Exploiting Powder X‑ray Diffraction to Establish the Solvent-Assisted Solid-State Supramolecular Assembly of Pillar[5]quinone

We report the solvent-mediated supramolecular
assembly of pillar[5]­quinone
(P[5]­Q), a symmetric cyclamer containing five benzoquinone moieties
bridged by five alternating methylene units. The supramolecular assembly
of P[5]­Q is shown to be facilitated by 1,1,2,2-tetrachloroethane (TCE)
as solvent, producing a microcrystalline solvate material P[5]­Q·2TCE
with a fluffy texture. Optical and electron microscopy reveal that
this material has a rod-shaped morphology, extending to several micrometers
in length. Due to the microcrystalline nature of the material, structure
determination was carried out directly from powder X-ray diffraction
data, augmented by high-resolution solid-state 13C NMR.
The two crystallographically distinct TCE molecules occupy different
types of void in the structure and have different dynamic properties.
Crystallization of P[5]­Q was attempted from a large number of different
solvents, but only TCE was found to facilitate the formation of a
crystalline phase. Indeed, features of the crystal structure suggest
that the TCE component plays an important role in promoting the columnar
assembly of P[5]­Q molecules.