A Fluorescent Sensor for 2,3‐Bisphosphoglycerate Using a Europium Tetra‐ N ‐oxide Bis‐bipyridine Complex for Both Binding and Signaling Purposes

Host 1 was designed and synthesized as a fluorescent sensor for 2,3‐bisphosphoglycerate (BPG, 3 ). The design features a tris‐functionalized triethylbenzene core to preorganize binding groups. The three cationic moieties, a tetra‐ N ‐oxide bipyridine–europium complex and two ammonium groups, were included to complement the three anionic functionalities on the guest. Beyond acting as a binding site, the europium complex was used to signal binding of the guest through modification of the charge transfer emission. A 1:1 complex with BPG was determined in 50 % methanol/acetonitrile with a K a of 6.7×10 5 mol −1 by monitoring the reduction of the fluorescence signal upon guest addition. In the titration of related glycolytic intermediates lacking a second phosphate ( 4 – 6 ) into host 1 , 2:1 host to guest binding was observed. Similarly, control compound 2 , which lacks the ammonium groups, binds BPG and 4 – 6 in a 2:1 fashion. Also, phenylphosphate 7 binds to host 1 in a 1:1 stoichiometry with a K a over three times less than 3 .