High-field NMR spectroelectrochemistry of spinning solutions: simultaneousin situ detection of electrogenerated species in a standard probe under potentiostatic control

This report summarizes the design and performance of the first practicable in situ electrogenerative high-field solution-NMR cell, designed for simult aneous NMR spectroelectrochemistry in a conventional 10- or 16-mm 300 MHz p robe. The axially symmetric three-electrode assembly is stationary and self -aligning. It dips into a standard spinning 10-mm sample tube and is adapte d for convenient operation in any commercial high-field, multi-nuclear, var iable-temperature FT NMR spectrometer. The tubular, rf-transparent working electrode (presently consisting of a gold film, coated on glass) completely spans the detection region; the recommended coating thickness is less than or equal to 0.01 delta, where delta is the rf-absorbing conductor skin dep th. With careful shimming, very narrow H-1 signals ( similar to 1 Hz) can b e obtained. The performance of the in situ NMR-electrochemical cell is illu strated by monitoring the progressive reduction of 'p-quinone' (1,4-benzoqu inone) to its dihydro-form by controlled-potential electrolysis in an acidi c medium. (C) 2000 Elsevier Science S.A. All rights reserved.