Tuning Selectivity of Bambus[6]urils toward Inorganic Anions


          Carola Rando,^1,2 Jan Sokolov,^1,2 Petr Kulhánek,^3 and Vladimír Šindelář*^,1,2
                                                 ^

 ^1Department of Chemistry, ^2RECETOX, and ^3National Centre for Biomolecular Research, Faculty of
               Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic

                                    e-mail: 503709@mail.muni.cz


Bambus[6]urils are a relatively new class of macrocycles with six glycoluril units held together by
six methylene bridges.^1 These compounds are characterized by an electropositive cavity that allows
them to bind to inorganic anions of different sizes, such as small fluoride and large iodide. This
behavior is due to the relatively high flexibility of the macrocycle, which can adapt to anions of
different sizes and shapes. The binding strength of bambus[6]urils could be modulated by different
functionalization of their portals. For example, the attachment of fluorinated benzyl substituents
increased the bambus[6]uril binding by several orders of magnitude.^2 However, the selectivity of
bambus[6]urils for different anions has remained the same independently of the type of substituent
attached to their portals. Recently, we reported the synthesis of chiral bambus[6]urils bearing
spacious 1-phenylethyl groups, which provide the macrocycles with higher rigidity compared to the
former derivatives.^3 Herein, we show that these chiral bambus[n]urils (BU1, BU2, Fig. 1) bind
inorganic anions with very different selectivity than previously reported bambus[6]urils
derivatives. Moreover, association constants of the host-guest complexes determined by ^1H NMR
titrations and isothermal titration calorimetry showed that the selectivity is dependent also on
type of solvent.


Fig. 1 Schematic representation and electrostatic surface potential of BU1 and BU2.


This work was supported by the Czech Science Foundation (reg. No. GA20-13922S).


1 Svec, J.; Necas, M.;  Sindelar, V. Angew. Chem. Int. Ed., 2010, 49, 2378–2381.

2 Valkenier, H.; Akrawi, O.; Jurček, P.; Sleziaková, K.; Lízal, T.; Bartik, K.; Šindelář, V. Chem,
2019, 5, 429–444.

3 Sokolov, J.; Šindelář, V. Chem. – Eur. J., 2018, 24, 15482–15485.