Fluorescent anion receptors with iminoylthiourea binding sites—selective hydrogen bond mediated recognition of CO32−, HCO3− and HPO42−

A number of structurally simple, fluorescent sensor molecules based on the iminoylthiourea/1,2,4-thiadiazole unit are presented, which display extraordinarily strong fluorescence enhancement selectively upon complexation of HCO3−, CO32− and HPO42−.