Photochemical Reaction of Metal Complexes Studied by Advanced EPR

本研究研制了新型EPR装置，并利用这些装置对金属配合物的光物理和光化学进行了研究。得到以下结果：1)通过改进自旋回波系统，构建了用于分析光化学反应的傅里叶变换（FT） EPR机。实现了高时间分辨率（10ns）和多维模式的实验。2)在Mobius实验室，构建了w波段EPR机，并在时间分辨和脉冲模式下使用，其中w波段EPR机具有更高的时间分辨（5ns）。3)利用激发的三重态金属卟啉和氮氧自由基，首次验证了电子自旋极化转移。利用这种方法，我们测量了自由基的自旋晶格弛豫时间，并观察了非极化自由基的光谱。4)二维章动法首次应用于瞬态EPR实验；胶束体系中的金属卟啉-醌。光化学中间体在光谱上与自由基分离，并确定为离子对。5)开发了新的微波脉冲序列，并将其应用于金属富勒烯分子动力学的研究。从分子链和自旋动力学的角度对信号的温度依赖性进行了检验和分析。6)以吡啶基氧自由基连接金属卟啉，构建了三元自由基对体系。利用w波段EPR技术分离了两种EPR信号，并利用二维章动技术将其划分为激发四重奏态和双重态。除了这些重要的科学成果外，我们还成功地与柏林自由大学物理系签订了合同，并两次举办了国际仙台研讨会。

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.