A new trans-dioxorhenium(V) complex with 4-aminopyridine: synthesis, structure, electrochemical aspects, DFT, and TD-DFT calculations

摘要

The reaction of 1 :4.4 M proportion of ez5-[ReO_2I(PPh_3)_2] and 4-aminopyridine (ampy) in acetone-water gives trans-[ReO_2(ampy)_4]I?2H_2O (la) in 85% yield, la has been characterized by C, H, and N microanalyses, FT-IR, UV-vis, 'H NMR spectroscopy, and molar conductivity. The X-ray crystal structure of la reveals an octahedral trans dioxorhenium(V) complex with a "N4O2" coordination for rhenium, la has an orthorhombic space group C2221 with a =17.576(4), 6=19.370(4), c= 15.730(4) A, K=5355(2) A~3, and Z=8. Geometry optimization of the trans-0,0 complex, la and its cis-O,O analog, lb performed at the level of density functional theory reveal that la is more stable than lb by 25 kcal M ' in the gas phase. The electronic spectrum of la was also analyzed at the level of time-dependent density functional theory. Excitation of 1 a in methanol at 450 nm leads to a fluorescent emission at 505 nm with a quantum yield (φ) of 0.04. Electrochemical studies of la in acetonitrile show a quasi-reversible Re(V) to Re(VI) oxidation at 0.618 V versus Ag/AgCI. This redox potential matches with the calculated redox potential of 0.621 V versus Ag/AgCI.