Lifetimes (k_obs), inverse lifetimes , and the hydration numbers (N_H2O) extracted from exponential fitting of the observed kinetic decays obtained from solutions containing Eu³⁺ (0.5 mg, 3.3 µmol) dissolved in aqueous solutions of HOTf_(aq) (0.11 M), (NH₄)O₂CMe_(aq):HO₂CMe_(aq) (0.1 M, 4 M, 15 M, pH 5).

Compound (matrix)	k obs (ms)		N H2O
Eu3+ HOTf(aq) (0.11 M)	0.11(1)	9.09	9.0(5)
Eu3+ (NH4)O2CMe(aq):HO2CMe(aq) (0.1 M, pH 5.5)	0.19(3)	5.26	5.0(5)
Eu3+ (NH4)O2CMe(aq):HO2CMe(aq) (4 M, pH 5.5)	0.27(1)	3.70	3.3(5)
Eu3+ (NH4)O2CMe(aq):HO2CMe(aq) (15 M, pH 5.5)	0.45(2)	2.20	1.8(5)