We report the discovery of a tandem catalytic process to reduce energy demanding substrates, using the [Ir(ppy) 2 (dtb-bpy)] + (1 + ) photocatalyst. The immediate products of photoinitiated electron transfer (PET) between 1 + and triethylamine (TEA) undergo subsequent reactions to generate a previously unknown, highly reducing species (2). Formation of 2 occurs via reduction and semisaturation of the ancillary dtb-bpy ligand, where the TEA radical cation serves as an effective hydrogen atom donor, confirmed by nuclear magnetic resonance, mass spectrometry, and deuterium labeling experiments. Steady-state and time-resolved luminescence and absorption studies reveal that upon irradiation, 2 undergoes electron transfer or proton-coupled electron transfer (PCET) with a representative acceptor (N-(diphenylmethylene)-1-phenylmethanamine; S). Turnover of this new photocatalytic cycle occurs along with the reformation of 1 + . We rationalize our observations by proposing the first example of a mechanistic pathway where two distinct yet interconnected photoredox cycles provide access to an extended reduction potential window capable of engaging a wide range of energy demanding and synthetically relevant organic substrates including aryl halides.

Alzheimer's disease is the most common form of age-related neurodegenerative dementia. The disease is characterised by the presence of plaques in the cerebral cortex. The major constituent of these plaques is aggregated amyloid-β peptide. This review focuses on the molecular aspects of metal complexes designed to bind to amyloid-β. The development of radioactive metal-based complexes of copper and technetium designed as diagnostic imaging agents to detect amyloid burden in the brain is discussed. Separate sections of the review discuss the use of luminescent metal complexes to act as non-conventional probes of amyloid formation and recent research into the use of metal complexes as inhibitors of amyloid formation and toxicity.

One of the pathological hallmarks of Alzheimer's disease is the presence of amyloid-β plaques in the brain and the major constituent of these plaques is aggregated amyloid-β peptide. New thiosemicarbazone-pyridylhydrazine based ligands that incorporate functional groups designed to bind amyloid-β plaques have been synthesized. The new ligands form stable four coordinate complexes with a positron-emitting radioactive isotope of copper, (64)Cu. Two of the new Cu(II) complexes include a functionalized styrylpyridine group and these complexes bind to amyloid-β plaques in samples of post-mortem human brain tissue. Strategies to increase brain uptake by functional group manipulation have led to a (64)Cu complex that effectively crosses the blood-brain barrier in wild-type mice. The new complexes described in this manuscript provide insight into strategies to deliver metal complexes to amyloid-β plaques.

A new strategy to create iridium(iii)-based ECL labels reveals limitations of conventional approaches.