Solid-state synthesis and characterization of Cu (II) complexes of 3,4,5-trihydroxybenzoic acid

Abstract

Copper(II) complexes of 3,4,5-trihydroxybenzoic acid, formulated as [Cu(THB)(CH₃COO)₂] (1a and 1b), prepared by the solid state mechanochemical method (1a) of grinding Cu(CH₃COO)₂.H₂O and 3,4,5-trihydroxybenzoic acid in a mortar using a pestle in the absence of a solvent, and a solvent-based method of stirring in ethanol at room temperature (1b) is herein described. Characterization of the synthesized complexes was done by the methods of FT-IR and UV-Vis spectroscopy, PXRD analysis, elemental analysis, and melting point determination. Data obtained from the analytical and spectroscopic techniques indicated that the synthesized compounds, 1a and 1b, are identical. The Cu(II) ion was observed to coordinate to the ligand via the oxygen atom of two of the hydroxyl groups of the ligand resulting in the synthesized [Cu(THB)(CH₃COO)₂] complexes having a tetrahedral geometry with the ligand binding in a bidentate manner. The solid state mechanochemical synthesis technique offers a simple, quick and environmentally friendly route towards the preparation of metal complexes at the same time giving quantitative yield compared to the solvent-based method of synthesis.