We report the design, synthesis, and characterization of BU1, the first bambusuril derivative bearing phenyl substituents directly attached to the glycoluril nitrogen atoms. The macrocycle BU1, decorated with p-nitrophenyl groups, exhibits distinct optical responses upon anion binding, enabling the evaluation of anion affinity by UV-Vis spectroscopy for the first time. Complementary 1H NMR titrations confirmed a 1:1 host-guest stoichiometry and yielded association constants consistent with the UV-Vis data. Despite the presence of electron-withdrawing p-nitrophenyl groups, BU1 forms relatively weak complexes with halide and perchlorate anions. NMR experiments and molecular modeling suggest that direct N-aryl substitution induces cavity distortion and reduces flexibility, which likely accounts for the observed decrease in binding strength.
Grunová et al. (Thu,) studied this question.