Isotope effects in electron spin resonance: the negative ion of cyclo-octatetraene-1-d

Carrington, Alan; Longuet‐Higgins, H. C.; Moss, R.E.; Todd, P. F.

doi:10.1080/00268976500100221

Cited by 42 publications

(15 citation statements)

References 3 publications

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“…It provides additional insights into vibronic coupling problems because the permutational sym-metry is reduced and vibrational zero-point energy effects make otherwise equivalent minima distinguishable. Partial isotopic substitution of JT systems has been a very useful tool in determining the distorted equilibrium structure of molecules undergoing an Ee Jahn-Teller effect, such as the cyclooctatetraene anion, [57] the benzene anion, [58] benzene, [59] and the cyclopentadienyl radical. [60] Partial deuteration of CH 4 + removes the equivalence of the six minima represented in Figure 8 because of the different zero-point energies of the resulting structures.…”

Section: Methodsmentioning

confidence: 99%

Jahn–Teller Effects in Molecular Cations Studied by Photoelectron Spectroscopy and Group Theory

Wörner

Merkt

2009

Angew Chem Int Ed

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The traditional “ball‐and‐stick” concept of molecular structure fails when the motion of the electrons is coupled to that of the nuclei. Such a situation arises in the Jahn–Teller (JT) effect which is very common in open‐shell molecular systems, such as radicals or ions. The JT effect is well known to chemists as a mechanism that causes the distortion of an otherwise symmetric system. Its implications on the dynamics of molecules still represent unsolved problems in many cases. Herein we review recent progress in understanding the dynamic structure of molecular cations that have a high permutational symmetry by using rotationally resolved photoelectron spectroscopy and group theory. Specifically, we show how the pseudo‐Jahn–Teller effect in the cyclopentadienyl cation causes electronic localization and nuclear delocalization. The fundamental physical mechanisms underlying the vaguely defined concept of “antiaromaticity” are thereby elucidated. Our investigation of the methane cation represents the first experimental characterization of the JT effect in a threefold degenerate electronic state. A special kind of isomerism resulting from the JT effect has been discovered and is predicted to exist in all JT systems in which the minima on the potential‐energy surface are separated by substantial barriers.

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Section: Methodsmentioning

confidence: 99%

Jahn–Teller Effects in Molecular Cations Studied by Photoelectron Spectroscopy and Group Theory

Wörner

Merkt

2009

Angew Chem Int Ed

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“…Besides its central role in organic chemistry, its allure has been heightened by its 2 E 1 ground state that is subject to a Jahn-Teller distortion, which was first observed in condensed phase electron paramagnetic resonance (EPR) spectra of the radical. [1][2][3][4][5] Following the early EPR observations, a number of experimentalists have reported the spectroscopy of the isolated radical. Most of this work centered on the vibrational structure revealed by theÃ 2 A 2 ←X 2 E 1 electronic transition.…”

Section: Introductionmentioning

confidence: 99%

The Jahn–Teller and related effects in the cyclopentadienyl radical. I. The ab initio calculation of spectroscopically observable parameters

Applegate¹,

Miller²,

Barckholtz³

2001

The Journal of Chemical Physics

133

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Ab initio calculations are performed for the X 2 E 1 and A 2 A 2 states of the cyclopentadienyl radical. An important goal of these calculations is to guide the analysis of the experimentally observed A 2 A 2-X 2 E 1 electronic spectrum. Vibrational frequencies for both theX andÃ state are reported. Large changes in frequency between the states for out-of-plane vibrations are found, leading to the expectation that overtones of these modes will appear strongly in the spectrum. Additionally, spectroscopically obtainable parameters describing the Jahn-Teller effect are calculated for theX state. Using all this information theX −Ã electronic spectrum is predicted for both C5H5 and C5D5.

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“…Partial substitution of molecules subject to a Jahn-Teller ͑JT͒ effect 1,2 has been considered theoretically for the E e problem 3,4 and its spectroscopic consequences were studied by electron paramagnetic resonance ͑EPR͒ in the cyclooctatetraene anion 5 and the benzene anion 6 and by optical spectroscopy in benzene 7 and the cyclopentadienyl radical. 8 All investigated systems possess a doubly degenerate ground electronic state that is subject to a dominantly linear interaction with some vibrational modes.…”

Section: Introductionmentioning

confidence: 99%

Jahn-Teller effect in CH3D+ and CD3H+: Conformational isomerism, tunneling-rotation structure, and the location of conical intersections

Wörner

Merkt

2007

The Journal of Chemical Physics

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High-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectra of CH(3)D and CD(3)H have been recorded at rotational resolution from the adiabatic ionization energy up to 600 cm(-1) of internal energy of the respective cations. The spectra are characterized by the effects of a large-amplitude pseudorotational motion exchanging the equivalent nuclei in each molecule. With increasing internal energy, a transition from the tunneling regime with splittings of the order of 1-10 cm(-1) to the free pseudorotation regime is observed. A theoretical model that treats the simultaneous rotational and pseudorotational motions and incorporates the effects of the geometric phase has been developed. The model provides the appropriate rovibronic symmetries in the C(3v)(M) molecular symmetry group and reaches a near-quantitative agreement with the experimental data. The complete group-theoretical analysis of the rovibronic problem is also given. The analysis of the spectra has revealed the existence of two different isomers for both CH(3)D(+) and CD(3)H(+), which differ in the bond length between the carbon atom and the unique ligand atom. All isomers are subject to a fast pseudorotational motion between three equivalent minima with a period of 3-5 ps in CH(3)D(+) and 18-28 ps in CD(3)H(+). The analysis has also provided the ordering of the tunneling sublevels for each isomer, which enables the location of the twofold conical intersections on the potential energy surface that could not be determined from experiments on CH(4) (+).

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Isotope effects in electron spin resonance: the negative ion of cyclo-octatetraene-1-d

Cited by 42 publications

References 3 publications

Jahn–Teller Effects in Molecular Cations Studied by Photoelectron Spectroscopy and Group Theory

Jahn–Teller Effects in Molecular Cations Studied by Photoelectron Spectroscopy and Group Theory

The Jahn–Teller and related effects in the cyclopentadienyl radical. I. The ab initio calculation of spectroscopically observable parameters

Jahn-Teller effect in CH3D+ and CD3H+: Conformational isomerism, tunneling-rotation structure, and the location of conical intersections

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