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Thermodynamic and Kinetic Stabilities of Al(III) Complexes with N2O3 Pentadentate Ligands

Authors :
Edoardo Callegari
Jonathan Martinelli
Nicol Guidolin
Mariangela Boccalon
Zsolt Baranyai
Lorenzo Tei
Source :
Molecules, Vol 28, Iss 9, p 3764 (2023)
Publication Year :
2023
Publisher :
MDPI AG, 2023.

Abstract

Al(III) complexes have been recently investigated for their potential use in imaging with positron emission tomography (PET) by formation of ternary complexes with the radioisotope fluorine-18 (18F). Although the derivatives of 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) are the most applied chelators for [Al18F]2+ labelling and (pre)clinical PET imaging, non-macrocyclic, semi-rigid pentadentate chelators having two N- and three O-donor atoms such as RESCA1 and AMPDA-HB have been proposed with the aim to allow room temperature labelling of temperature-sensitive biomolecules. The paucity of stability data on Al(III) complexes used for PET imaging instigated a complete thermodynamic and kinetic solution study on Al(III) complexes with aminomethylpiperidine (AMP) derivatives AMPTA and AMPDA-HB and the comparison with a RESCA1-like chelator CD3A-Bn (trans-1,2-diaminocyclohexane-N-benzyl-N,N′,N′-triacetic acid). The stability constant of [Al(AMPDA-HB)] is about four orders of magnitude higher than that of [Al(AMPTA)] and [Al(CD3A-Bn)], highlighting the greater affinity of phenolates with respect to acetate O-donors. On the other hand, the kinetic inertness of the complexes, determined by following the Cu2+-mediated transmetallation reactions in the 7.5–10.5 pH range, resulted in a spontaneous and hydroxide-assisted dissociation slightly faster for [Al(AMPTA)] than for the other two complexes (t1/2 = 4.5 h for [Al(AMPTA)], 12.4 h for [Al(AMPDA-HB)], and 24.1 h for [Al(CD3A-Bn)] at pH 7.4 and 25 °C). Finally, the [AlF]2+ ternary complexes were prepared and their stability in reconstituted human serum was determined by 19F NMR experiments.

Details

Language :
English
ISSN :
14203049
Volume :
28
Issue :
9
Database :
Directory of Open Access Journals
Journal :
Molecules
Publication Type :
Academic Journal
Accession number :
edsdoj.4a37ec81834d4188960775e0e4b7a7d4
Document Type :
article
Full Text :
https://doi.org/10.3390/molecules28093764