Anion and Cation Effects on Anion-Templated Assembly of Tetrahydroxytriptycene

A tetrahydroxytriptycene ligand 1 assembles through O–H···anion hydrogen bonds into a range of different structures. With tetrabutylammonium bromide, 1 forms a stable nanotube structure that is supported by O–H···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 1D polymers, giving a layered 2D morphology. The wide range of architectures prepared from a relatively simple ligand illustrates the potential utility of O–H···anion interactions for constructing solid-state materials.