Isotope effect on the static distortion and the dynamics of partially deuteriated Jahn-Teller active radical cations: cyclopropane-1,1-d2

1989 ◽  
Vol 93 (18) ◽  
pp. 6642-6645 ◽  
Author(s):  
K. Matsuura ◽  
K. Nunome ◽  
M. Okazaki ◽  
K. Toriyama ◽  
M. Iwasaki
Keyword(s):  
Isotope Effect ◽  
Radical Cations ◽  
Jahn Teller ◽  
Static Distortion

Studies of the Jahn-Teller effect. I. A survey of the static problem

1957 ◽  
Vol 238 (1215) ◽  
pp. 425-447 ◽  
Keyword(s):  
Electronic States ◽  
Static Problem ◽  
Electronic Energy ◽  
Tetragonal Symmetry ◽  
Linear Molecule ◽  
Subsequent Paper ◽  
Jahn Teller ◽  
Near Degeneracy ◽  
Static Distortion ◽  
Physical Features

According to the Jahn-Teller theorem, symmetrical molecules with degenerate electronic states are unstable. Such molecules therefore take up a distorted shape. If there is near-degeneracy, the symmetrical shape may also be unstable. We have studied the distortion in some particular cases. The approach is to minimize the total electronic energy with respect to distortions of the nuclear framework, the latter being considered to be static. There are always several equivalent distortions of equal energy, so that a static distortion fails to remove the degeneracy. The discussion of dynamic effects is postponed to a subsequent paper. A linear molecule of formula BAB , for which two electronic states of opposite symmetry are sufficiently nearly degenerate, will be stable in a configuration with unequal A—B separations, and unstable when symmetrical. This example illustrates some of the main physical features of Jahn-Teller distortions in a simple manner. Although we know of no example where the symmetrical structure is actually unstable, there are examples where the tendency towards distortion noticeably reduces the force constant of the asymmetric vibration. Octahedral complexes AB 6 with degenerate electronic states occur in many situations (e. g. paramagnetic crystals, F-centres, luminescent centres and exciton states in cubic crystals). The orbital degeneracy may be threefold ( T 1 and T 2 ) or twofold. In the former case the stable distortion is found to be either of tetragonal symmetry about a [100] direction, or of trigonal symmetry about a [111] direction. The twofold degenerate situation leads to a more complicated situation. If one neglects anharmonic effects there appears to be an infinity of distortions minimizing the energy; a more detailed consideration of the anharmonic terms shows that the stable distortions are of elongated tetragonal character. This result has an important bearing on complexes involving the cupric ion.

scholarly journals Geometrical Reorganization of a Methane Cation upon a Sudden Ionization: An Isotope Effect in Electronic Non Equilibrium Quantum Dynamics

2021 ◽  
Author(s):  
Cayo Gonçalves ◽  
Raphael D. Levine ◽  
Francoise Remacle
Keyword(s):  
Isotope Effect ◽  
Ground State ◽  
Quantum Dynamics ◽  
High Harmonic ◽  
Electronic States ◽  
Structural Rearrangement ◽  
Experimental Measurements ◽  
Strongly Coupled ◽  
Jahn Teller ◽  
Electronic Coherence

<p>An ultrafast structural, Jahn-Teller (JT) driven, electronic coherence mediated quantum dynamics in the CH<sub>4</sub><sup>+</sup> and CD<sub>4</sub><sup>+ </sup>cations that follows a sudden ionization by an XUV attopulse, exhibits a strong isotope effect. The JT effect makes the methane cation unstable in the T<sub>d</sub> geometry of the neutral. Upon the sudden ionization the cation is produced in a coherent superposition of three electronic states that are strongly coupled. On the ground state of the cation the few femtosecond structural rearrangement leads first to a geometrically less distorted D<sub>2d</sub> minimum followed by a reorganization to a shallow C<sub>2v</sub> minimum. The dynamics is computed for an ensemble of 8000 ions randomly oriented with respect to the polarization of the XUV pulse. The ratio, about 3, of the CD<sub>4</sub><sup>+</sup> and CH<sub>4</sub><sup>+</sup><sub> </sub>autocorrelation functions, is in agreement with experimental measurements of the high harmonic spectra. The high value of the ratio is attributed to the faster electronic coherence dynamics in CH<sub>4</sub><sup>+</sup>. </p>

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.

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