Synthesis and Detection Performance of Fluorescent Copper Clusters Regulated by Substituents

Fluorescent metal clusters are ideal fluorescent probe materials due to their small size and good photostability. In this work, three copper clusters ( 1–3 ) based on mercaptobenzothiazole-derived ligands were successfully synthesized and characterized, and their crystal structures were determined by single-crystal X-ray diffraction. The differences in substituents regulate their fluorescence. All three clusters exhibited highly selective and sensitive detection toward Fe(III) and Cr(VI) (CrO 4 2– and Cr 2 O 7 2– ) in aqueous solution, while 1 and 3 could also selectively recognize 2-nitrophenol (2-NP). Moreover, systematic investigations into the underlying recognition mechanisms were carried out in detail, and key sensing parameters, including the Stern–Volmer constant (K sv ) and limit of detection (LOD), were accurately determined via fluorescence titration experiments. This study provides effective guidance for the design and application of copper-sulfur clusters in environmental chemicals.