Synthesis of 4-dicyclohexylaminomethyl antipyrine and its metal complexes: Spectral characterization and evaluation of thermodynamic parameters

Complexes of Fe(III), Co(II), Ni(II), and Cu(II) with 4-dicyclohexylaminomethyl antipyrine (DCHAMA, L) were prepared and characterized by elemental and chemical analyses, IR, electronic absorption, H-1 NMR and EPR spectroscopies, thermal analysis, and magnetic susceptibility measurements. The stoichiometry of the complexes was found to be MLX2, MLX3, or MLX2(H2O)(2) where X = Cl or NO3. The ligand exhibits a bidentate mode of coordination. Thermal analysis of the chloro complexes shows a three stage decomposition pattern for the Cu(11) complex and a two stage decomposition pattern for Fe(III) and Co(II) complexes to yield the respective metal oxides as the end product. Kinetic and thermodynamic parameters such as n, E-a, DeltaH#, DeltaS#, and DeltaG# were calculated using Coats-Redfern and Madhusudhanan-Krishnan-Ninan integral methods. The coordination number of the metal atom is found to influence the thermal stability of the complexes. The antimicrobial screening shows that the four-coordinated complexes are more active than the five- and six-coordinated ones and DCHAMA.