Guest induced head-to-tail columnar assembly of 5,17-difunctionalized calix[4]arene

Abstract

Calix[4]arene possessing two catechol side arms 1 and organic molecules (nPrOH, AcOH, AcOEt, and CH₃CN) crystallized to afford cocrystals: 1·(nPrOH)₄, 1·(AcOH)₄, 1·(AcOEt), and 1·(CH₃CN)₂. In these cocrystals, calix[4]arene 1 is arranged one-dimensionally, forming head-to-tail columnar structures. The organic guests settle in the residual space between the columnar structures; they are captured by the catechol side arms through hydrogen bonding. In the cocrystal 1·(H₂O)₂, a continuous zigzag array of 1 is formed instead of the columnar assembly, demonstrating that the organic guests induced the formation of the head-to-tail columnar structures in the crystal packing. The crystalline apohost 1_apo was prepared by the desorption of the MeOH guests from the cocrystal 1·(MeOH)₄; this compound adsorbed the MeOH vapour, reconstructing the original crystal packing. When 1_apo adsorbed the iPrOH vapour, a cocrystal with a crystal structure similar to that of 1·(MeOH)₄ was formed, suggesting that 1_apo has a crystal structure similar to that of 1·(MeOH)₄.