Three copper (II) complexes of type [Cu(L)2(NCX)]ClO4, 1–3, (L = N,N-dimethyl,N0-benzyl-1,2-diaminoethane and X = O, S and Se) were synthesized and characterized on the basis of microanalytical, spectroscopic and molar conductance. An X-ray diffraction study of [Cu(L)2(NCO)]ClO4 (1) reveals that the copper (II) center located in a distorted square pyramidal environment through coordination of four amine N atoms and a N atom of the terminal NCO. Density functional theory (DFT) calculations were performed to understand the linkage isomerism of NCX ligand from a theoretical point of view, to study the electronic structure of the complexes and the relative stabilities of the Cu–NCX/Cu–XCN isomers. DFT computational results buttressed the experimental observations indicating that the Cu–NCX isomer is more stable than Cu–XCN linkage isomer. Complexes 1 and 2 exhibit solvatochromism as evidenced from visible study in different solvents.
