Triamidetriamine bearing macrobicyclic and macrotricyclic ligands: Potential applications in the development of copper-64 radiopharmaceuticals

K. Tan, P.A. Pellegrini, Brian Skelton, C.F. Hogan, I.D. Greguric, P.J. Barnard

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13 Citations (Scopus)

Abstract

A versatile and straightforward synthetic approach is described for the preparation of triamide bearing analogues of sarcophagine hexaazamacrobicyclic cage ligands without the need for a templating metal ion. Reaction of 1,1,1-tris(aminoethyl)ethane (tame) with 3 equiv of 2-chloroacetyl chloride, yields the tris(α-chloroamide) synthetic intermediate 6, which when treated with either 1,1,1-tris(aminoethyl)ethane or 1,4,7-triazacyclononane furnished two novel triamidetriamine cryptand ligands (7 and 8 respectively). The Co(III) and Cu(II) complexes of cryptand 7 were prepared; however, cryptand 8 could not be metalated. The cryptands and the Co(III) complex 9 have been characterized by elemental analysis, 1H and 13C NMR spectroscopy, and X-ray crystallography. These studies confirm that the Co(III) complex 9 adopts an octahedral geometry with three facial deprotonated amido-donors and three facial amine donor groups. The Cu(II) complex 10 was characterized by elemental analysis, single crystal X-ray crystallography, cyclic voltammetry, and UV-visible absorption spectroscopy. In contrast to the Co(III) complex (9), the Cu(II) center adopts a square planar coordination geometry, with two amine and two deprotonated amido donor groups. Compound 10 exhibited a quasi-reversible, one-electron oxidation, which is assigned to the Cu2+/3+ redox couple. These cryptands represent interesting ligands for radiopharmaceutical applications, and 7 has been labeled with 64Cu to give 64Cu-10. This complex showed good stability when subjected to L-cysteine challenge whereas low levels of decomplexation were evident in the presence of L-histidine. © 2013 American Chemical Society.
Original languageEnglish
Pages (from-to)468-477
Number of pages10
JournalInorganic Chemistry
Volume53
Issue number1
Early online date16 Dec 2013
DOIs
Publication statusPublished - Jan 2014

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