Solvatochromic, Halochromic and Thermochromic Effects of Copper(II) Complexes Containing N-tert-butyl 2-Picolylamine, and Halide Ion; a Computational Study

Abstract

The dihalido N-tert-butyl 2-picolylamine copper(II) complexes, [CuLX2], where X= Cl, Br were synthesized and characterized by elemental analysis, UV–Vis, FT-IR, and EPR spectra, and molar conductance measurements as well as TG and DTA. The crystal structures of the complexes were identified by single-crystal X-ray diffraction analysis, and the density functional theory (DFT) level calculations that reveal both complexes adopt distorted square-planar geometries. The complexes are thermochromic, solvatochromic, and halochromic. The chromotropism properties were investigated using visible electronic absorption spectroscopy. Their solvatochromism properties were investigated in solvents with different polarities and it was found that the observed solvatochromism originates from structural changes of the complexes in different solvents. The aqueous solutions of the complexes exhibit color changes in the pH range of 2.68 to 9.84due to protonation ad deprotonation of ligand. The compounds are also thermochromic and show reversible color changes in different temperatures in high boiling point solvents. Both compounds showed the same identity in an aqueous solution due to the substitution of the water molecules with the halide ligands. These spectroscopic changes were supported by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations.