Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

6-2013

Journal or Book Title

Journal of Physical Chemistry B

Volume

117

Issue

49

First Page

15386

Last Page

15394

DOI

10.1021/jp404686c

Abstract

Excited-state enol to keto tautomerization of 7-hydroxy-4-methylcoumarin (C456) with three water molecules (C456:3H2O), is theoretically investigated using time-dependent density functional theory (TDDFT) combined with the polarizable continuum model and 200 waters explicitly modeled with the effective fragment potential. The tautomerization of C456 in the presence of three water molecules is accompanied by an asynchronous quadruple hydrogen atom transfer reaction from the enol to the keto tautomer in the excited state. TDDFT with the PBE0 functional and the DH(d,p) basis set is used to calculate the excited-state reaction barrier height, absorption (excitation), and fluorescence (de-excitation) energies. These results are compared with the available experimental and theoretical data. In contrast to previous work, it is predicted here that the coumarin 456 system undergoes a hydrogen atom transfer, not a proton transfer. The calculated reaction barrier of the first excited state of C456:3H2O with 200 water molecules is found to be −0.23 kcal/mol without zero-point energy (−5.07 kcal/mol with zero point energy, i.e., the activation energy).

Comments

Reprinted (adapted) with permission from Journal of Physical Chemistry B 117 (2013): 15386, doi:10.1021/jp404686c. Copyright 2013 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Included in

Chemistry Commons

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