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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):7966–7979. doi: 10.1021/ic2012843

Table 1.

Protonation Constants of the Ligands (25 °C)a

S-RRRR-NB-DOTMA S-SSS-1 DOTAb NB-DOTA NB-DOTAc
I = 1.0 M KCl 1.0 M KCl 1.0 M KCl 1.0 M KCl 0.1 M Me4NCl
log K1 11.81 (0.01) 11.30 (0.01) 12.09 10.00 (0.01) 10.93
log K2H 8.23 (0.03) 9.96 (0.01) 9.68 9.54 (0.01) 9.14
log K3H 4.00 (0.04) 4.60 (0.05) 4.55 4.29 (0.03) 4.50
log K4H 3.46 (0.03) 5.41 (0.01) 4.13 4.72 (0.01) 4.19
log K5H 2.13 (0.03) 1.99 (0.01) 2.28 (0.02) 2.33
log K6H 1.40
Σ log KiH 29.62 33.26 30.45 30.83 32.49
fit 9.79 × 10−3 mL 5.00 × 10−3 mL 2.59 × 10−3 mL
data points 425 307 128
a

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

b

Data taken from ref 27.

c

Data taken from ref 21.