WO2012023100A1

WO2012023100A1 - Polymer bound metallophthalocyanines

Info

Publication number: WO2012023100A1
Application number: PCT/IB2011/053616
Authority: WO
Inventors: Ruphino Zugle; Godfred Darko; Nelson Torto; Christian Litwinski; Tebello Nyokong
Original assignee: Mintek
Priority date: 2010-08-17
Filing date: 2011-08-16
Publication date: 2012-02-23

Abstract

A composite metallophthalocyanine polymer material comprises lutetium(lll) phthalocyanine supported on a polymer support. The material can be synthesised by a process which includes forming a solution of a lutetium(lll) phthalocyanine and a polymer in a solvent, and electro-spinning the solution to form fibers of the composite metallophthalocyanine polymer material.

Description

POLYMER BOUND METALLOPHTHALOCYANINES

THIS INVENTION relates to functional ized polymer material. In particular, the invention relates to a composite metallophthalocyanine polymer material and to a process for forming a composite metallophthalocyanine polymer material.

The evolution of polymer composite technology is opening up prospects for creating materials made from synthetic phthalocyanine supported on a polymer matrix in which they exhibit high activity. Attaching or encapsulating the phthalocyanine (Pc) to a polymer support offers many advantages which do not exist when the phthalocyanine is used alone. These include cooperative reactions in polymer chains, separation of active sites and the possibility of specific binding to different substrates. New materials made from polymer bound phthalocyanines and the metal complexes of such phthalocyanines exhibit very unusual properties due to the inclusion of the metal in the polymer macromolecule, which opens up new possibility for their applications. For example, it has been reported that a zinc phthalocyanine (ZnPc) anchored on polyurethane polymer fiber leads to a red shifted Q-band maximum in its visible light absorption compared with those recorded in some solvents. Such a red shift is desirable and very promising in harvesting visible light for various applications.

Applications of these phthalocyanine bound polymers include the use of metal phthalocyanine containing chlorine or phosphorus and bound to polymers as fireproofing materials. They have also been applied in modelling biological systems and in medicine as well as in optics and nanoelectronics.

According to one aspect of the invention, there is provided a composite metallophthalocyanine polymer material comprising lutetium(lll) phthalocyanine supported on a polymer support.

Advantageously, lutetium has a diamagnetic nature providing opportunities for photocatalytic applications of the composite metallophthalocyanine polymer material of the invention. It also has a large molecular size which may enhance intersystem crossing to the triplet excited state of the phthalocyanine complex. This in turn leads to a large singlet oxygen quantum yield, which is important for some possible applications of the composite metallophthalocyanine polymer material of the invention. The composite metallophthalocyanine polymer material may be a particulate material.

In one embodiment of the invention, the composite metallophthalocyanine polymer material is in the form of fibers. The fibers may be cylindrical and may range in diameter from less than about 1 μηη, e.g. about 1 μηη, up to about 10μηη, or up to about 7μηη , e.g. from about 3.1 μιτι to about 6.8μηη.

The fibers may be electro-spun fibers. It is however to be appreciated that the fibers may instead be obtained from template synthesis or self-assembly techniques.

The fibers may have uniform composition.

The composite metallophthalocyanine polymer material may comprise lutetium(lll) phthalocyanine and polymer in a molar ratio of from about 1 :0.001 to about 1 :100, preferably from about 1 :0.01 to about 1 :10, e.g. between 1 :1 and 1 :10. As will be appreciated by those skilled in the art, this ratio will affect the diameter of electro-spun fibers of the composite metallophthalocyanine polymer material of the invention. The ratio will also affect the applications of the modified fibers, e.g. as photocatalysts.

The polymer may be selected from the group consisting of polyethylene glycol, polyesters, polyacrylates, acrylate copolymers, polystyrene,

polyvinylpolypyrrolidone, polyvinylamine, polyethylene oxide, N-acryloyl-β- alanine(aminoethylene)amide, N-acryloylpyrrolidone, N,N-bis(methacyloyl)-1 ,2- diaminoethane, polysulfone, and mixtures or copolymers of two or more of these.

In one embodiment of the invention, the polymer is polystyrene. The phthalocyanine may be of the general formula C3₂Hi₈N₈. The phthalocyanine may be ring mono, non-peripherally and peripherally tetra- or peripherally octa-substituted with alkyl or aryl groups. Non-peripherally and peripherally tetra- and octa-substituted phthalocyanines are prepared by cyclotetramerization substituted phthalonitriles, in the absence (for unmetallated phthalocyanines) and presence (for metallated phthalocyanines) of a metal salt. 2(3), 9(10), 16(17), 23(24)-tetra-substituted (peripheral position) phthalocyanines can be synthesized from 4-substituted phthalonitriles while 1 (4),8(1 1 ),15(18),22(25)-tetra-substituted (non-peripheral position) phthalocyanines are obtained from the 3-substituted analogues. In both cases, a mixture of four possible structural isomers is obtained. The four probable isomers can be designated by their molecular symmetry as C₄h, C_2v, C_s and D₂h- The peripherally tetra-substituted compounds always occur in the expected statistical mixture of 12.5% C₄h-, 25%C₂v-, 50%C_S- and 12.5%D_2h- isomers, but for the non-peripherally tetra-substituted ones the composition depends on the central metal ion and the structure of the peripheral substituent. Octa-substituted phthalocyanine dyes are generally prepared from di- substituted phthalonitriles. Substituents may advantageously be selected for their bulkiness and the possibility of preventing or reducing aggregation while enhancing solubility in an organic solvent.

