Theoretical study of one- and two-photon absorption spectra of azoaromatic compounds


Autoria(s): SILVA, D. L.; KRAWCZYK, P.; BARTKOWIAK, W.; MENDONCA, Cleber Renato
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

19/04/2012

19/04/2012

2009

Resumo

In this study, the one- and two-photon absorption spectra of seven azoaromatic compounds (five pseudostilbenes-type and two aminoazobenzenes) were theoretically investigated using the density functional theory combined with the response functions formalism. The equilibrium molecular structure of each compound was obtained at three different levels of theory: Hartree-Fock, density functional theory (DFT), and Moller-Plesset 2. The effect of solvent on the equilibrium structure and the electronic transitions of the compounds were investigated using the polarizable continuum model. For the one-photon absorption, the allowed pi ->pi(*) transition energy showed to be dependent on the molecular structures and the effect of solvent, while the n ->pi(*) and pi ->pi(*)(n) transition energies exhibited only a slight dependence. An inversion between the bands corresponding to the pi ->pi(*) and n ->pi(*) states due to the effect of solvent was observed for the pseudostilbene-type compounds. To characterize the allowed two-photon absorption transitions for azoaromatic compounds, the response functions formalism combined with DFT using the hybrid B3LYP and PBE0 functionals and the long-range corrected CAM-B3LYP functional was employed. The theoretical results support the previous findings based on the three-state model. The model takes into account the ground and two electronic excited states and has already been used to describe and interpret the two-photon absorption spectrum of azoaromatic compounds. The highest energy two-photon allowed transition for the pseudostilbene-type compounds shows to be more effectively affected (similar to 20%) by the torsion of the molecular structure than the lowest allowed transition (similar to 10%). In order to elucidate the effect of the solvent on the two-photon absorption spectra, the lowest allowed two-photon transition (dipolar transition) for each compound was analyzed using a two-state approximation and the polarizable continuum model. The results obtained reveal that the effect of solvent increases drastically the two-photon cross-section of the dipolar transition of the pseudostilbene-type compounds. In general, the features of both one- and two-photon absorption spectra of the azoaromatic compounds are well reproduced by the theoretical calculations.

FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)

CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)

European Commission[MRTN-CT-2006-035859]

Identificador

JOURNAL OF CHEMICAL PHYSICS, v.131, n.24, 2009

0021-9606

http://producao.usp.br/handle/BDPI/16453

10.1063/1.3271239

http://dx.doi.org/10.1063/1.3271239

Idioma(s)

eng

Publicador

AMER INST PHYSICS

Relação

Journal of Chemical Physics

Direitos

openAccess

Copyright AMER INST PHYSICS

Palavras-Chave #density functional theory #excited states #ground states #HF calculations #librational states #molecular configurations #molecular moments #molecule-photon collisions #organic compounds #oscillator strengths #perturbation theory #photoexcitation #solvent effects #two-photon spectra #DENSITY-FUNCTIONAL THEORY #NONLINEAR-OPTICAL-PROPERTIES #EXCITATION-ENERGIES #CONJUGATED MOLECULES #VISUAL CHROMOPHORES #ORGANIC-MOLECULES #TRANS-AZOBENZENE #CROSS-SECTIONS #EXCITED-STATES #APPROXIMATION #Physics, Atomic, Molecular & Chemical
Tipo

article

original article

publishedVersion