Charge neutral rhenium tricarbonyl complexes of tridentate N-heterocyclic carbene ligands that bind to amyloid plaques of Alzheimer's disease

Two tridentate ligand systems bearing N-heterocyclic carbene (NHC), amine and carboxylate donor groups coupled to benzothiazole- or stilbene-based amyloid binding moieties were synthesised. Reaction of the imidazolium salt containing pro-ligands with Re(CO)(5)Cl yielded the corresponding rhenium metal complexes which were characterised by NMR, and X-ray crystallography. These ligands are of interest for the potential preparation of technetium-99m imaging agents for Alzheimer's disease and the capacity of these rhenium complexes bind to amyloid fibrils composed of amyloid-beta peptide and amyloid plaques in human frontal cortex brain tissue was evaluated using fluorescence microscopy. These studies show that the complexes bound efficiently to amyloid-beta fibrils and some evidence of binding to amyloid-beta plaques.