β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH

Detalhes bibliográficos
Autor(a) principal: Dias, A.
Data de Publicação: 1996
Outros Autores: Varela, A. P., Miguel, M. da Graça, Becker, R. S., Burrows, H. D., Maçanita, A. L.
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/10316/10331
https://doi.org/10.1021/jp961406u
Resumo: The β-carbolines present a complex problem involving multiple equilibria in the excited state in hydrogen-bonding solvents including water. Three excited state species exist: neutral, cation, and zwitterion. Here we examine the multiple equilibria and excited state kinetics of harmine, using time-resolved and steady state fluorescence techniques. From an analysis of the multiexponential decays, measured at the emission wavelengths of the three species as a function of the pH, seven unknowns (four rate constants and three reciprocal lifetimes) were determined. Data analysis was made both by a previously reported numerical method and by analytical solution of the differential equation set. The results obtained accurately describe the independently obtained steady-state fluorescence results. The dramatic modifications of the equilibria and rate constants between the ground and excited states can be understood on the basis of the significative changes in charge densities on the two nitrogen atoms of harmine upon excitation. Mechanisms are proposed for the formation of excited state cation and zwitterion beginning with the excited state neutral molecule.
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spelling β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pHThe β-carbolines present a complex problem involving multiple equilibria in the excited state in hydrogen-bonding solvents including water. Three excited state species exist: neutral, cation, and zwitterion. Here we examine the multiple equilibria and excited state kinetics of harmine, using time-resolved and steady state fluorescence techniques. From an analysis of the multiexponential decays, measured at the emission wavelengths of the three species as a function of the pH, seven unknowns (four rate constants and three reciprocal lifetimes) were determined. Data analysis was made both by a previously reported numerical method and by analytical solution of the differential equation set. The results obtained accurately describe the independently obtained steady-state fluorescence results. The dramatic modifications of the equilibria and rate constants between the ground and excited states can be understood on the basis of the significative changes in charge densities on the two nitrogen atoms of harmine upon excitation. Mechanisms are proposed for the formation of excited state cation and zwitterion beginning with the excited state neutral molecule.American Chemical Society1996-11-07info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10316/10331http://hdl.handle.net/10316/10331https://doi.org/10.1021/jp961406uengThe Journal of Physical Chemistry. 100:45 (1996) 17970-17977Dias, A.Varela, A. P.Miguel, M. da GraçaBecker, R. S.Burrows, H. D.Maçanita, A. L.info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2021-09-22T11:00:52Zoai:estudogeral.uc.pt:10316/10331Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T21:01:13.657226Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
title β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
spellingShingle β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
Dias, A.
title_short β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
title_full β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
title_fullStr β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
title_full_unstemmed β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
title_sort β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
author Dias, A.
author_facet Dias, A.
Varela, A. P.
Miguel, M. da Graça
Becker, R. S.
Burrows, H. D.
Maçanita, A. L.
author_role author
author2 Varela, A. P.
Miguel, M. da Graça
Becker, R. S.
Burrows, H. D.
Maçanita, A. L.
author2_role author
author
author
author
author
dc.contributor.author.fl_str_mv Dias, A.
Varela, A. P.
Miguel, M. da Graça
Becker, R. S.
Burrows, H. D.
Maçanita, A. L.
description The β-carbolines present a complex problem involving multiple equilibria in the excited state in hydrogen-bonding solvents including water. Three excited state species exist: neutral, cation, and zwitterion. Here we examine the multiple equilibria and excited state kinetics of harmine, using time-resolved and steady state fluorescence techniques. From an analysis of the multiexponential decays, measured at the emission wavelengths of the three species as a function of the pH, seven unknowns (four rate constants and three reciprocal lifetimes) were determined. Data analysis was made both by a previously reported numerical method and by analytical solution of the differential equation set. The results obtained accurately describe the independently obtained steady-state fluorescence results. The dramatic modifications of the equilibria and rate constants between the ground and excited states can be understood on the basis of the significative changes in charge densities on the two nitrogen atoms of harmine upon excitation. Mechanisms are proposed for the formation of excited state cation and zwitterion beginning with the excited state neutral molecule.
publishDate 1996
dc.date.none.fl_str_mv 1996-11-07
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/article
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status_str publishedVersion
dc.identifier.uri.fl_str_mv http://hdl.handle.net/10316/10331
http://hdl.handle.net/10316/10331
https://doi.org/10.1021/jp961406u
url http://hdl.handle.net/10316/10331
https://doi.org/10.1021/jp961406u
dc.language.iso.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv The Journal of Physical Chemistry. 100:45 (1996) 17970-17977
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dc.publisher.none.fl_str_mv American Chemical Society
publisher.none.fl_str_mv American Chemical Society
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