AAZTA = 6-[bis(hydroxycarbonylmethyl)amino]-1,4-bis(hydroxycarbonylmethyl)-6-methylperhydro-1,4-diazepine.
Equilibrium, Kinetic and Structural Studies of AAZTA Complexes with Ga3+, In3+ and Cu2+†
Article first published online: 21 NOV 2012
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
European Journal of Inorganic Chemistry
Volume 2013, Issue 1, pages 147–162, January 2013
How to Cite
Baranyai, Z., Uggeri, F., Maiocchi, A., Giovenzana, G. B., Cavallotti, C., Takács, A., Tóth, I., Bányai, I., Bényei, A., Brucher, E. and Aime, S. (2013), Equilibrium, Kinetic and Structural Studies of AAZTA Complexes with Ga3+, In3+ and Cu2+ . Eur. J. Inorg. Chem., 2013: 147–162. doi: 10.1002/ejic.201201108
- Issue published online: 2 JAN 2013
- Article first published online: 21 NOV 2012
- Manuscript Received: 19 SEP 2012
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A detailed study of the structures, thermodynamic stabilities and kinetics of the dissociation of Ga3+, In3+ and Cu2+ complexes formed with the heptadentate ligand AAZTA is reported. The stability constants (log KML) of the AAZTA complexes of Ga3+, In3+ and Cu2+ are 22.18, 29.58 and 22.27, respectively, which suggests that the seven-membered-ring skeleton is suited to the accommodation of these metal ions. The solid-state structure of [Cu(H2AAZTA)]·H2O shows a distorted octahedral coordination. The equatorial coordination sites of Cu2+ are occupied by one of the ring N atoms, a water O atom, one of the carboxylate O atoms and the N atom of the iminodiacetate moiety. The other ring N atom and the carboxylate O atom of the iminodiacetate moiety coordinate to the Cu2+ in the axial positions. In the pH range 4.5–8.5, Ga3+ is present in the form of the highly stable [Ga(AAZTA)OH]2– (log βGaLH–1 = 17.69) The exchange reactions of [Ga(AAZTA)OH]2– with Cu2+ and transferrin are very slow and mainly occur through the spontaneous dissociation of the complex close to physiological conditions. The half-life for the dissociation of [Ga(AAZTA)OH]2– is t1/2 = 23 h at pH = 7.5 and 25 °C in 0.025 M NaHCO3 and 0.15 M NaCl. The high conditional stability, fast formation and sufficiently slow dissociation of [Ga(AAZTA)OH]2– represent promising properties for the complexation and diagnostic applications of radioactive Ga isotopes.