Proton-anion Ion-pair Recognition by a Hexaazatriphenylene-Hexaurea Receptor

Recognition behavior of a hexaazatriphenylene (HAT) derivative toward different acids in THF solution was investigated through H-1 NMR, UV-vis and fluorescence spectroscopic experiments, as well as SEM image and semi-empirical calculations, which revealed that this propeller-like HAT receptor could co-assemble into a layered complex by sandwiching protons and halogen (chloride or bromide) anions synergistically between the receptor molecules. What's more, reversible and remarkable color changes visible to the naked eye could be observed, when the halogen acid and base were introduced alternatively.