Determination limit of fluorescence turn-on probes for the acetate anion

Three fluorescent turn-on probes containing 3,6-dichloro-9H-carbazole as carbazyl part have been designed and synthesized. Among studied anions F-, AcO-, H2PO4-, Cl-, Br- and I-, AcO- showed the strongest binding ability with all probes. The strong basic anions, such as AcO-, H2PO4-, and F-, induced a significant red-shift in absorption and a concomitant increase in fluorescent emission of the probes caused by photoinduced electron transfer (PET). The determination limit of probe 3 (Scheme1) toward AcO- is 3.0x10(-7)M. H-1-NMR Titration experiments shed light on the nature of the interaction between the probes and the anions. Theoretical investigation further illustrated the possible binding mode in these hostguest interactions and the roles of molecular frontier orbitals in molecular interplay.