SEMIEMPIRICAL INVESTIGATION OF CHARGE-TRANSFER INTERACTIONS IN RIGID DIMETHOXYNAPHTHALENE BRIDGE PYRIDINIUM SYSTEMS

Semiempirical quantum chemical calculations on a series of related hth alene-{polynorbornyl,-(n,sigma-bonds)}-pyridine (DMN-n-Py) and {polyno rbornyl,(n,sigma-bonds)}-N-methylpyridinium (DMN-n-MePy+) compounds ha ve been carried out to gain insight into their electronic spectroscopy and into factors affecting photoinduced electron transfer in these no vel molecular systems. The experimental electronic absorption spectra are found to be well described using the CNDO/S method. Using a simple charge-shift model and outer-sphere electron-transfer theory to take into account solvent effects, a good correlation exists between experi mental charge-transfer state energies and those calculated from thermo dynamic and quantum chemical treatments. The distance dependence and m agnitude of the excited-state transfer integrals for photoinduced elec tron transfer are calculated and discussed within the framework of the McConnell model. The results of the calculations are compared with ex perimental data and previous studies on related DMN-n-dicyanovinyl don or-bridge-acceptor compounds.