Synthesis, structure, spectra and redox chemistry of mono- and dinuclear copper(II) complexes containing pyridyl groups

Copper(II) complexes generalized as Cu2N6 and CuN6 were prepared by using hexadentate ligands, and their spectral and electrochemical behavior was analysed. X-ray analysis of binuclear [(Cu2LCl2)-Cl-2](2+) reveals that one copper is trigonal bipyramidal and the other is square pyramidal. Electronic spectra used to determine their stereochemistry in solution indicate that dinuclear Cu2N6 has two visible bands that correspond to a typical five-coordinate copper( II) environment, whereas only one broad band was obtained for mononuclear CuN6. When NaN3 was added to the dinuclear compounds, their UV-visible spectra underwent significant changes and an isosbestic point at 650 nm was observed; however, no such feature was encountered for the mononuclear compounds.