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
Autor(a) principal: | |
---|---|
Data de Publicação: | 1996 |
Outros Autores: | , , , , |
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. |
id |
RCAP_350108f46f5ae3b86da82f1f7f34b01e |
---|---|
oai_identifier_str |
oai:estudogeral.uc.pt:10316/10331 |
network_acronym_str |
RCAP |
network_name_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository_id_str |
7160 |
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 |
format |
article |
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 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.publisher.none.fl_str_mv |
American Chemical Society |
publisher.none.fl_str_mv |
American Chemical Society |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
collection |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
repository.mail.fl_str_mv |
|
_version_ |
1799133904743956480 |