Synthesis, spectral, thermal and antibacterial studies of copper(II) complexes of a Schiff base derived from 2,3-dimethyl-1-phenyl-4-aminopyrazol-5-one

Abstract

The Schiff base 2,3-dimethyl-1-phenyl-4-(2,5-dihydroxyacetophenone)-5-pyrazolone (DHAAP) was prepared by reacting 4-aminoantipyrine with 2,5-dihydroxy acetophenone and a series of metal complexes with this ligand were synthesized by reaction with copper(II) having the compositions [Cu(DHAAP) 2 (Cl) 2 ] [Cu(DHAAP) 2 (NO 3 ) 2 ], [Cu(DHAAP) 2 (ClO 4 ) 2 ], [Cu(DHAAP) 2 (CH 3 COO) 2 ] and [Cu(DHAAP) 2 (NCS)(Cl)] (where DHAAP = dihydroxy-acetophenoneazoantipyrine). The complexes were characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility data, UV-Visible, IR and ESR spectral studies. The thermal behaviour of the complex, [Cu(DHAAP) 2 (NO 3 ) 2 ] was investigated by thermogravimetric technique. X-Ray diffraction studies of the complex, [Cu(DHAAP) 2 (Cl) 2 ] indicated orthorhombic crystal lattice with a = 13.6118 A, b = 5.2759 A and c = 3.2758 A. The ligand exhibits a neutral bidentate behaviour in all the complexes, coordinating to the metal ion through carbonyl oxygen and azomethine nitrogen. The X-band ESR spectrum of the complex, [Cu(DHAAP) 2 (CH 3 COO) 2 ] shows an axial ligand field symmetry. The ligand and the complex [Cu(DHAAP) 2 (NCS)(Cl)] were screened for their antibacterial activities against gram positive and gram negative bacteria.