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Triaza-macrocyclic complexes of aluminium, gallium and indium halides: fast 18F and 19F incorporation via halide exchange under mild conditions in aqueous solution

Triaza-macrocyclic complexes of aluminium, gallium and indium halides: fast 18F and 19F incorporation via halide exchange under mild conditions in aqueous solution
Triaza-macrocyclic complexes of aluminium, gallium and indium halides: fast 18F and 19F incorporation via halide exchange under mild conditions in aqueous solution
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. equivs. 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 mins on addition of 2.99 mol equivs. of [19F]-KFaq and 0.4 mL [18F]-KFaq (100 – 400 MBq) to [GaCl3(BzMe2-tacn)] with ca. 30% incorporation.
1478-6524
381-391
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Zhang, Wenjian
1f80ac5e-d4c2-4720-b19e-be700cd411e7
Sanderson, George
28c458aa-326b-4029-b8cc-cc3035d4acd2
Bhalla, Rajiv
685dca44-2474-4fca-a7ea-0075d641e7f2
Luthra, Sajinder
bcadc83e-6bc6-4a2c-9fc1-ae01a3a1de6c
McRobbie, Graeme
b12f273f-dd78-4ff8-a423-b0b5158091c7
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Zhang, Wenjian
1f80ac5e-d4c2-4720-b19e-be700cd411e7
Sanderson, George
28c458aa-326b-4029-b8cc-cc3035d4acd2
Bhalla, Rajiv
685dca44-2474-4fca-a7ea-0075d641e7f2
Luthra, Sajinder
bcadc83e-6bc6-4a2c-9fc1-ae01a3a1de6c
McRobbie, Graeme
b12f273f-dd78-4ff8-a423-b0b5158091c7

Reid, Gillian, Levason, William, Zhang, Wenjian, Sanderson, George, Bhalla, Rajiv, Luthra, Sajinder and McRobbie, Graeme (2014) Triaza-macrocyclic complexes of aluminium, gallium and indium halides: fast 18F and 19F incorporation via halide exchange under mild conditions in aqueous solution. Chemical Science, 5 (1), 381-391. (doi:10.1039/C3SC52104D).

Record type: Article

Abstract

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. equivs. 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 mins on addition of 2.99 mol equivs. of [19F]-KFaq and 0.4 mL [18F]-KFaq (100 – 400 MBq) to [GaCl3(BzMe2-tacn)] with ca. 30% incorporation.

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e-pub ahead of print date: 25 October 2013
Published date: 1 January 2014
Organisations: Organic Chemistry: Synthesis, Catalysis and Flow

Identifiers

Local EPrints ID: 359275
URI: http://eprints.soton.ac.uk/id/eprint/359275
ISSN: 1478-6524
PURE UUID: 7e3ae898-2cc6-40ef-a33a-2c1bd4b1df43
ORCID for Gillian Reid: ORCID iD orcid.org/0000-0001-5349-3468
ORCID for William Levason: ORCID iD orcid.org/0000-0003-3540-0971

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Date deposited: 24 Oct 2013 15:23
Last modified: 15 Mar 2024 02:45

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Contributors

Author: Gillian Reid ORCID iD
Author: William Levason ORCID iD
Author: Wenjian Zhang
Author: George Sanderson
Author: Rajiv Bhalla
Author: Sajinder Luthra
Author: Graeme McRobbie

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