Electrochiroptical response of a hexaarylethane derivative with a helical π-skeleton: drastic UV–Vis and CD spectral changes upon electrolysis of 4′,5′-dibromodispiro[xanthene-9,9′(9′H,10′H)-phenanthrene-10′,9″-xanthene]
Electrochiroptical response of a hexaarylethane derivative with a helical π-skeleton: drastic UV–Vis and CD spectral changes upon electrolysis of 4′,5′-dibromodispiro[xanthene-9,9′(9′H,10′H)-phenanthrene-10′,9″-xanthene]
Dynamic redox systems based on bis(spiroxanthene)-type donors with a polycyclic aromatic hydrocarbon: preparation, X-ray structures, and electrochromic response with fluorescence change
The long C-C bonds (1.614(2)-1.630(2) Angstrom) in newly prepared title donors 2-6 are cleaved upon two-electron oxidation to afford the bond-dissociated dicationic dyes 2(2+)-6(2+), whose electron affinities are stronger than the corresponding biphenyl-2,2'-diyl dications 1(2+) due to the spatial proximity of two xanthenylium units. Not only UV-vis but also fluorescence spectra changed drastically upon electrolysis since only colorless neutral donors are fluorescent. (C) 2004 Elsevier Ltd. All rights reserved.
Chiral Memory Units Based on Dynamic Redox Systems with a Dibenzoxepinone Skeleton: Drastic Change in Racemization Barrier and Electrochemical Bistability
The configuration of helical dicationic dyes 2(2+) with a dihydrodibenzoxepinone unit is stable, whereas the corresponding neutral electron donors 1 with a tetrahydrophenanthroxepinone skeleton easily undergo ring-flip. Thanks to their electrochemical bistability, electron exchange between 1 and 2(2+) is prohibited. Thus, the above electrochromic pairs 1/2(2+) can serve as new members of less well-explored redox-based chiral-memory units.