Ground and Singlet Excited State Pyridinic Protonation of N9-Methylbetacarboline in Water-N,N-Dimethylformamide Mixtures

Autor: María A. Muñoz, Manuel Balón, Antonio Sánchez Coronilla, Carmen Carmona
Rok vydání: 2009
Předmět:
Zdroj: Journal of Fluorescence. 19:1025-1035
ISSN: 1573-4994
1053-0509
DOI: 10.1007/s10895-009-0502-y
Popis: The ground and the singlet excited state pyridinic protonation of 9-methyl-9H-pyrido[3,4-b]indole, MBC, in water-N,N-dimethylformamide mixtures has been studied by absorption, steady state and time resolved fluorescence measurements. These proton transfer reactions elapse by a stepwise mechanism modulated by different hydrogen bonded adducts and exciplexes formed by water molecules and the pyridinic nitrogen atom of the MBC. Based in the present and previous studies, a general mechanistic Scheme for the ground and the singlet excited state MBC pyridinic protonation has been proposed. Accordingly, in the ground state, upon increasing the water proportion of the water-N,N-dimethylformamide mixtures, a hydrogen bonded complex, HBC, its hydrogen bonded proton transfer complex, PTC, a pre-cationic complex, PC, and the cation, C, are progressively formed. In the excited state, MBC, HBC and PC behave as independent fluorophores. Excited state cations, C*, are mainly formed by direct excitation of the ground state cations and, in minor proportion, by the excited state reaction of the PTC* through the CL* exciplex.
Databáze: OpenAIRE
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