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Unimolecular proton-transfer photoreactions in 2,4-dithiouracil and 6-aza-2,4-dithiouracil: A matrix isolation study

Paper ID Volume ID Publish Year Pages File Format Full-Text
28473 44076 2006 9 PDF Available
Title
Unimolecular proton-transfer photoreactions in 2,4-dithiouracil and 6-aza-2,4-dithiouracil: A matrix isolation study
Abstract

Unimolecular proton-transfer photoreactions were studied for 2,4-dithiouracil and 6-aza-2,4-dithiouracil isolated in low-temperature Ar matrices. The IR spectra have revealed that before UV irradiation the matrix-isolated dithiouracils adopted exclusively the dithione tautomeric forms. UV (λ > 320 nm) irradiation of the matrices led to transfer of protons from N(1)-H or N(3)-H groups to the sulfur atoms of the C(2) = S and C(4) = S thiocarbonyl moieties. The ultimate products of these photoreactions were dithiol tautomeric forms of the studied dithiouracils. For 6-aza-2,4-dithiouracil, photogeneration of a second species was clearly observed. This photoproduct was identified as the thiol–thione tautomer of 6-aza-2,4-dithiouracil. During UV irradiation, the population of this form first grew but then decreased, whereas the population of the dithiol tautomer was increasing monotonically. For 2,4-dithiouracil, the phototautomeric transformations are strongly dominated by the generation of the dithiol product. The second product, the thiol–thione form of 2,4-dithiouracil, was photogenerated only in trace amounts. The products of the investigated photoreactions were identified by comparison of their IR spectra with the spectra calculated at the DFT(B3LYP)/6-311++G(2d,p) level.

Keywords
2,4-Dithiouracil; 6-Aza-2,4-dithiouracil; Matrix isolation; IR spectra; Phototautomerism; Proton-transfer
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Unimolecular proton-transfer photoreactions in 2,4-dithiouracil and 6-aza-2,4-dithiouracil: A matrix isolation study
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 184, Issue 3, 15 December 2006, Pages 322–330
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