Monitoring of the ADP/ATP Ratio by Induced Circularly Polarised Europium Luminescence

A series of three europium complexes bearing picolyl amine moieties was found to possess differing binding affinities towards Zn2+ and three nucleotides: AMP, ADP, and ATP. A large increase in the total emission intensity was observed upon binding Zn2+, followed by signal amplification upon the addition of nucleotides. The resulting adducts possessed strong induced circularly polarised emission, with ADP and ATP signals of opposite sign. Model DFT geometries of the adducts suggest the diastereoisomer is preferred for ATP and the isomer for ADP/AMP. This change in sign allows the ADP/ATP (or AMP/ATP) ratio to be assessed by monitoring changes in the emission dissymmetry factor, g(em).