New Linear π-Conjugated Diruthenium Compounds Containing Axial Tetrathiafulvalene-acetylide Ligands

Abstract

Under the weak base conditions, diruthenium(III) tetrakis-N,N′-dimethylbenzamidinate (DMBA) nitrate (Ru2(DMBA)4(NO3)2) reacted with electroactive tetrathiafulvalene acetylene ligands, HC≡C–TTF1 (5-ethynyl-2-(4,5-dimethyl-1,3-dithiol-2-ylidene)benzo[d][1,3]dithiole) and HC≡C–TTF2 (2-(5-ethynylbenzo[d][1,3]dithiol-2-ylidene)benzo[d][1,3]dithiole), to afford new compounds trans-Ru2(DMBA)4(C≡C–TTF1)2 (1) and trans-Ru2(DMBA)4(C≡C–TTF2)2 (2), respectively. The trans orientation and the planar nature of the ethynyltetrathiafulvalene ligands around the Ru2(III,III) core were supported by the single-crystal X-ray diffraction study of compound 1. Both compounds 1 and 2 and their TTF ligand precursors were characterized with the spectroscopic and voltammetric techniques, which revealed a minimal electronic interaction between the two TTF moieties within the same compound. The electronic structure of trans-Ru2(DMBA)4(C≡C–TTF)2 was analyzed based on a DFT calculation of a model compound, and the resultant distribution of valence MOs is consistent with the voltammetric results.