Journal
INORGANICA CHIMICA ACTA
Volume 362, Issue 1, Pages 199-207Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.ica.2008.03.083
Keywords
Schiff base ligands; Copper(II) bis-ligand complexes; X-ray structures; Steric hindrance; Square planar geometry; EPR spectra
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Funding
- Council of Scientific and Industrial Research, New Delhi
- Department of Science and Technology, New Delhi
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The Schiff base ligands 2-(2,6-diisopropylphenyliminomethyl)phenol H(L1), 5-diethylamino-2-(2, 6-diisopropylphenyliminomethyl)phenol H(L2), 2,4-di-tert-butyl-6-(2,6-diisopropylphenyliminomethyl) phenol H(L3), 3-(2,6-diisopropylphenyliminomethyl)naphthalen-2-ol H(L4) and 4-(2,6-diisopropylphenyliminomethyl)-5- hydroxymethyl-2-methylpyridin-3-ol H(L5) have been synthesized by the condensation, respectively, of salicylaldehyde, 4-(diethylamino)salicylaldehyde, 3,5-di-tert-butylsalicyl-aldehyde, 2-hydroxy-1-napthaldehyde and pyridoxal with 2,6-diisopropylaniline. The copper(II) bisligand complexes [Cu(L1)(2)] 1, [Cu(L2)(2)] 2, [Cu(L3)(2)] 3, [Cu(L4)(2)] 4 and [Cu(L5)(2)] center dot CH3OH 5 of these ligands have been isolated and characterized. The X-ray crystal structures of two of the complexes [Cu(L1)(2)] 1 and [Cu(L5)(2)] center dot CH3OH 5 have been successfully determined, and the centrosymmetric complexes possess a CuN2O2 chromophore with square planar coordination geometry. The frozen solution EPR spectra of the complexes reveal a square-based CuN2O2 chromophore, and the values of g(parallel to) and g (parallel to)/A(parallel to) index reveal enhanced electron delocalization by incorporating the strongly electron-releasing -NEt2 group (2) and fusing a benzene ring on sal-ring (4). The Cu(II)/Cu(I) redox potentials of the Cu(II) complexes reveal that the incorporation of electron-releasing -NEt2 group and fusion of a benzene ring lead to enhanced stabilization of Cu(II) oxidation state supporting the EPR spectral results. The hydrogen bonding interactions between the two molecules present in the unit cell of 5a generate an interesting two-dimensional hydrogen-bonded network topology. (c) 2008 Elsevier B.V. All rights reserved.
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