Photoinduced Charge-Transfer Reactions of Tricyanoethylene with Aromatic Hydrocarbon Electron Donors. II. Semiempirical Studies of Naphthalene-Tricyanoethylene Exciplex

In this work we present the results of semiempirical AM1 calculations of the energy of electron-donor-acceptor system of naphthalene-tricyanoethylene complex in the ground and excited state with full optimization of the complex geometry. It was found that a ground state of the complex under consideration is stabilized almost exclusively by the electrostatic and Van der Waals interactions (presumably without charge-transfer resonance interaction). Its optimized equilibrium configuration has almost perpendicular head-to-face orientation of component molecules while in an excited state it is practically a charge-transfer electronic configuration with almost sandwich-like arrangement of both molecules. The energies of vertical electronic transitions between relevant ground and excited states and other spectroscopic parameters for these transitions were calculated with the use of ZINDO/S method and were compared with results of recent experimental observations of naphthalene-tricyanoethylene exciplex. This comparison led to a satisfactory explanation of the spectral properties and to a deeper insight into the kinetic parameters of the electron-donor-acceptor system under study.