Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations
Pyranoflavylium cations are synthetic analogues of pyranoanthocyanin, colored pigments, formed from grape anthocyanins during the maturation of red wines. Studies of a series of monosubstituted pyranoflavylium cations, ranging from methoxy (PF+-OMe) to cyano (PF+-CN), have shown that they display fl...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-06-01
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| Series: | Journal of Photochemistry and Photobiology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2666469022000033 |
| _version_ | 1818191763110625280 |
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| author | Eli M. Espinoza John A. Clark Cassio Pacheco da. Silva James B. Derr Gustavo Thalmer de Medeiros Silva Mimi K. Billones Maryann Morales Frank H. Quina Valentine I. Vullev |
| author_facet | Eli M. Espinoza John A. Clark Cassio Pacheco da. Silva James B. Derr Gustavo Thalmer de Medeiros Silva Mimi K. Billones Maryann Morales Frank H. Quina Valentine I. Vullev |
| author_sort | Eli M. Espinoza |
| collection | DOAJ |
| description | Pyranoflavylium cations are synthetic analogues of pyranoanthocyanin, colored pigments, formed from grape anthocyanins during the maturation of red wines. Studies of a series of monosubstituted pyranoflavylium cations, ranging from methoxy (PF+-OMe) to cyano (PF+-CN), have shown that they display fluorescence and form triplet states that sensitize singlet oxygen formation in acidified acetonitrile. In alcohol-water mixtures, they behave as photoacids, undergoing adiabatic excited state proton transfer (ESPT) to water on a picosecond timescale, as confirmed in this report by femtosecond pump-probe spectroscopy. In contrast, the corresponding dimethylamino substituted pyranoflavylium cation (PF+-NMe2) is virtually non-fluorescent under the same conditions and exhibits a long-wavelength absorption band that has been attributed to a charge-transfer (CT) transition. Indeed, pump-probe spectroscopy of PF+-NMe2 in acidified acetonitrile shows ultrafast (<1 ps) formation of a CT state that decays back to the ground state with a 12–13 ps lifetime. In acidified methanol, the initial Franck-Condon CT state (ca. 3 ps lifetime) converts to a 13 ps lifetime CT state analogous to that in acetonitrile. In 50:50 ethanol:water and 30:70 methanol:water mixtures, PF+-NMe2 exhibits a short-lived (3–8 ps) initial CT state, an intermediate lifetime (30 ps) CT state and a much longer lived (130 ps) species attributed to a twisted intramolecular CT state. Thus, in addition to demonstrating that the photophysics of PF+-NMe2 is dominated by CT rather than ESPT, pump-probe spectroscopy provides details of the solvent-dependent dynamics of the CT decay pathways. |
| first_indexed | 2024-12-12T00:19:46Z |
| format | Article |
| id | doaj.art-d35cc8c149c44680b5f070e317fe2e57 |
| institution | Directory Open Access Journal |
| issn | 2666-4690 |
| language | English |
| last_indexed | 2024-12-12T00:19:46Z |
| publishDate | 2022-06-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Photochemistry and Photobiology |
| spelling | doaj.art-d35cc8c149c44680b5f070e317fe2e572022-12-22T00:44:45ZengElsevierJournal of Photochemistry and Photobiology2666-46902022-06-0110100110Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cationsEli M. Espinoza0John A. Clark1Cassio Pacheco da. Silva2James B. Derr3Gustavo Thalmer de Medeiros Silva4Mimi K. Billones5Maryann Morales6Frank H. Quina7Valentine I. Vullev8Department of Chemistry, University of California, Riverside, CA 92521, USADepartment of Bioengineering, University of California, Riverside, CA 92521, USAInstituto de Química, Universidade de São Paulo, Avenida Lineu Prestes 748, Cidade Universitária, São Paulo 05508-900, BrazilDepartment of Biochemistry, University of California, Riverside, CA 92521, USAInstituto de Química, Universidade de São Paulo, Avenida Lineu Prestes 748, Cidade Universitária, São Paulo 05508-900, BrazilDepartment of Biology, University of California, Riverside, CA 92521, USADepartment of Chemistry, University of California, Riverside, CA 92521, USAInstituto de Química, Universidade de São Paulo, Avenida Lineu Prestes 748, Cidade Universitária, São Paulo 05508-900, BrazilDepartment of Chemistry, University of California, Riverside, CA 92521, USA; Department of Bioengineering, University of California, Riverside, CA 92521, USA; Department of Biochemistry, University of California, Riverside, CA 92521, USA; Materials Science and Engineering Program, University of California, Riverside, CA 92521, USA; Corresponding author.Pyranoflavylium cations are synthetic analogues of pyranoanthocyanin, colored pigments, formed from grape anthocyanins during the maturation of red wines. Studies of a series of monosubstituted pyranoflavylium cations, ranging from methoxy (PF+-OMe) to cyano (PF+-CN), have shown that they display fluorescence and form triplet states that sensitize singlet oxygen formation in acidified acetonitrile. In alcohol-water mixtures, they behave as photoacids, undergoing adiabatic excited state proton transfer (ESPT) to water on a picosecond timescale, as confirmed in this report by femtosecond pump-probe spectroscopy. In contrast, the corresponding dimethylamino substituted pyranoflavylium cation (PF+-NMe2) is virtually non-fluorescent under the same conditions and exhibits a long-wavelength absorption band that has been attributed to a charge-transfer (CT) transition. Indeed, pump-probe spectroscopy of PF+-NMe2 in acidified acetonitrile shows ultrafast (<1 ps) formation of a CT state that decays back to the ground state with a 12–13 ps lifetime. In acidified methanol, the initial Franck-Condon CT state (ca. 3 ps lifetime) converts to a 13 ps lifetime CT state analogous to that in acetonitrile. In 50:50 ethanol:water and 30:70 methanol:water mixtures, PF+-NMe2 exhibits a short-lived (3–8 ps) initial CT state, an intermediate lifetime (30 ps) CT state and a much longer lived (130 ps) species attributed to a twisted intramolecular CT state. Thus, in addition to demonstrating that the photophysics of PF+-NMe2 is dominated by CT rather than ESPT, pump-probe spectroscopy provides details of the solvent-dependent dynamics of the CT decay pathways.http://www.sciencedirect.com/science/article/pii/S2666469022000033Pyranoflavylium cationsPyranoanthocyaninsCharge transferProton transferPump-probe spectroscopy |
| spellingShingle | Eli M. Espinoza John A. Clark Cassio Pacheco da. Silva James B. Derr Gustavo Thalmer de Medeiros Silva Mimi K. Billones Maryann Morales Frank H. Quina Valentine I. Vullev Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations Journal of Photochemistry and Photobiology Pyranoflavylium cations Pyranoanthocyanins Charge transfer Proton transfer Pump-probe spectroscopy |
| title | Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations |
| title_full | Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations |
| title_fullStr | Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations |
| title_full_unstemmed | Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations |
| title_short | Charge transfer vs. proton transfer in the excited-state dynamics of biomimetic pyranoflavylium cations |
| title_sort | charge transfer vs proton transfer in the excited state dynamics of biomimetic pyranoflavylium cations |
| topic | Pyranoflavylium cations Pyranoanthocyanins Charge transfer Proton transfer Pump-probe spectroscopy |
| url | http://www.sciencedirect.com/science/article/pii/S2666469022000033 |
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