Supramolecular Chiral Helical Ribbons of Tetraphenylethylene-Appended Naphthalenediimide Controlled by Solvent and Induced by l- and d-Alanine Spacers.

Naphthalenediimide-tetraphenylethylene conjugates with an alanine spacer (coded as: NDI-(Ala-TPE)2 ) were synthesized to study the influence of the chirality of the amino acid spacer on its self-assemblies. Here we particularly show that NDI-Ala-TPE bearing l-alanine gives left-handed (M-type) helical superstructure, while d-alanine produces right-handed (P-type) helical ribbons in THF:H2 O at 40:60 % v/v ratio. However, particular aggregates were observed at 20:80 % v/v ratio. Circular dichroism was used to characterise the induction of chirality and the handedness of the helical superstructures, and the microstructure of the self-assembled materials was visualised using scanning electron microscopy while DLS analysis confirmed the formation of particular aggregates in solution.