An AIRE-active far-red ratiometric fluorescent chemosensor for specifically sensing Zn2+ and resultant Zn2+ complex for subsequent pyrophosphate detection in almost pure aqueous media

A simple Schiff-base fluorescent chemosensor (1) was synthesized by the reaction of 3-amino-pyrazine-2-carbohydrazide and 7-diethylamino-3-formylcoumarin; the sensor 1 displayed a notable green emission at 524 nm in DMSO and an aggregation-induced ratiometric emission (AIRE) at 555 nm in an almost buffered aqueous media (0.5% DMSO content). The AIRE of 1 was quenched following binding to Zn²⁺ ions, while the fluorescence emission in the far-red region was evidently enhanced at 628 nm. Notably, the ratiometric signal output could be utilized to specifically distinguish Zn²⁺ among various metal ions. Moreover, the 1-Zn²⁺ complex was effectively employed as a fluorescent ratiometric chemosensor for pyrophosphate (PPi) detection. The detection limit was 3.52 μM and 2.45 μM for Zn²⁺ and PPi, respectively. The binding mechanism was evaluated by ¹H NMR, ESI-MS, single-crystal X-ray diffraction, TEM, time-resolved fluorescence spectrophotometry, and density functional theory studies. Overall, owing to its sensitive fluorescence behavior, cell imaging studies demonstrated that this sensor is capable of sensing Zn²⁺ and PPi in living cells.

Crystal structure of ethanol-bis(N-((5-(ethoxycarbonyl)-3,4-dimethyl-1H-pyrrol-2-yl)methylene)benzohydrazonato-κ 2 N,O)copper(II), C36H42N6O7Cu

C20H29N3O5, triclinic, P1̄ (no. 2), a = 8.482(6) Å, b = 15.272(12) Å, c = 15.285(12) Å, a = 112.024(11)°, β = 95.325(9)°, γ = 98.958(9)°, V = 1788(2) Å3, Z = 2, R gt(F) = 0.0570, wR ref(F 2) = 0.1687, T = 296(2) K.