Unexpected Halogen Substituent Effects on the Complex Thermal Relaxation of Naphthopyrans after UV Irradiation

The kinetics of the thermal fading of four halogenated naphthopyrans (NP) have been analyzed using NMR spectroscopy in CD3CN. Two photomerocyanines (TT and TC) were detected after UV irradiation. The main relaxation process TC → NP was coupled with TT/TC isomerization. The activation parameters of t...

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Bibliographic Details
Published in:Journal of organic chemistry 2005-06, Vol.70 (13), p.5302-5304
Main Authors: Delbaere, Stephanie, Micheau, Jean-Claude, Frigoli, Michel, Vermeersch, Gaston
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
Heterocyclic compounds
Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives
Kinetics and mechanisms
Organic chemistry
Preparations and properties
Reactivity and mechanisms
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Summary:The kinetics of the thermal fading of four halogenated naphthopyrans (NP) have been analyzed using NMR spectroscopy in CD3CN. Two photomerocyanines (TT and TC) were detected after UV irradiation. The main relaxation process TC → NP was coupled with TT/TC isomerization. The activation parameters of the various processes were rationalized by considering electronegativity and polarizability of the halogen substituents and their selective solvation by the electronegative nitrogen of acetonitrile.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo050620o