Thermal Decomposition Kinetics of Fe(III) Complexes of Chalcone Schiff Bases

ABSTRACT: In present study three chalcones 1-(2-hydroxy-4-methylphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one [L1], – 1-(2-hydroxy-4-methylphenyl)-3-(p-tolyl)prop-2-en-1-one [L2] and 3-(4-chlorophenyl)-1-(2-hydroxy-4-methylphenyl)prop-2-en-1-one [L3] were synthesized by condensing 1-(2-hydroxy-4-methylphenyl)ethan-1-one with 4-hydroxybenzaldehyde, 4-methylbenzaldehyde and 4- chlorobenzaldehyde. The synthesized chalcones were characterized by IR, NMR and Mass spectral studies. With this chalcones Fe(III) metal complexes were prepared and also characterized by different spectroscopic techniques. The thermal decomposition study of a series of Fe(III) complexes of chalcone Schiff bases was monitored by non-isothermal analysis in atmosphere. The thermal degradation takes place in three steps for each of the complexes. The decomposition steps were analyzed and the kinetic parameters: order of the decomposition reaction (n), activation energy(Ea)and frequency factor (Z) of the non-isothermal decomposition steps were computed using Freemann-Caroll methods. Thermodynamic parameters: entropy (S) and Gibbs free energy (F) of activation, were calculated using a standard relations and discussed. On the basis of half decomposition temperature, the thermal stability of the compound was found to be Fe-L3> Fe-L2 > Fe-L1. The activation energies of the thermal degradation steps lie in the range 30.73 – 40.57 kJmol-1.