Tetra-radical and ionic S1/S0 conical intersections of cyclobutadiene

Sumita, Masato; Saito, Kazuya

doi:10.1016/j.chemphys.2010.03.024

Cited by 9 publications

(26 citation statements)

References 43 publications

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“…There are two excited states under 4.13 eV as shown in Table 1. One is the symmetry allowed single-electron excited state, on our qualitative discussion [10]. Indeed, this prediction will be proved throughout this paper.…”

Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 98%

“…[4]), the HOMO to next LUMO double-electron excited state is the most plausible as the active state for the reaction from CBD to THD since the electron configuration of the excited state becomes that of the ground state of THD. However, its vertically excited state is energetically too high according to our preliminary calculation [10]. We predicted that the HOMO to LUMO double-electron excited state is alternatively responsible for this photoreaction on the basis of qualitative discussion.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, the main reaction path of TB-CBD via the double-electron excited state is the bond alternation at the present calculation level. According to our qualitative predication, the channel from S 1 to S 0 for the criss-cross reaction [2,7] is tetra-radical CI (CI tetra ) [10]. We found S 1 /S 0 CI tetra by exploring the S 1 /S 0 degeneracy space for the parent CBD.…”

Section: Exploring S 1 /S 0 Degeneracy Spacementioning

confidence: 99%

“…In comparison with the experimental result (1.441 and 1.527 Å for the double and single bonds) [2,26], the lengthes of the double bonds of the four-membered ring are underestimated. We know that this discrepancy between the experimental and CASSCF-calculated lengths will be diminished by adding the !-orbitals of the four-membered ring to the active space [10]. Unfortunately, however, the present system is too large to expand the active space to the !-orbitals.…”

Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 99%

“…Indeed, this prediction will be proved throughout this paper. [10]. Therefore, the relaxation of the four-membered ring of TB-CBD is incomplete due to the steric repulsion between tert-butyl groups.…”

Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 99%

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Computational study on photo- and thermo-reactions between tetra-tert-butyl-substituted cyclobutadiene and tetrahedrane

Sumita

Saito

Tateyama

2011

Computational and Theoretical Chemistry

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We have investigated the photo-chemical reaction from tetra-tert-butylcyclobutadiene (TB-CBD) to tetra-tert-butyltetrahedrane (TB-THD) and its reverse thermo-chemical reaction processes in the ground state by using CASSCF and MRMP2 computational methods. According to our results, the initial step of the photochemical reaction is the show only photo-physical property without any reactions because the final point of the minimum-energy-path (MEP) calculation at the MRMP2//CASSCF level is the S 1 /S 0 conical intersection (ionic like structure), which results in turning back to TB-CBD in the S 0 state. However, on the way to the final point of the MEP, it is possible for some TB-CBD to transit at another S 1 /S 0 conical intersection (tetra radical like structure), which is related to the photoreaction from TB-CBD to TB-THD. On the other hand, two routes from TB-THD to TB-CBD were found in the S 0 state. One is the route via bicyclodiradical transition state. The other is the ionic transition state. In both reaction 3 paths, only one TS is there in contrast to the plural step reaction suggested previously.

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Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Exploring S 1 /S 0 Degeneracy Spacementioning

confidence: 99%

Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 99%

Section: 11vertical Excitation Energy Of Tb-cbdmentioning

confidence: 99%

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Computational study on photo- and thermo-reactions between tetra-tert-butyl-substituted cyclobutadiene and tetrahedrane

Sumita

Saito

Tateyama

2011

Computational and Theoretical Chemistry

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Intra and interatomic energy contributions in the photophysical relaxation of small aromatic molecules

Jara‐Cortés,

Pérez‐Pimienta,

Park

et al. 2024

ChemPhotoChem

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A theoretical study of the non‐radiative photophysical relaxation mechanisms of the first singlet excited state of benzene, cyclobutadiene and fulvene is presented. For these molecules, the calculation of the Minimum Energy Path (MEP) leading from the Franck‐Condon region to the surface crossing with the ground state is carried out. Subsequently, the decomposition of the electronic energies into atomic and pair contributions is performed using the Interacting Quantum Atom (IQA) method. The IQA approach provides the important mechanistic information necessary to rationalise some relevant aspects of the processes, such as the components that explain the appearance of an energy barrier or that favour the crossing between potential energy surfaces (PES); it also allows to quantify the direct effect on the MEP due to the inclusion of a substituent. In particular, it is shown how the IQA energies allow measuring the extent to which the formation of biradicaloid structures affects the crossing of the PES. The analysis of electron density functions suggest that aromaticity is not a driving force on the relaxation processes. Overall, this work shows the potential of the IQA method as a useful tool for the detailed description of photophysical processes.

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Cyclobutadiene automerization and rotation of ethylene: Energetics of the barriers by using Spin‐polarized wave functions

San‐Fabián

Moscardó

2014

J Comput Chem

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Spin-projected spin polarized Møller-Plesset and spin polarized coupled clusters calculations have been made to estimate the cyclobutadiene automerization, the ethylene torsion barriers in their ground state, and the gap between the singlet and triplet states of ethylene. The results have been obtained optimizing the geometries at MP4 and/or CCSD levels, by an extensive Gaussian basis set. A comparative analysis with more complex calculations, up to MP5 and CCSDTQP, together with others from the literature, have also been made, showing the efficacy of using spin-polarized wave functions as a reference wave function for Møller-Plesset and coupled clusters calculations, in such problems.

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Tetra-radical and ionic S1/S0 conical intersections of cyclobutadiene

Cited by 9 publications

References 43 publications

Computational study on photo- and thermo-reactions between tetra-tert-butyl-substituted cyclobutadiene and tetrahedrane

Computational study on photo- and thermo-reactions between tetra-tert-butyl-substituted cyclobutadiene and tetrahedrane

Intra and interatomic energy contributions in the photophysical relaxation of small aromatic molecules

Cyclobutadiene automerization and rotation of ethylene: Energetics of the barriers by using Spin‐polarized wave functions

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