A selective acetate anion binding receptor: participation via cationic CH3 donors

A novel receptor 1, which has only C-H hydrogen bonds as recognition element has been designed and synthesized. The receptor 1 utilizes cationic CH3 in 2-methyl benzimidazole and naphthalene benzylic C-H as hydrogen bonding donor. The binding cavity formed in receptor 1 prefers to accommodate small negatively charged atom such as oxygen. Therefore, acetate and nitrite show strong affinity for receptor 1 in acetonitrile due to negatively charged oxygen in them. In addition, the order of binding affinity for halides are Br−>Cl−>I−. These results reflect the size and basicities of halides. Further, 1H NMR titration of halide clearly indicates the anion-π interaction. The experimental data from UV-vis, fluorescence and 1H NMR titration are consistent with DFT results.