In one embodiment of the invention, the phthalocyanine is tetraphenoxy- phthalocyanine so that the composite phthalocyanine polymer material comprises lutetium(lll) phthalocyanine (tetrasubstituted with phenoxy groups at non-peripheral positions) supported on a polymer support.

The metallophthalocyanine polymer material of the invention may have a singlet oxygen quantum yield of greater than 0.53 in tetrahydrofuran, preferably greater than 0.6 in tetrahydrofuran, more preferably greater than 0.65 in tetrahydrofuran, e.g. about 0.71 in tetrahydrofuran. However it is important to determine singlet oxygen quantum yields in water for real life applications. The singlet quantum yield may be greater than 0.22, suggesting the possibility of it being used in the photo-conversion of 4-chlorophenol in aqueous media. The invention thus extends to the use of a composite metallophthalocyanine polymer material comprising lutetium(lll) phthalocyanine supported on a polymer support for the phototransformation of 4-chlorophenol. The phototransformation of 4-chlorophenol may take place in aqueous media.

Chlorophenols are very common aqueous organic pollutants, partly because of their importance in the production of fungicides and herbicides. As a result of the immense economic importance associated with the removal of chlorophenols during water purification, various attempts to degrade pollutants have been described using oxidants. However, processes involving no harmful oxidants are still preferred, such as in photodegradation, providing so called "green chemistry" for the removal of chlorophenols.

According to another aspect of the invention, there is provided a process for synthesising a composite metallophthalocyanine polymer material, the process including

forming a solution of a lutetium(lll) phthalocyanine and a polymer in a solvent; and

electro-spinning the solution to form fibers of the composite metallophthalocyanine polymer material.

Advantageously, electro-spinning is a simple, convenient, reproducible and versatile technique for generating fibers with diameters that range from several micrometers to tens of nanometers. To obtain optimal deposition conditions for fibers using the electro-spinning technique, the following parameters may be varied the distance between a jet nozzle and a collector

- the voltage applied between the jet nozzle tip (capillary tip) and a collecting target or collector

the type of solvent used

the concentration of the phthalocyanine dye

the concentration/viscosity of the polymer solution the rate of polymer delivery

ambient humidity and temperature

The polymer and the phthalocyanine and the fibers may be as hereinbefore described. The fibers may thus be cylindrical with a diameter of less than 10 μιτι, preferably less than 7 μιτι.

The lutetium(l l l) phthalocyanine and the polymer may be admixed in a molar ratio of from about 1 :0.001 to about 1 :100, preferably from about 1 :0.01 to about 1 :10, e.g. between 1 :1 and 1 :10.

The solvent may be selected from the group consisting of methanol, ethanol, dichloromethane (DCM), tetrahydrofuran (THF), toluene, chloroform dimethylsulfoxide (DMSO), dimethyl formamide (DMF), pyridine, acetonitrile, chloronaphthalene, pentanol, benzonitrile 1 ,4-dioxane, n-butylamine, triethylamine, benzene, o-xylene, chlorobenzene and mixtures of two or more thereof. In one embodiment of the process of the invention, the solvent is a mixture of dimethylformamide and tetrahydrofuran, in a volumetric ratio of 4:1 (v/v). The process may include synthesising the lutetium(l l l) phthalocyanine from lutetium(l l l) acetate and a phthalonitrile. For example, the lutetium(l l l) phthalocyanine, as 1 (4), 8(1 1 ), 15(18), 22(25)-(tetraphenoxyphthalocyaninato) lutetium(l l l) acetate, may be synthesised from lutetium(l l l) acetate and 3- phenoxyphthalonitrile by refluxing an admixture thereof under a nitrogen atmosphere in pentanol in the presence of a catalyst such as DBU (1 ,8-diazobicyclo[5.4.0] undec-7- ene).

The invention will now be described with reference to the following synthesis example and characterisation work, and the accompanying drawings.

