Open Access

Zain Mohamed, Tero Soukka, Christoph Arenz, Michael Schäferling

• The design of anion-sensitive probes with sufficient sensitivity and selectivity is a demanding task in analytical sciences and chemical sensor technology. The reversible binding of anions to lanthanide centers is a possible approach for the development of molecular anion sensors, as reversibility is a prerequisite for continuous sensing and monitoring of enzymatic reactions. Some anion species lead to a strong increase of luminescence intensities and lifetimes by the replacement of luminescence quenching water molecules, though the selectivity of the luminescence response is still a major problem. We synthesized a series of positively charged pyridyl-based multidentate europium complexes (five-, four- and three dentate) including sensitizing chromophores and studied their luminescence intensity and lifetime responses to different polyphosphates, pyrophosphate, phosphate anions, and carboxyanions. The results revealed that the number and symmetry of the binding sites have a significant impact on the response. The five-dentate complex was used for the real-time monitoring of the activity of the ATP hydrolyzing enzyme apyrase.