Characterization of chromium-tris (Catecholate) complex: A theoretical study

Abstract

Phenolic compounds generally have special smell and are easily soluble in water, organic solvents (alcohols, esters, chloroform, ethyl
acetate) and in alkali. Phenols produce coloured complexes with heavy metal ions, such as with chromium ion. The molecular details
underlying the cross-linking mediated by transition metal ions are largely unknown. Using HF/DFT hybrid approach B3LYP, this study
examines the structure, binding energy, spectroscopic and electronic properties of complex formed by the attachment of Cr3+ with a catechol
ligand. Our study shows that the binding of Cr3+ with the catechol ligand is not as strong as the binding of other metal ions with
catechol.The calculated FTIR spectra show strong IR intensities due to large charge polarization. The UV-Vis absorption spectrum of the
tris-catecholato-Cr3+complex shows a clear ligand-to-metal charge transfer. The calculated electronic band gap is 4.06 eV which is in the
range of transition metal ion tris-catechol complexes. Thermodynamic properties studied in this work show that the metal ion-ligand
binding energy (532.99 kcal/mol) is close to those of the hexa-aqua complexes (ranging from 540 to 553 kcal/mol).