Towards nanomaterials with tubular pores: synthesis and self-assembly of bis-pillar[5]arene

Recently, materials obtained using supramolecular chemistry approaches, and, in particular, spatially preorganized macrocyclic compounds, have attracted close attention of the researchers. Pillar[n]arenes are of special interest due to their tubular spatial structure and macrocyclic cavity. A similar tubular structure is retained in the supramolecular packaging of pillar[5]arene crystals, forming pores. In this study, we developed a block synthetic approach for the preparation of bis-pillar[5]arene containing amide groups. The ability of the synthesized bis-pillar[5]arene to form stable self-associates in solvents of different polarity (CHCl3 and CH3OH) was demonstrated by the DLS method. In trichloromethane at concentration of 1·10–3 M, monodisperse associates with average hydrodynamic diameter of 227 nm (PDI = 0.28) are formed; in methanol, stable associates (1·10–6 M) have an average hydrodynamic diameter of 136 nm (PDI = 0.21). The results obtained can be used to create new supramolecular systems, molecular machines, or capture and detect various organic molecules.

Towards Universal Stimuli-Responsive Drug Delivery Systems: Pillar[5]arenes Synthesis and Self-Assembly into Nanocontainers with Tetrazole Polymers

In this work, we have proposed a novel universal stimulus-sensitive nanosized polymer system based on decasubstituted macrocyclic structures—pillar[5]arenes and tetrazole-containing polymers. Decasubstituted pillar[5]arenes containing a large, good leaving tosylate, and phthalimide groups were first synthesized and characterized. Pillar[5]arenes containing primary and tertiary amino groups, capable of interacting with tetrazole-containing polymers, were obtained with high yield by removing the tosylate and phthalimide protection. According to the fluorescence spectroscopy data, a dramatic fluorescence enhancement in the pillar[5]arene/fluorescein/polymer system was observed with decreasing pH from neutral (pH = 7) to acidic (pH = 5). This indicates the destruction of associates and the release of the dye at a pH close to 5. The presented results open a broad range of opportunities for the development of new universal stimulus-sensitive drug delivery systems containing macrocycles and nontoxic tetrazole-based polymers