Ferrocene and Tetrathiafulvalene Redox Interplay across a Bis-acetylide-Ruthenium Bridge

The interplay between two different peripheral electrophores, ferrocene (Fc) and tetrathiafulvalene (TTF), across a bis-acetylide ruthenium organometallic bridge has been studied within the novel complex trans-[Ru(C CMe3TTF) (C CFc)(dppe)(2)] (3) (HC CMe3TTF = 4-ethynyl-4',5,5'-trimethyltetrathiafulvalene). A series of experimental data (electrochemistry, UV-visible spectroelectrochemistry, IR and EPR spectroscopy) and comparison with related complexes from the literature and with the properties of the Fc-C CMe3TTF species (4) have allowed the confident assignment of the electron transfer series in 3 and 4. Cyclic voltammetry experiments in dichloromethane in two supporting electrolytes ([NBu4][PF6] and [Na][B(C6H4(CF3)(2))(4)]) have evidenced the extent of the electrostatic effects on the redox potentials in 3. The results of theoretical calculations (DFT) are consistent with these redox potential assignments but suggest some electronic coupling among the three coupled electrophores, the TTF, the Pc, and the Ru(II) center in 3(center dot+) and 3(2+) and within Fc and TTF in 4(center dot+). Taken together, these data show that the organometallic bis-acetylide ruthenium bridges mediate some appreciable electronic coupling between the two different ferrocene and tetrathiafulvalene electrophores.