Synthesis, characterization, spectral and catalytic activity of tetradentate (NNNO) azo-imine Schiff base copper(II) complexes
authors Pratihar, JL; Mandal, P; Brandao, P; Mal, D; Felix, V
nationality International
journal INORGANICA CHIMICA ACTA
author keywords Copper(II); C=N bond cleavage; Crystal structures; Redox; Emission; Oxidation reactions
keywords METHYL PHENYL SULFIDE; HYDROGEN-PEROXIDE; CRYSTAL-STRUCTURE; SALEN COMPLEXES; SPECTROSCOPIC PROPERTIES; ASYMMETRIC OXIDATION; EFFICIENT CATALYST; COUPLING REACTIONS; ORGANIC-COMPOUNDS; HENRY REACTION
abstract The hexadentate ligand, 2,2'-bis(salicyhdeneamino)azobenzene, 1 has been synthesized from 2,2'-diaminoazobenzene and salicylaldehyde in refluxing diethyl ether. Reaction of ligand 1 with Cu(II) acetate and Cu(II) perchlorate separately in methanol afforded tetradentate (N,N,N,O) Cu(II) complexes, Cu(L) & [Cu(HL)]ClO4 respectively [where H2L represent the one lmine moiety cleavage product of ligand 1 (H represents the dissociable amino and phenolic protons)]. These were characterized by microanalytical data and spectroscopic studies. In addition, the crystal structures of the ligand 1 and complexes Cu(L) & [Cu(HL)]ClO4 were determined by X-ray diffraction analysis. The diffraction analysis revealed that the ligand (H2L) binds Cu(II) centers in (N,N,N,O) tetra dentate fashion in distorted square planer geometry. In complex [Cu(HL)]ClO4 the apical position of copper center is weakly coordinated with one perchlorate ion. The dimeric structure of the molecule [Cu(HL)]ClO4 is stabilized through NH2... O hydrogen bonds. The fluorescence and redox property of ligand 1 and complexes Cu(L) & [Cu(HL)]ClO4 were studied. Preliminary DFT calculations were carried out using crystallographic coordinates to understand the electronic spectra and redox properties of the ligand and complexes. The complex Cu(L) shows very good catalytic activities towards oxidation of benzyl alcohol to benzaldeyhde (under solvent-free condition) and organic thioethers to sulfoxide and sulfones using H2O2 as the oxidant.
publisher ELSEVIER SCIENCE SA
issn 0020-1693
year published 2018
volume 479
beginning page 221
ending page 228
digital object identifier (doi) 10.1016/j.ica.2018.04.042
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000433145300030
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