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Ultrafast excited state dynamics of 1-nitropyrene: Effect of H-bonding

Paper ID Volume ID Publish Year Pages File Format Full-Text
27279 44014 2013 7 PDF Available
Title
Ultrafast excited state dynamics of 1-nitropyrene: Effect of H-bonding
Abstract

•Femtosecond excited state dynamics of 1-nitropyrene, an environmental pollutant, has been studied.•Experimentally for the first time it has been shown that rotation of the nitro group in nitropyrene takes place in its photoexcited state.•In protic solvent, due to solute–solvent H-bonding interaction, rotation of the nitro group is absent.

Ultrafast excited state dynamics of 1-nitropyrene has been carried out using femtosecond fluorescence upconversion technique. Detailed time-resolved emission measurements were performed in protic and aprotic solvents of similar polarity. It is seen that although the singlet–triplet energy gap in polar solvents is quite large, the excited state decay shows intersystem crossing in sub-picosecond time scale as observed for nonpolar solvents with isoenergetic singlet and triplet state. The appearance of the sub-picosecond decay component in polar solvents has been explained on the basis of the dynamical nature of the solvent relaxation process. Further, the contribution of the sub-picosecond decay component is much more for the solvent with slower solvent relaxation time. Time-resolved area normalized emission spectra (TRANES) show the presence of two emissive species for 1-nitropyrene in aprotic solvent while only one emissive species has been observed in protic solvent. The additional emissive species in aprotic solvent has been assigned to the structurally relaxed excited singlet state formed due to the rotation of the nitro group around the pyrene moiety. However, such rotation of the nitro group is prevented in protic solvent due to the formation of H-bonded complex between the solute and the solvent. Formation of H-bonding between protic solvent and nitropyrene is also confirmed by quantum chemical calculations.

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Keywords
1-Nitropyrene; Ultrafast dynamics; Fluorescence; H-bonding
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 271, 1 November 2013, Pages 24–30
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
Full-text PDF Download
Online Support
Any Questions? feel free to contact us