NMR and luminescence binding studies of ytterbium, thulium, and europium macrocyclic complexes with phosphorus(V) oxy anions

The binding of a series of phosphate anions to coordinatively unsaturated macrocyclic complexes of Yb, Tm, and Eu was studied by H-1-NMR, emission and circularly polarized luminescence (CPL) spectroscopy. Each ternary adduct was distinguished by its spectral profile. With O-phosphorylated amino acids and peptides, chemoselective ligation of the phosphate moiety was favored by Eu over chelation involving the terminal amino group, which was competitive for Tm and Yb. A preference for binding O-phosphono-L-tyrosine sites was found with various Eu complexes, and was signalled by ratiometric changes in metal-based emission and CPL spectra.