Premium
Equilibrium, Kinetic and Structural Studies of AAZTA Complexes with Ga 3+ , In 3+ and Cu 2+
Author(s) -
Baranyai Zsolt,
Uggeri Fulvio,
Maiocchi Alessandro,
Giovenzana Giovanni B.,
Cavallotti Camilla,
Takács Anett,
Tóth Imre,
Bányai István,
Bényei Attila,
Brucher Ernő,
Aime Silvio
Publication year - 2013
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201201108
Subject(s) - chemistry , carboxylate , moiety , dissociation (chemistry) , crystallography , ligand (biochemistry) , octahedron , stereochemistry , metal , crystal structure , biochemistry , receptor , organic chemistry
Abstract A detailed study of the structures, thermodynamic stabilities and kinetics of the dissociation of Ga 3+ , In 3+ and Cu 2+ complexes formed with the heptadentate ligand AAZTA is reported. The stability constants (log K ML ) of the AAZTA complexes of Ga 3+ , In 3+ and Cu 2+ 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(H 2 AAZTA)] · H 2 O shows a distorted octahedral coordination. The equatorial coordination sites of Cu 2+ 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 Cu 2+ in the axial positions. In the pH range 4.5–8.5, Ga 3+ is present in the form of the highly stable [Ga(AAZTA)OH] 2– (log β GaLH–1 = 17.69) The exchange reactions of [Ga(AAZTA)OH] 2– with Cu 2+ 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 t 1/2 = 23 h at pH = 7.5 and 25 °C in 0.025 M NaHCO 3 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.