Complexation of curium(III) by adenosine 5′-triphosphate (ATP): A time-resolved laser-induced fluorescence spectroscopy (TRLFS) study

The complex formation of curium(III) with adenosine 5′-triphosphate (ATP) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The interaction between soluble species of curium(III) with ATP was studied at trace Cm(III) concentrations (3 × 10⁻⁷ M). The concentrations of ATP were varied between 6.0 × 10⁻⁷ and 1.5 × 10⁻⁴ M in the pH range of 1.5-7.0 using 0.154 M NaCl as background electrolyte.Three Cm-ATP species, M_pH_qL_r, could be identified from the fluorescence emission spectra: (i) CmH₂ATP⁺ with a peak maximum at 598.6 nm, (ii) CmHATP with a peak maximum at 600.3 nm, and (iii) CmATP⁻ with a peak maximum at 601.0 nm. The formation constants of these complexes were calculated from TRLFS measurements to be log β₁₂₁ = 16.86 ± 0.09, log β₁₁₁ = 13.23 ± 0.10, and log β₁₀₁ = 8.19 ± 0.16. The hydrated Cm-ATP species showed fluorescence lifetimes between 88 and 96 μs; whereas the CmATP⁻ complex has a significantly longer fluorescence lifetime of 187 ± 7 μs.