Issue 39, 2015

Four related mixed-ligand nickel(ii) complexes: effect of steric encumbrance on the structure, DNA/BSA binding, DNA cleavage and cytotoxicity

Abstract

Four closely related mononuclear nickel(II) complexes [Ni(L)(diimine)Cl](ClO4) (1–4), where L is a tridentate polypyridyl ligand of 4-methyl-N,N-bis(pyridin-2-ylmethyl)aniline and diimine is 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:20,30-f]quinoxaline (dpq, 3) or dipyrido[3,2-a:20,30-c]phenazine (dppz, 4), have been synthesized and characterized using various physico-chemical techniques. All Ni centers adopt a distorted octahedral geometry with N5Cl donor sets. From 1 to 4, the dihedral angles between the benzene ring of L and the plane of the diimine gradually decline (52.5–6.8°), leading to increasing steric encumbrance. The interactions of the complexes with CT-DNA and BSA have been explored using absorption and emission spectral methods. These complexes display binding propensity to CT-DNA in the order: 4 (dppz) > 3 (dpq) > 2 (phen) > 1 (bpy), and the quenching mechanisms of BSA by all the complexes are static procedures. In the absence of any external agents, only 1 (bpy) and 4 (dppz) exhibit apparent DNA cleavage activity, while with the addition of GSH or on the irradiation with UV-A light of 365 nm, the DNA cleavage abilities of the complexes are obviously enhanced, which vary as 1 > 2 > 3 > 4 (GSH) and 4 > 3 > 2 > 1 (UV-A). In addition, the in vitro cytotoxicity of the complexes on tumor cells lines (MCF-7, HepG-2 and SGC-7901) have been examined by MTT and the morphological assessment obtained using Hoechst 33342 staining reveals that 4 induces apoptosis against HepG-2.

Graphical abstract: Four related mixed-ligand nickel(ii) complexes: effect of steric encumbrance on the structure, DNA/BSA binding, DNA cleavage and cytotoxicity

Supplementary files

Article information

Article type
Paper
Submitted
23 Dec 2014
Accepted
20 Mar 2015
First published
20 Mar 2015

RSC Adv., 2015,5, 30768-30779

Four related mixed-ligand nickel(II) complexes: effect of steric encumbrance on the structure, DNA/BSA binding, DNA cleavage and cytotoxicity

C. Gao, Z. Ma, Y. Zhang, S. Li, W. Gu, X. Liu, J. Tian, J. Xu, J. Zhao and S. Yan, RSC Adv., 2015, 5, 30768 DOI: 10.1039/C4RA16755D

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