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

Zinc ions play an important role in many biological processes in the human body. To selectively detect Zn(2+) , 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 Zn(2+) recognition moiety were developed as suitable luminescent sensors. Their luminescence intensity is affected by the photoinduced electron transfer mechanism. Upon addition of Zn(2+) , both probes display an up to sevenfold enhancement in Eu(3+) emission. Competition experiments demonstrated their specificity toward Zn(2+) 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 Zn(2+) . The induced emission changes of Eu(3+) allow for precise quantitative analysis of Zn(2+) , establishing these lanthanide-based complexes as viable chemosensors for biological applications.