The missing link: NiII ions have been used to coordinate to 4,4′‐dipyridine included within β‐cyclodextrin to form a linear polymeric rotaxane (see schematic representation). The binding of the 4,4′‐dipyridine within the cyclodextrin has been examined both in solution and in the solid state.

A series of 6-O-(p-substituted phenyl)-modified beta-cyclodextrin derivatives, i.e., 6-O-(4-bromophenyl)-beta-CD (1), 6-O-(4-nitrophenyl)-beta-CD (2), 6-O-(4-formylphenyl)-beta-CD (3), 6-phenylselenyl-6-deoxy-beta-CD (4), and 6-O-(4-hydroxybenzoyl)-beta-CD (5), were synthesized, and their inclusion complexation behavior in aqueous solution and self-assembling behavior in the solid state were comparatively studied by NMR spectroscopy, microcalorimetry, crystallography, and scanning tunneling microscopy. Interestingly, (seleno)ethers 1-4 and ester 5 displayed distinctly different self-assembling behavior in the solid state, affording a successively threading head-to-tail polymeric helical structure for the (seleno)ethers or a mutually penetrating tail-to-tail dimeric columnar channel structure for the ester. Combining the present and previous structures reported for the relevant beta-CD derivatives, we further deduce that the pivot heteroatom, through which the aromatic substituent is tethered to beta-CD, plays a critical role in determining the helix structure, endowing the 2-fold and 4-fold axes to the N/O- and S/Se-pivoted beta-CD aggregates, respectively. This means that one can control the self-assembling orientation, alignment, and helicity in the solid state by finely tuning the pivot atom and the tether length. Further NMR and calorimetric studies on the self-assembling behavior in aqueous solution revealed that the dimerization step is the key to the formation of linear polymeric supramolecular architecture, which is driven by favorable entropic contributions.

Two novel β-cyclodextrin (β-CD) derivatives possessing azobenzene functional groups as a spectral probe, i.e., mono{6-O-[4-(phenylazo)phenyl]}-β-cyclodextrin (1) and mono{6-O-[4-((4-nitrophenyl)azo)phenyl]}-β-cyclodextrin (2), were synthesized in high yields, and their complexation behaviors with aliphatic alcohols were evaluated by using UV−vis, circular dichroism, and 1H NMR spectroscopy. The induced circular dichroism (ICD) and 2D NMR spectroscopy investigations revealed that azobenzene groups attached to the β-CD rim can be deeply embedded to the β-CD cavity to form the intramolecular inclusion complexes in 10% DMSO aqueous solution. Increasing the ratio of DMSO in solution results in the gradual exclusion of the azobenzene sidearm from the β-CD cavity. Upon complexation with guest adamantanols, modified β-CD 1 or 2 displays two different binding models, that is, the competitive inclusion model for 2-adamantanol and the co-inclusion model for 1-adamantanol. These two different models reasonably explain the different binding behaviors and molecular selectivities of host β-CDs toward guests. Therefore, besides acting as a spectral probe, azobenzene modified β-CDs can also effectively recognize the size/shape of guest molecules, giving good molecular selectivity up to 91 for 2-adamantanol/(+)-borneol pair by 1 and the moderate enantioselectivity (K - /K + = 2.1) for (−)-/(+)-borneol pair by 2.

A novel supramolecular assembly has been fabricated by the inclusion complexation between organo-selenium bridged bis(β-cyclodextrin)s 2 and calix[4]arene derivative 3 in water-acetonitrile (1:1) mixture solution and characterized by fluorescence, 2D NMR, TEM, SEM, and STM images, showing the nanometer structural wire-shaped aggregates.