AB-INITIO MO CALCULATIONS OF ELECTRONIC COUPLING MATRIX-ELEMENTS ON MODEL SYSTEMS FOR INTRAMOLECULAR ELECTRON-TRANSFER, HOLE TRANSFER, AND TRIPLET ENERGY-TRANSFER - DISTANCE DEPENDENCE AND PATHWAY IN ELECTRON-TRANSFER AND RELATIONSHIP OF TRIPLET ENERGY-TRANSFER WITH ELECTRON AND HOLE TRANSFER

The matrix elements for electron transfer (ET) for anions of 1,3- and 1,4-dimethylenecyclohexane and 2,7- and 2,6-dimethylenedecalin; those for anions of methylene chains, H2C-(CH2)n-CH2 (n = 3-5); and those for ET, hole transfer (HT), and triplet energy transfer (TI) of anion, cation, and neutral systems of 1,4-divinylcyclohexanes have been calculated with the ab initio MO method by using the UHF wave functions as diabatic states. Calculations for methylene chains indicate that the observed ''distance dependence' is determined not only by the number of CC bonds but also by subtle angular dependency of MO overlap. The most favorable all-trans path exists in 1,3-dimethylenecyclohexane and 2,7-dimethylenedecalin, whereas more than one unfavorable gauche pathway is available in 1,4-dimethylenecyclohexane and 2,6-dimethylenedecalin. The calculated matrix elements for the divinyl compounds point out that HT and TT are faster in the trans-equatorial-equatorial isomer than in the trans-axial-axial isomer. Though the matrix element for ET in the trans-axial-axial isomer is larger, the torsional angle in the real compound is likely to make ET in the trans-equatorial-equatorial isomer faster. The matrix element for TT, a two-electron process, is found to be approximately proportional to the product of those of ET and HT.