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](ClO 4 ) (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 by using various physico-chemical techniques. All Ni centers adopt distorted octahedral geometry with N 5 Cl donor sets. From 1 to 4, the dihedral angles between benzene ring of L and the plane of the diimine exhibit gradually decline (52.5-6.8°), leading to the increasing steric encumbrance. The interactions of the complexes with CT-DNA and BSA have been explored by using absorption and emission spectral methods. These complexes display binding propensity to the CT-DNA giving a relative order: 4 (dppz) > 3 (dpq) > 2 (phen) > 1 (bpy), and the quenching mechanisms of BSA by all 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 vitro  Corresponding authors. 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 by using Hoechst 33342 staining reveals that 4 against HepG-2 induces apoptosis.

Cu(II) and Ni(II) Complexes of Anthracene‐Affixed Schiff Base: A Conflict between Covalent and Stacking Interactions with DNA Bases

“…Among them, ruthenium, copper and cobalt complexes are the widely studied synthetic DNA‐targeted metallonucleases . Though nickel is also a vital element associated with life process and an active component in several enzymes, studies on the interactions of nickel(II) complexes with nucleobases are comparably fewer . Therefore it is also very essential to expand the role of nickel in bioinorganic chemistry.…”

Mononuclear Co(ii) polypyridyl complexes: synthesis, molecular structure, DNA binding/cleavage, radical scavenging, docking studies and anticancer activities

“…The relatively high binding affinity of 3 is due to the intercalative interaction associated with the extended aromatic ring of the coordinated phen ligand and also the non-covalent interaction among the π-systems of phen and DNA base pairs. 46 Thus, the incorporation of planar aromatic bidentate ligands in 2–4 suggested better intercalation towards ss-DNA. In contrast, the lack of bidentate ligand and planar aromatic ring moiety in 1 resulted in a comparatively low K b value.…”

“…The decreasing order of the dihedral angle is 4 > 2 > 3 , due to regular strong π–π interactions between the phenyl group of ligand L and the aromatic conjugated system of bidentate ligands (bpy, phen, pic). 46…”

Cell cytotoxicity and serum albumin binding capacity of the morin–Cu(ii) complex and its effect on deoxyribonucleic acid

“…al. 23 Again the binding of morin 24 and morin-Zn(II) complex 25 with BSA have been established by Hu et al (2012) 24 Protein-ligand binding studies considering serum albumins [26][27][28][29][30][31] as the carrier became an important aspect in the fields of clinical biology, pharmaceutical sciences and pharmacology that affects the drug absorption, distribution and excretion processes.…”

“…Protein-ligand binding studies considering serum albumins [26][27][28][29][30][31] as the carriers became an important aspect in the fields of clinical biology, pharmaceutical sciences and pharmacology, which affects the drug absorption, distribution and excretion processes. Considering the potential medicinal aspects of the morin-Cu(II) complex, its interaction with SAs has been investigated, as the distribution and metabolism of these biologically beneficial components are correlated with their binding affinities toward SAs.…”