Synthesis, structural characterization and catalysis of simple and encapsulated Co(II), Ni(II), Cu(II) and Zn(II) complexes of the ligand 3-{(E)-[(2-hydroxy-4-methylphenyl)imino]methyl}quinoxalin-2(1H)-one

Abstract New complexes of Co(II), Ni(II), Cu(II), and Zn(II) with the Schiff base, 3-{(E)-[(2-hydroxy-4-methylphenyl)imino]methyl}quinoxalin-2(1H)-one, derived from 3-hydroxyquinoxaline-2-carboxaldehyde and 2-amino-5-methylphenol and their corresponding zeolite-Y encapsulated metal complexes have been synthesized. The structural features of the ligand and complexes were characterized by various physicochemical and spectroscopic methods. The catalytic performances of the complexes in oxidation reaction of styrene using H2O2 were evaluated for both homogeneous and heterogeneous systems. The encapsulated complexes catalyze the reaction more efficiently than the neat complexes. Under the optimized conditions, the copper complex gave 65.6% conversion with benzaldehyde and 1-phenylethane-1,2-diol as the major product. The product formation depends on styrene: H2O2 ratio.