A turn-on green channel Zn2+ sensor and the resulting zinc(ii) complex as a red channel HPO42− ion sensor: a new approach

Abstract

A newly synthesized and spectroscopically characterized non-fluorescent organic moiety (L′H) selectively sensed Zn²⁺ ions based on a chelation-enhanced fluorescence (CHEF) process at the λ_em of 520 nm through the formation of a new dinuclear zinc(II) complex (1). Upon the addition of Zn²⁺ ions to the solution of L′H in dimethyl sulphoxide at 25 °C, a systematic enhancement of fluorescence was observed, which was not affected by the presence of competitive ions. The reaction of L′H with Zn²⁺ ions led to the formation of a dinuclear zinc(II) complex, featuring a new in situ formed macrocyclic ligand (L), which was isolated in pure form and then characterized. The formulation of 1 was established by spectroscopic tools along with a detailed structural analysis carried out using single crystal X-ray crystallography. In addition, the complex 1 also behaved as a red-shifted, HPO₄²⁻ ion-selective chemosensor at the λ_em of 595 nm based on a displacement approach in dimethyl sulphoxide. Interestingly, 1 showed remarkable sensitivity towards HPO₄²⁻ ions via fluorescence modulation of the dinuclear zinc(II) complex (1) compared with the other anions examined herein.