In the drawings,

Figure 1 shows UV-Visible spectra of 1 (4), 8(1 1 ), 15(18), 22(25) - (tetraphenoxyphthalocyaninato) lutetium(l l l) acetate (hereinafter LuTPPc) showing variation of absorbance with concentration ranging from (a) minimum concentration: 1 .35 x 10^"6 M to (i) maximum concentration 1 .04 x 10^"5 M;

Figure 2 shows singlet oxygen decay profiles for LuTPPc in THF with λ_βχ0 = 695nm;

Figure 3 shows (a) a fiber mat of polystyrene, and (b) a fiber mat of LuTPPc/Polystyrene composite, 100 μιτι resolution and inserts are 50 μιτι resolution; Figure 4 shows (a) theoretical and (b) experimental Raman spectra of polystyrene;

Figure 5 shows Raman spectra of (a) polystyrene and (b) polystyrene/LuTPPc composite fibers in accordance with the invention;

Figure 6 shows UV-Visible absorbance spectra of : (a) 3.8 x 10^"6 M LuTPPc in THF solution, (b) solid LuTPPc, (c) polystyrene fiber and (d) polystyrene/LuTPPc composite fiber in accordance with the invention; Figure 7 shows the variation of absorbance of the polystyrene/LuTPPc composite fiber of the invention with fiber mat thickness r ^« 0.1 cm placed on glass plate, for (a) r, (b) 2r and (c) 4r;

Figure 8 shows UV-Visible spectra of water, THF and hexane after immersing the functionalized LuTPPc/Polystyrene composite fiber in them for various time intervals (a) 18 h in water, (b) 4 h in hexane, (c) 12 h in hexane and (d) momentarily in THF;

Figure 9 shows (a) the degradation of 1 ,3-diphenylisobenzofuran (DPBF) in THF in the presence of functionalized LuTPPc/Polystyrene composite polymer fiber in accordance with the invention in hexane at various photolysis times and (b) the regeneration of LuTPPc from the fiber of the invention by immersing the LuTPPc/Polystyrene composite fiber of the invention in THF and recording the spectra in THF; Figure 10 shows the degradation of anthracene-9,10-bis-methylmalonate (ADMA), in aqueous media in the presence of functionalized LuTPPc/Polystyrene composite polymer fiber in accordance with the invention in water at various photolysis times, where spectrum (a) is the starting spectrum and spectrum (j) is the spectrum after 20 minutes of photolysis, the starting ADMA concentration being 5.53 x 10^"5 mol dm^"3 and the irradiation interval is 2 minutes;

Figure 1 1 shows singlet oxygen decay profile for LuTPPc/Polystyrene fiber composite material in accordance with the invention in the solid state, where λ_βχ0 = 696 nm;

Figure 12 shows a synthesis route for LuTPPc used in the Example to prepare the composite metallophthalocyanine polymer material in accordance with the invention;

Figure 13 shows electronic absorption spectral changes of 3.58 x 10^"4 molL^"1 4-chlorophenol (4-CP) during its visible light photocatalysis in the presence of 10 mg of functionalized LuTPPc/Polystyrene composite polymer fiber in accordance with the invention, where the spectra were recorded at 15 minute intervals and the insert is a plot of absorbance versus time for the two peaks; and

Fig. 14 shows gas chromatographic traces of 3.58 x 10^"4 M 4-chlorophenol after being photolysed for 12 hours in the presence of 10 mg functionalized LuTPPc/Polystyrene composite polymer fiber in accordance with the invention.

Example

Material used

The following materials were obtained: Polystyrene (Mw = 192,000g/mol), Ν,Ν-dimethylfomamide (DMF) 99%, and tetrahydrofuran (THF) 98% from MERCK Chemical Ltd, 1 ,3-diphenylisobenzofuran (DPBF) 97%, 1 ,8-diazabicyclo[5.4.0] undec-7- ene (DBU), potassium carbonate, phenol, lutetium(lll) acetate, anthracene-9,10-bis- methylmalonate (ADMA), 4-chlorophenol 99%, tert-butanol 99%, hydroquinone and sodium azide 99% were from Aldrich. 1 -Pentanol was from SAARCHEM. Column chromatography was performed on silica gel 60 (0.04-0.063 mm) and preparative thin layer chromatography was performed on silica gel 60 P F₂5₄.

General equipment used

Infrared (IR) spectra were recorded on a Perkin-Elmer Fourier transform-

IR (FT-!R) SPECTRUM 2000 spectrometer using potassium bromide (KBr) disks. UV- Vis absorption (UV-Vis) spectra were recorded on a Varian-Cary 500 Vis/NIR spectrophotometer or a Shimadzu UV-2550 spectrophotometer. ¹ H-N R spectra were recorded on a Bruker AMX6QQ MHz in detuerated DMSO. Microanalyses were performed using a Vario-Elementar Microcube ELIII, Mass spectral data were recorded on ABI Vogager De-STR Maldi-TOF instrument at the University of Stellenbosch, South Africa using 2,5-dihydroxy benzoic acid as a matrix. Scanning electron microscope (SEM) images were obtained using a JOEL JSM 840 scanning electron microscope. Raman data was obtained using a Bruker Vertex 70-Ram II spectrometer equipped with a Nd:YAG laser that emit at 1064 nm and a liquid nitrogen cooled germanium detector. The Gaussian 03 programme running on an Intel/Linux cluster was used to perform DFT calculations. The calculations were done at the B3LYP/6-31 G(d) level for geometry optimization and excited energy calculations (TDDFT). All visualisation used the Gausview 4.1 program.

