Phosphangulene
(“Phang”) is an analogue of triphenylphosphine
with a conical shape and electron-rich aromatic surface that complements
the electron-poor surface of fullerenes, both geometrically and electronically.
Large molecular surfaces with multiple areas of concavity can be made
by grafting units of Phang onto selected cores, using the ability
of phosphorus to form covalent bonds with many other elements. Incorporating
multiple conical subunits of Phang creates molecules that are awkwardly
shaped, unable to pack efficiently, and predisposed to form cocrystals.
To demonstrate the potential of this approach, we made salts of the
bis(phosphangulene)iminium cation ([(Phang)2N]+), in which the phosphorus atoms of two Phang groups are bonded to
a single atom of nitrogen. Analysis of the structures of various salts
shows that [(Phang)2N]+ has a unique ability
to stabilize unusual anions, including those incorporating fullerenes.