Selective Complexation in Three Component Cocrystals Composed of Pyrogallol[4]arene and Fluorescent Probes Pyrene and 1‑(2-Pyridylazo)-2-naphthol

Cocrystals composed of a pyrogallol[4]­arene
molecule (one of C-propylpyrogallol­[4]­arene in ethanol
and one of C-hexylpyrogallol­[4]­arene in isopropanol)
and a pyrene molecule
were crystallized and investigated with the aim to develop trends
based on solvent and aliphatic tail length of the pyrogallol[4]­arene.
These new trends along with previously determined trends for the fluorescent
probe 1-(2-pyridylazo)-2-naphthol (PAN), were then used to crystallize
a cocrystal composed of C-hexylpyrogallol­[4]­arene
and two fluorescent probes, pyrene and PAN. Within a two-component
cocrystal of pyrene or PAN, the probe molecules are complexed in both
the endo (inside the pyrogallol[4]­arene bowl) and exo (outside the
pyrogallol[4]­arene bowl) positions. However, in the three component
system, selective complexation of the probes is demonstrated whereby
the PAN molecules prefer to be endo and the pyrene molecules occupy
exo positions.