Photocatalytic reactions

Photocatalytic reactions were carried out in a magnetically stirred batch reactor (glass vial). Irradiation experiments were carried out using a General Electric Quartz lamp (300W), 600 nm glass (Schott) and water filters, to filter off ultra-violet and far infrared radiations respectively. An interference filter (670 nm with a band width of 40 nm) was additionally placed in the light path before the sample to ensure the excitation of the Q-band of the Pc within the fiber matrix. The intensity of the light reaching the reaction vessel was measured with a power meter (POWER MAX 5100, Molelectron Detector Inc) and found to be 3.5 x 10²⁰ photons cm^"2 s^~1. The transformation of the analyte was monitored by observing the absorption bands of 4-chlorophenol after each photolysis cycle of fifteen minutes using a Shimadzu UV-2550 spectrophotometer. The experiments were carried out using a variety of concentrations of 4-chlorophenol in water, each sample containing 10 mg of functionalized LuTPPc/Polystyrene composite polymer fiber in accordance with the invention.

Chromatographic analysis

The photolysis products of 4-chlorophenol were separated and analysed using both gas chromatography (GC) and by direct injection into an ion trap mass spectrometer fitted with an electrospray ionization (ESI-MS) mass source. In the case of the gas chromatographic analyses, an Agilent Technologies 6820 GC system fitted with a DB-MS Agilent J & W GC column was employed. A Finnigan MAT LCQ ion trap mass spectrometer equipped with an electro-spray ionization (ESI) source was used for mass analysis. Spectra were acquired in the negative ion mode, with the capillary temperature set at 200°C and sheath gas set at 60 arbitrary units, with the capillary and tube lens voltage set at -20 and -5V respectively. The aqueous photocatalysed sample solution was extracted with dichloromethane and then injected into the GC.

Synthesis of 1 (4),8(11),15(18), 22(25)-(tetraphenoxyphthalocyaninato) lutetium(lll) acetate

The synthesis route illustrated in Fig. 12 was used to produce 1 (4), 8(1 1 ), 15(18), 22(25)-(tetraphenoxyphthalocyaninato) lutetium(lll) acetate.

3-Phenoxyphthalonitrile was firstly prepared through base catalysed nucleophilic aromatic displacement reaction as described in McKeown N.B., Painter J., J Mater. Chem., 1994, 4, 1 153 -1 156. Thereafter, a mixture of anhydrous lutetium(lll) acetate (133 mg, 0.38 mmol) and 3-phenoxyphthalonitrile (339 mg, 1 .54 mmol) in pentanol (2 ml_) was refluxed for 7 h under a nitrogen atmosphere with DBU as catalyst. After cooling, the crude product was precipitated with n-hexane, filtered and washed with excess n- hexane and then air-dried. Column chromatography (silica gel) was employed using THF: methanol (10:1 ) as the eluting solvent mixture.

1 (4), 8(1 1 ), 15(18) ,22(25) - (tetraphenoxyphthalocyaninato) lutetium(lll) acetate was obtained as the major product, which was re-crystallized from hexane. Yield: 23%. IR [KBr, ucm^"1] 748, 802, 862, 880, 969, 1024 (Pc skeleton), 1248, 1324, 1482 (C-O-C), 1727, 1771 (C=0), 2955 (C-H, aromatic), 3635 (CH₃). UV-Vis (THF): X_max nm (log ε) 321 (4.55), 430(4.30), 627(4.31 ), 690(5.12). Calculated for CssHssNsOeLu; C 62.48%, H 3.16%, N 10.05%. Found: C 61 .50%, H 4.86% N 8.37%; ¹ HNMR (DMSO-d): δ, ppm 7.76-7.86 (12-H, m, Pc-H), 6.58-6.87 (20-H m, Phenyl-H), 2.09 (3-H, s, acetate-CHs); (ES⁺), (m/z): Calculated: 1 1 15; Found: 1 1 19 [M + 4H⁺].

Characterization of 1 (4), 8(11), 15(18), 22(25)- (tetraphenoxyphthalocyaninato) lutetium(lll) acetate (LuTPPc)

The MALDI-TOF technique was used for mass spectrometry study, with 2,5-dihydroxy benzoic acid as the matrix. LuTPPc showed molecular ion peak corresponding to [M+4H]⁺ at 1 1 19 amu which is consistent with the calculated values of 1 1 15 amu. ¹H NMR and IR data were consistent with the structure for LuTPPc.

Figure 1 shows a typical dependence of the absorbance of compound LuTPPc with concentration and the insert in Figure 1 is the Beer-Lambert law for concentrations ranging from 1 .35 x 10^"6 M to 1 .04 x 10^"5 M. Thus the LuTPPc complex was not aggregated in DMSO or THF at concentrations less than 1 x 10^"5 M.

