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Effect of copper-sulphur bond on the DNA photo-cleavage activity of 2-(methylthio)ethylpyridine-2-carbaldimine copper(II) complexes

Gupta, Tarkeshwar and Patra, Ashis K and Dhar, Shanta and Nethaji, Munirathinam and Chakravarty, Akhil R (2005) Effect of copper-sulphur bond on the DNA photo-cleavage activity of 2-(methylthio)ethylpyridine-2-carbaldimine copper(II) complexes. In: Journal of Chemical Sciences, 117 (2). pp. 123-132.

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Abstract

The binding and photo-induced DNA cleavage activity of a binary complex $[CuL_2](ClO_4)_2$ (1) and the in situ generated ternary complexes $[CuLB](ClO_4)_2$ from 1 (B: 1,10-phenanthroline, phen, 2;dipyrido[3,2-d: 2',3'-f]quinoxaline, dpq, 3) are studied, where L is a $N_2S-donor$ tridentate Schiff base2(methylthio)ethylpyridine-2-carbaidimine. Complex 1, structurally characterized by X-ray diffraction study, has six-coordinate meridional geometry showing $CuN_4S_2$ coordination. The Cu-N bond lengths are in the range of 1.968(3) to 2.158(4) angstrom. The Cu-S bond lengths of2.599(2) and 2.705(2) angstrom are significantly long indicating weakcovalent interaction between copper and sulphur atoms. The thiomethylgroups are cis to each other giving S-Cu-S angle of 75-82(5)degrees.The Cu-N(pyridyl) bond distances are longer than the Cu-N(imine) bonds.The complexes are redox active and display a quasi-reversible cyclicvoltammetric response assignable to the Cu(II)/Cu(I) couple near 0.0 Vvs SCE in DMF-Tris buffer (1 : 4 v/v) using 0. 1 M KCl as supporting electrolyte. Electronic spectra of the complexes show a d-d band in therange 630 to 700 nm in DMF along with higher energy charge transfer bands. While complex 1 is a poor binder to DNA, the ternary complexess how good DNA binding propensity. The photo-nuclease activity of 1-3 isstudied using UV and visible wavelengths. The DNA cleavage activity at 365 nm follows the order: 3 > 2 > 1. The cleavage reaction involves theformation of singlet oxygen as the reactive species in a type-II process.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Indian Academy of Sciences.
Keywords: DNA photo-cleavage;copper (II) complexes;Schiff base;crystal structure;phenanthroline bases
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 05 May 2005
Last Modified: 19 Sep 2010 04:18
URI: http://eprints.iisc.ernet.in/id/eprint/3158

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