Synthesis and Luminescence Studies of Ir(III) Complexes and Iridium/Lanthanide Dyads

This thesis is concerned with the preparation and photophysical studies of various Ir(III) complexes and Ir(III)/Ln(III) dyads. Chapter 1 provides an introduction to the background of d-metal and f-metal luminescence and their use in biological applications. The emphasis is on the use of Ir(III) chromophores based on phenylpyridine ligands to stimulate emission from Ln(III) ions via an energy-transfer mechanism (the ‘antenna effect’). Examples of these Ir(III)/Ln(III) dyads from literature are given. Chapter 2 describes the preparation of the complexes [Ir(fppy)2Lpytz] and [Ir(fppy)2Lpic] and looks at their photophysical properties when titrated with [Ln(hfac)3] (Ln = Eu, Tb and Gd). The studies showed that the complexes were able to sensitise luminescence from Eu(III) and partially from Tb(III) through a combination of PEnT and PET mechanisms. Chapter 3 describes the preparation of [Ir(fppy)2Lpytz] and [Ir(fppy)2Ltol].(PF6) and the change of their luminescence properties during pH titrations. The two water soluble complexes [Ir(ppy-PEG)2Lpytz] and [Ir(ppy-PEG)2Ltol], based on the architecture of the first two complexes, were prepared. Their photophysical properties during pH titrations are reported. Preliminary cell imaging data for the latter two complexes showed they can undergo two-photon excitation at 780 nm and staining within the cytoplasm of MCF7 cells. Chapter 4 describes the preparation of [Ir(fppy)2Lnappic] and [Ir(fppy)2L2]; where in both cases a naphthalene unit is used as a bridging ligand. Their photophysical properties after the addition on Ln(III) (Ln = Eu, Tb and Gd) are reported and showed naphthalene acts as a ‘stepping stone’ resulting in a two-step energy-transfer process from Ir(III) → 3nap → Ln(III) resulting in quenching of Ir(III)-based luminescence. The preparation of [Ir(fppy)2L3] which contains a phenyl spacer unit is reported. Addition of Eu(III) showed good balance between Ir(III) and sensitised Eu(III) emission. Chapter 5 gives the experimental procedures and characterisation data for all the ligands and complexes reported in this thesis.