Configuration interaction study of singlet excited state of thiophene and its cyano derivative oligomers

Citation
D. Chakraborty et Jb. Lagowski, Configuration interaction study of singlet excited state of thiophene and its cyano derivative oligomers, J CHEM PHYS, 115(1), 2001, pp. 184-194
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF CHEMICAL PHYSICS
ISSN journal
0021-9606 → ACNP
Volume
115
Issue
1
Year of publication
2001
Pages
184 - 194
Database
ISI
SICI code
0021-9606(20010701)115:1<184:CISOSE>2.0.ZU;2-L
Abstract
Using the singles configuration interaction (CIS) theoretical approach, we investigated the nature of the geometric conformations and electronic trans itions in pi -conjugated oligo(thiophene)s, and their cyano derivatives. Ge ometry optimizations were carried at the restricted Hartree-Fock (RHF/3-21G *) level for the ground-state configurations, which were followed by calcul ations of first (lowest) singlet excitation energies using the CIS (CIS/3-2 1G*) method. In agreement with several previous theoretical/experimental st udies, this investigation indicates that the cyano substituted thiophene po lymer has a considerably smaller intrinsic band gap than its parent polymer . CIS calculations produce singlet excitation energies in excellent agreeme nt with the experimental values (similar to0.1-0.5 eV). They also show that delocalized first singlet excited states (CIS) are accompanied by a strong geometry relaxation in comparison to their ground-state (HF) geometries. T he shape and the location of the relaxation depends on the oligomer length. (C) 2001 American Institute of Physics.