TY - JOUR
T1 - Singlet La and Lb Bands for N-Acenes (N = 2-7)
T2 - A CASSCF/CASPT2 Study
AU - Bettanin, Fernanda
AU - Ferrão, Luiz F.A.
AU - Pinheiro, Max
AU - Aquino, Adélia J.A.
AU - Lischka, Hans
AU - Machado, Francisco B.C.
AU - Nachtigallova, Dana
N1 - Funding Information:
*E-mail: ferrao@ita.br. *E-mail: fmachado@ita.br. *E-mail: dana.nachtigallova@uochb.cas.cz. ORCID Adeĺ ia J. A. Aquino: 0000-0003-4891-6512 Hans Lischka: 0000-0002-5656-3975 Francisco B. C. Machado: 0000-0002-2064-3463 Dana Nachtigallova: 0000-0002-9588-8625 Funding The authors acknowledge the research and fellowship support of the Fundaca̧ õ de Amparo à Pesquisa do Estado de Saõ Paulo (FAPESP) under process 2014/24155-6, to Coordenaca̧ õ de Aperfeicoamento̧ de Pessoal de Nivél (CAPES), under processes CAPES/ITA No. 23038.005811/2014-89 and CAPES/PVE No. 8881.066022/2014-01, and to Conselho Nacional de Desenvolvimento Cientifí co e Tecnológico (CNPq), Process Nos. 307052/2016-8 and 309051/2016-9. We also want to thank the FAPESP/Texas Tech University SPRINT program (project no. 2015/50018-9) for travel support. D.N. acknowledges the support of the Czech Science Fundation (project no. 16-16959S). This work was part of the Research Project RVO: 61388963 of the Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic. Notes The authors declare no competing financial interest.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/9/12
Y1 - 2017/9/12
N2 - In this work CASPT2 calculations of polyacenes (from naphthalene to heptacene) were performed to find a methodology suitable for calculations of the absorption spectra, in particular of the La (B2u state) and Lb (B3u state) bands, of more extended systems. The effect of the extension of the active space and of freezing σ orbitals was investigated. The MCSCF excitation energy of the B2u state is not sensitive to the size of the active space used. However, the CASPT2 results depend strongly on the amount of σ orbitals frozen reflecting the ionic character of the B2u state. On the other hand, the excitation energies of the B3u state are much more sensitive to the size of the active space used in the calculations reflecting its multiconfigurational character. We found a good agreement with experimental data for both bands by including 14 electrons in 14 π orbitals in the active space followed by the CASPT2(14,14) perturbation scheme in which both σ and π orbitals are included.
AB - In this work CASPT2 calculations of polyacenes (from naphthalene to heptacene) were performed to find a methodology suitable for calculations of the absorption spectra, in particular of the La (B2u state) and Lb (B3u state) bands, of more extended systems. The effect of the extension of the active space and of freezing σ orbitals was investigated. The MCSCF excitation energy of the B2u state is not sensitive to the size of the active space used. However, the CASPT2 results depend strongly on the amount of σ orbitals frozen reflecting the ionic character of the B2u state. On the other hand, the excitation energies of the B3u state are much more sensitive to the size of the active space used in the calculations reflecting its multiconfigurational character. We found a good agreement with experimental data for both bands by including 14 electrons in 14 π orbitals in the active space followed by the CASPT2(14,14) perturbation scheme in which both σ and π orbitals are included.
UR - http://www.scopus.com/inward/record.url?scp=85029222760&partnerID=8YFLogxK
U2 - 10.1021/acs.jctc.7b00302
DO - 10.1021/acs.jctc.7b00302
M3 - Article
C2 - 28719203
AN - SCOPUS:85029222760
SN - 1549-9618
VL - 13
SP - 4297
EP - 4306
JO - Journal of Chemical Theory and Computation
JF - Journal of Chemical Theory and Computation
IS - 9
ER -