Synthesis, structures and DNA binding of ternary transition metal complexes M(II)L with the 2,2 ′-bipyridylamine (L = p-HB, M = Co, Ni, Cu and Zn)

Abstract

New ternary transition metal complexes of formulations [Co(bpa)( p-HB) 2](bpa = 2,2′-bipyridylamine, p-HB = p-hydroxybenzenecarboxylic acid) ( 1), [Ni(bpa)( p-HB)(H 2O) 2] +(NO 3) − · H 2O ( 2), [ Ni ( bpa ) 2 ( p - HB ) ] 2 2 + ( NO 3 ) - ( p - HB ) - · 5 H 2 O ( 3 ) , [Cu(bpa)( p-HB)Cl] ( 4) and [Zn(bpa)( p-HB) 2] 2 · 0.5H 2O ( 5) are prepared, their structural features are characterized by crystal structural studies, and their DNA binding propensity has been evaluated by fluorescence method. The molecular structure of complex 1 shows the six coordinate octahedral geometry with one bpa and two p-HB ligands, complex 2 is the cationic complex and has the six coordinate octahedral structure with one bpa, one p-HB and two aqua ligands, complex 3 is also the cationic complex of octahedral coordination with two bpa and one p-HB ligands, complex 4 is five coordinate distorted square pyramidal with one bpa, one p-HB and chloride ligands and complex 5 has the distorted octahedral coordination with two p-HB and one bpa ligands. In all of the complexes, both bpa and p-HB act as the bidentate N and O-donor ligands, respectively. The intermolecular H-bond networks, together with π–π interaction in their solid state are also described. The complexes show the competitive inhibition of ethidium binding to DNA, and the DNA binding propensity can be reflected as the relative order: 3 > 2 > 1 > 5 > 4, in which the cationic charged Ni(II) complexes 2 and 3 show the most effective inhibition ability.