Anomalous Halogen–Halogen Interaction Assists Radial Chromophoric Assembly

The design of highly efficient supramolecular
architectures that
mimic competent natural systems requires a comprehensive knowledge
of noncovalent interactions. Halogen bonding is an excellent noncovalent
interaction that forms halogen–halogen (X2) as well
as trihalogen interacting synthons. Herein, we report the first observation
of a symmetric radial assembly of chromophores (R3̅c space group) composed of a stable hexabromine
interacting synthon (Br6) that further push the limits
of our understanding on the nature, role, and potential of noncovalent
halogen bonding. Contrary to the destabilization proposed for Type-I
X2 interactions, Br6-synthon-possessing Type-I
X2 interactions exhibit a stabilizing nature owing to the
exchange-correlation component. The radial assembly of chromophores
is further strengthened by intermolecular through-space charge transfer
interaction. Br6-synthon-driven 3-fold symmetric radial
assembly render a lattice structure that reminisces the chromophoric
arrangement in the light harvesting system 2 of purple bacteria.