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Compared to isolated, simple Ln3+/Q[6] complexes in the absence of polychloridometallate ions, linear coordination polymers have been assembled from lanthanide cations (Ln3+) and cucurbituril (Q[6]) in the presence of polychloridometallate ions as inorganic structure inducers in HCl solution. X-ray diffraction analysis has revealed that not only [CuCl4]2− anions but also [FeCl2(H2O)4]+ cations can induce the coordination of Ln3+ cations to Q[6] so as to form Ln3+/Q[6]-based tubular coordination polymers. The driving forces are considered to be interaction of the electron-deficient carbon sites of the carbonyl dipoles of Q[n] molecules with the chloride ends of the Md-block−Cl bonds in the [Md-blockClx]n− anions or [Md-blockClx]m+ cations, as well as unusual hydrogen bonding between the methine and methylene groups on the back of adjacent Q[n] molecules and the chlorine atoms of the [Md-blockClx]n− ions. We have classified such interactions as ‘back-interaction of Q[n]s’.

The host–guest interactions between phenazine hydrochloride salt (PheH+) and hemicucurbit[n]uril (n = 6 or 12) (HemiQ[6 or 12]) have been studied by 1H NMR, UV–vis, IR, mass spectrometry (MS) and quantum chemistry. In 1H NMR spectra, the broadening of proton resonances of the hosts suggests the interactions of PheH+ with HemiQs. The quantitative stabilities of the host–guest systems have been obtained by UV–vis titration experiments, that is, the stoichiometric interactions of PheH+ with HemiQ[6] have been observed with an association constant of Ka = (2.5 ± 1.2) × 106 L mol− 1, while the 2:1 ratio complexes of PheH+ with HemiQ[12] are formed with stepwise association constants of K1 = (9.2 ± 2.8) × 104 L mol− 1 and K2 = (6.4 ± 0.9) × 105 L mol− 1, respectively, which induce a total association constant of Ka = 5.9 × 1010 L2 mol− 2. Both the 1:1 and 2:1 complexes have been detected by MS. Quantum chemistry calculations have been used to understand the static structures and thermodynamic stabilities of the supramolecular assemblies.

Interaction between tetramethylcucurbit[6]uril (TMeQ[6], host) and the hydrochloride salt of α-furaldehyde-isonicotinyl-hydrazone hydrochloride (FIHH+, guest) was investigated using X-ray crystallography and spectroscopic methods. X-ray crystallography showed that the π–π stacking effect and hydrogen bonding resulted in the formation of a dumbbell-shaped supramolecule which contained two FIHH+@TMeQ[6] host–guest inclusion complexes. The host–guest interaction provided identifiable changes in the vibrational frequencies in the IR spectra. 1H NMR spectral analysis established a similar interaction model and revealed that TMeQ[6] preferred to include the furan moiety over the pyridine moiety of the FIHH+ guest molecule. Absorption spectrophotometric analysis suggested that the host and guest interact in a ratio of 1:1 with a stability constant K s = (3.52 ± 0.74) × 106 l mol− 1.pH titration confirmed that the host–guest interaction led to a clear change in the protonation constant of the title guest. Quantum...

The host–guest interaction of symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with the hydrochloride salts of N,N′-bis(4-pyridylmethyl)-1,6-hexanediamine (P6), N,N′-bis(3-pyridyl-methyl)-1,6-hexanediamine (M6) and N,N′-bis(2-pyridylmethyl)-1,6-hexanediamine (O6) was investigated via single crystal X-ray diffraction, 1H NMR spectroscopy, electronic absorption spectroscopy and fluorescence spectroscopy. Single crystal X-ray diffraction showed that the hexyl moiety of P6 or M6 was incorporated in the cavity of TMeQ[6], while the two pyridylmethyl moieties of O6 were incorporated in the TMeQ[6] cavity in the solid state. The 1H NMR results in aqueous solution revealed that the TMeQ[6]-P6 and TMeQ[6]-M6 host–guest interaction systems produce a kinetic dumbbell-shaped inclusion complex at the initial stage and then an equilibrium pseudorotaxane-shaped inclusion complex as the only product after heating. However, only the pseudorotaxane-shaped inclusion complex was observed for the TMeQ[6]-O6 host–gu...