Département de chimie moléculaire

A new method based on the electrochem. oxidn. of thiols was used to easily generate multilayer assemblies of coordination complexes on a Au surface. For this purpose, two complexes bearing two anchoring groups for surface attachment were prepd.: [Ru(tpySH)2]2+ (1) and [Fe(tpySH)2]2+ (2) (tpySH = 4'-(2-(p-phenoxy)ethanethiol)-2,2':6',2''-terpyridine). Cyclic voltammetry of 1 in MeCN exhibits two successive oxidn. processes. The 1st is irreversible and attributed to the oxidn. of the thiol substituents, whereas the 2nd is reversible and corresponds to the 1 e- metal-centered oxidn. In the case of 2 both processes are superimposed. Monolayers of 1 or 2 were formed on Au electrodes by spontaneous adsorption from micromolar solns. of the complexes in MeCN. SAMs (self-assembled monolayers) exhibit redox behavior similar to the complexes in soln. The high surface coverage value obtained ($\Gamma$ = 6 × 10-10 and 4 × 10-10 mol cm-2 for 1 and 2, resp.) is consistent with a vertical orientation for the complexes; thus, one thiol is bound to the Au electrode, with the 2nd unreacted thiol moiety exposed to the outer surface. Successive cyclic voltammetry induced a layer-by-layer nanostructural growth at the surface of the SAMs, and this is presumably due to the electrochem. formation of disulfide bonds, where the thiol moieties play a double role of both an anchoring group and an electroactive coupling agent. The conditions of the deposition were studied. Modified electrodes contg. both 1 and 2 alternatively can be easily prepd. following this new approach. The film proved to be stable, displaying a similar current/voltage response for {\textgreater}10 repeating cycles in oxidn. up to 0.97 V vs. Ag/AgNO3 (10-2 M). [on SciFinder(R)]