Syntheses, characterization, spectral properties, and catalytic activity of azo amido complexes of copper(II)

Abstract A potentially terdentate ligands 1N-(N,N-diethylaminoethyl)-2-arylazoaniline HL, [where HL = ArN=NC 6 H 4 N(H){C 2 H 4 N(C 2 H 5 ) 2 }; Ar = C 6 H 5 (for HL 1 , 3a ) or p -MeC 6 H 4 (for HL 2 , 3b ) or p -ClC 6 H 4 (for HL 3 , 3c )] have been used, in its deprotonated form, to prepare a copper(II) complexes which has been structurally characterized. The ligands (L ̶ ) afford a mononuclear complex Cu(L)Cl ( 4 ). In complex ( 4 ), (L ̶ ) binds to the copper(II) center in a terdentate (N,N,N) fashion. The Cu II N(azo)N / (amido)N // (amine) and Cl coordination environment is severely distorted from ideal square planar geometry. The Cu-N(amido) bond length is shortest and Cu-N(amine) bond length is larger. The distorted phenyl ring adjacent to the six-membered azo-amido chelate ring consist four longer and two shorter bonds indicates the delocalization. The delocalization of negative charge of the anionic ligands that formed in situ from the precursor (L ̶ ) due to dissociation of an amino proton. The emission property of copper(II) complexes was examined in dichloromethane solvent. Cyclic voltammetry of 4c complex shows a Cu(II)–Cu(I) oxidation at 0.68 V vs. SCE, followed by an oxidation of the coordinated ligand 3c at 1.01 V vs. SCE. Two reductions of the coordinated 1N-(N,N-diethylaminoethyl)-2-arylazoaniline ligand 3c are observed – 1.14 V and – 0.65 V vs. SCE. The catalytic activity of complex 4a has been investigated in the oxidation of benzyl alcohol by using H 2 O 2 as oxidant. The effects of two influential parameters in catalytic reactions, amount of catalyst and temperature have been studied to obtain the optimum condition.