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Sc(III) Complexes of 1,4,7-Triazacyclononane-1,4,7-triacetic Acid and Its Monoamides

Year: 2025

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Scandium(III) complexes with H 3 nota and its N -ethyl (H 2 L 1 ) and N,N -diethyl (H 2 L 2 ) monoamides were studied in the solid state and solution. Potentiometric measurements showed high stabilities of the binary Sc III complexes with the ligands (log K [Sc(L)] = 19.50, 16.64, and 17.94 for H 3 nota, H 2 L 1 and H 2 L, 2 respectively) and weak coordination of the second ligand molecule under the ligand excess. The chemical model was confirmed by 45 Sc NMR. Multinuclear NMR spectroscopy was used to study the ternary Sc III -ligand-oxalate systems. The results showed the presence of species with 2:1 and 1:1 [Sc(L)]-to-oxalate stoichiometry. Ternary complexes with the nota-monoamides form two isomers differing in the position of oxalate versus amide pendant arm. In the solid state, the [Sc(L)] complexes form oligomers interconnected through ligand carboxylate groups. Crystallization from solutions containing H 2 O 2 or oxalate anions yielded ternary complexes. In all binary and ternary complexes, the Sc III ion is octacoordinated with the N 3 O 4 O 1 coordination mode. All of the carboxylate groups of the ligands are coordinated in the O 4 -plane. The apical position is occupied by an oxygen atom of water, peroxide, or carboxylate anion. The apical Sc–O bonds are usually longer compared to those of the oxygen atoms forming the O 4 -plane.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.5c04142