Molecular Face-Rotating Cube with Emergent Chiral and Fluorescence Properties

Chiral
cage compounds are mainly constructed from chiral precursors
or based on the symmetry breaking during coordination-driven self-assembly.
Herein, we present a strategy to construct chiral organic cages by
restricting the P or M rotational
configuration of tetraphenylethylene (TPE) faces through dynamic covalent
chemistry. The combination of graph theory, experimental characterizations
and theoretical calculations suggests emergent chirality of cages
is originated from complex arrangements of TPE faces with different
orientational and rotational configurations. Accompanied by the generation
of chirality, strong fluorescence also emerged during cage formation,
even in dilute solutions with various solvents. In addition, the circularly
polarized luminescence of the cages is realized as a synergy of their
dual chiral and fluorescence properties. Chirality and fluorescence
of cages are remarkably stable, because intramolecular flipping of
phenyl rings in TPE faces is restricted, as indicated by calculations.
This study provides insight into construct chiral cages by the rational
design through graph theory, and might facilitate further design of
cages and other supramolecular assemblies from aggregation-induced
emission active building blocks.