Chiral Assembly of AIE-Active Achiral Molecules: An Odd Effect in Self-Assembly

The induction of chirality in supramolecular structures through hierarchical self-assembly of achiral compounds and the control of their handedness are closely related to the evolution of life and the chiral amplification found in nature. Herein, it is shown that the combination of achiral tetraphenylethylene, an aggregation-induced emission (AIE)-active luminophore bearing four alkyl chains with an odd or even number of carbon atoms via an amide linkage in the molecular structure allows the induction and control of supramolecular chirality in well-defined helical superstructures by controlling the solvent composition and polarity. In particular, right-handed supramolecular structures were produced for an even number of carbon atoms in the alkyl chains, whereas an odd number led to the assembly of left-handed superstructures. The twisted superstructure was visualised by SEM, and circular dichroism was used to observe chirality in the assembly. These controlled assemblies of AIE-active molecules are of potential practical value, such as templates for helical crystallisation, catalysis and formation of chiral mechanochromic luminescent superstructures.