Preparation of LuTPPc-Polystyrene fibers

Functionalised LuTPPc-Polystyrene fibers were prepared by electro- spinning using a method reported by Tang S., Shao C, Liu Y., Li S., Mu R., J. Phys. Chem. Solids, 2007, 68,2337-2340, with modifications as follows: a solution containing 2.5 g (1 .3 x 10^"5 moles of polystyrene (PS) and 1 .35 mg (1 .2 x 10^"6 moles) of LuTPPc in 10 ml DMF/THF(4:1 ) was stirred for 24 h to produce a homogeneous solution. The solvent mixture was employed to allow both PS and LuTPPc to dissolve. The solution was then placed in a cylindrical glass tube fitted with a capillary needle. A potential difference of 20 kV (-5kV and 15kV) was applied to a cathode and an anode respectively to provide charge for the spinning process. The distance between the cathode (static fiber collection point) and anode (tip of capillary needle) was 15 cm and a pump rate was 0.01 mL/h. The flow rate was however increased to 0.02 mL/h in the case of the polystyrene/phthalocyanine composite material to avoid sputtering of the solution. Characterization of LuTPPc-Polystyrene fiber

Elemental analyses - Consistency of composition

Since LuTPPc has a relatively smaller size and is much more electrically conducting than polystyrene, a separation of the composite LuTPPc-Polystyrene material during the electro-spinning process similar to what has been observed by the inventors in gel electrophoresis is possible. This would result in fibers at different stages of the electro-spinning process having different compositions, with fiber at the first stage of electro-spinning having higher phthalocyanine content than those at later stages. In order to assess the uniformity in composition of the fiber during the different stages of its formation from the mixture of polystyrene and phthalocyanine, three samples of the fiber were collected at different stages of the electro-spinning process and analysed using elemental analyses. The elemental compositions are given in Table 1 .

Table 1 : Elemental composition of samples of

polystyrene/phthalocyanine composite fiber

The nitrogen content in the mixture was overshadowed by the high carbon and hydrogen content in the polystyrene and the phthalocyanine. However, the fibers have generally the same composition and are expected to show reproducible behaviour in any application. Thus elemental analyses results confirm that there was no separation of the LuTPPc and fiber during synthesis. One important deduction from the elemental analysis is the fact that the molecules of the phthalocyanine and the polystyrene have interacted strongly throughout the synthesis. Although not wishing to be bound by theory, the inventors believe that the interaction is probably through the ττ- π electrons of the two aromatic systems. Scanning electron microscopic (SEM) images

Cylindrically shaped fibers of polystyrene (PS) alone and the polystyrene/LuTPPc composite material (LuTPPc/PS) were formed. Characteristic features of the fibers were examined using scanning electron microscopy (SEM) to assess fiber morphology and diameters. Both LuTPPc/PS and PS fibers did not form appreciable amount of beads under the above experimental conditions and consist of mostly long unbranched strands of cylindrical fibers as shown in Fig. 3. The fiber diameters of the polystyrene alone ranged from 1800-3200 nm (1 .8-3.2 μιτι). These fiber diameters were thinner than those obtained for polystyrene (3.52-4.09 μιτι) by Pai C.-L. et al (Pai C-L, Boyce M. C, Rutledge G. C, Biomaterials, 2009, 42(6), 2122- 21 14), using DMF alone as solvent, instead of the THF:DMF solvent mixture used here. This is expected because higher concentration of the polymer in the solvent (30%) was used by Pai ei al, while polymer concentration of 25% was used in the present case. This observation is consistent with theory which predicts that the fiber diameter depends allometrically on solution viscosity.

In the case of LuTPPc functional ized polystyrene fiber, the diameters ranged from 3100-6800 nm (3.1 -6.8 μιτι) and are thus larger than those of polystyrene alone. Again although not wishing to be bound by theory, this may be attributed to the increased flow rate during the electro-spinning process of the composite as well as the increased concentration of the composite material compared to fibers of the polystyrene alone. The range of fiber diameters obtained for the composite fiber suggests that a larger surface area is exposed, which is advantageous for application of the composite fiber material in catalysis.

Raman spectra

This was done to ascertain any electronic interactions between the polymer and the phthalocyanine. Interpretation of these spectra has been aided by the theoretical spectrum of the pure polystyrene polymer. Density functional theory (DFT) calculations were carried out on a subunit of polystyrene polymer. Figure 4 shows the theoretical (a) and experimental (b) Raman spectra of the polystyrene.

As indicated in Fig. 4, there is a good correlation between the theoretically obtained spectra and the experimental one. The peaks between 2500 and 3000 cm^"1 are attributed to stretches due to the aromatic ring of the polystyrene, and are consistent with the theoretical calculations. To determine any electronic interaction between the polystyrene and the phthalocyanine, the Raman spectrum of the composite fiber was taken and compared with that of the polymer alone as depicted in Fig. 5. The observed changes in the peak positions of the composite (Fig. 5(b) graph), compared to polystyrene alone (Fig. 5(a) graph), suggest that the phthalocyanine is interacting very strongly with the polystyrene aromatic system, as evidenced by the changes in the polystyrene spectrum in the 2500 to 3000 cm^"1 region. This might be due to the strong ττ-π interactions of the phthalocyanine and polystyrene aromatic systems.

