Thermal and kinetic analysis of a new hydrazone-oxime ligand and its cadmium(II) complex: Synthesis, spectral characterization, crystallographic determination and Hirshfeld surface analysis

Abstract

A novel cadmium complex, [Cd(L)2](NO3)2(H2O)2, (hereinafter simply designated as CdIIL2) has been synthesized by reacting a hydrazone-oxime ligand, (2E,3E)-3-(2-(6-chloropyridin-2-yl)hydrazono)butan-2-one oxime (L), with cadmium nitrate tetrahydrate. The ligand L and CdIIL2 were characterized by LC/MS-MS, FT-IR, elemental analysis, NMR, molar conductivity, UV–Vis spectroscopy and thermal analysis. The structure of the CdIIL2 was also elucidated by the single-crystal X-ray diffraction technique. The X-ray powder diffraction pattern of CdIIL2 was then performed to confirm the purity of the crystalline compound. Additionally, as a result of analytical and spectroscopic data suggested that the metal in CdIIL2 exhibits a distorted octahedral geometry. Hirshfeld surface analysis (HSA) was used in conjunction with 2D fingerprint plots to evaluate intermolecular forces, involving hydrogen bonds, in the crystal lattice of CdIIL2. Thermal and kinetic studies of the synthesized compounds were performed between 30 and 1000 °C using different heating rates of 5, 10, and 15 °C/min under two different atmosphere (N2 and O2). The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) integral methods have been selected to determine the values of the reaction activation energies (Ea). According to the Ea values, FWO was selected to investigate the thermodynamic parameters, i.e., the free energy change (ΔG), entropy (ΔS) and enthalpy (ΔH) changes. The ligand and its complex exhibited better thermal stability and higher thermodynamic values in O2 atmosphere than in N2 atmosphere.