Polar and nonpolar iron (II) complexes of isatin hydrazone derivatives as effective catalysts in oxidation reactions and their antimicrobial and anticancer activities

Abstract

Two iron (II) complexes of various derivatives (polar with 5‐sodium sulfoante group and nonpolar with di‐tert butyl groups, HLSO3Na and HLDBu, respectively) of isatin hydrazones were synthesized within 1:2 molar ratios of Fe2+ ion to the isatin hydrazone ligand giving Fe (LSO3Na)2 and Fe (LDBu)2, respectively. The polar and nonpolar isatin hydrazone derivatives behaved as O,N,O‐tridentate pincer chelating agents with Fe2+ ions. The variation in polarity of the two Fe2+‐complexes controlled their catalytic action in the oxidation of alcohols using tBuOOH (tert‐butyl hydroperoxide). The polar catalyst showed more enhanced catalytic behavior than that of the nonpolar one. The optimized conditions for Fe (LDBu)2 was found to be better at 70°C after 4 h with 86% of benzaldehyde than that with Fe (LSO3Na)2 (at 90°C after 2 h with 84% of benzaldehyde). Their kinetic studies were used to derive the thermodynamic parameters of Ea and ΔG# for the catalytic processes.Biologically, based on their high reactivity toward some bacterial and fungal strains and some human cancer cell lines, the calf thymus‐DNA (ctDNA) interaction of the current compounds were studied. The nonpolar Fe2+‐complex (Fe (LDBu)2) assigned more reactivity with ctDNA more than that of the polar reagent (Fe (LSO3Na)2) and also more than that of their uncoordinated ligands depending on their lipophilicity. Their reactivities toward ctDNA was established spectrophotometrically and within the changes in the DNA solution viscosity. The binding strength was evaluated with the magnitudes of the binding constant (Kb = 3.03, 3.21, 9.79, and 11.51 × 108 mol−1 dm3 for HLDBu, HLSO3Na, Fe (LDBu)2, and Fe (LSO3Na)2, respectively), which supported by the Gibbs' free energy values −3.12, −31.42, −34.18, and −34.58 kJ mol−1, respectively.