UV-Visible absorbance spectra

Figure 6 shows the electronic spectrum of the LuTPPc in THF together with the solid state electronic spectra of phthalocyanine, polystyrene fiber and that of polystyrene and phthalocyanine composite fiber. The spectra of the solids were recorded from the fiber (or LuTPPc modified fiber) or LuTPPc alone adsorbed on a glass plate.

As shown in Fig. 6, the electronic spectrum of LuTPPc shows a Q-band absorption maximum of 690 nm in solution (Fig. 6(a) graph). This is attributed to the ττ- TT* transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) of the Pc ring. The solid state electronic spectrum of the phthalocyanine alone (Fig. 6(b) graph) shows band broadening. When two or more Pc macrocycles are close to each other, whether they are chemically bonded or not, the transition diplole moments can couple (exciton coupling) to cause drastic spectral changes particularly in the Q-band region. Depending on the conformation between the chromophores, shifts of the Q-band (generally to the blue, while to the red in less common cases), splitting and/or broadening can be observed. The red-shifts of the Q-band have mostly been observed in the solid-state phase where the chromophores are aligned in a slipped-cofacial manner (the degeneracy of Q band is lifted in this arrangement) and can be rationalized in terms of exciton coupling. The differences in the solid state and solution spectra for phthalocyanines have been reported in the open literature. Aggregation in the solid state however does not favour generation of singlet oxygen. In the Fig. 6(c) graph, the non-functionalized polystyrene fibers show no obvious absorption band. However for the functionalized fiber (Fig. 6(d) graph), the Q- band absorption is relatively broader and more red-shifted (6 nm) compared to that of the phthalocyanine in THF solution, but less red shifted compared to solid LuTPPc ( Fig. 6(b) graph). It could also be deduced from the Fig. 6(d) graph that the phthalocyanine is uniformly dispersed within the fiber matrix, since there is less broadening (hence less aggregation) compared to solid LuTPPc. These UV-visible spectral features of the functionalized fiber jointly suggest that the phthalocyanine functionalized fiber can be used in applications where aggregation would have been a disadvantage such as in sensing and photocatalysis.

For further evidence of a uniform dispersal of the LuTPPc on the fiber matrix and for possible quantitative applications of the functionalized polystyrene fiber, the electronic spectra of various packing of the fiber were obtained as in Fig. 7. As shown, there is considerable quantitative correlation between the concentration of phthalocyanine on the fiber, since doubling the thickness of the fiber on the glass substrate, almost doubles the LuTPPc absorbance. This observation also suggests that the composite fiber is uniform in composition. Leaching has been reported to be a major problem associated with the application of functionalized polymer fibers in general in various solvent media. An attempt has thus been made to find a suitable solvent in which the functionalized polystyrene could be applied with minimal or no leaching of the phthalocyanine from the fiber. It was observed that in purely hydrocarbon based solvents, such as hexane, there was no leaching or minimal leaching of the Pc. Similarly there was no leakage of the Pc in water. Fig. 8 shows that even after 12 h in hexane and 18 h in water, there was no sign of the phthalocyanine in solution and thus hexane and water could serve as a solvent for a heterogeneous catalytic application of the functionalized fiber. This suggests that the functionalized fiber can be applied in real-life environment especially in aqueous media. However, in some organic solvents (e.g. THF as shown in the Fig. 8(d) graph), there is considerable leaching or even a complete dissolution of the fiber to liberate the phthalocyanine. Singlet oxygen detection

A chemical method involving the decay of 1 ,3-diphenylisobenzofuran (DPBF) in organic media or anthracene-9,10-bis-methylmalonate (ADMA) in water, both of which are singlet oxygen (¹O₂) quenchers, were employed for functionalized fiber and an optical method involving time resolved phosphorescence decay of singlet oxygen at 1270 nm were employed for both LuTPPc in THF and the modified functionalized fiber. For the determination of singlet oxygen generating capability of the LuTPPc on the fiber, the modified functionalized fiber was immersed in a solution of DPBF in hexane or ADMA in water contained in a UV-Vis spectrophotometer quartz cell of 1 cm pathlength.

