Solvent Induced Pseudopolymorphism in a Calixarene-Based Porous Host Framework

The self-assembly properties of the proximal p-tert-butylcalix[4] dihydroquinone compound have been studied to investigate the role played by crystallization conditions in driving the formation of a previously reported cubic porous framework. In chloroform and anhydrous ethyl acetate, the mutual inclusion of the tert-butyl groups is favored, leading to the cubic porous structure; otherwise, in the presence of a higher water amount, the OH groups provide H-bonds with bridging water molecules and a new triclinic crystal structure is obtained, in which the calixarene molecules include chloroform inside their cavities. By exposing a cubic/triclinic powder mixture to acetonitrile vapors, a new monoclinic chiral crystal structure is obtained by supramolecular assembly of calixarene, acetonitrile, and water molecules with the formation of single handed helices.