Torsional effects on excitation energies of thiophene derivatives induced by beta-substituents: comparison between time-dependent density functional theory and approximated coupled cluster approaches |
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Authors: | Piacenza M Della Sala F Fabiano E Maiolo T Gigli G |
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Institution: | National Nanotechnology Laboratory of INFM, Distretto Tecnologico ISUFI, Università degli Studi di Lecce, Via per Arnesano, I-73100 Lecce, Italy. mpiacenza@web.de |
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Abstract: | The influence of methyl or phenyl substitution in beta-position of dioxygenated terthiophene and diphenylthiophene on the optical properties is investigated by first-principles calculations. We compare the approximated singles and doubles coupled cluster (CC2) approach with time-dependent density functional theory methods. CC2 reproduces experimental excitation energies with an accuracy of 0.1 eV. We find that the different substituents modify the inter-ring torsional angle which in turn strongly influences the excitation energies. The steric contribution to the excitation energies have been separated from the total substituent effects. |
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Keywords: | density functional theory coupled cluster excited state oligothiophenes torsional potential |
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