Table 1.

Rate Constant for Proton Exchange with Bulk Water of Each Pool of Exchanging Protons in EuCNPHC^{3+ a}

	exchange rate constant/103 s−1
H2O molecules per EuL	OH (19 ppm)	OH (16 ppm)	OH (14 ppm)	Eu–OH2b	amideb
0.4	0.014	0.015	0.016	0.14	0.008
7.8	0.34	0.35	0.36	0.036	2. 9
15	1.1	0.88	1.2	0.021	*
23	1.9	2.0	1.6	0.011	*
30		3.0c		*	*
45		2.7c		*	*
60		4.6c		*	*
75		4.8c		*	*

^aThe entries are the averages of the results from fitting of the B₁ = 86 and 108 Hz CEST spectra. For samples with higher water concentrations, average values for the rate constants of the three hydroxyl protons are given, due to the difficulty of resolving the peaks in the fitting process.

^bAsterisks represent values that could not be satisfactorily determined in the fitting process due to the poor resolution of the CEST peak arising from this pool at the water concentration in question.

^cAverage values for all three hydroxyl protons.