The charge-transfer states in a stacked nucleobase dimer complex: A benchmark study
Adélia J. A. Aquino1,2,*, Dana Nachtigallova3,
Pavel Hobza3, Donald G. Truhlar4, Christof Hättig5, Hans Lischka1,3,*
1Institute for Theoretical Chemistry, Währingerstrasse 17,
University of Vienna, A-1090 Vienna, Austria
2Institute of Soil Research, University of Natural Resources and Life Sciences Vienna,
Peter-Jordan-Stra&sslig;e 82, A-1190 Vienna, Austria
3Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic
and Center for Biomolecules and Complex Molecular Systems, Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
4Department of Chemistry and Supercomputing Institute, University of Minnesota, Minneapolis,
5Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Universitätsstrasse 150,
D-44801 Bochum, Germany
J. Comput. Chem. 32, 1217-1227 (2011).
Received 9 August 2010; Revised 27 September 2010; Accepted 1 October 2010;
Published online: 29 November 2010
Keywords: charge transfer; excited states; coupled cluster; DFT; stacked nucleobases
Electronic singlet excitations of stacked adenine-thymine (AT) and guanine-cytosine (GC) complexes have
been investigated with respect to local excitation and charge-transfer (CT) characters.
Potential energy curves for rigid displacement of the nucleobases have been computed
to establish the distance dependence of the CT states.
The second-order algebraic diagrammatic construction [ADC(2)] method served
as reference approach for comparison to a selected set of density functionals
used within the time-dependent density functional theory (TD-DFT).
Particular attention was dedicated to the performance of the recently
developed family of M06 functionals.
The calculations for the stacked complexes show that at the ADC(2) level,
the lowest CT state is S6 for the AT and as S4 for the GC pair.
At the reference geometry, the actual charge transferred is found to be 0.73 e for AT.
In case of GC, this amount is much smaller (0.17 e).
With increasing separation of the two nucleobases, the CT state is strongly destabilized.
The M06-2X version provides a relatively good reproduction of the ADC(2) results.
It avoids the serious overstabilization and overcrowding of the spectrum found with the B3LYP functional.
On the other hand, M06-HF destabilizes the CT state too strongly.
TD-DFT/M06-2X calculations in solution (heptane, isoquinoline, and water)
using the polarizable continuum model show a stabilization of
the CT state and an increase in CT character with increasing polarity of the solvent.
(access restricted to domain theochem.rub.de)
Back to the list of Publications by the Quantum Chemistry (Hättig) Group