Thermal Analysis and Kinetic Studies of Oximino Metal Complexes: Insights into Stability and Decomposition Mechanisms

Abstract

This study explores the thermal characterization of metal chelates, a field that remains relatively under-investigated despite its potential applications across various scientific and industrial domains. A brief overview of previous research is presented, highlighting the limited but growing body of work in this area. The utility of the Freeman–Carroll equation for evaluating isothermal stability systems is discussed, with reference to a previously published study by our research group (2022) on substituted thiourea, which examined similar kinetic parameters as those evaluated in the present work. The preparation and characterization of oximino ligands and their metal complexes with copper(II) acetate, copper (II) nitrate, uranyl (II) nitrate, manganese (II) chloride, and lead (II) acetate have been carried out in the solid state. A total of twenty complexes—eight copper (II), four uranyl, four manganese (II), and four lead (II)—were subjected to thermal analysis using thermogravimetric (TG), differential thermal (DTA), and differential thermogravimetric (DTG) techniques. Based on the observed decomposition behaviour, the complexes were classified into two categories: those undergoing simultaneous reactions and those undergoing successive reactions. Kinetic parameters such as order of reaction, activation energy, enthalpy changes, and thermal stability were calculated using the Freeman–Carroll method and the peak-and-area approach. The decomposition patterns obtained from thermal analysis not only confirm the formation of the metal complexes but also provide insight into their stability and structural characteristics.