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

New ternary transition metal complexes of formulations [Ni(bpa)(p-AB)Cl]n · 3nH2O (bpa = 2,2′-bipyridylamine, p-AB = aminobenzenecarboxylic acid) (1), [Cu(bpa)(p-AB)Cl] · H2O (2), [Zn(bpa)(p-AB)2] · H2O (3) are prepared, their structural features are characterized by crystal structural studies, and their DNA binding propensity has been evaluated by fluorescence and viscosity method. In complex 2 and 3, both bpa and p-AB act as the bidentate N and O-donor ligand, respectively. While in complex 1, p-AB acts as a rare tridentate ligand. In the packing pattern of each complex, π–π interaction in their solid state is 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: 1 > 2 > 3.

Graphical abstractIn each complex cation unit, Ni2+ is coordinated to two carboxylate O atoms from p-AB ligand, two N atoms from BPA ligand, one aqua O atom from water, and one amino N atom from the adjacent p-AB (symmetry code: −1/2 + x, 1/2 − y, 1/2 + z). In case of complex 1, the bond Ni–N4(−1/2 + x, 1/2 − y, 1/2 + z) connects the adjacent units to form an infinite zig-zag chain along a direction, which is very rare among p-AB complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide