Tricarbonyl Mono- and Dinuclear Rhenium(I) Complexes with Redox-Active Bis(pyrazole)-Tetrathiafulvalene Ligands: Syntheses, Crystal Structures, and Properties

Two new bis(3,5-dimethylpyrazole)-substituted tetrathiafulvalene ligands, 2,6(7)-bis(methylthio)-3,7(6)-bis(3-sulfany1-3,5-dimethylpyrazole)tetrathiafulvalene (L-1) and 2,3-bis(methylthio)-6,7-bis(3-sulfany1-3,5-dimethylpyrazole)-tetrathiafulvalene (L-2), have been prepared and characterized. On the basis of the two ligands, three interesting rhenium(I) tricarbonyl mono- or dinuclear complexes, ClRe(CO)(3)(cis-L-1) (1), [ClRe(CO)(3)(trans-L-1)](2) (2), and [ClRe(CO)(3)(L-2)](2) (3), have been prepared and structurally characterized. Electrochemical studies show sequential oxidation processes of the compounds to the corresponding radical cation and dication states, suggesting that redox events are essentially dependent on the structures of the rhenium(I) complexes. The results have evidenced electronic interactions between the TTF cores in complexes 1 and 2. Geometric and electronic structures as well as the spectroscopic properties for complexes 1-3 have been investigated by using DFT and TDDFT calculations.