Trismaleimide Dendrimers: Helix-to-Superhelix Supramolecular Transition Accompanied by White-Light Emission.

Reported here are unprecedented fluorescent superhelices composed of primary, supramolecular polymers of the opposite helical twist. A new class of functional dendrimers was synthesized by amino-ene click reactions, and they demonstrate an alternating OFF/ON fluorescence with generation growth. A peripherally alkyl-modified dendrimer displays helix-sense-selective supramolecular polymerization, which predominantly forms right-handed (or left-handed) helical supramolecular polymers in the solution containing chiral solvents. With increasing the concentration, these primary helical supramolecular polymers spontaneously twist around themselves in the opposite direction to form superhelical structures. Atomic force microscopy and circular dichroism measurements were used to directly observe the helix-to-superhelix transition occurring with a reversal in the helical direction. Exceptional white-light emission was observed during superhelix formation.