Calculations on the Jahn-Teller configurations of the benzene cation

Klaus Muller-Dethlefs, J. Barrie Peel

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    The analysis of the zero-electron-kinetic-energy photoelectron spectra of benzene has led to a reinvestigation by ab initio methods of the electronic states of the C6H+6 cation resulting from Jahn-Teller distortions on ionization. The calculations involving a range of currently used methodologies all verify that the two cation configurations, 2B2g and 2B3g of D2h symmetry, resulting from removal of an electron from the e1g(π) degenerate MOs of C6H6, comprise a true minimum and a transition state, differing only slightly in energy. These are linked through the in-plane b1g vibration, confirming that b1g is actually a pseudorotational coordinate. Hence C6H+6 exhibits similar structural floppiness to the cations of methane and cyclopropane although with a much smaller barrier to pseudorotation than for these smaller species. These results support the general proposition that such Jahn-Teller distortions associated with molecular ionization (of stable closed-shell hydrocarbon molecules of high symmetry) generally involve a quadratic contribution which leads to a single global minimum cation structure, with all other derived stationary states being transition states each characterized by a single imaginary vibration frequency. © 1999 American Institute of Physics.
    Original languageEnglish
    Pages (from-to)10550-10554
    Number of pages4
    JournalJournal of Chemical Physics
    Issue number23
    Publication statusPublished - 15 Dec 1999


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