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Synthesis, characterization, and SAMs electroactivity of ruthenium complexes with sulfur containing ligands

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JOURNAL OF ORGANOMETALLIC CHEMISTRY, 692 (17): 3691-3699 (2007)
DOI: 10.1016/j.jorganchem.2007.05.024

Abstract

The vibrational and H-1 NMR data hints that the coordination of the 2,2'-dithiodipyridine (2-pySS) ligand to the Ru(CN)(5)(3-) metal center occurs through the sulfur atom instead of the nitrogen atoms which is usually observed for N-heterocyclic ligands. Electrochemical results show that this coordination mode implies an additional thermodynamic stabilization of the Ru-II over Ru-III oxidation state due to a relative stronger pi-back-bonding interaction with the empty low-lying d pi orbitals of the sulfur atom. Computational data reinforce the experimental results showing that the 2-pySS Lewis base centers are located on the sulfur atoms. Ligands containing only sulfur atoms as coordination sites (2,2'-dithiodipyridine N-oxide (2-pySSNO), 1,4-dithiane (1,4-dt), and 2,6-dithiaspiro3.3heptane (asp)) were also coordinated to the Ru(CN)(5)(3-) metal center to undoubtedly correlate the electrochemical results with the ligand coordination atom. Among the synthesized compounds, the Ru(CN)5(1,4-dt)3- and Ru(CN)5(asp)3- complexes showed to be able to form self-assembled monolayers (SAMs) on gold. These SAMs, which were characterized by SERS (surface-enhanced Raman scattering) spectroscopy, successfully assessed the heterogeneous electron transfer reaction of the cytochrome c metalloprotein in physiological medium. (c) 2007 Elsevier B.V. All rights reserved.

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