Local structure analysis of short-lived reaction intermediates by means of a time-resolved stopped-flow extended X-ray absorption fine-structure technique.

INADA Yasuhiro

doi:10.2116/bunsekikagaku.49.563

Three types of time-resolved stopped-flow extended X-ray absorption fine-structure(EXAFS)instruments have been developed by combining an EXAFS spectrometer equipped with the original time-resolved detection system and a stopped-flow unit to analyze the local structure around the metal center in short-lived reaction intermediates.The whole X-ray energy region used to obtain in EXAFS spectrum could be measured simultaneously for the instrument in the dispersive mode, and a time-resolution on the order of ms has been acheived in the case of the instrument using synchrotron radiation as an X-ray source.By using these time-resolved stopped-flow EXAFS instruments, we have analyzed the local structure around the metal center in some short-lived reaction intermediates, such as a peroxochromium intermediate formed in a reduction reaction of chromate ion by hydrogen peroxide in an acidic aqueous solution;a Cu(II)/Hg(II)heterodinuclear porphyrin intermediate formed in the Cu(II)ion incorporation process into 5, 10, 15, 20-tetrakis(4-sulfonatophenyl)porphyrin in the presence of the Hg(II)ion in water, and a chloride-bridged precursor intermediate formed in the inner-sphere reduction of CoCl(NH₃)₅²⁺ by Fe²⁺ in N, N-dimethylformamide.According to the obtained local structure of the reaction intermediate, the reaction mechanisms and the structural characteristics of the reaction intermediates have been microscopically clarified.

Local structure analysis of short-lived reaction intermediates by means of a time-resolved stopped-flow extended X-ray absorption fine-structure technique.

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