Sumanene-based triazole-linked receptors
Designing molecular receptors featuring the bowl-shaped sumanene motif for detecting metal cations constitutes an emerging field of applied supramolecular chemistry of this buckybowl. In this work, we successfully synthesized a new class of sumanene-based receptors, whose key structural feature was the presence of two or three sumanene units linked via 1,2,3-triazole skeletons generated in a 1,3-dipolar cycloaddition reaction (click chemistry approach). It was found that the designed compounds detect metal cations in solution (spectrofluorometric studies), as well as in heterogeneous systems (polymeric membranes of potentiometric sensors). In terms of optical studies in solution, the title molecules exhibited fluorescence quenching behaviours upon addition of metal cations, with Stern–Volmer constant values at the level of 106 M−1. The spectrofluorometric and potentiometric results were in good agreement, revealing the preferential binding of lithium (Li+), caesium (Cs+), or copper(II) (Cu2+) cations, depending on the receptor structure. Density functional theory (DFT) computational studies were also performed on the structure and receptor properties of the title molecules. The results indicate attractive possibilities for the design of novel organic materials based on the sumanene scaffold and the ability to tune the properties of sumanene-based receptors for recognition of different metal cations.
A New Generation of Sumanene-Based AIEgens for the Effective Recognition of Metal Cations in Solutions Containing 95 vol % of Water
In recent years, the application of sumanene derivatives for the optical detection of metal cations was demonstrated. Unfortunately, known sumanene-based receptors enable the detection process in purely organic solutions or in aqueous media containing not lower than 50 vol % of organic solvent. Designing easy-to-synthesize sumanene-based optical receptors able to effectively recognize metal cations in aqueous solutions containing a slight volume fraction of organic solvent remained an important and vital challenge. In this work, we show that water-insoluble sumanene receptors composed of only carbon and hydrogen atoms enable the effective detection of cesium (Cs+)
or lithium (Li+) cations in solutions containing 95 vol % of water. Their key feature is related to the exhibition of an aggregation-induced emission (AIE) effect. We discovered that the designed sumanene receptors exhibit excellent detection parameters expressed by Stern-Volmer constant values at the level from 108 to 1010 M−1. This work also shows that by simple modification of the sumanene receptor structure, it is possible to drastically change its detection preference from large Cs+ cations to small Li+ cations. The highest sensitivity of the designed receptors was concluded for Na+ or Li+, depending on the receptor structure. This work opens new avenues in designing sumanene-based optical receptors.
