Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT

ABSTRACT - Internet Electron. J. Mol. Des. September 2002, Volume 1, Number 9, 462-466

Theoretical Studies on the Validity of B3LYP Density Functional Theory for Symmetrical Electrocyclic Reactions Shogo Sakai Internet Electron. J. Mol. Des. 2002, 1, 462-466

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Abstract:
The reactions including orbital symmetry allowed and forbidden mechanisms are studied by theoretical multireference correlation molecular orbital methods such as complete active space (CAS) self-consistent field (SCF) or broken symmetry unrestricted methods. Although the CASSCF MO method can describe the electronic states between the singlet electronic coupling state and the singlet diradicals state, no information is available regarding the accuracy of the broken symmetry unrestricted method for these electronic states. We compared the validity of the geometry parameters and the relative energies for three symmetrical electrocyclic reaction systems by broken symmetry unrestricted and restricted methods on the basis of the (U)B3LYP density functional theory with those by CASSCF and MP2-CASSCF levels. (U)B3LYP density functional methods with 6-31G(d) basis set are used in this study. The geometry parameters of the stationary points for three symmetrical electrocyclic reactions and their relative energies are calculated by (U)B3LYP methods. The geometry parameters of the stationary points determined by the (U)B3LYP method agreed well with those by CASSCF levels. The relative energies calculated by the (U)B3LYP method agreed qualitatively with those by MP2-CASSCF levels, but the energy difference by both methods is significant.

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