Helquat dyes are the first helicene-like cationic styryl dyes obtained as separate enantiomers. Their remarkable chiroptical properties are due to the unique combination of a cationic hemicyanine chromophore and a helicene-like motif. The magnitude of the ECD response and the pH switching along with their positioning in the visible region are unprecedented among helicenoids.

Racemic [5]helquat as a triflate salt has been synthesized using a robust, three-step procedure. Subsequent exchange of triflate anions for inexpensive (R,R)-dibenzoyltartrate anions via an ion exchange resin afforded two diastereoisomeric salts. Crystallization led to the resolution of the helquat (ee 4 98%). This is the first time that a non-racemic helquat has been obtained; its helicity having been assigned and its racemization barrier determined. Capillary electrophoresis with a sulfated b-cyclodextrin chiral selector is introduced for the first time as a straightforward method to analyze the enantiocomposition of charged, helicene-like species.

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