Three new mono-di-trinuclear cobalt complexes of selectively and non-selectively condensed Schiff bases with N2O and N2O2 donor sets: Syntheses, structural variations, EPR and DNA binding studies

Three new mono-di-trinuclear cobalt complexes of three different Schiff bases have been synthesised. In all the three complexes psuedohalides (NCO- and N-3(-)) have been incorporated to generate structural variation. Of the three Schiff bases, HL1 and HL2 were obtained by selective condensation of two different 1,3-diamines with 2-hydroxyacetophenone and H2L3 resulted from non-selective condensation of 1, 3-diamine with 2-hydroxyacetophenone. Only one -NH2 functionality of 1,3-diaminopropane and 1, 3-diaminopentane was selectively condensed with 2-hydroxyacetophenone to generate Schiff bases HL1 and HL2, respectively. H2L3 was obtained by condensing both the amine functionality of 1,3-diaminopropane with 2-hydroxyacetophenone. Therefore HL1 and HL2 behave as a N2O donors, whereas H2L3 provides a N2O2 donor coordination environment for the cobalt ions in the respective complexes. in [Co(L-1)(2)](2) [Co(NCO)(4)] (1) the asymmetric unit comprises of five mononuclear cobalt centers, [Co-2(mu-N-3)(2)-(L-2)(2)(N-3)(2)] (2) is a dinuclear and [(H2O)(2)Co(mu-N-3)(2)(mu-L-3)(2)Co-2(N-3)(1.25)(CH3O)(0.75)] center dot H2O (3) is a trinuclear cobalt species. The three complexes have been characterised using IR, UV-Vis spectroscopy and cyclic voltammetry. Structural aspects of 1, 2 and 3 have been described by performing single crystal X-ray analysis. EPR analyses of I and 3, and DNA binding abilities of all three cobalt complexes have been studied in detail. (C) 2009 Elsevier Ltd. All rights reserved.