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. Author manuscript; available in PMC: 2022 Aug 18.
Published in final edited form as: Inorg Chem. 2021 Oct 7;60(20):15808–15817. doi: 10.1021/acs.inorgchem.1c02462

Table 2.

Ionic radii and pKa for the hydrated LnIII and their stability constants (logβ and pLn) for DPTA and 2,2-Li-HOPO (1).

Ionic Radii
(Å)a 		pKab logβ
LnDTPAc 		pLn
(DTPA) d 		ΔpLn

(1 – DTPA)		 pLn (1)
LaIII 1.160 9.24 19.48 16.1 − 1.1 15.0
PrIII 1.126 8.58 21.07 17.7 − 0.5 17.2
NdIII 1.109 8.37 21.60 18.2 0.1 18.3
SmIII 1.079 8.05 22.34 19.0 0.1 19.1
EuIII 1.066 8.02 22.39 19.0 0.6 19.6
GdIII 1.053 8.08 22.46 19.1 0.7 19.8
TbIII 1.040 7.91 22.71 19.4 0.6 20.0
DyIII 1.027 7.91 22.82 19.5 0.9 20.4
HoIII 1.015 7.76 22.78 19.4 1.1 20.5
ErIII 1.004 7.78 22.74 19.4 1.5 20.9
TmIII 0.994 7.91 22.72 19.4 1.8 21.2
YbIII 0.985 7.44 22.62 19.3 2.4 21.7
LuIII 0.977 7.52 22.44 19.1 > 3 >22
a

Ref. 10, coordination number of 8.

b

Ref. 25, ionic strength of 0.1 M.

c

Ref. 26

d

Calculated using Hyss from the stability constant values and the protonation constants of DTPA.28