Synthesis and characterization of some new Cu(II) complexes of azo dyes derived from 1,2-dihydro-1,5 -dimethy1-2-pheny 1-4-amino-3H-pyrazol-3-one

Abstract

Some novel complexes of the ligands 1,2-dihydro-1,5- dimethyl-2-phenyl-4-(2-hydroxy-5-methyl phenylazo)-3H-pyrazol- 3-one (CAAPH) and 1,2-dihydro-l,5-dimethyl-2-phenyl-4- (2-hydroxy-5-chlorophenylazo)-3H-pyrazol-3-one (CPAAPH) with Cu(II) having the formulae [Cu(LH)Cl₂), [CuLH(Ac)₂]

[CuLH(NO₃)₂ ] [CuLH(SO₄)], [CuLH(ClO₄)₂ ], [CuLH(NCS)Cl] and [Cu(L H)Cl₂], [CuL’H (Ac₂)], [CuL’ - (NO₃)₂], [CuL’H (SO₄)], [CuL’H (ClO₄)₂], [CuL’H (NCS)Cl] (LH=CAAPH and L H =CPAAPH) have been synthesized and characterized by elemental analysis, IR, electronic, ESR, NMR, magnetic, conductance measurements and cyclic voltammetric studies. The ligands are found to behave in a neutral bidentate manner. All the complexes are non-electrolytes and square planar with magnetic moment ranging from 1.79 to 1.88 B.M. The X-band ESR spectra of the complexes [Cu(CAAPH)Cl₂], [Cu(CAAPH)-(Ac₂], [Cu(CAA PH)(NO₃)₂], [Cu (CAA PH)(SO₄)], [Cu(CPAAPH)(ClO₄)₂] and [Cu(CPAAPH)(NCS)Cl] are seen to be characteristic of Cu(II) in the ligand field with axial symmetry. The complexes [Cu (CAAPH)(SO₄)] and [Cu(CPAAPH)Cl₂)] are found to be orthorhombic with the unit cell dimensions such as <i>a=</i>5.8564<i> </i>, Å, b=9.4817<i> </i>Å and <i>c=</i>12.8383<i> </i>Å; and <i>a=</i>5.3029<i> </i>Å, <i>b=</i>10.2028<i> </i>Å and <i>c</i>=11.6127 Å, respectively. The cyclic voltammograms of [Cu(CAAPH)Cl₂] and [Cu(CPAAPH)(Cl O₄)₂] show quasi-reversible peaks which indicates that metal-ligand linkage is more covalent in nature²⁹.