Showing papers by "Thomas Bally published in 1992"
TL;DR: In this paper, the radical cations of tert-butyl-capped polyenes containing 3-13 conjugated double bonds were generated radiolytically in Freon matrices and investigated by electronic absorption spectroscopy.
Abstract: The radical cations of tert-butyl-capped polyenes containing 3-13 conjugated double bonds were generated radiolytically in Freon matrices and investigated by electronic absorption spectroscopy. The observed spectra are in accord with a qualitative MO/CI model which predicts two bands of disparate intensity which both undergo a shift to lower energies as the chain grows longer. Extrapolation to infinite chain length leads to an energy of {approximately}0.4 eV for the second, intense band and {approximately}0.1 eV for the first, weak band. This finding and its implications with regard to the structure of polarons in polyenes and the nature of doped and/or photoexcited polyacetylene are discussed. 41 refs., 7 figs., 1 tab.
82 citations
TL;DR: In this article, radiolytic ionization of o-methylacetophenone in low temperature matrices, the radical cation of the corresponding enol is formed, and the kinetics of this process indicate a significant contribution of quantum-mechanical tunnelling in the hydrogen atom transfer.
Abstract: Upon radiolytic ionization of o-methylacetophenone in low temperature matrices, the radical cation of the corresponding enol is formed. The kinetics of this process indicate a significant contribution of quantum-mechanical tunnelling in the hydrogen atom transfer. The same species is also formed by ionizing 1-methyl-1,2-dihydrobenzocyclobutenol but the composition of the rotameric mixture of enol radical cations is different in this case. Analogous experiments with 5,8-dimethyl-1-tetralone demonstrate that enol radical cations are stable in their Z-conformation under cryogenic conditions in contrast to the corresponding neutrals.
17 citations
16 citations
TL;DR: In this paper, the electronic absorption spectra of the radical cations of vinylacetylene (VA) and diacetylene(DA) in argon matrices were analyzed for the first time and compared with the EA spectrum of butadiene (BD) radical cation.
15 citations
TL;DR: In this paper, the potential energy surface of H 4 + was analyzed using the Jahn-Teller distortions from the square geometry of H4 + and it was shown that the optimal distorted geometries are slightly different from those obtained by following the Jahtler active modes and the reliability of the single reference CI-SD approach to this problem is discussed.
13 citations
TL;DR: In this paper, it is argued that the valence isomeric o -quinoid vinylketene (QK) arises by the neutralization of QK +, which forms spontaneously upon ionization of BCB in Ar.
Abstract: Upon X-ray irradiation of benzocyclobutenone (BCB) in an Ar matrix, the valence isomeric o -quinoid vinylketene (QK) is formed efficiently next to its radical cation (QK +. ) which is characterized for the first time by its UV/ vis and IR spectrum. It is argued that QK arises by the neutralization of QK +. which forms spontaneously upon ionization of BCB in Ar. The mechanism of the facile BCB +. → QK +. rearrangement is discussed on the basis of semi-empirical and ab initio quantum chemical calculations.
6 citations
TL;DR: The radical cation of bicyclo[2.2]octa-2,5-diene produced in a γ-irradiated Freon matrix at 77 K shows a broad charge-resonance absorption band with λ max =680 nm.
Abstract: The radical cation of bicyclo[2.2.2]octa-2,5-diene produced in a γ-irradiated Freon matrix at 77 K shows a broad charge-resonance absorption band with λ max =680 nm. In contrast to earlier experiments in argon matrices, it was found that the primary photoreaction of this species is a cleavage to yield the recently described complex cation between benzene and ethylene whose λ max happens to coincide with that of the above precursor cation. This complex cation can in turn be converted eventually to 1,3,5,7-octatetraene radical cation
3 citations