Upon two-electron oxidation of the title electron donor 1a, the elongated central C9–C10 bond [1.656(5)Å(X-ray)] is cleaved to give the biphenyl-2,2′-diyl bis(xanthenylium) dye 2a2+, which regenerates the colorless dispiro compound 1a by two-electron reduction. The presence of isosbestic points in the UV–Vis spectra during the electrochemical oxidation of 1a to 2a2+ indicates the negligible steady-state concentration of the intermediate cation radical. Interconversion between optically resolved 1a and 2a2+ is accompanied by drastic changes in the CD spectra again with several isosbestic points, and racemization of (P)- and (M)-1a and (S)- and (R)-2a2+ does not occur at ambient conditions. This redox pair represents a new motif for the multi-output response system, where the electrochemical input is transduced into two independent spectral outputs.
|Number of pages||6|
|Journal||Journal of the Chemical Society. Perkin Transactions 2|
|Publication status||Published - Oct 31 2002|
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