Pyrene‐Based “Turn‐Off” Probe with Broad Detection Range for Cu2+, Pb2+ and Hg2+ Ions

Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited for the fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra‐ and intermolecular excimers, which is however limiting the sensitivity range due to masking of e. g. quenching effects by the excimer emission. Herein we report a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This sensor can quantitatively detect Cu2+, Pb2+ and Hg2+ in organic solvents over a broad concentrations range, even in the presence of ubiquitous ions such as Na+, K+, Ca2+ and Mg2+. The strongly emissive sensor's fluorescence with a long lifetime of 165 ns is quenched by a 1 : 1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi‐Hildebrand, and a non‐linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health‐relevant nM range and could be used e. g. for the monitoring of the respective ions in waste streams. An efficient pyrene‐based probe using fluorescence quenching to detect mercury, lead and copper in organic solvents with high selectivity and specificity was synthetized. The rigid tris‐pyrene chromophore architecture ensures a very broad dynamic range of the sensor's response. Spectroscopic investigation elucidated the stoichiometry and mode of action and revealed a unique aggregation behavior at high analyte concentrations.