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

Under the weak base conditions, diruthenium-(III) tetrakis-N,N'-dimethylbenzamidinate (DMBA) nitrate (Ru-2(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-Ru-2(DMBA)(4)(C C-TTF1)(2) ( 1) and trans-Ru-2(DMBA)(4)(C C-TTF2)(2) (2), respectively. The trans orientation and the planar nature of the ethynyltetrathiafulvalene ligands around the Ru-2(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-Ru-2(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.