Solvent Induced Photophysics and Photochemistry of the (2p3s) Rydberg State ofDiazabicyclooctane: Intersystem Crossing, Electron Transfer, and Energy Transfer

摘要

SOlvent induced singlet (2p3s) Rydberg state relaxation dynamics ofdiazabicyclooctane (DABCO) are studied in van der Waals clusters generated in a supersonic jet expansion. The excited state decay is determined by a pump (excitation)/probe(ionization) mass selective technique. Solvents employed for these cluster studies include rare gases, saturated hydrocarbons and fluorcarbons, amines, ethers, methylsulfide, acetonitrile, acetonitrile and aromatics. The nature of intermediate state to which the nascent singlet (2p3s) Rydberg state decays is determined based on excited state lifetimes, cluster dissociation products, and ionization energies. At least three solvent induced relaxation pathways can be identified for the nascent DABCO Rydberg state: (1) intersystem crossing to the triplet (2p3s) Rydberg state; (2) internal conversion to an intermolecular charge transfer state; and (3) energy transfer to an excited valence state of the solvent molecule. The (2p3s) triplet state origin is determined to lie at 564 cm below the singlet state origin. The DABCO intersystem crossing rate is small but it can be significantly enhanced by the solvent molecule. Intermolecular electron transfer occurs in DABCO/amine, ether, and acetonitrile clusters. The electron transfer state is determined to lie at least 650/cm below the (2p3s) singlet Rydberg state.