Tunable carots: Construction of the stable carotenoid wires with a specific conductance value is possible by the attachment of phenyl groups to the polyene chain to overcome the in vitro instability of natural carotenoids, the perfect molecular wires utilized in various biological processes. Diverse electronic natures of the substituents on the phenyl groups provide the carotenoids with tunable conductance (see figure).

A convergent synthetic method for new types of carotenoid compounds containing phenyl substituents at C(13) and C(13') has been developed by the coupling of allylic sulfone and 2,7-diphenyloct-4-enedials, followed by the double elimination strategy. These carotenoid compounds are fairly stable and legitimate candidates for nanosized molecular wires, which show diverse conductance values according to the electronic nature of the substituent group in the phenyl ring.