Pseudopolymorphism of a Highly Adaptable Tetraarylpyrene Host that Exhibits Abundant Solid-State Guest Inclusion

Tetraarylpyrene host 1,3,6,8-tetrakis­(2,6-dimethyl-4-methoxyphenyl)­pyrene
(TP) is found to crystallize with inclusion of diverse guests in two
different modifications with simple variation of the crystallization
conditions involving addition of a cosolvent. While the guest stoichiometry
is found to vary in the pseudopolymorphs with some guests, polymorphic
behavior of the host–guest compounds is observed with cyclohexenone
and toluene as guests. The crystal structures of the polymorphic inclusion
compounds constitute rather rare examples of supramolecular isomerism.
The thermogravimetric analyses of the inclusion compounds show that
the guest in one of the modifications is released in a relatively
higher temperature range. The structural diversity exhibited by the
host TP with various guest molecules and its ability to exhibit different
forms with the same guest has been to attributed its unique structural
features that inherently confer the system with guest inclusion behavior,
conformational freedom associated with the methoxy groups and the
near-orthogonal p-anisyl rings, and its potential
to exploit weak C–H···O and C–H···π
hydrogen bonds in response to the guest.