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Synthesis, crystal structure and photo-induced DNA cleavage activity of ternary copper(II) complexes of NSO-donor Schiff bases and NN-donor heterocyclic ligands

Dhar, Shanta and Nethaji, Munirathinam and Chakravarty, Akhil R (2005) Synthesis, crystal structure and photo-induced DNA cleavage activity of ternary copper(II) complexes of NSO-donor Schiff bases and NN-donor heterocyclic ligands. In: Inorganica Chimica Acta, 358 (7). pp. 2437-2444.

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Abstract

ew ternary copper(II) complexes $[CuL^{n}B](ClO_{4})(1-3)$, where $HL^{n}$ is the NSO donor Schiff base derived from the condensation of 2-mercaptoethylamine hydrochloride with salicylaldehyde $(HL^{1})$ or 2-hydroxy-3-methoxybenzaldehyde $(HL^{2})$ and B is NN-donor heterocyclic base like 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) or 2,9-dimethyl-1,10-phenanthroline (dmp, 3), are prepared, structurally characterized by X-ray crystallography and their DNA cleavage activity studied. The complexes show distorted square-pyramidal $(4 + 1)CuN_{3}OS$ coordination geometry in which the NSO-donor Schiff base is bonded at the basal plane and the NN-donor heterocyclic base displays axial-equatorial mode of bonding [Cu-S distance: 2.4 ]. The one-electron paramagnetic $(\mu_{eff} = 1.9 \mu_{B})$ complexes display axial EPR spectra in DMF glass at 77 K giving g = 2.2 (A = 162 G) and g = 2.0, indicating ${d_{x}2_{-y}2}^1$ ground state. The complexes exhibit visible spectral d-d band in MeCN near 650 nm and two charge transfer bands near 400 nm. Complexes 1 and 2 display quasireversible cyclic voltammetric response in DMF-Tris buffer (1:4 v/v, pH 7.2) for the Cu(II)/Cu(I) couple at ca. -0.1 V vs. SCE. Complex 3 exhibits an irreversible reduction process forming $[Cu^{I}(dmp)_{2}]^+$. Binding of 1-3 to calf thymus DNA shows the relative order: 2 (phen) 3 (dmp) > 1 (bpy). Complex 2 efficiently cleaves supercoiled pUC19 DNA in the presence of mercaptopropionic acid (MPA) forming hydroxyl radical or on irradiation with light of 312, 532 and 632.8 nm wavelength in a type-II process. Complexes 1 and 3 are cleavage inactive.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Elsevier.
Keywords: Ternary copper(II) complex;NSO-donor Schiff base;Heterocyclic base;Photo-induced DNA cleavage;Crystal structure
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 24 May 2005
Last Modified: 19 Sep 2010 04:19
URI: http://eprints.iisc.ernet.in/id/eprint/3240

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