The complexes 1–8 have been characterized by elemental analyses, ESI-MS, IR, UV–Vis, EPR and electrochemical (CV and DPV) studies.
Electronic absorption spectra of 1–8 clearly suggested that position of the absorption bands depend on the nuclearity and coordination geometry about the copper(II) centres.
Structures of 1, 2, 3 and 7 have been determined by X-ray single crystal anal-yses.
The spectral and structural studies revealed that copper(II) in 1 and 2 adopted square pyramidal geometry, whereas in 7 a square planar geometry.
On the other hand in trinuclear complex 3 one cop-per(II) adopted square planar, while other two square pyramidal geometry.
In their cyclic voltammo-grams, 1–6 exhibited an irreversible oxidation and two reduction waves whereas 7 and 8 displayed one oxidation and reduction wave.
Variable temperature magnetic susceptibility measurements sug-gested paramagnetic nature of the complexes 1–3.
The X-ray photoelectron spectroscopic (XPS) studies indicated that copper(II) centres in complex 3 are present in two different coordination environments.
Room temperature EPR studies on 1–8 (g|| > g > 2.003) suggested a typical d9 copper(II) with unpaired electron lying in a dx2 y2 orbital.