Abstract
This thesis describes the synthesis and photophysical studies of octahedral coordination complexes of Ir(III), and Ir(III)/Ln(III) dyads.
Chapter One: provides an introduction to the principles of luminescence, and a brief background to the photophysical properties of Ir(III) complexes, as well as Ir(III)/Ln(III) energy transfer processes.
Chapter Two: describes the synthesis and characterization series of a novel mononuclear-Ir(III) complexes with different substitution patterns on the cyclometalated ligands, and a pendant pyrene group: namely F/FIr•Lpyrene•NO3, F/HIr•Lpyrene•NO3 and H/HIr•Lpyrene•NO3 complexes. The X-ray crystal structure of F/FIr•Lpyrene•NO3 complex is briefly described. The dual emission of these complexes, and further photophysical properties have been studied.
Chapter Three: describes the synthesis, characterisation and X-ray structures of a series of mono-Ir(III) complexes based on the presence or absence of F atom substituents on the cyclometated phenylpyridine ligands, and different types of the ancillary ligand. The chapter also presents a systematic study of their excited states. Furthermore, the tunability of photophysical properties of Ir(III) complexes was observed because of position and number of electron-withdrawing groups in the cyclometalated ligands, and changes in the ancillary ligand.
Chapter Four: describes the synthesis, characterization and photophysical properties of novel Ir(III) complexes with an +N-CH3 substituent in the cyclometalated ligands, namely 22IrCl2•PF6, 23IrCl2•PF6, 24IrCl2•PF6, 23Ir•pypz•3PF6, 24Ir•pypz•3PF6, 22Ir•Lbi-ph•3PF6, 23Ir•Lbi-ph •3PF6 and 24Ir•Lbi-ph•3PF6. A strong luminescence was observed from all Ir(III) complexes. Moreover, sensitisation of emission from Ln, when Ln = Eu(III) and Tb(III), via an intermolecular energy transfer mechanism has been observed.
Chapter Five: describes the synthesis, characterization and X–ray crystal structures of a new bridging ligand which was used to prepare new mononuclear Ir(III) and dinuclear Ir(III)/Ir(III) and Ir(III)/Re(I) complexes. Luminescence measurements for all complexes have been performed. The effect of the role of the naphthyl group in the bridging ligand as a “stepping stone” in the energy transfer quenching of Ir(III) emission and on the energy transfer in the Ir(III)/Re(I) dyads has been established.
Chapter Six: describes an Ir(III)/ Eu(III) dyad as the basis of a ratiometric sensor for anions. Photoinduced energy-transfer occurs in Ir(III)/Eu(III) dyad resulting in partial quenching of the Ir(III) – based emission with concomitant sensitisation of the Eu(III)-based emission. This sensitised emission is quenched by a range of anions, which act as competing ligands for the Eu(III) centre and separate it from the dyad; therefore, excitation of Ir(III) only results in blue Ir(III)-based luminescence. Thus, the anions act as selective quenchers of the Eu(III) based luminescence in the Ir(III)/Eu(III) dyads, leading to the change in overall luminescence colour from red [from Eu(III)] to blue [from Ir(III)]. The hydrogen sulfate anion displays less efficient quenching of the Eu-based luminescence component in comparison with the acetate, dihydrogen phosphate and benzoate anions which show stronger quenching of the Eu(III)-based luminescence.
Chapter Seven: describes the synthetic procedures and characterisation data for the ligands and complexes that were reported in this thesis.
