On the structure of copper(II) coordination compounds with L-histidine

Abstract

Quantum chemical calculations are performed for the spatial and electron structure of complex compounds of L-histidine and its ionized forms with copper(II) for a variety of compositions within the density functional theory (DFT) using the B3LYP functional and 6-311G(d) basis. The solvent (water) is considered within the PCM approximation. EPR spectroscopy is used to study the equilibrium in the copper(II)–L-histidine system in an aqueous solution at рН 2–11. A comparison between the theoretical calculations and the EPR spectra suggests the following geometry for the coordination environment of the copper(II) ion in the complex compounds: CuHLL–square-planar coordination; CuL₂, CuHLL′, and CuLL′–distorted square pyramid; and CuL₂′–octahedral environment.