In-laboratory stopped-flow extended x-ray absorption fine structure apparatus in the dispersive mode for determination of the structure of short-lived intermediates

Abstract

We have constructed an in-laboratory stopped-flow extended x-ray absorption fine structure (EXAFS) apparatus by combining laboratory EXAFS equipment in the dispersive mode and a stopped-flow unit with two 150-μm-thick boron nitride windows. The rotating anode x-ray generator with a Mo target was used as an x-ray source. The self-scanning photodiode array was adopted as a position sensitive-linear x-ray detector. In order to obtain a suitable x-ray flux intensity, the accumulation of weak intensities during a short gate time was carried out by repeating the measurements. We have confirmed the performance of our apparatus by repeatedly measuring a number of static EXAFS spectra of 0.20 mol dm−3 aqueous solution of copper(II) sulfate. By use of our newly developed apparatus, we have succeeded in the direct determination of the structure of the reaction intermediate, the heterodinuclear copper(II)/mercury(II) complex, formed in the copper(II) ion incorporation into the homodinuclear mercury(II) complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine.