Synthesis and properties of metal trifluoride complexes with amide-functionalised tacn macrocycles and radiofluorination of [GaF₃(L1)] by ¹⁸F/¹⁹F isotopic exchange

Abstract

Three amide-functionalised tacn macrocyclic derivatives (tacn = 1,4,7-triazacyclononane) are reported, two tris-amide derivatives, L1 containing three -CH₂C(O)NHPh pendant arms, L2 containing three -CH₂CH₂C(O)NHⁱPr pendant arms, and one mono-amide, L3, containing ⁱPr groups on two of the tacn amine functions and a single -CH₂C(O)NHPh function on the third. The reactions of these new ligands towards [MF₃(dmso)(OH₂)₂] (M = Al, Ga) and towards FeF₃·3H₂O in alcoholic solution afford the complexes [MF₃(L)] (L = L1-L3) in good yields as powdered solids. These complexes are characterised by IR and multinuclear NMR spectroscopy (diamagnetic species only) and mass spectrometry. [GaF₃(L1)], [GaF₃(L3)] and [FeF₃(L3)] are also characterised by single crystal X-ray analysis. The corresponding reactions involving [InF₃(dmso)(OH₂)₂] yield mixtures of products (along with F⁻), consistent with the M-F bond strengths decreasing as group 13 is descended. A few crystals of the target complex, [InF₃(L2)], were also obtained from one such reaction. All of the complexes adopt fac-octahedral coordination via the amine N-donor atoms and retain the three fluoride ligands both in solution and in the solid state. Extensive intramolecular hydrogen-bonding involving the amide NH pendant groups and the MF₃ moieties is evident in the crystal structures. In the isostructural [MF₃(L3)] (M = Ga, Fe) complexes the head-to-tail C(O)NH⋯F H-bonded dimers observed in the solid state resemble those found frequently in organic compounds and that form the cornerstone of many supramolecular assemblies. This is consistent with the MF₃ fragments being strong H-bond acceptors. Radiofluorination of [GaF₃(L1)] by ¹⁸F/¹⁹F isotopic exchange in MeOH at 3 μmol mL⁻¹ precursor concentration and using aqueous [¹⁸F]F⁻ in target water (75% : 25%) with gentle heating (80 °C, 10 min) gave ca. 20% radiochemical yield of [Ga¹⁸FF₂(L1)]. In contrast, no ¹⁸F incorporation occurs with [GaF₃(L3)] under any of the conditions explored.

More information

Identifiers

Catalogue record

Export record

ASCII CitationAtomBibTeXData Cite XMLDublin CoreDublin CoreEP3 XMLEndNoteHTML CitationHTML CitationHTML ListJSONMETSMODSMPEG-21 DIDLOpenURL ContextObjectOpenURL ContextObject in SpanRDF+N-TriplesRDF+N3RDF+XMLRIOXX2 XMLReferReference ManagerSimple Metadata

Altmetrics