A molecular sensor for selective recognition of Fe³⁺ by a functional seven-nuclear Zn(II) cluster compound formed...

In this paper, we designed and synthesized a novel based on quinoline modification half-salamo-type Zn(II) complex([Zn₇(L)₆(μ₃-OCH₃)₆]·(ClO₄)₂), namely ZP. The structure of ZP was determined by X-ray single-crystal diffraction, in which the Zn(II) ions displayed in two different coordination modes, ultimately forming a highly symmetric heptanuclear structure. The Zn(II) complex probe modified by quinoline luminescent group has excellent luminescence properties and selectively recognizes Fe³⁺ in aqueous solution. When Fe³⁺ is added to the aqueous solution of ZP, ZP exhibits an obvious fluorescence quenching effect in a relatively short period of time, with a high sensitivity. The lowest detection limit of ZP for Fe³⁺ was further determined by fluorescence titration to be 5.8 × 10^-8 M^-1. In order to further explore the mechanism of Fe³⁺ quenching on ZP fluorescence, we performed fluorescence titration experiments, XPS as well as ESI-MS characterization, which proved that the recognition of Fe³⁺ by ZP is the substitution of metal ions leading to fluorescence quenching. At the same time, we also examined the practical application of ZP in life, and found that ZP can quantitatively detect the content of Fe³⁺ in drugs and actual water samples, and the experimental results were highly consistent with test result of ICP-MS, which further demonstrated that the detection of ZP was highly accurate. In addition, the detection of Fe³⁺ by ZP can be applied over a wide pH range without interference from other metal ions.