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 [Cu₂L²Cl₂]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.