title: Torsional effects on excitation energies of thiophene derivatives induced by beta-substituents: comparison between time-dependent density functional theory and approximated coupled cluster approaches.
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.
authors.affiliation: National Nanotechnology Laboratory of INFM, Distretto Tecnologico ISUFI, Università degli Studi di Lecce, Via per Arnesano, I-73100 Lecce, Italy. mpiacenza@web.de
authors.forename: M
authors.initials: M
authors.lastname: Piacenza
authors.forename: F
authors.initials: F
authors.lastname: Della Sala
authors.forename: E
authors.initials: E
authors.lastname: Fabiano
authors.forename: T
authors.initials: T
authors.lastname: Maiolo
authors.forename: G
authors.initials: G
authors.lastname: Gigli
mesh_terms: D016000:Cluster Analysis; D004583:Electrons; D008958:Models, Molecular; D008968:Molecular Conformation; D013876:Thiophenes / Q000737:chemistry*; D013997:Time Factors
chemical_list: D013876:Thiophenes