Bimodal Magneto‐Luminescent Response of Lanthanide Metallopolymers for Distinguishing of Phosphates in Aqueous Solutions

Linear N ‐substituted polyacrylamides bearing tricarboxylic moieties pendant to the backbone are synthesized, and coordinative binding approach is developed to convert them into Gd 3+ /Eu 3+ ‐metallopolymers. Inner‐sphere coordination of the lanthanide ions with the pendant chelating moieties, together with their outer‐sphere stabilization by the randomly coiled backbone, are the reasons for peculiar water proton relaxation and luminescence properties of the metallopolymers obtained. Indeed, for Gd 3+ ‐metallopolymer, the values of longitudinal and transverse relaxivity (r 1 and r 2 ) are 50 and 60 m m −1 ·s −1 , respectively, while for the Eu 3+ ‐counterpart, Eu 3+ ‐centered luminescence is significantly raised compared to Eu 3+ aquaions. Coil‐like conformation of the metallopolymer molecules undergoes a swelling at pH values above 5.0 as evidenced by transmission electron microscopy TEM and dynamic light scattering (DLS) data, which is followed by the changes in the Eu 3+ ‐centered luminescence and r 1(2) ‐values of Gd 3+ /Eu 3+ ‐metallopolymers. The phosphates additives (adenosine monophosphoric acid (AMP), adenosine diphosphoric acid (ADP), HPO 4 2− and adenosine triphosphoric acid (ATP) induce well detectable changes in both water proton relaxation and luminescence of Gd 3+ /Eu 3+ ‐metallopolymers. The luminescent changes distinguish AMP from the other phosphates, while the changes in water proton relaxation are greater for HPO 4 2− and ATP compared to AMP and ADP. This study explains this by interplay of the effects associated with the formation of ternary phosphate‐lanthanide‐polymer complexes and stripping of lanthanide ions from the polymer molecules.