CIDNP AND CIDEP STUDIES ON INTRAMOLECULAR HYDROGEN ABSTRACTION REACTION OF POLYMETHYLENE-LINKED XANTHONE AND XANTHENE - DETERMINATION OF THE EXCHANGE INTEGRAL OF THE INTERMEDIATE BIRADICALS

Hydrogen abstraction reaction of a polymethylene-linked system is investigated by using chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) methods. The reaction scheme is determined from the CIDNP and CIDEP spectra of the unlinked xanthene and xanthone system. The exchange integral J between the two terminal radicals of the system is obtained from the simulation process by using the spin-correlated CIDEP theory modified with (a) the fast population relaxation between the central S-T0 mixed states, (b) the contribution from the triplet mechanism, and (c) hyperfine line dependent line width. The mechanism of the fast population relaxation and the dependence of the J value on the temperature and polymethylene chain length are discussed.