescence provides a starting value high enough to allow for measurable decrease and is well within the linear region of the Centaur’s luminometer. Chemiluminescence was measured on the Centaur periodically over the period of about one month using five replicates of 25µL for each time point. Chemiluminescence reactions were initiated in the cuvettes with the sequential addition of 0.30 mL of flash reagent 1 followed 60s later by the addition of 0.30 mL of flash reagent 2. The chemiluminescence acquisition time was the nominal 3.500s. The dark count time was 2.000s. Chemiluminescence was reported as net chemiluminescence being the gross chemiluminescence minus adjusted dark counts. The residual chemiluminescence percentages were calculated and tabulated in relation to the initial chemiluminescence from the means of five replicates gathered from each time point. [0118] Two sets of experiments were performed. Tables 9 and 10 show the stabilities of several presentative ADO acridinium esters at three pH conditions (pH 6, 7, and 8) at 4°C (common reagent storage temperature, Table 9) and 37°C (accelerated temperature, Table 10) over 33 days for the first set of experiments and over 35 days for the second set of experiments. All ADOAEs showed better chemiluminescence stability than TSPAE at nominal 4°C storage. At 37°C where the instability of acridinium esters was accelerated by elevated temperature, all new ADOAEs revealed significantly better chemiluminescence stability than TSPAE. This is particularly apparent at pH 7 and pH 8; at this pH range most immunoassays are performed. For instance, on day 33 at 37°C, the chemiluminescence activity of TSPAE had dropped to less than 1% of the original chemiluminescence at pH 7 and pH 8, while chemiluminescence activities of new ADO AEs had maintained the respective values as high as 73% and 85%. Table 9

Table 10

Example 6: Synthesis of ADOAE A (4) and ADOAE B (5)

[0119] The synthesis of compounds ADOAE A (4) and ADOAE B (5) began from the know starting material 5-Methoxyisatin (4B). The N-Arylation of 5-Methoxy-isatin was done on a 2 g scale with 12 (2.1g, 11mmol) using NaH (11 mmol) as a base and CuI (22 mmol) as a coupling agent in 8 h at 150 ^oC in DMF. The LC/MS analysis showed that the 70% N-Arylisatin proceeded with further rearrangement to Acridine 9-carboxylic acid (4C). At this stage, DMF was removed from the reaction mixture with a high vacuum at 60 ^oC, added 10% KOH solution, and reflux continued for 2 h at 120 ^oC. The LCMS analysis confirmed the reaction intermediate was completely converted to 4C. The mixture was filtered through the sintered funnel and the resulting filtrate was cooled to room temperature and acidified to pH=2 with concentrated HCl. The orange precipitate was separated at 5 ^oC, filtered and dried under vacuum obtained Acridine 9-carboxylic acid (4C) in 85% yield over two steps. The Acridine 9-carboxylic acid (4C) (1.32g, 4.44 mmol) esterification with phenol derivative 4D (400 mg, 2.22 mmol) with tosyl chloride in pyridine was completed in 8 h at 35 ^oC to obtain the Acridine 9-carboxylate 4Ein 70% yield. The N-sulfopropanation of 4E (50 mg, 0.11 mmol) was done in a microwave reactor at 155 ^oC with 10 eq. of 1,3-propane sultone in an ionic liquid 1-butyl-3- methylimidazolium hexafluorophosphate [BMIM][PF6] and 2,6-Di-tert-butylpyridine used as a base. The 60% of the reaction was completed in 6 h, at this stage 2 N HCl was added to the reaction mixture and continued stirring at 120 ^oC for 2 h afforded ADOAE A (4) with 14% overall yield. Next, the active NHS-ester synthesis was prepared for protein conjugation. The ADOAE A (9 mg, 0.015 mmol) was treated with TSTU and N, N-Diisopropylethylamine in DMF for 30 min at room temperature obtained the final ADOAE B (5) as a yellow solid.

[0120] The synthesis of ADOAE C (6) and ADOAE D (7) started from the starting material 5-Methoxyisatin (4B) and Bromo derivative 6A. The coupling between the 4B (2g, 11mmol) and Bromo derivative 6A (2.1g, 11mmol) was completed in 8 h at 150 ^oC in DMF using NaH (11 mmol) as a base and CuI (22 mmol) as a coupling agent. The LC/MS analysis confirmed that the 50% N-Arylisatin product was rearranged to the Acridine-9-carboxylic acid 6B. At this stage, DMF was removed from the reaction mixture with a high vacuum at 60 ^oC, added 10% KOH solution, and continued reflux for 2 h at 120 ^oC. The N-arylisatin intermediate was completely converted to Acridine 9-carboxylic acid and confirmed through LCMS analysis. The mixture was filtered through the sintered funnel and the resulting filtrate was cooled to room temperature and further acidified to pH=2 with concentrated HCl. After 30 min at 5 ^oC, the orange-yellow precipitate was filtered and dried under vacuum obtained Acridine 9- carboxylic acid 6B as an orange powder in 86% yield over two steps. The acid 6B (1.44g, 4.44 mmol) was esterified with phenol derivative 4D (400 mg, 2.22 mmol) with tosyl chloride in pyridine was completed in 8 h at room temperature to obtain the acridine ester 6C in 70% yield. The N-sulfopropanation of 6C (50 mg, 0.11 mmol) was done in a microwave reactor at 155 ^oC with 10 molar eq. of 1,3-propane sultone in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] and 2,6-Ditertiarybutyl pyridine used as a base. The 80% of the reaction was completed in 6 h, at this stage 2 N HCl was added to the reaction mixture and continued stirring at 105 ^oC for 2 h afforded ADOAE C (6) with 50 % overall yield. Next, the active NHS-ester synthesis was prepared. The compound 6 (10 mg, 0.017 mmol) was treated with TSTU (0.051 mmol)

