PH-Responsive switching properties of a water-soluble dinuclear Cu(II) complex containing oximato bridges chelating ligand: Synthesis, crystal structure and computational study

Abstract

This study presents a combined experimental and computational investigation on a dinuclear Cu(II) complex containing 3-[2-[(ethanol amino)ethyl]imino]-2-butanoneoxime ligand (L). The compound [CuL]2(NO3)2 was studied by IR, UV–Vis spectroscopy, thermogravimetry analysis, and molar conductance measurements. The square-pyramid geometry of the complex was confirmed by both the density functional theory level (DFT) calculation and X-ray crystallography. The complex was halochromic, and its halochromism was studied in an aqueous solution. The original green complex displayed reversible color change to blue in alkaline and colorless in acidic solutions. The pH effect on the visible absorption spectrum of the complex was studied that functions as pH-induced “off–on–off” switches triggered by the protonation and loss of the ligand L in acidic medium and deprotonation of ligand in a basic aqueous solution. Further computational analysis of the electronic structure of the complex was carried out to gain a deeper insight into the properties associated with molecular orbitals. Its electronic spectrum was analyzed, and bands were assigned through the time-dependent density functional theory level (TDDFT) calculation.