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Synthesis, crystal structure and photo-induced DNA cleavage activity of ternary copper(II)-thiosemicarbazone complexes having heterocyclic bases

Thomas, Anitha M and Naik, Anil D and Nethaji, Munirathinam and Chakravarty, Akhil R (2004) Synthesis, crystal structure and photo-induced DNA cleavage activity of ternary copper(II)-thiosemicarbazone complexes having heterocyclic bases. In: Inorganica Chimica Acta, 357 (8). pp. 2315-2323.

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Abstract

New ternary copper(II) complexes of formulations [Cu(Ph-tsc)B] (B¼1,10-phenanthroline, phen (1); dipyridoquinoxaline, dpq (2); dipyridophenazine, dppz (3); $Ph-H_2tsc,$ salicylaldehyde-N(4)-phenylthiosemicarbazone) and [Cu(Me-tsc)(phen)] $(4, Me-H_2tsc,$ salicylaldehyde- N(4)-methylthiosemicarbazone) are prepared, and their DNA binding and cleavage properties studied. Complex 1 has been characterized by single crystal X-ray crystallography. The molecular structure shows a distorted square pyramidal (4+ 1) geometry of the complex with the dianionic NSO-donor N(4)-phenyl-substituted thiosemicarbazone binding at the basal plane and the NN-donor planar heterocyclic base (phen) displaying axial–equatorial coordination. The one-electron paramagnetic complexes exhibit axial EPR spectra and show a d–d band near 580 nm for the phen and near 720 nm for the dpq, dppz complexes in their electronic spectra in DMF. The complexes show quasireversible cyclic voltammetric response near 0.08 V vs. SCE in DMF–0.1 M TBAP assignable to the Cu(II)/Cu(I) couple. The Ph-tsc complexes display good binding propensity to calf thymus (CT) DNA. They also show oxidative cleavage of supercoiled (SC) pUC19 DNA in dark under aerobic condition in the presence of mercaptopropionic acid. The complexes exhibit light-induced DNA cleavage activity at 312 and 532 nm. Mechanistic investigations reveal DNA minor groove binding for the phen and dpq complexes, and major groove binding for the dppz species. The complexes are cleavage inactive under argon atmosphere. In the ternary structure, the thiosemicarbazones, dpq and dppz act as photosensitizers, while the planar heterocyclic bases are binder to DNA. The mechanistic pathways involved and the role of metal in the DNA cleavage reactions are discussed.

Item Type: Journal Article
Additional Information: The copyright belongs to Elsevier.
Keywords: Ternary copper(II) complex;Thiosemicarbazones;Heterocyclic bases;DNA Photocleavage;Crystal structure
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 06 May 2006
Last Modified: 19 Sep 2010 04:26
URI: http://eprints.iisc.ernet.in/id/eprint/6560

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