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Issue 1, 2014
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Electronically excited states and photochemical reaction mechanisms of β-glucose

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Abstract

Carbohydrates are important molecular components of living matter. While spectroscopic and computational studies have been performed on carbohydrates in the electronic ground state, the lack of a chromophore complicates the elucidation of the excited-state properties and the photochemistry of this class of compounds. Herein, we report on the first computational investigation of the singlet photochemistry of β-glucose. It is shown that low-lying singlet excited states are of nσ* nature. Our computations of the singlet vertical excitation energies predict absorption from 6.0 eV onward. Owing to a dense manifold of weakly-absorbing states, a sizable and broad absorption in the ultraviolet-C range arises. We have explored two types of photochemical reaction mechanisms: hydrogen-detachment processes for each of the five O–H groups and a C–O ring-opening process. Both types of reactions are driven by repulsive nσ* states that are readily accessible from the Franck–Condon region and lead to conical intersections in a barrierless fashion. We have optimized the geometries of the conical intersections involved in these photochemical processes and found that these intersections are located around 5.0 eV for the O–H hydrogen-detachment reactions and around 4.0 eV for the C–O ring-opening reaction. The energies of all conical intersections are well below the computed absorption edge. The calculations were performed using linear-response methods for the computation of the vertical excitation energies and multiconfigurational methods for the optimization of conical intersections and the computation of energy profiles.

Graphical abstract: Electronically excited states and photochemical reaction mechanisms of β-glucose

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Supplementary files

Article information


Submitted
06 Jun 2013
Accepted
24 Jul 2013
First published
20 Aug 2013

Phys. Chem. Chem. Phys., 2014,16, 38-47
Article type
Paper

Electronically excited states and photochemical reaction mechanisms of β-glucose

D. Tuna, A. L. Sobolewski and W. Domcke, Phys. Chem. Chem. Phys., 2014, 16, 38
DOI: 10.1039/C3CP52359D

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