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Chemistry

Research project: Reid: Metal Fluoride Coordination Chemistry

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Until relatively recently metal fluoride coordination complexes, in contrast to the heavier halide counterparts, were rather neglected and little was known about their properties. However, it has become clear that the study of coordination complexes of inorganic fluorides is important and often the properties conferred on the acceptor centre by fluorine co-ligands are very significantly different – this is mainly a reflection of the strong M-F bonding imposing a different chemistry upon the metal centre.

a) High Oxidation State Metal Fluoride Chemistry

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Work in the group has investigated this area of coordination chemistry quite extensively (Chemical Society Reviews, 2013, 42, 1460; doi:10.1021/ic902068z; Coordination Chemistry Reviews, 2019, 391, 90; doi.org/10.1016/j.ccr.2019.04.005), focussing both on high oxidation state early transition metal complexes, such as MF4 (M = Ti, Zr, Hf), M’F5 (M’ = V, Nb, Ta) and WF6 (Chem. Commun., 2018, 54, 11681; 10.1039/C8CC05598J) incorporating neutral soft donor phosphines or chalcogenoether ligands (Dalton Trans. 2014, 43, 9557; doi:10.1039/c4dt01029a; Dalton Trans. 2012, 41, 12548; doi:10.1039/c2dt31501g; Dalton Trans. 2010, 39, 10264; doi:10.1039/c0dt00747a; J. Fluorine Chem. 2012, 137, 77; doi:10.1016/j.jfluchem.2012.02.014; Dalton Trans. 2010, 39, 883; doi:10.1039/b916336k), as well as main group fluoride complexes, such as the remarkably stable [SiF3(Me3-tacn)]+ cation (Chem. Commun. 2009, 1334; doi:10.1039/b822236c) and phosphine complexes of Ge(IV) (Dalton Trans. 2008, 2261; doi:10.1039/b716765b).

b) Fluoride Coordination Complexes as Scaffolds for Next Generation Medical Imaging Agents

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The radioisotope 18F is widely used in medical imaging agents for positron emission tomography (PET) since it is easily produced via a cyclotron, has a short half-life (t1/2 = 109 min) and no radioproducts (18O is the decay product). Originally, the 18F was incorporated into organofluorine species, but more recent work has developed a range of non-C-F containing carrier molecules, including species with both metal and non-metal to fluorine bonds. Recent work in our group and in collaboration with GE Healthcare has developed complexes of both AlF3 and GaF3 based upon neutral and anionic macrocyclic N-donor ligands as carrier molecules (Chemical Science, 2014, 5, 381; doi:10.1039/C3SC52104D; Dalton Trans., 2015, 44, 9569; doi:10.1039/C5DT01120E).


 

 

 

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Whilst it is clear that the strength of the metal-fluorine bond provides an important driving force for rapid, late-stage introduction of 18F, the stability of the radiolabelled complexes in competitive media (PBS or HSA) is also subtly dependent upon the co-ligands present in the metal coordination sphere (Chemistry – a European Journal, 2015, 21, 4688; doi:10.1002/chem.201405812).

Our recent work has shown that [GaF3(BnMe2-tacn)] can be radiofluorinated under very mild conditions in water at sub-30 nM concentration via 18F/19F isotopic exchange (Angew. Chem. Int. Ed. 2018, 57, 6658; 10.1002/anie.201802446).

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Our current work with GE Healthcare and through the EPSRC-funded Mithras Programme in collaboration with a team at King’s College London and Imperial College, is developing this chemistry towards bioconjugated F-18 PET imaging agents that will target specific receptors in the body. 

Related research groups

Functional Inorganic, Materials and Supramolecular Chemistry
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