Synthesis, characterization and crystal structure of bis{5-(diethylamino)-2-[(methylimino)methyl]phenolato}-nickel(II)

Abstract

A Schiff base nickel(II) complex, bis{5-(Diethylamino)-2-[(methylimino)methyl]phenolato}-nickel(II), was synthesized using 4-(Diethylamino)salicylaldehyde, methylamine, and nickel chloride hexahydrate. Understanding the crystal structure and its characterization is essential for potential applications in catalysis, materials science, and coordination chemistry. The crystal was analyzed by single-crystal X-ray diffraction and was found to crystallize in a monoclinic crystal system with a P21/c space group. It was characterized using UV–vis, IR, 1H and 13C NMR, mass spectrometry, and thermogravimetry (TG). The azomethine (–C=N) group was confirmed by a peak at 1591 cm−1 from IR. The monomeric mass, m/z = 468 g mol−1, was obtained from mass spectrometry. The complex was thermally stable up to 312 °C and melted between 215 and 219 °C. It produced a carbonaceous nickel(II) oxide (NiO/C) residue at 500 °C. The Hirshfeld surface study showed that the H…H interaction (66.68%) contributes the most to crystal packing, followed by C…H (21.7%), O…H (4.8%), and N…H (4.0%). The DFT study yielded a value of 3.79 eV for the HOMO–LUMO band gap (ΔE).