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Abstract: (Chemical Abstract 1996, 126:15958)
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Quantum chemical calculations of the electronic ground and first excitedstates
S0 and S1 of the protonated Schiff base
2,4-pentadien-1-iminium cation (CH2=CH-CH=CH-CH=NH2)+
are presented. In order to compare different multi reference CI approaches
which differ in their choice of reference configurations and basis sets,
potential energy surfaces with respect to two dihedral angles have been
calculated for the states S0 and S1.
The study reveals that the characteristic features of the two potential
energy surfaces, i.e. the appearence of two minima and four maxima in the
case of the S0 surface and of three maxima and two minima
in the case of the S1 surface are correctly predicted
at all applied levels of theory. The energies of torsional barriers and
of higher energy maxima, however, depend considerably on the applied quantum
chemical procedure. Ground state calculations are also compared to the
results of Møller-Plesset perturbation theory calculations up to
the MP4 level.
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