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. Author manuscript; available in PMC: 2012 Sep 5.
Published in final edited form as: Inorg Chem. 2011 Aug 5;50(17):7955–7965. doi: 10.1021/ic2012827

Table 3.

Protonation and Thermodynamic Stability Constants of DOTMA, DOTA and NB-DOTA (I = 1.0MKCl, 25 °C). a

log KiH DOTMA DOTAb NB-DOTAc,d (TCE-DOTAc,e
Protonation Constants
log K1 12.59 (0.02) 12.60 10.93 12.22
log K2H 9.28 (0.02) 9.70 9.14 9.18
log K3H 4.66 (0.05) 4.50 4.44 4.17
log K4H 5.78 (0.02) 4.14 4.19 3.93
log K5H 1.84 (0.02) 2.32 2.33 2.88
log K6H 1.40 n.d.
Σ log KiH 33.43 33.26 32.43 32.38f
Thermodynamic Stability Constants
log KCeL 20.47 (0.09) 23.4g
log KCeLh 20.96 (0.02)
log KEuL 23.52 (0.05) 24.7g
log KGdL 23.6i 24.7g 24.2 24.03
log KYbL 23.56 (0.05) 25.0g
log KLuL 24.5
a

Values in bold highlight instances were the fourth pKa is higher than the third.

b

Data taken from ref 40.

c

I = 0.1 M NMe4Cl;

d

Data taken from ref 26.

e

Data taken from ref 15, pKa’s of peripheral carboxylates are not given herein.

f

i = 1–5 only;

g

Data taken from ref 38.

h

Determined by spectrophotometry.

i

Data taken from ref 41; n.d. = not accurately determined.