N-Diisopropylethylamine (0.034 mmol) in DMF for 30 min obtained ADOAE D (7) in 52% yield after prep-HPLC purification. Example 8: Synthesis of ADOAE E (8)

[0121] The synthesis of ADOAE E (8) synthesis began with an intermediate Acridine 9-ester (6C). The methyl ether cleavage of the 6C (400 mg, 0.084 mmol) was done using 10 eq BBr₃ (1M, CH2Cl2) at 0 ^oC in 5 h, obtained the hydroxy derivative 8A in 75.5% yield. Next, the di- alkylation was done with using 1,3 propane sultone in ionic liquid at high temperature. Compound 8A (50 mg, 0.11 mmol) was reacted with 20 eq of 1,3 propane sultone, 10 eq of 2,6-Di-tert-butylpyridine, and K₂CO₃ (2 eq) in 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] for 6 h at 160 ^oC in a microwave reactor. The 80% of the reaction was completed in 6 h. At this stage, the crude reaction mixture was hydrolyzed with 2 N HCl at 120 ^oC for 2 h. The resulting acid compound was directly purified on prep-HPLC. The lyophilized HPLC fractions led to the pure acid 8B (17 mg, 23% yield). Finally, the NHS- ester synthesis was done by using 3 eq of TSTU and 2 eq of N, N-diisopropylethylamine in DMF. After the prep-HPLC purification of the crude reaction mixture, 8 mg of ADOAE E (8) was obtained. Example 9: Synthesis of ADOAE F (9)

[0122] The acid derivative 6 (10 mg, 0.015 mmol) was directly coupled to HEG-amine spacer in one step by in-situ activation of acid with TSTU in 30 min, then followed by the addition of this reaction mixture to diamino-HEG in DMF. After 2 h, the reaction mixture was purified on prep-HPLC and the prep-HPLC fractions were lyophilized for 48 h to obtain the amine compound 9A with 79% yield. The resulting amine derivative (10 mg, 0.11 mmol) was converted to NHS ester by using 3 eq of DSG and pH=7.2 phosphate buffer in DMF at room temperature. The reaction mixture was directly purified on HPLC, after the lyophilization of prep fractions to get the 6.2 mg of ADOAE F (9) as a yellow-colored compound.

[0123] The synthesis of symmetric-dioxane-AEs began from the known commercially available (5,6)-ethylenedioxy-isatin 10A. The isatin (1g, 4.47 mmol) and Bromo derivative 6A (1.83g, 8.94 mmol) were coupled together in the presence of CuI, NaH in dry DMF at 155 ^oC for 12 h, but here the reaction was proceeded to further and rearranged to Acridine-9-carboxylic acid. The crude product was purified by using acid/base extractions yielding the desired pure acid 10B in a 30% yield. Next, the esterification reaction, the acid derivative 10B (200 mg, 0.59 mmol) was reacted with phenol derivative 4D (106 mg, 0.59 mmol) by using tosyl chloride in the mixture of solvent CH₂Cl₂ and pyridine (9:1, 10 mL) led to 10C in 70% yield. The synthesis of NSP-AE-acid synthesis was involved in two reactions in a one-pot synthesis. First step: the acridine 9-carboxylate 10C (80 mg, 0.16 mmol) was N-alkylated with 1,3-propane sultone in a microwave reactor, this reaction was monitored on LCMS, N-alkylation went to complete in 8 h. Second step: the methyl ester hydrolysis was done with 2N HCl at 120 ^oC in 2 h and the acid compound was purified by using prep-HPLC, obtained 19 mg of the 10D in 20% yield. Last in the NHS-ester synthesis, the HPLC purified material 10D (6mg, 0.001 mmol) was treated with 3 eq of TSTU and 2 eq of N, N-diisopropylethylamine in DMF. After 30 min, the reaction was purified on the prep-HPLC and obtained the 8 mg of ADOAE G (10). [0124] The synthesis of ADOAE H (11) started from the acid derivative 10D. The acid derivative (10 mg, 0.016 mmol) was coupled with the HEG diamine (13.4 mg, 0.048 mmol) via the acid-activated with TSTU followed by amide formation with HEG-diamine. The reaction was completed in 30 min. The crude product was directly purified on preparative- HPLC, obtained 2 mg of the terminal amine 11A. The final NHS ester synthesis was done by treating 11A (2 mg. 0.0028 mmol) with DSG and pH=7.5 phosphate buffer in DMF at room temperature for 30 min. The crude product was purified on preparative-HPLC yielding the 2 mg of ADOAE H (11) in 64% yield.

