Diruthenium(III,III) Ethynyl-phenyleneimine Molecular Wires: Preparation via On-Complex Schiff Base Condensation

The diruthenium compound trans-Ru2(DMBA)4(CC–C6H4-4-CHO)2 (1; DMBA is N,N′-dimethylbenzamidinate) was prepared from the reaction between Ru2(DMBA)4(NO3)2 and HCC–C6H4-4-CHO under the weak base conditions. The aldehyde groups of 1 undergo a condensation reaction with NH2C6H4-4-Y (Y = H and NH2) to afford new compounds trans-Ru2(DMBA)4(CC–C6H4-4-CHN–C6H4-4′-Y)2 (Y = H (2) and NH2 (3)). A related compound, Ru2(DMBA)4(CC–C6H4-4-NC­(Me)­Fc)2 (4), was also prepared from the reaction between Ru2(DMBA)4(NO3)2 and HCC–C6H4–NC­(Me)­Fc. X-ray structural studies of compounds 1 and 2 revealed significant deviation from an idealized D4h geometry in the coordination sphere of the Ru2 core. Voltammetric measurements revealed four one electron redox processes for compounds 1–3: the Ru2 centered oxidation and reduction, and a pair of reductions of the imine or aldehyde groups. Compound 4 displays an additional oxidation attributed to the Fc groups. DFT calculations were performed on model compounds to gain a more thorough understanding of the interaction of the organic functional groups across the diruthenium bridge.