Quantum chemical studies on excited state intermolecular proton transfer of oxazine dyes

The excited state lifetimes of oxazine dyes nile blue and oxazine 720 show a significant solvent dependence. As an aid to the interpretation of the decay in acidic environments the ground electronic states and the first singlet excited states of oxazine monocations and dications have been studied by...

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Bibliographic Details
Published in:Journal of molecular structure 2000-11, Vol.555 (1-3), p.15-19
Main Authors: Grofcsik, A, Kubinyi, M, Ruzsinszky, A, Veszprémi, T, Jones, W.J
Format: Article
Language:English
Subjects:
Intermolecular relaxation
Oxazine dyes
Quantum chemical calculations
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Summary:The excited state lifetimes of oxazine dyes nile blue and oxazine 720 show a significant solvent dependence. As an aid to the interpretation of the decay in acidic environments the ground electronic states and the first singlet excited states of oxazine monocations and dications have been studied by methods of quantum chemistry. Ab initio calculations carried out on the lower members on this series show a significant increase of the electron densities of the ring nitrogen on excitation. The calculated electron energies also suggest that the second proton attaches to the ring nitrogen in the excited states, in contrast to the ground states where (in the case of oxazine 720) the second proton attaches to the terminal nitrogen. A kinetic scheme is proposed for the decay process in which in acidic environments the main deactivation path is the reaction of excited state monocations with protons, followed by internal conversion and subsequent deprotonation of the ground state dications.
ISSN:0022-2860
1872-8014
DOI:10.1016/S0022-2860(00)00583-4