FT-ESR Study of Initial Process of Phtochemical Reactions

At the international symposium on spin and magnetic field effects held in Novosibirsk in August，1996 hirota,van Willigen和Ohara discussed the detailed plan of the cooperative work.这是决定的原始程序photochemical reactions of xanthone of which a number of unsolved problemsexist should be studied by FT-EPR方法. Following this discussion，Ohara went to Boston in September to make FT-EPR measurements. in this work he obtained the1) Emissive polarization found in xanthone/2-propanol is mainly determined by thehydrogen abstraction of xanthone及其mechanism是radical pair mechanism (RPM).2the absorptive polarization observed in xanthone/2-propanol + h2o +HCl is very rapiddetermined by the time -resolution of the spectrometer and the mechanism is likely to be tripletmechanism . However, the intensity of the polarization is very weak.In November，Hirota made further measurement in波士顿，examined the effect of the concentration of HCl on thepolarization.这是发现的：inversion of the hydroxypropyl radical from Eto A takes place at A relatively low concentration of HCl. Moreover，这是发现xanthone ketyl radical showed an inversion from A to E. it虽然additional transient absorption experiments are needed to clarify the initialprocesses in the photochemistry of xanthone and work althis line was tried in Kyoto with Prof.van Willigen. However, this work has not been completed yetand further work will be continued.In addition to the above work Nakagawa made FT-EPR work on thehydrated electron in the SDS micelle produced by the photoionization of phenothiazine and itsderivatives. He obtained detailed information about the phase of the CIDEP signal of the hydratedelectron dynamics of disappearance and quenching of the CIDEP signal of the hydrated electron。

At the international symposium on spin and magnetic field effects held in Novosibirsk in August, 1996 Hirota, van Willigen and Ohara discussed the detailed plan of the cooperative work. It was decided that the initial processes of photochemical reactions of xanthone of which a number of unsolved problems exist should be studied by FT-EPR method. Following this discussion, Ohara went to Boston in September to make FT-EPR measurements. In this work he obtained the following results.1) Emissive polarization found in xanthone/2-propanol is mainly determined by the hydrogen abstraction of xanthone and its mechanism is radical pair mechanism (RPM).2) The rise of the absorptive polarization observed in xanthone/2-propanol +HィイD22ィエD2O +HCl is very rapid determined by the time -resolution of the spectrometer and the mechanism is likely to be triplet mechanism (TM). However, the intensity of the polarization is very weak.In November, Hirota made further measurement in Boston and examined the effect of the concentration of HCl on the polarization. It was found that inversion of the polarization of the hydroxypropyl radical from E to A takes place at a relatively low concentration of HCl. Moreover, it was found that the polarization of the xanthone ketyl radical showed an inversion from A to E. It was though that additional transient absorption experiments are needed to clarify the initial processes in the photochemistry of xanthone and work along this line was tried in Kyoto with Prof. van Willigen. However, this work has not been completed yet, and further work will be continued.In addition to the above work Nakagawa made FT-EPR work on the hydrated electron in the SDS micelle produced by the photoionization of phenothiazine and its derivatives. He obtained detailed information about the phase of the CIDEP signal of the hydrated electron, dynamics of disappearance and quenching of the CIDEP signal of the hydrated electron.