Phosphatase activity and DNA binding studies of dinuclear phenoxo-bridged zinc(II) complexes with an N,N,O-donor ligand and halide ions in a rare cis-configuration

Abstract

Three new dinuclear zinc(II) complexes of the types [Zn2(L)2(Cl)2]·2(CH3OH) (1) and [Zn2(L)2(X)2] (HL=2-(((2-(dimethylamino)ethyl)amino)methyl)phenol; X=Br for 2 and I for 3), having a rare cis-configuration of the halide ions, were isolated using the one-pot synthesis of the building components in appropriate molar ratios and characterized. X-ray structural studies reveal that 1–3 contain a discrete dinuclear unit bridged by two phenoxo oxygen atoms of the deprotonated Schiff base ligand (HL) and adopt an overall rare cis-configuration where two halide ions are on the same side of the Zn–Zn axis and the ligand occupies the other side. Each Zn(II) centre in 1–3 has a distorted square pyramidal geometry with a ZnO2N2X chromophore (X=Cl for 1; Br for 2; I for 3). The initial rate values for the hydrolysis of 4-nitrophenylphosphate to 4-nitrophenolate by the complexes 1–3 are respectively 590, 334 and 705min−1. The complexes show an external binding propensity to calf thymus DNA with binding constant values 9.45×102, 7.06×102 and 6.51×102M−1 for 1, 2 and 3 respectively.