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Structure and fluorescent properties of merocyanines based on N,N-diethylthiobarbituric acid

Paper ID Volume ID Publish Year Pages File Format Full-Text
29135 44124 2008 10 PDF Available
Title
Structure and fluorescent properties of merocyanines based on N,N-diethylthiobarbituric acid
Abstract

Fluorescent properties of a series of positively and negatively solvatochromic merocyanines based on N,N-diethylthiobarbituric acid containing heterocycles of various electron-donating properties are explored in solvents of various polarity. It is shown, that their solvatofluorochromic range is less than the solvatochromic range. A lengthening of the polymethine chain causes a growth of the vinylene shifts, a decrease of the deviations and a narrowing of the fluorescent spectral bands, as opposed to the absorption ones. The transition to the higher vinylogues is also accompanied by a decrease of the Stokes shifts and an increase of the fluorescent quantum yields. However, a growth of the latter for merocyanines absorbing light in the near-IR range is levelled by an amplification of internal conversion. An absence of a mirror symmetry of the absorption and fluorescence spectra has been revealed. The quantum-chemical analysis of an electronic structure of the merocyanines by the semi-empirical method AM1 is also carried out. The transitions between their ideal electronic states – non-polar polyene, polymethine and dipolar polyene – are investigated. It is shown, that the electronic structure of the fluorescent state of merocyanines approaches the cyanine limit at polymethine chain lengthening.

Keywords
Donor–acceptor systems; Merocyanines; Fluorescence; Solvatochromism; Electronic structure
First Page Preview
Structure and fluorescent properties of merocyanines based on N,N-diethylthiobarbituric acid
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 197, Issue 1, 10 June 2008, Pages 40–49
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering