CALCULATION OF THE LONG-RANGE COUPLING BETWEEN ELECTRONS IN LONE PAIRS AND DOUBLE-BONDS USING SEMIEMPIRICAL AND ABINITIO METHODS

The electronic coupling between symmetrically placed lone pairs or pi electrons are calculated using semiempirical and ab initio methods and the results compared to experimental numbers. The agreement is satisfactory in cases when there is a small tendency for cancellation between contributions of different signs. We have found nonexponential behavior when the number of intervening cyclohexane units is increased in the case of phenyl endgroups. In this case as well as in the cases with exponential decrease, the CNDO/S Method shows a similar behavior as that of the ab initio Hartree-Fock method, which suggests that the former method may be used to calculate the electronic factor in electron transfer systems.