Synthesis, structure and DNA binding studies of a mononuclear cobalt(III) complex with a NNO donor Schiff base derived from 4-methyl-2,6-dibenzoylphenol and ethane-1,2-diamine

The mononuclear cationic cobalt(III) complex 1 [Co(L)2]+ [where HL is H2N(CH2)2NC(Ph)C6H2(Me)(OH)COPh] has been obtained by the condensation of 4-methyl-2,6-dibenzoylphenol and ethane-1,2-diamine in the presence of CoCl2 · 6H2O and isolated as the chloride solvate {1 · Cl · 2H2O · EtOH}. The water and ethanol do not form part of the cobalt(III) pseudo-octahedral [Co(L)2]+ coordination sphere, which is cis-CoN4O2 with the NNO-ligands mer. Compound 1 has been characterised by mass spectrometry, IR, electronic, 1H and 13C NMR spectroscopy, conductivity measurements, elemental analysis, TGA, cyclic voltammetry and an X-ray structural determination. The average Co–N and Co–O distances are, respectively, 1.929(4) and 1.882(3) Å. The N⋯N intraligand bite distance is 2.73(4) Å and the N–Co–N and O–Co–O angles are, respectively, 86.2(15)° and 93.3(13)°. Cyclic voltammetric studies of complex 1 indicate an irreversible cathodic peak (Epc, ca. −0.61 V) corresponding to the reduction of cobalt(III) to cobalt(II). Absorption titration experiments gave a binding constant for DNA interaction of 1.4 × 104 M−1 and a binding site size 0.16 base pairs.