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A series of eight Rhenium(I)-N-heterocyclic carbene (NHC) complexes of the general form [ReCl(CO)3(C^C)] (where C^C is a bis(NHC) bidentate ligand), [ReCl(CO)3(C^C)]2 (where C^C is a bis-bidentate tetra-NHC ligand) and [Re(CO)3(C^N^C)](+)[X](-) (where C^N^C is a bis(NHC)-amine ligand and the counter ion X is either the ReO4(-) or PF6(-)) have been synthesised using a Ag2O transmetallation protocol. The novel precursor imidazolium salts and Re(I) complexes were characterized by elemental analysis, (1)H and (13)C NMR spectroscopy and the molecular structures for two imidazolium salt and six Re(I) complexes were determined by single crystal X-ray diffraction. These NHC ligand systems are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and as such the stability of two complexes of the form [ReCl(CO)3(C^C)] and [Re(CO)3(C^N^C)][ReO4] were evaluated in ligand challenge experiments using the metal binding amino acids L-histidine or L-cysteine. These studies showed that the former was unstable, with the chloride ligand being replaced by either cysteine or histidine, while no evidence for transchelation was observed for the latter suggesting that bis(NHC)-amine ligands of this type may be suitable for biological applications.

Original publication

DOI

10.1039/c5dt03295d

Type

Journal article

Journal

Dalton transactions (Cambridge, England : 2003)

Publication Date

11/2015

Volume

44

Pages

19126 - 19140

Addresses

Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Victoria, 3086, Australia. p.barnard@latrobe.edu.au.

Keywords

Chlorides, Oxides, Rhenium, Silver Compounds, Methane, Cysteine, Heterocyclic Compounds, 2-Ring, Heterocyclic Compounds, 3-Ring, Histidine, Indicators and Reagents, Radiopharmaceuticals, Ligands, X-Ray Diffraction, Magnetic Resonance Spectroscopy, Isotope Labeling, Models, Molecular