Luminescent Cyclometallated Ir(III) Complexes: Synthesis, Characterisation and Applications

A range of luminescent Ir(III) complexes [Ir(C^N)2(X^Y)]n+ (n = 0, 1) containing different cyclometallated (C^N) and ancillary (X^Y) ligands has been synthesised. All new compounds were fully characterised by 1H and 13C NMR spectroscopy, mass spectrometry and elemental analyses and several compounds have been structurally characterised by X-ray crystallography. The photophysical and electrochemical properties of the complexes were also studied. Chapter one provides an introduction to luminescent transition metal complexes, in particular Ru(II) and Ir(III) complexes and gives an overview of the factors controlling the emission wavelengths of cyclometallated Ir(III) complexes and their applications, particularly as biological labels and probes. Chapter two discusses the synthesis and properties of [Ir(C^N)2(bipy)]+ and shows that substituents para to the metal on the cyclometallated phenyl have a significant effect on the emission wavelength. Chapter three describes complexes [Ir(C^N)2(X^Y)]n+ (n = 1, X^Y = pyridine imine; n = 0, X^Y = pyrrolylimine) and the effect of substituents on the redox properties and emission wavelength. Some of these complexes have been employed in live-cell imaging. In Chapter four the synthesis, characterisation and application of [Ir(C^N)2(phencat-OH)]+ complexes as molybdate sensors is discussed. Chapter five describes the synthesis of [Ir(C^N)2(X^Y)]n+ (n = 0, 1) containing a homochiral X^Y ligand i.e. (S)-soxH, (S)-pepH, (S)-phglyH, (+)-tfacH and (S)-ppea. The complexes are all formed as 1:1 mixtures of diastereomers with Δ or Λ chirality at the metal. Diastereomers containing the (S)-sox and (S)-pep ligands can often be separated via crystallisation or column chromatography. Treatment of a single diastereomer (ΛS or ΔS) with an appropriate acid removes the sox or pep ligand hence provides a route to complexes with only metal-centred chirality, for example Λ- and Δ-[Ir(ppz)2(bipy)]+.