Highly selective imidazole-appended 9,10-N,N″-diaminomethylanthracene fluorescent probe for switch-on Zn²⁺ detection and switch-off H₂PO₄ ⁻ and CN⁻ detection in 80% aqueous DMSO, and applications to sequential logic gate operations

A new imidazole-appended anthracene-based photoinduced electron transfer (PET) probe (P) was designed and synthesized. Probe P detected Zn²⁺ selectively in an 80% aqueous solution of dimethyl sulfoxide (DMSO) through a switch-on response at pH 7.5 without any interference from other metal ions. Probe P exhibited a moderately strong association constant (K_a) of 1.41 × 10⁵ M⁻¹ and associated with Zn²⁺ ions with 1:1 stoichiometry. The in situ-generated P•Zn²⁺ (1:1) ensemble detected H₂PO₄ ⁻ and CN⁻ ions sequentially through switch-off responses. The selective discrimination of H₂PO₄ ⁻ and CN⁻ ions occurred both in the absence and presence of Ca²⁺ ions at pH 7.5 in a N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (HEPES) buffer. The switch-on response was driven by the selective complexation of P with Zn²⁺ ions, mediated by the combined effects of PET and chelation-induced enhanced fluorescence, resulting in a more structurally rigid complex. Applications of P to real water sample analysis and sequential logic gate operations were demonstrated. The lowest detection limits for Zn²⁺, H₂PO₄ ⁻, and CN⁻ ions in 80% aqueous DMSO were determined to be 1.0 × 10⁻⁹, 1.0 × 10⁻⁹, and 8.0 × 10⁻⁹ M, respectively.