Building Large Structures with Curved Aromatic Surfaces by Complexing Metals with Phosphangulene

Phosphangulene (1) is
a hexacyclic triarylphosphine
with a distinctive conical shape and an electron-rich aromatic surface
that is geometrically and electronically complementary to fullerenes
such as C60 and C70. As a result, suitable derivatives
of phosphangulene can cocrystallize with fullerenes or even bind them
in solution. Surprisingly, previous work has largely overlooked the
potential of phosphangulene to form complexes with metals, which offers
a simple way to create large molecular structures with curved aromatic
surfaces. To explore this approach, we have prepared and characterized
a series of complexes of phosphangulene with Ag+ and Cu+. Our results show that Phang ligands are exceptional for
many reasons. In particular, they can yield metal complexes with unique
coordination, and the metal centers hold the concave aromatic surfaces
of multiple ligands in various divergent arrays. Moreover, the rigid
conical structure of phosphangulene gives the complexes an awkward
shape that cannot be packed efficiently without complementary partners.
As a result, metal complexes of phosphangulene are predisposed to
cocrystallize with fullerenes, thereby yielding materials in which
metals and fullerenes are brought together in ordered arrangements.