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A new calixpyridinium-based light-responsive host-guest recognition motif was found in this work. This host-guest recognition motif was further discovered to be applied as a selective turn-on fluorescent sensor for lysine over other natural amino acids.

In this work, a comparative study on the supramolecular assemblies formed by calixpyridinium and two alginates with different viscosities was performed. We found that sodium alginate (SA) with medium viscosity (SA-M) had a better capability to induce aggregation of calixpyridinium in comparison with SA with low viscosity (SA-L) because of the stronger electrostatic interactions between calixpyridinium and SA-M. Therefore, the morphology of calixpyridinium-SA-M supramolecular aggregates was a compact spherical structure, while that of calixpyridinium-SA-L supramolecular aggregates was an incompact lamellar structure. As a result, adding much more amount of 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt to calixpyridinium-SA-M solution was required to achieve the balance of the competitive binding, and in comparison with calixpyridinium-SA-L supramolecular aggregates, calixpyridinium-SA-M supramolecular aggregates were more sensitive to alkali. However, for the same reason, in comparison with calixpyridinium-SA-M supramolecular aggregates, calixpyridinium-SA-L supramolecular aggregates were much more stable in water not only at room temperature but also at a higher temperature, and even in salt solution. Therefore, in comparison with calixpyridinium-SA-L supramolecular aggregates, calixpyridinium-SA-M supramolecular aggregates exhibited a completely opposite response to acid because of the generation of salt. Because SA is an important biomaterial with excellent biocompatibility, it is anticipated that this comparative study is extremely important in constructing functional supramolecular biomaterials.

The information in the literature concerned with lowering the critical aggregation concentration of anionic surfactants by macrocyclic compounds is scarce. This research develops an effective route for lowering the critical aggregation concentration of anionic gemini surfactants by the complexation of calixpyridinium. Furthermore, the size of complex self-assembled nanostructures can be well controlled by the different mixing ratio of the host and the guest.

The inclusion complex of p-sulfonatocalix[5]arene (SC5A) with N-methyl-N′-(naphthalen-2-ylmethyl)-4,4′-bipyridinium (MVNp2+) guest was successfully prepared in single-crystal form. The obtained structure shows that SC5A is significantly distorted from the common ‘cone’ conformation induced by the complexation of MVNp2+. Moreover, the crystal packing of MVNp2+⊂SC5A reveals that the SC5A hosts do not assemble into a typical bilayer array, but arrange themselves into an unseen face-to-back bis-chain. As a result, hydrophobic molecular channels are fabricated rarely by SC5A hosts. A host–guest solution study was further performed by using NMR spectroscopy and microcalorimetry, the results of which are in accordance with the above crystallographic results. The molecular binding behaviors of SC5A with N-methyl-N′-adamantane carbomethyl-4,4′-bipyridinium (MVAd2+) guest that is structurally similar to MVNp2+ but with a different side group were also studied by using NMR spectroscopy and microcalorimetry in solution, the results of which are similar to those of SC5A with MVNp2+ guest as well.

We have successfully implemented the supramolecular tandem assay principle for the real-time, continuous, direct, and label-free monitoring of alkaline phosphatase activity through a fluorescence "switch-off" assay based on a novel calixpyridinium/dye reporter pair. Because several diseases can be preliminarily diagnosed in light of an abnormal level of alkaline phosphatase in serum, the application of tandem assays to selectively monitor alkaline phosphatase activity has feasible implications in disease diagnosis.

The molecular binding behavior of water-soluble calix[4]arenes (p-sulfonatocalix[4]arene (SC4A) and p-sulfonatothiacalix[4]arene (STC4A)) with two asymmetric 4,4′-bipyridinium guests (N-methyl-N′-adamantane carbomethyl-4,4′-bipyridinium dibromide (MVAd2+) and N-methyl-N′-(naphthalen-2-ylmethyl)-4,4′-bipyridinium bromide iodide (MVNp2+)) was systematically studied using NMR spectroscopy and microcalorimetry in a neutral aqueous solution. Either the methyl group or the adamantane moiety in MVAd2+ could enter into the SC4A and STC4A cavities, without regioselectivity. The STC4A cavity can also accommodate MVNp2+, either through incorporation of the methyl group or the naphthalene moiety, without regioselectivity. However, we were surprised to find that MVNp2+ could only be included within the SC4A cavity through incorporation of the methyl group, with regioselectivity, which is rare for a flexible host. Furthermore, both SC4A and STC4A can form stable inclusion complexes with the two investigated asymmetric 4,4′-bipyridinium guests, driven by very favorable enthalpy changes, and the thermodynamic origins of the host selectivities for MVAd2+ and MVNp2+ can be well explained through their binding modes. The finding of this novel regioselective recognition is promising for potential applications in the development of more sophisticated biomimetic materials.

Strong dipole moments have been built into two hexa-peri-hexabenzocoronene (HBC) derivatives (1 and 2) originating from the push-pull structure of the molecules with one electron-donating and one electron-withdrawing substituent. The influence of dipole moment on the self-assembly of HBCs in solution and in bulk has been investigated. Chemical Communications