Insights into interactions of cellulose acetate and metal ions (Zn2+, Cu2+, and Ag+) in aqueous media using DFT study

Abstract

In this work, we investigate the interaction(adsorption) between cellulose acetate (CA) and three kinds of trace elements (Zn2+, Ag+, and Cu2+) via the DFT. Several parameters have been found after the structure optimization, such as molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), reactivity indexes in addition to the parameters of QTAIM analysis, and the noncovalent interaction (NCI) method with the Multiwfn program. The results of FMOs and MEPs show that the CA has a cite of interaction in the oxygen atom, and the interactions of all complexes occur spontaneously (free energies ΔG<0). Moreover, QTAIM analysis and NCI revealed that the interactions are non-covalent for CA-Ag+and CA-Cu2+ and partially covalent for CA-Zn2+with the apparition of an Hbond for CA-Zn2+and CA-Ag+ and a steric effect for CA-Cu2+. The DFT study has also shown that tetra-coordinated geometry was occurred spontaneously and assigned for Zn2+, Ag+, and Cu2+complexes and di-coordination for Ag+complexes which indicate that the CA polymer can be exploited as a carrier of these ions for pharmaceutical applications.