ChemInform Abstract: Computational Study of Jahn-Teller Type Distortions in Radical Cations of Methyl-Substituted Cyclopropanes

ChemInform ◽  
2010 ◽  
Vol 24 (7) ◽  
pp. no-no
Author(s):  
K. KROGH-JESPERSEN ◽  
H. D. ROTH
Keyword(s):  
Computational Study ◽  
Radical Cations ◽  
Jahn Teller ◽  
Substituted Cyclopropanes

The structures and stabilities of singlet and triplet dithiatriazines: a computational study

1988 ◽  
Vol 66 (9) ◽  
pp. 2279-2284 ◽  
Author(s):  
R. E. Hoffmeyer ◽  
W.-T. Chan ◽  
J. D. Goddard ◽  
R. T. Oakley
Keyword(s):  
Excited States ◽  
Electron Correlation ◽  
Computational Study ◽  
Geometry Optimization ◽  
Hartree Fock ◽  
Structural Distortions ◽  
Energy Gaps ◽  
Jahn Teller ◽  
Moller Plesset ◽  
Triplet Excited States

Ab initio molecular orbital and Møller–Plesset perturbation theory calculations have been carried out on two model dithiatriazines RCN3S2 (R = H, NH2). With geometry optimization and the inclusion of electron correlation both of these dithiatriazines are predicted to be ground state singlets. Both molecules have low-lying triplet excited states, with energy gaps of 6.6 (R = H) and 13.0 (R = NH2) kcal mol−1. The singlet dithiatriazines distort from high (C2v) to low (Cs) symmetry, and these changes are important in determining the relative energies of the singlet and triplet molecules. The structural distortions experienced by these molecules are related to Hartree–Fock and Jahn–Teller instabilities in other thiazene heterocycles.

Description of Bond Pseudorotation, Bond Pseudolibration, and Ring Pseudoinversion Processes Caused by the Pseudo-Jahn–Teller Effect: Fluoro Derivatives of the Cyclopropane Radical Cation

2014 ◽  
Vol 67 (3) ◽  
pp. 435 ◽  
Author(s):  
Wenli Zou ◽  
Dieter Cremer
Keyword(s):  
Radical Cation ◽  
Positive Charge ◽  
Radical Cations ◽  
Molecular Geometry ◽  
Teller Effect ◽  
Curvilinear Coordinates ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Derivatives Of ◽  
Fluoro Derivatives

Curvilinear coordinates are used to describe the molecular geometry and the pseudo-Jahn–Teller surface of F-substituted cyclopropane radical cations using the equation-of-motion coupled cluster EOMIP-CCSD/cc-pVTZ approach. The monofluoro derivative 2 undergoes bond pseudolibration (incomplete bond pseudorotation) between two symmetry-equivalent biradicaloid forms separated by a barrier of 2.2 kcal mol–1 (1 kcal mol–1 = 4.186 kJ mol–1) at low temperature. Bond pseudorotation and ring pseudoinversion have barriers of 12.1 and 16.5 kcal mol–1 respectively. The relative energies of 2 are affected by the distribution of the positive charge in the C3 ring and the formation of a CF bond with partial π character. There is a change of the CF bond length from 1.285 to 1.338 Å along the bond pseudorotation path. The changes of the CF bond outweigh the deformation effects of the C3 ring; however, both are a result of the pseudo-Jahn–Teller effect according to an (A′ + A′′) ⊗ (a′ + a′′) interaction. For the pentafluoro derivative 3 of the cyclopropane radical cation, bond pseudorotation has a barrier of 16.3 kcal mol–1 whereas ring pseudoinversion is hindered by a barrier of 21.7 kcal mol–1. Radical cation 3 is the first example of a trimethylene radical cation.

scholarly journals Table-Top X-ray Spectroscopy of Benzene Radical Cation

2020 ◽  
Author(s):  
Michael Epshtein ◽  
Valeriu Scutelnic ◽  
Zheyue Yang ◽  
Tian Xue ◽  
Marta L. Vidal ◽  
...  
Keyword(s):  
Transient Absorption ◽  
High Harmonic ◽  
Radical Cations ◽  
Spin Coupling ◽  
X Rays ◽  
X Ray ◽  
Two Photon ◽  
Jahn Teller ◽  
Theoretical Paper ◽  
High Level

<p></p><p>Ultrafast table-top x-ray spectroscopy <a>at the carbon K-edge </a>is used to measure the x-ray spectral features of benzene <a>radical cations (Bz<sup>+</sup>). The ground state of the cation is prepared selectively by </a><a>two-photon ionization of neutral benzene, and the x-ray spectra are probed at early times after the ionization by transient absorption using x-rays produced by high harmonic generation (HHG). </a><a>Bz<sup>+</sup> is well known to undergo Jahn-Teller </a>distortion, leading to a lower symmetry and splitting of the π orbitals. Comparison of the x-ray absorption spectra of the neutral and the cation reveals a splitting of the two degenerate π* orbitals as well as an appearance of a new peak due to excitation to the partially occupied π -subshell. The <a>π*</a> orbital splitting of the cation, elucidated on the basis of high-level calculations in a companion theoretical paper [Vidal et al, submitted to J. Phys. Chem. Lett.; ChemRxiv link: doi XXXXX], is discovered to be due to both the symmetry distortion and even more dominant spin coupling of the unpaired electron in the partially vacant π orbital (from ionization) with the unpaired electrons resulting from the transition from the 1s<sub>C</sub> core orbital to the fully vacant <a>π* </a>orbitals.</p><br><p></p>

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