Chromotropism behavior of dinuclear copper(II) complexes containing chelating ligands derived from pyridine

Two dinuclear copper(II) complexes [LCu(-Cl)Cl]2(DMF) (1) and [LCu(-Br)Br]2 (2), with bidentate ligand N-(pyridin-2-ylmethyl)cyclohexanamine, L, were synthesized and characterized by physicochemical and spectral (IR, UV–Vis) data. The crystal structural analysis of 1 shows that both copper(II) ions are in a distorted square pyramidal N2Cl3 environment with the apical position of the copper(II) being occupied by the bridging chloride anion, equatorial to the other copper, forming a dimeric copper(II) complex. The chromotropic properties of both complexes including solvato-, thermochromism were investigated in detail. The complexes show reversible thermochromism in solution but irreversible in solid state. It was found that the solvatochromism phenomenon is due to structural change followed by solvation of the vacant sites of the complexes.

Keywords:

Dinuclear copper(II) , Bis(-chloro)-bridge , Chromotropism , Pyridine derivative , Crystal structure