Tetra- and hexadentate Schiff base ligands and their Ni(II), Cu(II) and Zn(II) complexes. Synthesis, spectral, magnetic and thermal studies

Tetradentate N2O2, N-4 Schiff bases, 1,2-bis(4-oxopent-2-ylideneamino) benzene (BOAB), 1-(4-oxopent-2-ylideneamino-2-[(2-hydroxyphenynethylideneamino] benzene (OAHAB), 7,16-bis(4-chlorobenzylidene)-6,8,15,17-tetra-methyl-7,16-dihydro -5,9,14,18-tetraza-dibenzo[a,h] cyclo tetradecene (BCB-DCT), 7,16-bis(2-hydroxy-benzylidene)-6,8,15,17-tetramethyl-7,16-dihydro-5,9,14,18-tetraza-dibenzo la,h] cyclo tetradecene (BHBDCT) and hexadentate N4O2 Schiff bases, 2,4-bis {2-[1-(2-hydroxyphenyl) ethylideneamino] phenylimino}-3-(2-hydroxybenzylidene) pentane (BHAPHP), 2,4-bis {2-[1-(2hydroxyphenyl) ethylideneamino] phenylimino}-3-(4-chlorobenzylidene) pentane (BHAPCP) were prepared and characterized by elemental analysis, IR, UV Vis, H-1 NMR and mass spectra. The solid complexes of the prepared Schiff base ligands with Ni(II), Cu( II) and Zn(II) ions were isolated and characterized by elemental and thermal analyses, IR, electronic and ESR spectra as well as conductance and magnetic susceptibility measurements. The results showed that most complexes have octahedral geometry but few can attain the tetrahedral arrangement. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. The kinetic and thermodynamic parameters for decomposition steps in Cu(II) complexes thermograms have been calculated. (C) 2011 Elsevier B.V. All rights reserved.