Triazole–Carbasugar Macrocycles: Anion Receptors and Template‐Controlled Synthesis

Cyclic tetramer 1 , obtained by click cyclooligomerization of an azido–alkyne monomer 4 , was investigated as a neutral host for anion recognition. 1 H nuclear magnetic resonance (NMR) titration experiments in CD 3 CN with a range of ions revealed a clear binding preference towards anionic guests, particularly halide and nitrate anions, with association constants spanning over one order of magnitude (log K a = 2.57 (NO 3 − ) − 3.47 (I − ); T = 18°C–21°C). Density functional theory (DFT) calculations showed that the macrocyclic cavity is conformationally flexible and can adapt to the size and geometry of the guest, while the binding affinities arise from a balance between receptor deformation, hydrogen bonding, and dispersive van der Waals interactions. Based on these host–guest studies, chloride was identified as an effective template on the click oligomerization of 4 , selectively favouring the formation of cyclic tetramers and hexamers as the main products.