Self-Assembly of Rigid Three-Connecting Mesitylenetribenzoic Acid: Multifarious Supramolecular Synthons and Solvent-Induced Supramolecular Isomerism

We have explored O–H···O
hydrogen bonded self-assembly of rigid three-connecting mesitylenetribenzoic
acid (H3MTB). The
triacid is shown to exploit the acid dimer motif and self-assemble,
in the solid state, into a 6-fold interpenetrated (6,3) honeycomb
net with the pores of the dimension of ca. 24–26 Å. It
is shown that crystallization of H3MTB with K+/NH4+ salts in the presence of 18-crown-6 leads to mono-deprotonation
followed by self-assembly of the resultant H2MTB– into multicomponent
crystals of different network structures sustained by charge-assisted
hydrogen bonds. The X-ray crystal structure analyses reveal that the
solvent employed to access the multicomponent crystals plays the role
of a chaperon in modifying the supramolecular structures adopted.
Crystallization of H3MTB in the presence of dibenzo-18-crown-6 is found to lead likewise
to a (6,3) net that is 6-fold interpenetrated with K+⊂dibenzo-18-crown-6
occupying the voids. Thus, the strategy involving partial deprotonation
of rationally designed polycarboxylic acids with KX/crown is shown
to lead to multicomponent crystals sustained by charge-assisted hydrogen
bonds. The structural studies have led to identification of water-mediated
paddlewheel and carboxylate···carboxylate dimer synthons.