The Binding Interactions between Cyclohexanocucurbit[6]uril and Alkyl Viologens Give Rise to a Range of Diverse Structures in the Solid and the Solution Phases

摘要

The binding interactions between the cyclohexanocucurbit[6]uril (Cy6CB6) host and a series of dialkyl-4,4'-bipyridinium (viologen) dicationic guests were investigated in the solution phase, using H-1 NMR spectroscopy, and in the solid phase, using X-ray diffraction methods. In D2O solution, methyl viologen (MV2+) and ethyl viologen (EV2+) form 1:1 complexes in which the bipyridinium aromatic nucleus is partially included inside the Cy6CB6 cavity. Propyl viologen (PV2+), butyl viologen (BV2+), pentyl viologen (FV2+), and heptyl viologen (HV2+) form 2:1 complexes with Cy6CB6, in which each of the viologen aliphatic chains is included by a host molecule. In the solid state, EV2+ forms a polypseudorotaxane via pseudorotaxane interdigitation of Cy6CB6 hosts. The PV2+ guest forms a dumbbell-shaped structure with a Cy6CB6 host residing over each of the terminal propyl groups of the guest. In contrast to this, the BV2+ guest and Cy6CB6 form a different polypseudorotaxane structure in which dumbbell-shaped structures, formed by two host molecules interacting with a single guest, are interconnected through metal-host coordination.