Complexes of a model trimeric acylphloroglucinol with a Cu2+ ion: a DFT study

Abstract

Abstract Acylphloroglucinols (ACPLs, derivatives of phloroglucinol having at least one R−C=O group) are gaining increasing attention for their pharmacological potentialities. The presence of phenol OHs in their molecules confers antioxidant properties to ACPLs. Some ACPLs have already been identified as promising antioxidants for pharmaceutical purposes. Antioxidant properties may also be useful for a variety of other applications, including industrial ones. A viable option to verify and compare the antioxidant efficacy of compounds considers their ability to form complexes with a metal ion and reduce its charge. The present work considers a model structure maintaining all the identifying features of trimeric ACPLs (ACPLs containing three phloroglucinol moieties linked by methylene bridges) and studies the complexes of representative conformers with a Cu2+ ion, with the ion binding in turn to each of the available binding sites. Two series of calculations are performed at the DFT/B3LYP/6-31+G(d,p) level, without and with the Grimme’s D3 dispersion correction: the former series enables meaningful comparisons with previous calculations of complexes of other ACPLs, and the latter series is meant to evaluate the effect of taking dispersion into account on the estimation of the complexes’ properties. The results show that the Cu2+ ion is reduced to Cu+ ion. The molecule–ion interaction energy and the charge and spin density on the ion are comparable with those of complexes of known antioxidant ACPLs.