Photochemical Reaction of Metal Complexes Studied by Advanced EPR

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In this study we developed new EPR machines and studied photophysics and photochemistry of metal complexes with these laboratory-made EPR apparatus. The following results were obtained :1) The Fourier transform (FT) EPR machine was constructed by modifying our spin echo system for analyzes of photochemical reactions. The experiments of high time-resolution (10ns) and multi-dimensional modes were made possible with this machine.2) In Mobius' laboratory, the W-band EPR machine was constructed and used both in time-resolved and pulsed modes, which has the higher time-resolution (5ns).3) The electron spin polarization transfer was verified for the firsr time in the triplet-doublet system, where we used excited triplet metalloporphyrins and nitroxide radicals. By means of this technique we measured the spin-lattice relaxation times of radicals and observed the spectra of non-polarized radicals.4) The two-dimensional nutation method was applied for the first time in the transient EPR experiment ; mettalloporphyrin-quinone in micellar system. The photochemical intermediate was separated spectroscopically from the radicals and definitely assigned as an ion pair.5) New microwave-pulse sequences were developed and applied to the study of molecular dynamics of metallofullerenes. Temperature dependence of the signal was examined and analyzed in terms of molecular liblations and spin dynamics.6) Triplet-radical pair systems were constructed with metalloporphyrins ligated by pyridinyl-nitroxied radicals. Two kinds of EPR signals were separeted by the W-band EPR technique and assigned by the two-dimensional nutation technique as those of the excited quartet and doublet states.In addition to these scienfically important results, We succeeded in making acontract between our Laboratory and Department of Physics of Berlin Free University and in holding the international Sendai Symposium twice.