Reversible Thermochromism and Halochromism of a Homoleptic Copper (II) Complex Containing Aminoethylethanolamine Ligand, and DFT Study

Two copper(II) complexes of general formula [CuL2]X2 where L= aminoethylethanolamine and X= ClO4- and Cl- were prepared with a relatively high yield. These complexes were characterized by elemental microanalysis, UV-Vis, and IR spectroscopy techniques, thermal analysis, and molar conductance measurements. The proposed structure of the complex was geometrically optimized, and its structural parameters were calculated based on B3LYP/LanL2DZ level using Density Functional Theory (DFT) that is implemented in the Gaussian09 program and the data were correlated with the current experimental data. The complexes demonstrated reversible halochromism with distinctive color change over the pH range of 0.66 to 13.00 attributed to protonation and deprotonation of the coordinated ligand. The complexes exhibited reversible thermochromic behavior in DMF over a temperature range of room to 140 °C. The complexes showed dark blue at room temperature and yellow-brown at 140 °C, due to the dissociation of the coordinated ethanolic groups of the ligand at the axial position and substitution by solvent molecules at the elevated temperature.