Spectral and thermal investigation of novel biologically active (N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl-amino)-2-oxo-cetimidic acid) ligand and its metal complexes

Abstract

Novel Schiff base ligand (N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl-amino)-2-oxo-cetimidic acid) was synthesized from 4-aminoantipyrine and diethyloxalate, but with small yield. The stable chelates with different metal ions (Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Fe(III) and Ru(III)) were formed by template reaction. Their structures were confirmed via elemental microanalyses, spectral techniques and thermal studies. The molar conductance values indicated that the complexes derived from Mn(II), Ni(II), Zn(II), Pd(II) chloride and Cu(II) bromide have nonelectrolytic nature, whereas, those derived from Co(II), Cu(II), Fe(III) and Ru(III) chloride have electrolytic nature. IR spectra indicated that the ligand acted as a neutral ONNO tetradentate moiety in all complexes except in Pd(II) complex, it behaved as a neutral bidentate moiety. All complexes exhibited octahedral geometry, while Pd(II) complex possess square planar structure. The thermal decomposition process of all metal complexes ended with formation of metal except in case of Fe(III) and Ru(III) complexes, it ended with metal oxides. X-ray diffraction supported the nanometer size of Fe2O3 oxide that resulted from thermal decomposition of Fe(III) complex. The ESR spectra for Cu(II) complexes demonstrated this trend, g‖>g⊥>2.0023 revealing the axially symmetric system with the unpaired electron residing in (dx2-y2) orbital. The biological measurements showed that the tested metal complexes have antimicrobial and cytotoxic activities in comparison to the free ligand.