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Exciton delocalization, charge transfer, and electronic coupling for singlet excitation energy transfer between stacked nucleobases in DNA: An MS-CASPT2 study

Exciton delocalization and singlet excitation energy transfer have been systematically studied for the complete set of 16 DNA nucleobase dimers in their ideal, single-strand stacked B-DNA conformation, at the MS-CASPT2 level of theory. The extent of exciton delocalization in the two lowest (π,π*) states of the dimers is determined using the symmetrized one-electron transition density matrices between the ground and excited states, and the electronic coupling is calculated using the delocalization measure and the energy splitting between the states [see F. Plasser, A. J. A. Aquino, W. L. Hase, and H. Lischka, J. Phys. Chem. A 116, 11151-11160 (2012)]. The calculated couplings lie between 0.05 eV and 0.14 eV. In the B-DNA conformation, where the interchromophoric distance is 3.38 Å, our couplings deviate significantly from those calculated with the transition charges, showing the importance of orbital overlap components for the couplings in this conformation. The calculation of the couplings is based on a two-state model for exciton delocalization. However, in three stacks with a purine in the 5′ position and a pyrimidine in the 3′ one (AT, GC, and GT), there is an energetically favored charge transfer state that mixes with the two lowest excited states. In these dimers we have applied a three-state model that considers the two locally excited diabatic states and the charge transfer state. Using the delocalization and charge transfer descriptors, we obtain all couplings between these three states. Our results are important in the context of DNA photophysics, since the calculated couplings can be used to parametrize effective Hamiltonians to model extended DNA stacks. Our calculations also suggest that the 5′-purine-pyrimidine- 3′ sequence favors the formation of charge transfer excited state

This work was funded by the Spanish Ministerio de Economia y Competividad (MINECO) (CTQ2011-26573 and UNGI10-4E-801 from FEDER (European Fund for Regional Development)), and the Catalan Agencia de Gestio d’Ajuts Universitaris i de Recerca (SGR0528) and Direccio General de la Recerca (Xarxa de Referencia en Quimica Teorica i Computacional de Catalunya).

© Journal of Chemical Physics, 2014, vol. 140, núm. 9, p. 095102

American Institute of Physics (AIP)

Author: Blancafort San José, Lluís
Voityuk, Alexander A.
Date: 2014
Abstract: Exciton delocalization and singlet excitation energy transfer have been systematically studied for the complete set of 16 DNA nucleobase dimers in their ideal, single-strand stacked B-DNA conformation, at the MS-CASPT2 level of theory. The extent of exciton delocalization in the two lowest (π,π*) states of the dimers is determined using the symmetrized one-electron transition density matrices between the ground and excited states, and the electronic coupling is calculated using the delocalization measure and the energy splitting between the states [see F. Plasser, A. J. A. Aquino, W. L. Hase, and H. Lischka, J. Phys. Chem. A 116, 11151-11160 (2012)]. The calculated couplings lie between 0.05 eV and 0.14 eV. In the B-DNA conformation, where the interchromophoric distance is 3.38 Å, our couplings deviate significantly from those calculated with the transition charges, showing the importance of orbital overlap components for the couplings in this conformation. The calculation of the couplings is based on a two-state model for exciton delocalization. However, in three stacks with a purine in the 5′ position and a pyrimidine in the 3′ one (AT, GC, and GT), there is an energetically favored charge transfer state that mixes with the two lowest excited states. In these dimers we have applied a three-state model that considers the two locally excited diabatic states and the charge transfer state. Using the delocalization and charge transfer descriptors, we obtain all couplings between these three states. Our results are important in the context of DNA photophysics, since the calculated couplings can be used to parametrize effective Hamiltonians to model extended DNA stacks. Our calculations also suggest that the 5′-purine-pyrimidine- 3′ sequence favors the formation of charge transfer excited state
This work was funded by the Spanish Ministerio de Economia y Competividad (MINECO) (CTQ2011-26573 and UNGI10-4E-801 from FEDER (European Fund for Regional Development)), and the Catalan Agencia de Gestio d’Ajuts Universitaris i de Recerca (SGR0528) and Direccio General de la Recerca (Xarxa de Referencia en Quimica Teorica i Computacional de Catalunya).
Format: application/pdf
ISSN: 0021-9606 (versió paper)
1089-7690 (versió electrònica)
Document access: http://hdl.handle.net/10256/11471
Language: eng
Publisher: American Institute of Physics (AIP)
Collection: MICINN/PN 2012-2014/CTQ2011-26573
MICINN/2010/UNGI10-4E-801
AGAUR/2009-2014/2009 SGR-528
Reproducció digital del document publicat a: http://dx.doi.org/10.1063/1.4867118
Articles publicats (D-Q)
Is part of: © Journal of Chemical Physics, 2014, vol. 140, núm. 9, p. 095102
Rights: Tots els drets reservats
Subject: Transferència de càrrega
Charge transfer
Dinàmica molecular
Molecular dynamics
Title: Exciton delocalization, charge transfer, and electronic coupling for singlet excitation energy transfer between stacked nucleobases in DNA: An MS-CASPT2 study
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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