Synthesis, structure characterization and biological studies on a new aromatic hydrazone, 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-2,2-dimethyl-1,3-dioxane-4,6-dione, and its transition metal complexes

Abstract

A new aromatic hydrazone 5-(2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)hydrazono)-2,2-dimethyl-1,3-dioxane-4,6-dione has been synthesized by Japp-Klingemann reaction from diazotized 4-aminoantipyrine and Meldrum's acid. A few 3d-metal ion complexes of this hydrazone were synthesized. The compound and its complexes were characterized by UV–Visible, 1H NMR, ESR, Mass spectral, molar conductance and magnetic susceptibility measurements. The compound was found to exist in hydrazone form in solid state and solution from SXRD and 1H NMR study. The influence of pH on the molecule was studied and found that it shows azo/enol-hydrazone tautomerism in solution. This molecule act as a univalent tridentate ligand and the complexes were assigned to have a 1:2 stoichiometry (M:L). The antioxidant properties of the compounds were explored by DPPH assay and found that the ligand possesses better free radical scavenging effect than the complexes. Antimicrobial activities of these compounds were investigated and were found to be active.