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Spectroscopy of Ru(II) polypyridyl complexes used as intercalators in DNA: Towards a theoretical study of the light switch effect

Paper ID Volume ID Publish Year Pages File Format Full-Text
28096 44059 2007 11 PDF Available
Title
Spectroscopy of Ru(II) polypyridyl complexes used as intercalators in DNA: Towards a theoretical study of the light switch effect
Abstract

The absorption spectroscopy of [Ru(phen)2dppz]2+ and [Ru(tap)2dppz]2+ (phen = 1,10-phenanthroline, tap = 1,4,5,8-tetraazaphenanthrene; dppz = dipyridophenazine) complexes used as molecular light switches by intercalation in DNA has been analysed by means of Time-Dependent Density Functional Theory (TD-DFT). The electronic ground state structures have been optimized at the DFT (B3LYP) level of theory. The absorption spectra are characterized by a high density of excited states between 500 nm and 250 nm. The absorption spectroscopy of [Ru (phen)2dppz]2+ in vacuum is characterized by metal-to-ligand-charge-transfer (MLCT) transitions corresponding to charge transfer from Ru(II) either to the phen ligands or to the dppz ligand with a strong MLCT (dRu→πdppz*) absorption at 411 nm. In contrast, the main feature of the lowest part of the vacuum theoretical spectrum of [Ru(tap)2dppz]2+ between 522 nm and 400 nm is the presence of various excited states such as MLCT (dRu→πTAP*), ligand-to-ligand-charge-transfer LLCT (πdppz→πTAP*) or intra-ligand IL (πdppz→πdppz*) states. When taking into account solvent corrections within the polarizable continuum model (PCM) approach (H2O, CH3CN) the absorption spectrum of [Ru(tap)2dppz]2+ is dominated by a strong absorption at 388 nm (CH3CN) or 390 nm (H2O) assigned to a 1IL (πdppz→πdppz*) corresponding to a charge transfer from the outside end of the dppz ligand to the site of coordination to Ru(II). These differences in the absorption spectra of the two Ru(II) complexes have dramatic effects on the mechanism of deactivation of these molecules after irradiation at about 400 nm. In particular, the electronic deficiency at the outside end of the dppz ligand created by absorption to the 1IL state will favour electron transfer from the guanine to the Ru(II) complex when it is intercalated in DNA.

Keywords
Spectroscopy; Ruthenium polypyridyl; Photophysics; Theoretical chemistry; DNA intercalators
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Spectroscopy of Ru(II) polypyridyl complexes used as intercalators in DNA: Towards a theoretical study of the light switch effect
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 190, Issues 2–3, 15 August 2007, Pages 310–320
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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