17O NMR study of LnIIIcomplexes of H4do3apOEt ligand

Macrocyclic complexes of H4dota-like ligands are used in various fields, mainly in medicine. e. g. as MRI contrast agents or luminescent probes. Their applications are greatly influenced by stereochemistry. Stereoisomers of these complexes mostly interconvert with each other in solution. This interconversion can be studied by NMR spectroscopy This work is intended to test 17 O NMR spectroscopy as a tool for monitoring dynamic processes where phosphonate group in the complexes of methylphosphonate derivatives of H4dota is involved. To this end, ligand H4do3apOEt and his LnIII -complexes (Ln ≠ Pm) containing 17 O-labeled phosphonate group were synthesized. Next, 17 O NMR spectra of these complexes were measured and analysed. In an analogy with H4dota complexes, signals of both non-coordinated and coordinated oxygen atoms (except GdIII ) in the complexes could be detected. Fraction of TSA (twisted square-antiprism) and SA (square-antiprism) isomers was determined from the acquired 17 O NMR spectrum for each complex. The determined values were compared with those obtained by analysing 1 H and 31 P NMR spectra of the complexes, which were also measured. The TbIII , DyIII and YbIII complexes (because of high resolution of their 17 O NMR spectra) and CeIII complex (because of anomalous properties of its..