Electrochemical fabrication and characterization of thin films of redox-active molecular wires based on extended Rh-Rh bonded chains

An original electrochemical synthesis of {[Rh-4(mu-OOCCH3)(4)(phen)(4)](2+)}(n) (1) molecular wire films from a solution of binuclear bridged Rh complexes [Rh-2(mu-OOCCH3)(2)(phen)(2)(X)(2)](Y)(2) (X = H2O, Y = BF4- (2a) and X= CH3CN, Y = BF4- (2b)) in MeCN electrolyte is reported. UV-vis spectroscopy and quartz crystal microbalance electrochemical coupled techniques have been used to demonstrate the electrosynthesis process. The resulting polymetallic compound 1 has been characterized on the basis of its physicochemical properties, which have been compared with those of a chemically synthesized sample. Furthermore, according to EPR, H-1 NMR and electrochemical behaviour, the mechanism of the oxidation of this polymetallic wire, containing mixed valent rhodium centers and alternatively acetate bridged Rh-Rh bonds, has been investigated in detail.