[0125] The synthesis of ADOAE I (12) and J (13) started from the commercially available 5-Methoxyisatin. The 5-Methoxyisatin 4B (2g, 13.6 mmol) was N-arylated with Bromo 12A (1 g, 5.64 mmol) using CuI, NaH in dry DMF for 12h at 150 ^oC, but here the maximum reaction (90%) further proceeded and rearranged to Acridine-9-carboxylic acid. At this stage, DMF was removed from the reaction mixture under reduced pressure at 60 ^oC and the crude mixture was refluxed for 30 min with 10% KOH (10 mL). The crude acid product was acidified with conc. hydrochloric acid to obtain the 1.2 g of acridine 9-carboxylic acid 12B in a 67% overall yield. Next, the esterification reaction of 12B (0.5g, 1.53 mmol) with phenol derivative 4D (221 mg, 1.23 mmol) using tosyl chloride in CH2Cl2:pyridine (9:1) mixture of solvents at 35 ^oC overnight to obtain the Acridne 9-phenylcarboxylate 12C with 67% yield. The synthesis of NSP-AE-acid 12D was involved in two reactions in a one-pot synthesis protocol. First step: the acridine 9- carboxylate 12C (100 mg, 0.205 mmol) was N-alkylated with 10 equivalents of 1,3-propane sultone in a microwave reactor, this reaction was monitored on LCMS, N-alkylation went to complete in 8 h. Second step: the methyl ester hydrolysis was done with 2N HCl (10 mL) in a microwave reactor at 105 ^oC in 2 h and purified the acid compound by using prep-HPLC, obtained Acridinium NSP-DMAE-acid 12D in 17% yield. Next, the HPLC purified material 12D (10mg, 0.017 mmol) was treated with 3 eq of TSTU and 2 eq of N, N- diisopropylethylamine in DMF. After 30 min, the reaction was purified on the prep-HPLC and obtained the 8 mg of ADOAE I (12). [0126] The HEG-Amine synthesis was carried out from acid 12D in two steps. Step 1: Acid 12D (8 mg, 0.015 mmol) was treated with TSTU (7.7 mg, 0.026 mmol) in DMF with 2 eg of DIPEA, and the reaction was completed in 30 min by LCMS mass analysis. At this stage, the NHS-ester intermediate mixture was transferred to a stirred mixture of Diamino-PEG6 and 4 eq of DIPEA in DMF at room temperature. After 2h, the mixture was purified on HPLC yielding the 3 mg of HEG-amine 13A in a 26% yield. The resulting HEG-amine derivative 13A (3mg, 0.0035 mmol) was reacted with DSG (3.4 mg) in DMF with 5 eq of pH=7.5 buffer as a base at room temperature. After 30 min stirring at room temperature the final product was purified on HPLC to obtain the 2.8 mg of ADOAE J (13) in 76% yield. Example 12: Synthesis of ADOAE K (14) and L (15)

[0127] The synthesis of ADOAE K (14) began from the known commercially available isatin (14A) and 6-Bromo-1,4-benzo dioxane 6A. The Isatin (2g, 13.6 mmol) was N-arylation with Bromo 6A (4.36 g, 20.4 mmol) using CuI, NaH in dry DMF at150 ^oC in 12 h, but here the maximum reaction was further proceeded and completely rearranged to Acridine-9-carboxylic acid. At this stage, DMF was removed from the reaction mixture under reduced pressure at 60 ^oC, and the crude acid product was acidified with conc. hydrochloric acid to obtain the 2 g of acridine 9-carboxylic acid 14B in 52% overall yield. Next, the esterification reaction of 14B (0.5g, 1.77 mmol) with phenol derivative 4D (256 mg, 1.54 mmol) using tosyl chloride in CH₂Cl₂:pyridine (9:1) solvent at 35 ^oC overnight gave the Acridne 9-methyl carboxylate 14C with 76% yield. The synthesis of NSP-AE-acid synthesis was involved in two reactions in a one-pot. First step: the acridine 9-carboxylate 14C (120 mg, 0.127 mmol) was N-alkylated with 10 equivalents of 1,3-propane sultone in a microwave reactor, this reaction was monitored on LCMS, N-alkylation went to complete in 8 h. Second step: the methyl ester hydrolysis was done with 2N HCl (10 mL) in a microwave reactor at 110 ^oC for 2 h. The resulted crude product was filtered through the sintered funnel and filtrate was purified on prep-HPLC, obtained Acridinium NSP-AE-acid 14D in 56% yield. The HEG-Amine synthesis was carried out from Acid 14D (30 mg, 0.054 mmol) in two steps. Step 1: 20 mg of the acid derivative treated with TSTU (24 mg, 0.082 mmol) in DMF with 2 eg of DIPEA base, reaction completed in 30 min and it was confirmed by LCMS. At this stage, 50% of the reaction mixture was directly purified on prep-HPLC and isolated 6mg of ADOAE K (14). Step 2: the remaining 50% of the reaction mixture (step 1) reacted with Diamino-PEG6 and 4 eq of DIPEA in DMF. The mixture was purified on HPLC and lyophilized after the prep fraction was obtained pure material of 5mg of HEG-amine (15A). The final NHS ester synthesis was done with DSG in DMF with 5 eq of pH=7.5 buffer as a base and the final product was purified on HPLC, obtained 3 mg of ADOAE L (15). Example 13: Synthesis of ADOAE M (16), ADOAE N (17), ADOAE P (19), and

