Upon two-electron oxidation of the title electron donor 1a, the elongated central C9-C10 bond was cleaved to give the biphenyl-2,2'-diyl bis(9-xanthenylium) dye 2a2+, which regenerated the colorless dispiro compound 1a by two-electron reduction. 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 intermediary cation radical. Interconversion between optically resolved 1a and 2a2+ is accompanied by drastic changes in CD spectra again with several isosbestic points, and racemization of (<I>P</I>),(<I>M</I>)-1a and (<I>S</I>),( <I>R</I>)-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.
|Translated title of the contribution||Electrochiroptical Response of Dispiro[4,5-dibromo-9,10-dihydrophenanthrene-9,9':10,9'-bixanthene] Derivatives|
|Number of pages||1|
|Publication status||Published - 2002|