4-tritylbenzoic acid. A molecular scaffold for wheel-and-axle host-guest inclusion compounds with a supramolecular axis

Abstract

4-Tritylbenzoic acid crystallises via the carboxy dimer supramolecular synthon to produce a wheel-and-axle host lattice that includes different aromatic solvents in its microporous framework. The clathrate structures were characterised by single crystal X-ray diffraction. Solvents like xylenes, chlorobenzene and anisole are included in a channel of cross-sectional area 42 Å2 with 2:1 host-guest stoichiometry while mesitylene occupies a channel of 71 Å2 as a 1:1 clathrate. The host architecture is robust and yet adaptive. The carboxy dimer synthon together with the phenyl-phenyl interactions (edge-to-face, ef and offset face-to-face, off) produce recurring, zigzag tapes of wheel-and-axle supermolecules. A plethora of aromatic ef and off motifs in the intra- and inter-tape regions modulate the cavity area to accommodate solvents of different size/shape. The ability to tune the pore volume and still retain the target wheel-and-axle topology is a notable feature in this family of isomorphous structures. The unsolvated acid adopts a different crystal packing with the triphenylmethyl groups filling the voids in the structure.