[0128] General synthesis: ADOAE M (16), ADOAE N (17), ADOAE P (19), and ADOAE Q (20) synthesis were carried out from the AE-acid intermediate intermediates 14D, 10D, ADOAE C (6), and 12D in two steps. [0129] Step 1: The AE-acid 3 mg of each compound was separately activated with 2 eq of TSTU in DMF with 2 eq of DIPEA, and the reaction was completed in 30 min by LCMS mass analysis. At this stage, the NHS-activated mixture(AE-NHS ester) was transferred dropwise to a stirred mixture of 1.5 eq of HEG-diamine and DIPEA (2 eq) in DMF at 0 ^oC. The reaction temperature was slowly raised to room temperature in 30 min. After 2 h at rt, LCMS indicated the AE-NHS ester was completely converted to AE-HEG-amine product. Step 2: 2 eq of (sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate) Sulfo-SMCC was added to the reaction mixture, raised the temperature to 40 ^oC, and the reaction was completed in 1 h by LCMS mass analysis. The resulting crude mixtures were directly purified on prep- HPLC. The lyophilized HPLC fractions led to the pure ADOAE M (16): 3 mg (53%), ADOAE N (17): 2 mg (37.2%), ADOAE P (19): 1.5 mg (28.3%), and ADOAE Q (20): 2mg (37%). Example 14. Synthesis of ADOAE O (18)

[0130] The ADOAE O (18) synthesis was carried out from acid 8B in a single step. Acid 8B (3.5 mg, 0.015 mmol) was treated with TSTU (2.3 mg, 0.076 mmol) and DIPEA in DMF, and the reaction was completed in 30 min by LCMS mass analysis. At this stage, the aminoethylmaleimide (3.81 mg, 0.015 mmol) was added to the reaction mixture at room temperature. After 2h, the mixture was purified on HPLC yielding 2.5 mg of ADOAE O (18) in a 60.6% yield. Example 15. Synthesis of ADOAE R (21) H

[0131] The synthesis of ADOAE R (21) started from the acid derivative 8B. The acid derivative (5 mg, 0.009 mmol) was coupled with the HEG diamine (3.64 mg, 0.013 mmol) via the acid-activated with TSTU followed by amide formation with HEG-diamine. The reaction was completed in 30 min. The crude product was directly purified on preparative-HPLC and obtained 3 mg of the terminal amine 21A in a 43% yield. The final acridinium ester- maleimidylcyclohexanecarboxylate (AE-MCC) synthesis was done by reacting 21A (3 mg. 0.0028 mmol) with 1.5 eq of SULFO-SMCC in DMF/pH = =7.5 phosphate buffer at room temperature for 30 min. The crude product was directly purified on preparative-HPLC yielding 2 mg of ADOAE R (21) in 54% yield. Example 16: Preparations of acridinium ester-antiTSH antibody conjugates [0132] The following procedure was typical to produce conjugates described herein. A solution of AntiTSH-mAb (2 mg) in 1 mL of 0.1 M phosphate buffer (pH=8) was treated with 10 equivalents of the acridinium ester (TSPAE (2), ADOAE D (7), ADOAE E (8), ADOAE F (9), ADOAE G (10), ADOAE H (11), ADOAE J (13), ADOAE K (14), and ADOAE L (15) (FIGS. 3A-3C provide structures) which was added as a solution in DMSO (0.033 mL of a 4 mmole/L solution in DMSO). The reaction was stirred at room temperature in dark at 2 to 5 ^oC for 16 h. The labeling reactions were transferred into an Amicon Ultra-4 30kDa molecular weight cut-off filter and diluted with 3 mL of deionized water. The filter was centrifuged at 5000×G for 10 min to reduce the volume to ~0.2 mL. This process was repeated four more times. The final conjugate in ~0.2 mL was brought to 1 mL in total with deionized water to give a 2 mg/mL solution. The AE-antiTSH mAb protein concentrations were determined with a micro BCA assay. The acridinium ester incorporation onto the antiTSH mAb was measured through MALDI-TOF mass spectroscopy. [0133] All references including patent applications and publications cited herein are incorporated herein by reference and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMS 1. A compound (e.g., a detectable conjugate of an analyte or a binding partner for an analyte) having the structure of formula (I): (^I) wherein A is an analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker optionally comprising a group L^C or Z^L, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “

” R1 is hydrogen, –R, –X, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z, or R₂ and R₃ together form a 5-7 membered fused heterocyclic group; Z is a zwitterionic group independently at each occurrence having the structure:

