Synthesis and Photophysics of Cyclometalated Ir(III) Complexes with Novel 4-Substituted-2-Phenyl-Pyridine Ligands

This thesis reports the design, synthesis and photophysical characterisation of a series of novel cyclometalated iridium complexes with 4-substituted-2-phenyl-pyridine ligands. A synthetic strategy based on preparation of 4-substituted pyridine and subsequent phenylation was applied, and related challenges, for instance, the preparation of 4-(4’(-iodo-2’,3’,5’,6’-tetramethylphenyl)pyridine from 1,4-diiododurene, low yields of the Sonogashira reactions due to the steric hindrance and low yields of phenylation reactions with phenyl lithium have been overcome. Photophysical studies show that the π-conjugation of iridium complexes broken by rotating the 4-substituents out of plane, and this kind of complexes exhibit similar emission spectra to the unsubstituted parent compound Ir(ppy)2(acac). C4 shows an extremely long luminescence lifetime for a complex of this type, and the nature of this characteristic may be due to the triplet energy being distributed between the ligand and the metal centre.