Self-Assembly of Complementary Components Using a Tripodal Bismuth Compound: Pnictogen Bonding or Coordination Chemistry?

Triple
pnictogen bonding refers to the ability of a pnictogen atom
to engage in three simultaneous pnictogen bonds (PnBs) to a complementary
partner through a single pnictogen atom. This supramolecular strategy
was recently introduced as a unique facet of pnictogen bonding as
compared to other named supramolecular interactions. Here, the ability
of bismuth to participate in this phenomenon is demonstrated using
Bi­((NC9H7)3CH3). The study
reveals that Bi engages in stronger PnBs than the analogous Sb system.
The results have been contrasted with Bi systems that form strong
coordination bonds, and analysis of the electron density along the
bond path reveals key differences. The solution behavior of these
newly synthesized supramolecules were studied by PFGSE NMR spectroscopy
and they are found to remain intact in solution. Molecular design
strategies that allow for triple pnictogen bonding should find use
in the fields of molecular recognition and crystal engineering.