“r” is independently an integer from 0 to 10 (e.g., from 1 to 10); L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, – C(O)–O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)– (CH2)1-3–, –(CH2)1-3–C(O)–N(R^N)–, –NH–S(O)1-2–, –N(R^N)–S(O)1-2–, –S(O)1-2–N(R^N)–, – S(O)_1-2–NH–, –(CH₂)_1-3–NH–S(O)_1-2–, –(CH₂)_1-3–N(R^N)–S(O)_1-2–, –(CH₂)_1-3–S(O)_1-2– N(R^N)–, –(CH2)1-3–S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S– , –NH–(CH2)1-4–, –N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, – (OCH₂CH₂)_1-10–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl groups; with 1-10 substituents such as a group –X); R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl groups; with 1-20 substituents such as a group –X); R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl); L^C is a divalent C1-35 hydrocarbon optionally having one or more (e.g., 1-10, 1-5) points of substitution one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl groups; with 1-20 substituents); and Z^L is a zwitterionic linker group having the structure:

“m” is 0 (i.e. it is a bond) or 1; “n” and “p” are independently at each occurrence an integer from 0 (i.e. it is a bond) to 10; X^a is independently at each occurrence an anionic group; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., substituted with 1-10 heteroatoms, substituted with 1-10 substituents); and R’ is hydrogen or a C1-10 alkyl; or salt thereof (e.g., a halide salt such as a chloride salt). 2. The compound of claim 1, wherein R1 is –R, –X, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z. 3. The compound of claim 1 or claim 2, wherein R3 is hydrogen. 4. The compound of any one of claims claim 1-3, wherein R2 is alkoxy optionally substituted at one or more (e.g., one, two, three) positions with one or more independently selected substituents (e.g., –X such as –S(=O)1-2–R*, –O–S(=O)2–R*, –S(=O)2–OR*, –O– SO₃, –O–S(=O)₂–OR*, –O–S(=O)–OR*, –O–S(=O)–R*, –S(=O)–OR*, or –S(=O)–R*, where R* is H or a C1-10 hydrocarbon). 5. The compound of claim 1, wherein Ψ comprises the structure:

wherein “h” is 1,

2,

3,

4,

5, or 6.

6. The compound according to any one of claims 1-5, wherein Ψ comprises the structure:

.

7. The compound of any one of claims 1-6, wherein Ψ has the structure of formula (II)

wherein Ω is S, O, or N; Y is selected from –R, –L1–R, –R^L–Z, –L1–R^L–Z, or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L₁–, –R^L–, –R^L–L₁–, –L₁–L₁–, –L₁– R^L–, –L1–R^L–L1, or –R^L–L1–R^L–; and Y’ comprises one or more linkages to A (e.g., when L is absent) or L (e.g., to L^C or Z^L); R₁ is hydrogen, –R, –X, –R^L–X, –L₁–R, –L₁–X, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z; Z is a zwitterionic group having the structure:

; where “q” and “l” are independently 0 or 1; “r” is independently an integer from 0 to 10; L1 is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH2)1-10–, –S(=O)1-2–, –C=C–, –C=C–(CH₂)_1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH₂)_1-4–, –(CH₂)_1-4–C(O)–, –C(O)– O–, –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH2)1-3–, –(CH₂)_1-3–C(O)–N(R^N)–, –NH–S(O)_1-2–, –N(R^N)–S(O)_1-2–, –S(O)_1-2–N(R^N)–, –S(O)_1-2– NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, – (CH₂)_1-3–S(O)_1-2–NH–, –O–(CH₂)_1-4–, –(CH₂)_1-4–O–, –S–(CH₂)_1-4–, –(CH₂)_1-4–S–, –NH– (CH2)1-4–, –N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH₂CH₂)_1-10–, or –(CH₂CH₂O)_1-10–; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally substituted with 1-10 heteroatoms; R is independently at each occurrence hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally substituted with 1-20 heteroatoms; R’ and R” are independently at each occurrence hydrogen or a C1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C_1-5 alkyl (e.g., methyl, ethyl, propyl).

8. The compound of claim 7, wherein Ω is S, O, or N and R1 is –R, –X, –R^L–X, –L1–R, – L₁–X, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z.

9. The compound of any one of claims 6-8, wherein Ψ has the structure of formula (IIa)

wherein “h” is 1, 2, 3, 4, 5, or 6.

10. The compound according to any one of claims 1-9, wherein Ψ has the structure of formula (IIb):

wherein R5-R8 are independently hydrogen or C1-35 alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, or amino; and wherein L₁ is covalently bonded to A (

, L absent) or L (e.g., to L^C or Z^L).

11. The compound of claim 10, wherein L1 is –NH–C(O)–, –C(O)–NH– or –C(O)–O– or –O–C(O)–.

12. The detectable conjugate of claim 10 or 11, wherein R₅ and R₆ are each lower alkyl (e.g., C1-C4 alkyl, methyl) and R7 and R8 are each hydrogen.

13. The compound of any one of claims 1-9, wherein Ψ has the structure of formula (IIc):

wherein Y” is either absent or is –L1–, –R^L–, –L1– R^L–, or –R^L–L1–, where Y” is covalently attached to A (e.g., L is absent) or L (e.g., to L^C or Z^L).

