Anion and Cation Effects on Anion-Templated Assembly of Tetrahydroxytriptycene

A tetrahydroxytriptycene ligand 1 assembles through O-H center dot center dot center dot anion hydrogen bonds into a range of different structures. With tetrabutylammonium bromide, 1 forms a stable nanotube structure that is supported by O-H center dot center dot center dot anion hydrogen bonds, but its space is occupied by the large cation. In an effort to produce the nanotubes with different cations and anions, 1 was crystallized with different salts. The reaction of 1 with tetraethylammonium bromide gives a 2D net structure, while 1 and tetrapropylammonium bromide give a discrete 1:2 complex. Attempting to co-crystallize 1 and tetramethylammonium bromide gave crystals of an oxidized quinone form of the ligand. When 1 was crystallized with tetrabutylammonium terephthalate, two different one-dimensional anion coordination polymers were obtained, depending on the crystallization solvent: acetonitrile gave a zigzag polymer, while methanol gave a linear structure. In both cases, the tetrabutylammonium cations fill the gaps between the ID polymers, giving a layered 2D morphology. The wide range of architectures prepared from a relatively simple ligand illustrates the potential utility of O-H center dot center dot center dot anion interactions for constructing solid-state materials.