The chemical method involved irradiating the sample containing the fiber (in air without bubbling oxygen through the sample solution) using a General Electric Quartz lamp (300W), 600 nm glass (Schott) and water filters, to filter off ultra-violet and far infrared radiations respectively. An interference filter (670 nm with band of 40 nm) was placed in the light path just before a cell containing the sample. The sample was irradiated at 15 min intervals and the degradation of DPBF monitored by a UV-Visible spectrophotometer. The dynamic phosphorescence decay of singlet oxygen ¹O₂, was demonstrated using time resolved phosphorescence of ¹O₂ at 1270 nm. The determination was made in the absence and in the presence of sodium azide (NaN₃), a physical quencher of singlet oxygen. An ultra sensitive germanium detector (Edinburgh Instruments, El-P) combined with a 1000 nm long pass filter (Omega, RD 1000 CP) and a 1270 nm band-pass filter (Omega, C1275, BP50) was used to detect ¹O₂ phosphorescence under the excitation using a Quanta-Ray Nd:YAG laser providing 400 mJ, 9 ns pulses of laser light at 10 Hz pumping a Lambda-Physik FL3002 dye (Pyridin 1 dye in methanol), with a pulse period of 7 ns and a repetition rate of 10 Hz. The near- infrared phosphorescence of the sample was focused onto the germanium detector by a lens (Edmund, NT 48-157) with a detection direction perpendicular to the excitation laser beam. The detected signals were averaged with a digital oscilloscope (Tektronics, TDS 360) to show the dynamic decay of ¹O₂. The data obtained was analysed using Microsoft Excel and origin Pro 8 software. The dynamic course of ¹O2 concentration [¹O2] was followed using Equation 1 as theoretically described in literature.

I(t) = B ^T° \_e ^tl * - e ^t,TD ] (1 )

T— _D

where, l(t) is the phosphorescence intensity of ¹O2 at time t, TD is the lifetime of ¹O2 phosphorescence decay, ττ is the triplet state lifetime of standard or sample and B is a coefficient involved in sensitizer concentration and ¹O2 quantum yield.

¹O2 quantum yields, ΦΔ of LuTPPc in THF, was then determined using

Equation 2:

B - A

Φ _Λ = (2)

B ■ A where Φ_Δ is the singlet oxygen quantum yield for a standard ZnPc ( Φ_Α = 0.53 in THF). B and B^Sfd refer to coefficient for the sample and standard respectively and A and A^Sfd to the absorbances of the sample and standard respectively at the excitation wavelength.

The ability of the functionalized fiber to generate singlet oxygen was thus demonstrated by observing the decay of 1 ,3-diphenylisobenzofuran (DPBF), or anthracene-9,10-bis-methylmalonate (ADMA), both singlet oxygen quenchers, using UV-Visible spectroscopy. Fig. 9 shows spectral changes of the DPBF and Fig. 10 shows spectral changes of the ADMA, on exposure to light in the presence of the functionalized fiber. As seen in Fig. 9 and Fig. 10, the DPBF and ADMA degraded indicating that oxygen was generated. It is also apparent that the Pc could be regenerated after use as shown in the Fig. 9(b) graph, where the LuTPPc was re- dissolved from the fiber and the spectra recorded in THF. When re-dissolving the LuTPPc from the modified fiber (which was used for DPBF studies), the fact that the peak due to DPBF was not evident confirms that the DPBF was not adsorbed onto the fiber. Singlet oxygen decay profile for LuTPPc observed in THF is shown in Fig.

2. There was evidence of its ability to generate singlet oxygen, with a singlet oxygen quantum yield (Φ_Δ = 0.71 ), a value much higher than that of the ZnPc standard used for comparison purposes. For real applications, singlet oxygen was determined in water and found to be 0.22 using ADMA as a chemical quencher. Figure 1 1 shows the decay curve for singlet oxygen phosphorescence as further evidence of the ability of the immobilized Pc to generate ¹ O2 with a lifetime of 18 s. The determination was done by exciting at the Q band of the LuTPPc (696 nm) on the fiber. There is close resemblance of this decay profile and the one obtained in THF solution (Fig. 2). This suggests that the properties of the Pc are maintained within the fiber matrix, especially the ability to generate singlet oxygen.

Studies of the photocatalysed degradation of 4-chlorophenol (4-CP) using the LuTPPc/polystyrene fiber were carried out at a pH of 1 1 . The electronic absorption spectral changes showed that the 4-chlorophenol peaks around 243 nm and 297 nm decrease in intensity during irradiation of the sample in the presence of the functionalised fiber (Fig. 13), accompanied by the emergence of two new absorbance bands, observed at 227 nm and 280 nm, which increase in intensity with time (Fig 13 insert). The absorption peak at 227 nm could be assigned to benzoquinone while that at 280 nm to hydroquinone.

The reaction products were identified using chromatography. This was done by spiking sample solutions with standard solutions of the products. 4- Chlorophenol degraded to benzoquinone and hydroquinone when using the LuTPPc/polystyrene fiber (Fig. 14).

The type of mechanism involved was investigated by conducting the photolysis in an oxygen saturated solution and in a solution containing sodium azide, a singlet oxygen quencher. The production of p-benzoquinone at 227 nm was quite enhanced in the oxygen saturated solution, while drastically reduced in the azide saturated solution, thus supporting the Type II mechanism proposed below in Scheme 1 for its formation. he * TSC *

LuTPPc »■ ^!LuTPPc , ³LuTPPc (4)

³0₂ + ³LuTPPc^* - LuTPPc + ^τ0₂ (5) τ0₂ + Subs ». Products (6)

Scheme 1: Type II mechanism

Production of the hydroquinone, on the other hand under the above conditions was not affected at all, thus also suggesting the Type II mechanism. Also when a free radical scavenger, tert-butyl alcohol, was used, hydroquinone was not produced, suggesting the Type I mechanism proposed below in Scheme 2.