14. The compound of any one of claims 1-9, wherein Ψ has the structure of formula (IId):

wherein Y” is either absent or is –L₁–, –R^L–, –L₁– R^L–, or –R^L–L₁–, where Y” is covalently attached to A (e.g., L is absent) or L (e.g., to L^C or Z^L).

15. The compound of any one of claims 1-9 and 14, wherein Ψ has the structure of formula (IIe):

16. The compound according to any one of claims 1-15, wherein L has the structure –L^C– (Z^L)z– where “z” is 0 or 1; L^C is a divalent C1-35 alkyl, alkenyl, alkynyl, aryl, or arylalkyl radical, optionally substituted with 1 to 20 heteroatoms; and Z^L is a zwitterionic linker group having the structure:

“m” is 0 (i.e. it is a bond) or 1; “n” and “p” are independently at each occurrence an integer from 0 (i.e. it is a bond) to 10; X^a is an anionic group; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., substituted with 1-10 heteroatoms, substituted with 1-10 substituents); and R’ is hydrogen or a C1-10 alkyl.

17. The compound according to claim 16, wherein L^C has the structure: –(X1)0-1–(R^L)0-5–(X2)0-1– (R^L)0-5–(X3)0-1–(R^L)0-5–(X4)0-1–(R^L)0-5– wherein X₁ is selected from =N–, –O–, –S–, or –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)–NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S– or X1 is a group

wherein indicates the point of attachment to either neighboring group; X2–X4 are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)– NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from –(CH2)1-5–, –(CH2CH2O)1-5–, or – (OCH₂CH₂)_1-5–.

18. The compound according to any one of claims 1-17, wherein X^a and X^b are independently at each occurrence carboxylate (–C(O)O-), sulfonate (–SO_ଷି ), sulfate (– OSO_ଷି ), phosphate (–OP(O)(OR^P)O-), or oxide (–O-), and R^P is hydrogen or C1-12 hydrocarbon optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents).

19. The compound according to any one of claims 1-18, wherein R₁ comprises –R^L–SO₃-.

20. The compound according to any one of claims 1-18, wherein R₁ comprises (or is) sulfopropyl.

21. The compound according to any one of claims 1-18, wherein R1 is –S(O)2–NH–Z or – (CH₂)_1-3–S(O)₂–NH–Z.

22. The compound according to any one of claims 1-21, wherein R2 and R3 are independently at each occurrence hydrogen, alkyl, or alkoxy (e.g., lower alkoxy such as C₁- C4 alkoxy, methoxy, ethoxy, propoxy, isopropoxy).

23. The compound according to any one of claims 1-21, wherein R2 and R3 are each hydrogen.

24. The compound according to any one of claims 1-21, wherein one of R₂ or R₃ is hydrogen and the other of R2 or R3 is alkoxy (e.g., lower alkoxy such as C1-C4 alkoxy, methoxy, ethoxy, propoxy, isopropoxy).

25. The compound according to any one of claims 16-24, wherein X^a is sulfonate (–SO_ଷି ), m is 1, R^L is propyl, and n and p are each 3, such that Z^L has the structure:

.

26. The compound according to any one of claims 1-25, wherein said compound has the structure of formula (IIIa) or (IIIb):

; where “z” is 0 or 1.

27. The compound according to any one of claims 1-26, wherein the analyte is a thyroid hormone (e.g., a thyroid stimulating hormone and, for example, A is a binding partner therefor such as an anti-thyroid stimulating hormone monoclonal antibody (AntiTSH-mAb)), a troponin, a steroid hormone (e.g., androstenedione, testosterone), thyroglobulin, anti- thyroid peroxidase antibody, triiodothyronine (T3) hormone, thyroxine (T4) hormone, thyroxine-binding globulin (TBG), neurofilament light chain (e.g., serum neurofilament light chain), a vitamin (e.g., vitamin-D such as 25-hydroxy-vitamin D), or an antibody for a virus (e.g., hepatitis).

28. The compound according to any one of claims 1-12 and 16-27, wherein said compound is formed by reacting the analyte or binding partner thereof with:

, , ,

,

.

29. A reagent composition for the detection of an analyte comprising a compound of any one of claims 1-28 in a pH buffered medium.

30. An assay for the detection or quantification of an analyte in a sample comprising: (a) providing a detectable conjugate of any one of claims 1-28; (b) providing a solid support having immobilized thereon a molecule capable of forming a binding complex with said analyte and/or capable of forming a binding complex with said detectable conjugate; (c) mixing said compound, said solid support, and said sample; (d) separating said solid support from said mixture; (e) triggering chemiluminescence of any acridinium label complexed to said solid phase; (f) measuring the amount of light emission with a luminometer; and (g) detecting the presence or calculating the concentration of said analyte by comparing the amount of light emitted with a standard dose response curve which relates the amount of light emitted to a known concentration of the analyte.

