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Oxovanadium(IV) complexes of phenanthroline bases: the dipyridophenazine complex as a near-IR photocytotoxic agent

Sasmal, Pijus K and Saha, Sounik and Majumdar, Ritankar and De, Swati and Dighe, Rajan R and Chakravarty, Akhil R (2010) Oxovanadium(IV) complexes of phenanthroline bases: the dipyridophenazine complex as a near-IR photocytotoxic agent. In: Dalton Transactions (2003), 39 (8). pp. 2147-2158.

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Oxovanadium(IV) complexes [VOCl(B)(2)]Cl (1-3) of phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d: 2', 3'-f] quinoxaline (dpq in 2) and dipyrido[3,2-a: 2', 3'-c] phenazine (dppz in 3), have been prepared, characterized and their DNA and protein binding, photo-induced DNA and protein cleavage activity andm photocytotoxicity have been studied. Complex 2, structurally characterized by X-ray crystallography, shows the presence of a vanadyl group in VOClN4 coordination geometry. The dpq ligand displays a chelating mode of binding with a N-donor site trans to the oxo-group. The chloride ligand is cis to the oxo-group. The one-electron paramagnetic complexes show a d-d band near 715 nm in 15% DMF-Tris-HCl buffer. The complexes are redox active exhibiting a V(IV)/V(III) redox couple within -0.5 to -0.7 V vs. SCE in 20% DMF-Tris-HCl/0.1 M KCl. The complexes bind to calf thymus (CT) DNA in the order: 3 (dppz) > 2 (dpq) > 1 (phen). The binding data reveal the groove and/or partial intercalative DNA binding nature of the complexes. The complexes show chemical nuclease'' activity in the dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide via a hydroxyl radical pathway. The dpq and dppz complexes are efficient photocleavers of DNA in UV-A light of 365 nm forming reactive singlet oxygen (O-1(2)) and hydroxyl radical ((OH)-O-center dot) species. Complexes 2 and 3 also show DNA cleavage activity in red light (> 750 nm) by an exclusive (OH)-O-center dot pathway. The complexes display a binding propensity to bovine serum albumin (BSA) protein giving K-BSA values in the range of 7.1 x 10(4)-1.8 x 10(5) M-1. The dppz complex 3 shows BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via (OH)-O-center dot pathway. The dppz complex 3 exhibits significant PDT effect in human cervical cancer HeLa cells giving IC50 values of 1.0 mu M and 12.0 mu M in UV-A and visible light, respectively (IC50 = > 100 mu M in the dark).

Item Type: Journal Article
Publication: Dalton Transactions (2003)
Publisher: Royal Society of Chemistry
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Biological Sciences > Molecular Reproduction, Development & Genetics
Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 05 Mar 2010 09:51
Last Modified: 19 Sep 2010 05:56
URI: http://eprints.iisc.ac.in/id/eprint/25911

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