Structural, electrochemical, phosphate-hydrolysis, DNA binding and cleavage studies of new macrocyclic binuclear nickel(ii) complexes

Abstract

New macrocyclic binuclear nickel(ii) complexes have been synthesized by using the bicompartmental mononuclear complex [NiL] [3,30-((1E,7E)-3,6-dioxa-2,7-diazaocta-1,7-diene-1,8-diyl)bis(3-formyl-5-methyl-2-diolato)nickel(II)] with various diamines like 1,2-bis(aminooxy)ethane (L(1)), 1,2-diamino ethane (L(2)), 1,3-diamino propane (L(3)), 1,4-diamino butane (L(4)), 1,2-diamino benzene (L(5)), and 1,8-diamino naphthalene (L(6)). The complexes were characterized by elemental analysis and spectroscopic methods. The molecular structures of the symmetrical binuclear complex [Ni(2)L(1)(H(2)O)(4)](ClO(4))(2) (1) and unsymmetrical binuclear complex [Ni(2)L(3)(H(2)O)(4)](ClO(4))(2).(H(2)O)(4) (3) were determined by single-crystal X-ray diffraction. The geometry around both the nickel(II) ions in each molecule is a slightly distorted octahedral. The distance between the Ni...Ni centers for complex 1 is 3.039 A and for complex 3 is 3.059 A. The influence of the coordination geometry and the ring size of the binucleating ligands on the electronic, redox, phosphate hydrolysis, DNA binding and cleavage properties have been studied. Electrochemical studies of the complexes show two quasi-reversible one electron reduction processes between -0.49 to -1.69 V. The reduction potential of the binuclear Ni(II) complexes shifts towards anodically upon increasing the macrocyclic ring size. The observed first order rate constant values for the hydrolysis of 4-nitrophenyl phosphate reaction are in the range from 8.69 x 10(-3) to 1.85 x 10(-2) s(-1). The complexes show good binding propensity to calf thymus DNA giving binding constant values in the range from 1.4 x 10(4) to 17.5 x 10(4) M(-1). The absorption, fluorescence and CD spectral data suggests that the complexes are strongly interacting with DNA. These complexes display hydrolytic cleavage of supercoiled pBR322DNA in the presence of H(2)O(2) at pH 7.2 and 37 degrees C. The hydrolytic cleavage of DNA by the complexes is supported by the evidence from free radical quenching and T4 ligase ligation. The pseudo-Michaelis-Menten kinetic parameters k(cat) = 1.27 +/- 0.4 h(-1) and K(M) = 7.7 x 10(-2) M for naphthalene diimine containing macrocyclic binuclear nickel(II) complex, (6) were obtained.

4,4'-(DIPHENYLMETHANE-4,4'-DIYLDINITRILO)DIPENTAN-2-ONE AND 4,4'-(DIPHENYLETHER-4,4'-DIYLDINITRILO)DIPENTAN-2-ONE LIGANDS AND THEIR Ni(II), Cu(II) COMPLEXES: SYNTHESIS, CHARACTERIZATION, DNA CLEAVAGE STUDIES

“…On the other hand, the pBR322 DNA treated with the ligands (3)(4)(5)(6)(7)(8) are remarkably degrading the pBR322 DNA by oxidative (O 2 -dependent pathway) cleavage mechanism using the singlet oxygen as the reactive species [44,46]. These results are similar to that observed for some Cu(II) and Ni(II) complexes as chemical nuclease [47][48][49][50][51][52]. ) were determined by the picrate extraction method developed by Pedersen [53].…”

Role of Electronegative Atom Present on Ligand Backbone and Substrate Binding Mode on Catecholase‐ and Phosphatase‐Like Activities of Dinuclear NiII Complexes: A Theoretical Support

“…Thus, the general rate of spontaneous hydrolysis was not separately determined. Kinetic data for phosphatase like activities of previously reported dinuclear nickel complexes,,,,,,, are presented in Table . Comparing the Tables and , it is evident that both the complexes 1 and 2 belong to high catalytically active group towards hydrolysis of 4‐NPP and the activity is higher for 1 .…”

Unique mononuclear MnIIcomplexes of an end-off compartmental Schiff base ligand: experimental and theoretical studies on their bio-relevant catalytic promiscuity

“…Selected inter-atomic bond distances and angles are listed in Table S1 ( †ESI), and geometrical parameters of intermolecular 6 interactions are listed in Table S2 and S3 ( †ESI). The SHELXS, SHELXL and SHELXTL.…”