Rapid and complete fluorination of the complexes [MCl₃(L)] (L = Me₃-tacn, BzMe₂-tacn, M = Al, Ga, In) occurs at room temperature via reaction of a MeCN solution of the complex with 3 mol equiv. of KF in water. The Ga and In complexes are also readily fluorinated using R₄NF (R = Me or ⁿBu) in MeCN solution, whereas no reaction occurs with the Al species under these conditions. The distorted octahedral fac-trifluoride coordination at M is confirmed in solution by multinuclear (¹⁹F, ²⁷Al, ⁷¹Ga and ¹¹⁵In) NMR spectroscopic studies, leading to sharp resonances with ¹⁹F–⁷¹Ga and ¹⁹F–¹¹⁵In couplings evident. The [MF₃(L)] are extremely stable in aqueous solution and at low pH; they crystallise as tetrahydrates, [MF₃(Me₃-tacn)]·4H₂O, with extended H-bonding networks formed through both F⋯H–O and O⋯H–O contacts. [InF₃(BzMe₂-tacn)]·1.2H₂O also shows intermolecular F⋯H–O hydrogen bonding contacts. The prospects for developing this coordination chemistry further to take advantage of the high metal–fluoride bond energies to enable rapid, late-stage fluorination of large macromolecules under mild conditions for PET imaging applications in nuclear medicine are discussed. This work also demonstrates that F-18 radiolabelling to form [F-18] [GaF₃(BzMe₂-tacn)] is effected readily at room temperature in aqueous MeCN over 30–60 min on addition of 2.99 mol equiv. of [¹⁹F]–KF_aq and 0.4 mL [¹⁸F]–KF_aq (100–500 MBq) to [GaCl₃(BzMe₂-tacn)] with ca. 30% incorporation.

As part of a study to investigate the factors influencing the development of new, more effective metal‐complex‐based positron emission tomography (PET) imaging agents, the distorted octahedral complex, [GaCl(L)]⋅2 H₂O has been prepared by reaction of 1‐benzyl‐1,4,7‐triazacyclononane‐4,7‐dicarboxylic acid hydrochloride (H₂L⋅HCl) with Ga(NO₃)₃⋅9 H₂O, which is a convenient source of Ga^III for reactions in water. Spectroscopic and crystallographic data for [GaCl(L)]⋅2 H₂O are described, together with the crystal structure of [GaCl(L)]⋅MeCN. Fluorination of this complex by Cl⁻/F⁻ exchange was achieved in high yield by treatment with KF in water at room temperature over 90 minutes, although the reaction was complete in approximately 30 minutes if heated to 80 °C, giving [GaF(L)]⋅2 H₂O in good yield. The same complex was obtained by hydrothermal synthesis from GaF₃⋅3 H₂O and Li₂L, and has been characterised by single‐crystal X‐ray analysis, IR, ¹H and ¹⁹F{¹H} NMR spectroscopy and ESI⁺ MS.Radiofluorination of the pre‐formed [GaCl(L)]⋅2 H₂O has been demonstrated on a 210 nanomolar scale in aqueous NaOAc at pH 4 by using carrier‐free ¹⁸F⁻, leading to 60–70 % ¹⁸F‐incorporation after heating to 80 °C for 30 minutes. The resulting radioproduct was purified easily by using a solid‐phase extraction (SPE) cartridge, leading to 98–99 % radiochemical purity. The [Ga¹⁸F(L)] is stable for at least 90 minutes in 10 % EtOH/NaOAc solution at pH 6, but defluorinates over this time scale at pH of approximately 7.5 in phosphate buffered saline (PBS) or human serum albumin (HSA). The subtle role of the Group 13 metal ion and co‐ligand donor set in influencing the pH dependence of this system is discussed in the context of developing potential new imaging agents for PET.

A series of 1 ^st row transition metal trifluoride complexes with neutral N ₃ -donor ligands is described; radiolabelling of [FeF ₃ (BnMe ₂ -tacn); in aqueous MeCN is achieved by ¹⁸ F/ ¹⁹ F isotopic exchange and its stability in PBS and serum established.

The syntheses of configurationally restricted mono- and bis-macrocyclic copper(II) perchlorate complexes (copper(II) 5-benzyl-1,5,8,12-tetraazabicyclo[10.2.2]hexadecane and dicopper(II) 5,5′-[1,4-phenylenebis(methylene)]-bis(1,5,8,12-tetraazabicyclo[10.2.2]hexadecane)) are reported and the X-ray structure of the copper(II) mono-macrocyclic complex has been determined. EXAFS studies on the bis-macrocyclic species in aqueous solution show that the copper coordination spheres are essentially identical to the solid state structure, and do not vary in the presence of 20 equivalents of sodium acetate per metal centre. DFT calculations were carried out at the BP86/TZP level to determine the nature of potential binding interactions with CXCR4 aspartate residues. The alkylated single macrocyclic compound was modelled with an acetate included to represent the aspartate residue, demonstrating that the predicted macrocycle configuration has the lowest energy and the acetate interaction is effectively monodentate giving a distorted trigonal bipyramidal geometry at the copper centre. In vitro anti-HIV infection assays show that the configurationally restricted dicopper(II) complex is more active (average EC₅₀ = 0.026 μM against HIV-1) than the non-constrained dicopper(II) 1,1′-[1,4-phenylenebis(methylene)]-bis(1,4,8,11-tetraazacyclotetradecane) (average EC₅₀ = 0.047 μM against HIV-1) although it is an order of magnitude less active than the configurationally restricted dizinc(II) complex.