Unusually slow intramolecular proton transfer dynamics of 4'-N,N-dimethylamino-3-hydroxyflavone in high n-alcohols: involvement of solvent relaxation.
Photochem Photobiol Sci
; 15(2): 266-77, 2016 Feb.
Article
en En
| MEDLINE
| ID: mdl-26811025
ABSTRACT
Excited state intramolecular proton transfer (ESIPT) time-constants of 4'-N,N-dimethylamino-3-hydroxyflavone (DMA3HF) in high n-alcohols--1-butanol, 1-hexanol and 1-decanol--were measured to be 90 ps, 130 ps and 190 ps, respectively, which are unusually slow. At the same time, the solvation time-constants of the DMA3HF enol in the same set of solvents were measured as 100 ps, 150 ps and >300 ps, respectively. Thus, both the ESIPT and enol solvation time-constants in high n-alcohols increase monotonically with the alkyl chain-length of the solvent, although the increase is not strictly proportional. It appears that the H-bonding capacity of the solvent is the single major factor influencing both processes, causing them to become closely correlated. Solvation causes a drastic change in the solvent molecular configuration around the excited enol, E*, inducing the breakage of DMA3HF···solvent inter-molecular H-bonding, which in turn promotes ESIPT. Following previously reported theoretical work on ESIPT, a qualitative description of the S1 potential energy surface can be formulated, where the involvement of solvent relaxation with the ESIPT process is explained.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Protones
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Flavonoides
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1-Butanol
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Hexanoles
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Alcoholes Grasos
Tipo de estudio:
Prognostic_studies
/
Qualitative_research
Idioma:
En
Año:
2016
Tipo del documento:
Article