Specific Recognition of Hg2+ and other Cations by a Hoechst33258@inverted Cucurbit[7]uril Fluorescence Probe Using Different pH Media

A host-guest inclusion complex comprising an inverted cucurbit[7]uril (iQ[7]) and a biologically important dye, Hoechst-33258 (H33258), was selected as a probe to test the response to various metal cations, including alkali metals, alkali earth metals, lanthanides, transition metals and other cations in aqueous HCl solution (pH=2) and NaOH solution (pH=11), respectively. The experimental results revealed that the host-guest interaction showed a similar inclusion mode in the two selected aqueous solution conditions (pH=2 and 11), which was a dumbbell-like inclusion complex in which one iQ[7] included the piperazine moiety, and another iQ[7] included the phenol moiety of H33258. The probe exhibited specific recognition of Hg2+ cation in all metal systems containing Hg2+ via obvious fluorescence quenching under acidic solution conditions. The probe also exhibited specific recognition of Al3+, Fe3+, Cr3+, and especially Ce3+ cations in the lanthanide system via obvious fluorescence enhancement under basic solution conditions.