31. A compound (e.g., for conjugating to an analyte or a binding partner for an analyte) having the structure of formula (IV): (^IV) wherein RFG is a reactive functional group for conjugating to an analyte or binding partner for an analyte, L is absent (i.e., it is a bond) or a linker optionally comprising a group Z^L or L^C, and Ψ is a chemiluminescent acridinium comprising the structure:

wherein “

R₁ is hydrogen, –R, –X^b, –R^L–X^b, –L₁–R, –L₁–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R₂ and R₃ are independently selected from hydrogen, –R, an electron donating group, or –Z, or R2 and R3 together form a 5-7 membered fused heterocyclyl group; Z is a zwitterionic group independently at each occurrence having the structure: ;

“ ” is independently an integer from 0 to 10; L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, – (

S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S–, –NH–(CH2)1-4–, – N(R^N)–(CH₂)_1-4–, –(CH₂)_1-4–N(R^N)–, –(OCH₂)_1-10–, –(CH₂O)_1-10–, –(OCH₂CH₂)_1-10–, or – (CH2CH2O)1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl, with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-20, 1-10, 1-5) points of substitution (e.g., with 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl,, with 1-20 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl); L^C is a divalent C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, aryl, or arylalkyl), having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl, with 1-10 substituents); and Z^L is a zwitterionic linker group having the structure:

“m” is 0 (i.e. it is a bond) or 1; “n” and “p” are independently at each occurrence an integer from 0 (i.e. it is a bond) to 10; X^a is an anionic group; R^L is independently at each occurrence a C_1-20 bivalent hydrocarbon radical (e.g., alkyl, alkenyl, aryl, alkynyl, arylalkyl), optionally having one or more having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl, with 1-10 substituents); and R’ is hydrogen or a C1-10 alkyl; or a salt thereof (e.g., a halide salt such as a chloride salt).

32. The compound of claim 29, wherein R1 is–R, –X, –R^L–X^b, –L1–R, –L1–X^b, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z.

33. The compound of claim 31 or 32, wherein R3 is hydrogen.

34. The compound of any one of claims 31-35, wherein R2 is alkoxy optionally substituted at one or more (e.g., one, two, three) positions with one or more independently selected substituents (e.g., –X such as –S(=O)1-2–R*, –O–S(=O)2–R*, –S(=O)2–OR*, –O–SO3, –O– S(=O)₂–OR*, –O–S(=O)–OR*, –O–S(=O)–R*, –S(=O)–OR*, or –S(=O)–R*, where R* is H or a C1-10 hydrocarbon).

35. The compound of claim 31, wherein Ψ comprises the structure:

wherein “h” is 1, 2, 34.

36. The compound according to any one of claims 31-35, wherein Ψ comprises the structure:

.

37. The compound of any one of claims 31-36, wherein Ψ has the structure of formula (V)

wherein Ω is S, O, or N; Y is selected from –R, –L1–R, –R^L–Z, –L1–R^L–Z, or in the case where Ω is O or S then Y is absent; Y’ is either absent (i.e. it is a bond), or is selected from –L₁–, –R^L–, –R^L–L₁–, –L₁–L₁–, –L₁– R^L–, –L1–R^L–L1, or –R^L–L1–R^L–; and Y’ comprises one or more linkages to A (e.g., when L is absent) or L (e.g., L^C or Z^L); R₁ is hydrogen, –R, –X, –R^L–X, –L₁–R, –L₁–X, –Z, –R^L–Z, –L₁–Z, or –R^L–L₁–R^L–Z; R2 and R3 are independently selected from hydrogen, –R, an electron donating group, or –Z; Z is a zwitterionic group having the structure: ;

“r” is independently an integer from 0 to 10; L₁ is independently at each occurrence –O–, –S–, –NH–, –N(R^N)–, –(CH₂)_1-10–, –S(=O)_1-2–, –C=C–, –C=C–(CH2)1-3–, –C(O)–, –O–C(O)–, –C(O)–(CH2)1-4–, –(CH2)1-4–C(O)–, –C(O)–O– , –C(O)–N(R^N)–, –C(O)–NH–, –N(R^N)–C(O)–, –NH–C(O)–, –C(O)–N(R^N)–(CH₂)_1-3–, –(CH2)1-3–C(O)–N(R^N)–, –NH–S(O)1-2–, –N(R^N)–S(O)1-2–, –S(O)1-2–N(R^N)–, –S(O)1-2–NH–, –(CH2)1-3–NH–S(O)1-2–, –(CH2)1-3–N(R^N)–S(O)1-2–, –(CH2)1-3–S(O)1-2–N(R^N)–, –(CH2)1-3– S(O)1-2–NH–, –O–(CH2)1-4–, –(CH2)1-4–O–, –S–(CH2)1-4–, –(CH2)1-4–S–, –NH–(CH2)1-4–, – N(R^N)–(CH2)1-4–, –(CH2)1-4–N(R^N)–, –(OCH2)1-10–, –(CH2O)1-10–, –(OCH2CH2)1-10–, or –(CH2CH2O)1-10–; R^L is independently at each occurrence a C1-20 bivalent hydrocarbon (e.g., alkyl, alkenyl, aryl, phenyl, mono alkyl substituted phenyl, di alkyl substituted phenyl, alkynyl, arylalkyl), optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl, with 1-10 substituents); R is independently at each occurrence hydrogen or C1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, or aralkyl) radical, optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-20 or 1-20 heteroatoms such as heteroalkyl, heteroalkenyl, heteroaryl, heteroalkynyl, heteroarylalkyl, with 1-20 or 1-10 substituents); R’ and R” are independently at each occurrence hydrogen or a C_1-10 alkyl; X^b is independently at each occurrence an anionic group; and R^N is independently selected at each occurrence from hydrogen, or C1-5 alkyl (e.g., methyl, ethyl, propyl).

