1.D.321.  The Chemosynthetic Macromolecule -

Extended Pillararene Macrocycle NanoPore (EPM-NP) Family

Pillararenes are a unique group of supramolecular macrocycles, presenting important features and potential applications on account of their intrinsic structural properties and functionalities (Zhang et al. 2018). Pillararenes are macrocyclic oligomers of alkoxybenzene akin to calixarenes but tethered at the 2,5-positions via methylene bridges. Benefiting from their unique pillar-shaped architecture favorable for diverse functionalization and versatile host-guest properties, pillararenes decorated with chelating groups work well by  supporting platforms to construct extractants or adsorbents for metal ion separation (Chen et al. 2019).

Qiao et al. 2021 introduced a chemosynthetic macromolecule-extended pillararene macrocycle (EPM) as a chemically defined transmembrane nanopore that exhibits selective transmembrane transport. The ionic current measurements revealed stable insertion of individual EPM nanopores into a lipid bilayer membrane and remarkable cation type-selective transport, with up to a 21-fold selectivity for potassium over sodium ions.  Other cations could also be transported (Qiao et al. 2021).  This resulted in a new class of synthetic nanopores with custom transport functionality imprinted in their atomically defined chemical structures.

Linear pillar[5]arene-containing conjugated polymers were designed and synthesized via metathesis cyclopolymerization of pillar[5]arene-functionalized 1,6-heptadiyne (Wu et al. 2019). Upon addition of an ionic guest, such polymers could form inclusion complexes, of which the glass transition temperature decreased dramatically. With the aid of ionic guest and host-guest complexations between the pendant pillararenes and guest, these supramolecular materials exhibited tunable conductivity from 10-12 to 10-3 S·cm-1 at 30 °C. In addition, compared with the polymers without pendant pillar[5]arenes, such polymers showed better compatibility with the ionic guest, which could prevent the leakage of the latter one and was good for the conductivity of the material.


 

References:

Chen, L., , Y. Cai, , W. Feng, , and L. Yuan,. (2019). Pillararenes as macrocyclic hosts: a rising star in metal ion separation. Chem Commun (Camb) 55: 7883-7898.
Qiao, D., H. Joshi, H. Zhu, F. Wang, Y. Xu, J. Gao, F. Huang, A. Aksimentiev, and J. Feng. (2021). Synthetic Macrocycle Nanopore for Potassium-Selective Transmembrane Transport. J. Am. Chem. Soc. 143: 15975-15983.
Wu, Y., H. Li, Y. Yan, X. Shan, M. Zhao, Q. Zhao, X. Liao, and M. Xie. (2019). Pillararene-Containing Polymers with Tunable Conductivity Based on Host-Guest Complexations. ACS Macro Lett 8: 1588-1593.
Zhang, H., , Z. Liu, , and Y. Zhao,. (2018). Pillararene-based self-assembled amphiphiles. Chem Soc Rev 47: 5491-5528.