³LuTPPc* + ³O₂ - LuTPPc-⁺ + (7)

LuTPPc ^"+ + Subs ^ LuTPPc + Subs"^"1" (⁸)

|_| +

³°2 HO₂- (9)

H0₂- + Subs ». H₂0₂ + Subs" (10)

Subs^{' "1"} , Subs^", HO₂ ^" , H₂0₂ ^Oxidation Products (11)

Scheme 2: Type I mechanism. Subs = 4-CP

Thus the functionalised fiber is capable of degrading 4-chlorophenol via both the proposed Type II and Type I mechanisms, which starts with the photogeneration of singlet oxygen and a radical, respectively, by the immobilised phthalocyanine.

The process of the invention, as illustrated and exemplified, advantageously allows a tetraphenoxyphthalocyanine complex of lutetium and polystyrene to be electro-spun into fibers of fine diameters. Raman and UV-Visible spectra of the fiber suggest interactions of the aromatic systems of the two. The properties of the Pc are also maintained in the fiber core, especially its ability to generate singlet oxygen. The material or fiber thus formed can be applied reproducibly for any application such as heterogeneous catalysis involving the phthalocyanine, as photocatalysts and quantitatively in aqueous solvents or media and some hydrocarbon solvents or media without leaching of the phthalocyanine. The LuTPPc/polystyrene fiber is capable of degrading 4-chlorophenol to less chlorinated derivatives. Hence, the invention as illustrated and exemplified shows that the LuTPPc/polystyrene fiber may be useful as a pre-treatment technique for reducing toxicity of toxic/hazardous wastewaters.

Claims

CLAIMS:

1 . A composite metallophthalocyanine polymer material comprising lutetium(lll) phthalocyanine supported on a polymer support.

2. The material of claim 1 , which is a particulate material.

3. The material of claim 2, in which the composite metallophthalocyanine polymer material is in the form of fibers.

4. The material of any of claims 1 to 3 inclusive, in which the composite metallophthalocyanine polymer material comprises lutetium(lll) phthalocyanine and polymer in a molar ratio of from about 1 :0.001 to about 1 :100.

5. The material of any of claims 1 to 4 inclusive, in which the polymer is selected from the group consisting of polyethylene glycol, polyesters, polyacrylates, acrylate copolymers, polystyrene, polyvinylpolypyrrolidone, polyvinylamine, polyethylene oxide, N-acryloyl- -alanine(aminoethylene)amide, N-acryloylpyrrolidone, N,N-bis(methacyloyl)-1 ,2-diaminoethane, polysulfone, and mixtures or copolymers of two or more of these.

6. The material of any of claims 1 to 5 inclusive, in which the phthalocyanine is tetraphenoxy-phthalocyanine so that the composite phthalocyanine polymer material comprises lutetium(lll) phthalocyanine (tetrasubstituted with phenoxy groups at non- peripheral positions) supported on a polymer support.

7. The material of any of claims 1 to 6 inclusive, which has a singlet oxygen quantum yield of greater than 0.53 in tetrahydrofuran and at least 0.22 in water.

8. The use of a composite metallophthalocyanine polymer material comprising lutetium(lll) phthalocyanine supported on a polymer support for the phototransformation of 4-chlorophenol.

9. A process for synthesising a composite metallophthalocyanine polymer material, the process including

10. The process as claimed in claim 9, in which the polymer is selected from the group consisting of polyethylene glycol, polyesters, polyacrylates, acrylate copolymers, polystyrene, polyvinylpolypyrrolidone, polyvinylamine, polyethylene oxide, N-acryloyl- -alanine(aminoethylene)amide, N-acryloylpyrrolidone, N,N-bis(methacyloyl)- 1 ,2-diaminoethane, polysulfone, and mixtures or copolymers of two or more of these.

1 1 . The process as claimed in claim 9 or claim 10, in which the fibres are cylindrical with a diameter of less than 10 μιτι, preferably less than 7 μιτι.

12. The process as claimed in any of claims 9 to 1 1 inclusive, in which the lutetium(lll) phthalocyanine and the polymer are admixed in a molar ratio of from about 1 :0.001 to about 1 :100.

13. The process as claimed in any of claims 9 to 12 inclusive, in which the solvent is selected from the group consisting of methanol, ethanol, dichloromethane (DCM), tetrahydrofuran (THF), toluene, chloroform dimethylsulfoxide (DMSO), dimethyl formamide (DMF), pyridine, acetonitrile, chloronaphthalene, pentanol, benzonitrile 1 ,4- dioxane, n-butylamine, triethylamine, benzene, o-xylene, chlorobenzene and mixtures of two or more thereof.

14. The process as claimed in any of claims 9 to 13 inclusive, which includes synthesising the lutetium(lll) phthalocyanine from lutetium(lll) acetate and a phthalonitrile.