Syntheses, crystal structures, and properties of two macrocyclic dinuclear Ni(II) complexes bearing 2-pyridylmethyl pendant-arms

Two new dinuclear nickel macrocyclic complexes, [Ni2(II)L1(OAc)] center dot ClO4 center dot CH3OH center dot 0.5H2O (1) and [Ni2(II)L2(OAc)] center dot CH3CN center dot ClO4 center dot 0.5H2O (2), have been obtained and fully characterized [where H2L = macrocycle as the [2 + 2] condensation product of 4-X-2,6-diformylphenol (X = CH3, Cl) and N,N-bis(2-aminopropyl)-N-(2-pyridylmethyl)amine]. The interactions of the complexes with calf thymus-DNA were studied by UV-Vis and CD spectroscopic techniques. The binding constants of 1 and 2 are 1.5 x 105 and 4.9 x 105 (mol L-1)-1, respectively. The complexes exhibit powerful DNA cleavage activity. The cleavage process occurs via an oxidative cleavage and a hydrolytic mechanism for 1, while the mechanism for 2 was a hydrolytic cleavage. The variable-temperature magnetisms show that there are weak antiferromagnetic couplings between Ni(II) ions in [Ni2L(OAc)]+, and the cyclic voltammograms of the complexes are also investigated.