Structural and Physical Investigations of Coordination Complexes Involving Pyridylethylenedithio-Tetrathiafulvalene Ligands Decorated with Cyanoethylsulfanyl and Cyano-ethylselanyl Moieties

The two new ligands 4,5-bis(2-cyanoethylthio)-4',5'-(4-pyridylethylene-1,2-dithio)tetrathiafulvalene (L-1) and 4,5-bis(2-cyanoethylseleno)-4',5'-(4-pyridylethylene-1,2-dithio)tetrathiafulvalene (L-2) have been elaborated and used to synthesize five new coordination complexes of transition-metal ions, namely, [Mn-2(hfac)(4)(L-1)(2)](2) (1; hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate), [Cd(hfac)(2)(L-1)(2)].2CHCl(3) (2), [Cu(hfac)(2)(L-1)(2)] (3), [Co(hfac)(2)(L-1)(2)].2C(6)H(14) (4) and [Mn(hfac)(2)(L-2)(2)].2C(6)H(14) (5), which were characterized by single-crystal X-ray diffraction. Compounds 2-5 were identified as mononuclear complexes with different crystal packing depending on the nature of the metal centre. On the contrary, compound 1 was identified as a cyclic tetranuclear complex in which L-1 is coordinated to the Mn-II ions through two different pyridyl and nitrile functionalizations. The photophysical properties of the ligands L-1 and L-2 were studied in solution and rationalized with time-dependent density functional theory calculations.