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

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.