Synthesis and characterization of gallic acid complexes with cobalt(II), nickel(II), and copper(II) ions: Spectral analysis, x-ray structures, and microscopic imaging

This study examines the synthesis, characterization, thermal stability, and microscopic analysis of gallic acid (abbreviated as GA) complexes formed with three transition metal ions: Co(II), Ni(II), and Cu(II). The researchers carried out a multi-step process, beginning with a series of chemical reactions between GA, acting as an organic ligand, and the respective metal ions. These reactions were conducted at a temperature of 65 °C and a pH of approximately 8, with a molar ratio of 2:1 between the GA ligand and the metal ion. The resulting products were referred to as the GA-Co complex, the GA-Ni complex, and the GA-Cu complex. Various physicochemical techniques were employed to thoroughly understand the structural, compositional, morphological, and thermal properties of the generated GA-Co, GA-Ni, and GA-Cu complexes, contributing to the field's knowledge. The synthesized complexes with Co(II), Ni(II), and Cu(II) ions have formulae of (NH4)2[Co(NH4HL)2(H2O)2].4H2O, (NH4)2[Ni(NH4HL)2(H2O)2].6H2O, and (NH4)2[Cu(NH4HL)2(H2O)2].5H2O, respectively. The complexation of the GA ligand with metal ions altered the microstructural features of the pristine ligand, as observed in the TEM images, indicating that the complexation significantly affected the microstructure of the synthesized materials. KEY WORDS: Gallic acid, Metal ions, Spectroscopic techniques, Thermal decomposition, TEM Bull. Chem. Soc. Ethiop. 2025, 39(7), 1335-1348. DOI: https://dx.doi.org/10.4314/bcse.v39i7.8