38. The compound of claim 37, wherein Ω is S, O, or N and R₁ is –R, –X, –R^L–X, –L₁–R, –L1–X, –Z, –R^L–Z, –L1–Z, or –R^L–L1–R^L–Z.

39. The compound of any one of claims 35-38, wherein Ψ has the structure of formula (Va)

wherein “h” is 1, 2, 3, 4, 5, or 6;

40. The compound according to any one of claims 31-39, wherein Ψ has the structure of formula (Vb):

wherein R₅-R₈ are independently hydrogen or C_1-35 hydrocarbon (e.g., alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, or amino); and wherein L1 is covalently bonded to A (e.g., L absent) or L (e.g., to L^C or Z^L).

41. The compound of claim 40, wherein L₁ is –NH–C(O)–, –C(O)–NH– or –C(O)–O– or –O–C(O)–.

42. The compound of claim 40 or 41, wherein R5 and R6 are each lower alkyl (e.g., C1-C4 alkyl, methyl) and R₇ and R₈ are each hydrogen.

43. The compound of any one of claims 31-39, wherein Ψ has the structure of formula (Vc):

44. The compound of any one of claims 31-39, wherein Ψ has the structure of formula (Vd):

45. The compound of any one of claims 31-39 and 44, wherein Ψ has the structure of formula (Ve):

46. The compound according to any one of claims 31-45, wherein L has the structure –L^C– (Z^L)z– where “z” is 0 or 1; L^C is a divalent C1-35 alkyl, alkenyl, alkynyl, aryl, or arylalkyl radical, optionally substituted with 1 to 20 heteroatoms; and Z^L is a zwitterionic linker group having the structure:

47. The compound according to claim 46, wherein L^C has the structure: –(X1)0-1–(R^L)0-5–(X2)0-1– (R^L)0-5–(X3)0-1–(R^L)0-5–(X4)0-1–(R^L)0-5– wherein X₁ is selected from =N–, –O–, –S–, or –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)–NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; X2–X4 are independently selected from –O–, –S–, –NR^N–, –C(O)–, –NR^N–C(O)–, –C(O)– NR^N–, –O–C(O)–, or –C(O)–O–, –S–C(O)–, or –C(O)–S–; and R^L is independently selected at each occurrence from–(CH₂)_1-5–, –(CH₂CH₂O)_1-5–, – (OCH2CH2)1-5–, or optionally substituted cycloalkylene (e.g., C5 cycloalkylene, C6 cycloalkylene).

48. The compound according to any one of claims 31-47, wherein X^a and X^b are independently at each occurrence carboxylate (–C(O)O-), sulfonate (–SO3-), sulfate (–OSO3- ), phosphate (–OP(O)(OR^P)O-), or oxide (–O-), and R^P is hydrogen or C_1-12 hydrocarbon optionally having one or more (e.g., 1-10, 1-5) points of substitution (e.g., with 1-10 heteroatoms, with 1-10 substituents).

49. The compound according to any one of claims 31-48, wherein R₁ comprises –R^L–SO₃- .

50. The compound according to any one of claims 31-49, wherein R1 comprises (or is) sulfopropyl.

51. The compound according to any one of claims 31-50, wherein R1 is –S(O)2–NH–Z or –(CH2)1-3–S(O)2–NH–Z.

52. The compound according to any one of claims 31-51, wherein R₂ and R₃ are independently at each occurrence hydrogen, alkyl, or alkoxy (e.g., lower alkoxy such as C1- C₄ alkoxy, methoxy, ethoxy, propoxy, isopropoxy).

53. The compound according to any one of claims 31-51, wherein R₂ and R₃ are each hydrogen.

54. The compound according to any one of claims 31-51, wherein one of R2 or R3 is hydrogen and the other of R₂ or R₃ is alkoxy (e.g., lower alkoxy such as C₁-C₄ alkoxy, methoxy, ethoxy, propoxy, isopropoxy).

55. The compound according to any one of claims 47-54, wherein X^a is sulfonate (–SO3-), m is 1, R^L is propyl, and n and p are each 3, such that Z^L has the structure:

.

56. The compound according to any one of claims 31-42 and 47-55 having the structure of formula (VIa) or (VIb):

.

57. The compound according to any one of claims 31-56, wherein the reactive functional group is selected from: , – ,

58. The compound according to any one of claims 31-42 and 46-57, wherein said compound is:

. 59. A method comprising reacting the compound according to any one of claims 31-58 with an analyte or binding partner for an analyte (e.g., an antibody).