Yb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F]2+ and [Yb⋅DTMA⋅OH2]3+ are in slow exchange on the relevant NMR timescale (<2000 s-1), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding. This changes the magnetic anisotropy of the YbIII ground state from easy-axis to easy-plane type, and this change is easily detected in the observed magnetic anisotropy despite thermal population of more than just the ground state. The spectroscopic consequences of such drastic changes to the ligand field represent important new opportunities in developing fluoride-responsive complexes and contrast agents.
F macht den Unterschied: [Yb⋅DTMA⋅OH2]3+ und [Yb⋅DTMA⋅F]2+ befinden sich relativ zur NMR‐Zeitskala in langsamem Austausch (kex<2000 s−1) und unterscheiden sich deutlich in ihren NMR‐ und EPR‐Spektren. Dieses Verhalten kann durch einen Wechsel der magnetischen Anisotropie des YbIII‐Grundzustandes von einer Vorzugsrichtung in eine Vorzugsebene erklärt werden (siehe Bild).WILEY-VCH.
Keywords: Anionenkoordination; Lanthanoide; Magnetische Anisotropie; NMR‐Spektroskopie; Spektroskopische Methoden.