Theoretical investigations on valence vibronic transitions

Borges, Itamar; Rocha, Alexandre B.; Bielschowsky, Carlos Eduardo

doi:10.1590/s0103-97332005000600011

Cited by 12 publications

(6 citation statements)

References 54 publications

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“…[28] with the difference that while here all degrees of freedom are included and a Monte-Carlo integration is performed; in Ref. [28], a few degrees are selected for analytical integration.…”

Section: Methodsmentioning

confidence: 99%

Electronic spectra of nitroethylene

Borges

Barbatti

Aquino

et al. 2011

Int J of Quantum Chemistry

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A systematic study of the electronic excited states of nitroethylene (C₂H₃NO₂) was carried out using the approximate coupled-cluster singles-and-doubles approach with the resolution of the identity (RI-CC2), the time dependent density functional theory with the CAMB3LYP functional (TDDFT/CAMB3LYP) and the DFT multireference configuration interaction (DFT/MRCI) method. Vertical transition energies and optical oscillator strengths were computed for a maximum of 20 singlet transitions. Semiclassical simulations of the ultraviolet (UV) spectra were performed at the RI-CC2 and DFT/MRCI levels. The main features in the UV spectrum were assigned to a weak n-π* transition, and two higher energy π_CC+O−π* bands. These characteristics are common to molecules containing NO2 groups. Simulated spectra are in good agreement with the experimental spectrum. The energy of the bands in the DFT/MRCI simulation agrees quite well with the experiment, although it overestimates the band intensities. RI-CC2 produced intensities comparable to the experiment, but the bands were blue shifted. A strong π_CC+O−π* band, not previously measured, was found in the 8–9 eV range

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Section: Methodsmentioning

confidence: 99%

Electronic spectra of nitroethylene

Borges

Barbatti

Aquino

et al. 2011

Int J of Quantum Chemistry

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“…The calculated excitation energy of the S 2 (1 1 A 2 ) state would agree well with the measured CT band II energy, but it is symmetry forbidden; on the other hand, intensity can be gained due to vibronic effects. 83 The next transition (1 1 B 2 ) would be too high (0.55 eV) in comparison with the CT band II when using the SOS-ADC(2) method.…”

Section: Geometry Statementioning

confidence: 99%

Intermolecular interactions and charge transfer transitions in aromatic hydrocarbon–tetracyanoethylene complexes

Aquino

Borges

Nieman

et al. 2014

Phys. Chem. Chem. Phys.

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A comprehensive theoretical study of the electronically excited states in complexes between tetracyanoethylene (TCNE) and three aromatic electron donors, benzene, naphthalene and anthracene, was performed with a focus on charge transfer (CT) transitions. The results show that the algebraic diagrammatic construction method to second order (ADC(2)) provides excellent possibilities for reliable calculations of CT states. Significant improvements in the accuracy of the computed transition energies are obtained by using the scaled opposite-spin (SOS) variant of ADC(2). Solvent effects were examined on the basis of the conductor-like screening model (COSMO) which has been implemented recently in the ADC(2) method. The dielectric constant and the refractive index of dichloromethane have been chosen in the COSMO calculations to compare with experimental solvatochromic effects. The computation of optimized ground state geometries and enthalpies of formation has been performed at the second-order Møller-Plesset perturbation theory (MP2) level. By comparison with experimental data and with high-level coupled-cluster methods including explicitly correlated (F12) wave functions, the importance of the SOS approach is demonstrated for the ground state as well. In the benzene-TCNE complex, the two lowest electronic excitations are of CT character whereas in the naphthalene and anthracene TCNE complexes three low-lying CT states are observed. As expected, they are strongly stabilized by the solvent. Geometry optimization in the lowest excited state allowed the calculation of fluorescence transitions. Solvent effects lead to a zero gap between S1 and S0 for the anthracene-TCNE complex. Therefore, in the series of benzene-TCNE to anthracene a change from a radiative to a nonradiative decay mechanism to the ground state is to be expected.

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“…These molecules have been excited at the valence7–14 and inner shell regions,8, 15–21 using synchrotron radiation and electron energy loss, or laser spectrometers. Theoretical studies have been done for both DMSO1, 3, 22–24 and acetone,25–29 in the valence region, mainly using configuration interaction methods.…”

Section: Introductionmentioning

confidence: 99%

Photoabsorption spectroscopy of dimethyl sulfoxide at the O1s, C1s, S2s, and S2p Regions: A comparison with acetone

Leite

Barros

Ferreira

et al. 2012

Int J of Quantum Chemistry

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The S2p, S2s, C1s, and O1s Total Ion Yield (TIY) spectra of gaseous dimethyl sulfoxide (DMSO) and the C1s and O1s TIY spectra of acetone were measured using tunable synchrotron radiation. To establish a complete and accurate spectral analysis, the assignments for the main experimental bands were carried out using density functional theory (DFT) calculations based on half core hole (HCH) method, as implemented in the StoBe-deMon program, and ab initio calculations, based on the improved virtual orbital (IVO) method, as implemented in the GSCF3 program, using Hartree-Fock. The hole state was calculated in Huzinaga basis sets for the IVO method and IGLO-III basis sets for the HCH method. A nonlocal BE88-PD86 DFT method was used. The geometric parameters were calculated using the DFT-B3LYP method with the 6-311þG** basis sets. The experimental and theoretical results for the ionization potentials and the threshold energies are quite similar. The results reflect some differences for both molecules, likely caused by the presence of the S¼O (C s symmetry) as well as the C¼O (C 2v symmetry) groups.

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Theoretical investigations on valence vibronic transitions

Cited by 12 publications

References 54 publications

Electronic spectra of nitroethylene

Electronic spectra of nitroethylene

Intermolecular interactions and charge transfer transitions in aromatic hydrocarbon–tetracyanoethylene complexes

Photoabsorption spectroscopy of dimethyl sulfoxide at the O1s, C1s, S2s, and S2p Regions: A comparison with acetone

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