Sumanene-Conjugated Poly(amidoamine) Dendrimer for the Detection of Metal Cations in Aqueous Solution

Chemistry and applications of sumanene derivatives as molecular receptors of cations have been an area of interest in applied supramolecular chemistry of this buckybowl. Notably, creating sumanene-based receptors enabling the detection of alkali metals in purely aqueous solutions has been a vital challenge. This work reports the design of sumanene conjugate with poly(amidoamine) dendrimer (PAMAM; generation 2.0). The designed dendrimer was found to be highly water-dispersible and was tested for the first time as an optical receptor of metal cations in aqueous solution, with the selectivity found for cesium (Cs⁺) or sodium (Na⁺) cations. The association constants for noncovalent complexes formed via dynamic cation-π interactions between the sumanene bowl and Cs⁺/Na⁺ in water in aqueous solution are found to be comparable (at the level of 10⁴-10⁵ M^-1) to those observed in analogous systems containing a significant volume of organic solvents. The bowl-shape of sumanene is also found to provide improved detection properties of the resultant receptor compared to the respective PAMAM dendrimer modified with planar triphenylene. It is believed that the findings of this work will further stimulate the field of sumanene-based receptors, as well as the chemistry of water-soluble buckybowls in general.