Binuclear copper(II), cobalt(II) and Nickel(II) complexes of N1-ethyl-N2-(pyridin-2-yl) hydrazine-1,2-bis(carbothioamide): Structural, spectral, pH-metric and biological studies

Binuclear Cu(II), Co(II) and Ni(II) complexes derived from N-1-ethyl-N-2-(pyridin-2-yl) hydrazine-1,2-bis(carbothioamide) (H2PET) have been prepared and characterized by elemental analysis, spectral (IR, UV-vis, El mass, ESR and (HNMR)-H-1) and magnetic measurements. The isolated complexes assigned the general formula, [M(HPET)(H2O)(n)Cl](2)center dot xH(2)O where M = Cu(II), Co(II) and Ni(II), n = 2, 1,0 and x = 0, 0.5 and 0, respectively. IR data revealed that the ligand behaves as monobasic tridentate through (C=N)(py), (C-S) and new azomethine, (N=C)* groups in the Co(II) complex but in Cu(II) complex, the ligand coordinate via both (CS) groups, one of them in thiol form as well as the new azomethine group. In Ni(11) complex, H2PET acts as NSNS monobasic tetradente via (C=N)py, (C-S), (C=S) and the new azomethine, (N=C)* groups. An octahedral geometry is proposed for all complexes. pH- metric titration was carried out in 50% dioxane-water mixture at 298, 308 and 318 degrees K, respectively and the dissociation constant of the ligand as well as the stability constants of its complexes were evaluated. Also the kinetic and thermodynamic parameters for the different thermal decomposition steps of the complexes were determined by Coats-Redfern and Horowitz-Metzger methods. Moreover, the anti-oxidant, anti-hemolytic, and cytotoxic activities of the compounds have been tested. (C) 2012 Elsevier B.V. All rights reserved.