Europium(III) Macrocyclic Chelates Appended with Tyrosine-based Chromophores and Di-(2-picolyl)amine-based Receptors: Turn-On Luminescent Chemosensors Selective to Zinc(II) Ions

[Abstract] Zinc ions play an important role in many biological processes in the human body. To selectively detect Zn²⁺, two EuDO3A‐based complexes (DO3A=1,4,7,10‐tetraazacyclododecane‐1,4,7‐tricarboxylic acid) appended with tyrosine as a chromophore and di‐(2‐picolyl)amine (DPA) as the Zn²⁺ recognition moiety were developed as suitable luminescent sensors. Their luminescence intensity is affected by the photoinduced electron transfer mechanism. Upon addition of Zn²⁺, both probes display an up to sevenfold enhancement in Eu³⁺ emission. Competition experiments demonstrated their specificity toward Zn²⁺ over other metal ions, while also revealing the nonspecificity of the derivatives lacking the DPA‐moiety, thus confirming the essential role of the DPA for the recognition of Zn²⁺. The induced emission changes of Eu³⁺ allow for precise quantitative analysis of Zn²⁺, establishing these lanthanide‐based complexes as viable chemosensors for biological applications.German Research Foundation; AN 716/7-