Strong Electronic Couplings between Ferrocenyl Centers Mediated by Bis-Ethynyl/Butadiynyl Diruthenium Bridges

A series of trans-(FcC2n)Ru2(Y-DMBA)4(C2mFc) with n, m = 1 and 2 and Y-DMBA as
N,N‘-dimethylbenzamidinate or N,N‘-dimethyl-(3-methoxy)benzamidinate have been synthesized and
characterized. The intramolecular Fc···Fc distances, established through single-crystal X-ray diffraction
studies, range from 11.6 to 16.6 Å. Results from both voltammetric and spectroelectrochemical studies
indicate that the (−C2n)Ru2(Y-DMBA)4(C2m−) fragments are among the most efficient mediators of
intramolecular hole transfer. Density-functional calculations offer both the insight on the ground-state
electronic properties and unambiguous assignment for the observed electronic absorptions.