Synthesis, characterisation and optoelectronic properties of formyl group containing ligands and their phosphorescent heteroleptic iridium (III) complexes

In this thesis, three main ligands are selected for functionilisation: 2-phenylpyridine (1), 2-(9'-hexylcarbazol-3'-yl)pyridine (9) and 2-phenylquinoline (4). The pyridine rings of ligands (1) and (9) and the phenyl ring of ligand (4) were functionalized with a electron withdrawing formyl group in the 4- and 5-positions. Thus, 2-phenyl-4/5-formylpyridine (3a-b), 2-(9'-hexylcarbazol-3'-yl)4/5-formylpyridine (8a-b) and 2- (3'/4'-formylphenyl) quinoline (11a-b) were synthesized. The synthesized ligands were purified and fully characterized by 1H NMR, 13C NMR, FT-IR, Elemental Analysis, Mass Spectrometry and HRMS. These ligands 3a-b, 8a-b, and 11a-b were then converted into heteroleptic iridium (III) complexes K1a-b, K2a-b and K3a-b, respectively. Complexes were purified and fully characterized by 1H NMR, 13C NMR, FT-IR, Elemental Analysis, Mass Spectroscopy and HRMS. Photophysical and electroluminescence properties of synthesized ligands (3a-b, 8a-b and 11a-b) and complexes (K1a-b, K2a-b and K3a-b) were investigated. Ligands 3a and 3b emit blue light at λemmax: 450 and 425 nm in toluene. Ligand 8a and 8b emits yellow and blue light at λemmax: 562 and 482 nm and ligands 11a and 11b emit blue light at λemmax: 313 and 313, 350 (sh) nm in dichloromethane, respectively. Heteroleptic iridium (III) complexes K1a and K1b emit red light at λemmax: 675 and 625 nm in toluene, respectively. K2a and K2b emit at red light at λemmax: 662 and 661 nm in dichloromethane, respectively. OLED device made with K2b emits red light at λemmax: 624 nm. K3a and K3b emit yellowish green and red light at λemmax: 579 and 630 nm in dichloromethane. OLED devices made with K3a and K3b also emit yellowish green and red light at λemmax: 572 and 628 nm, respectively.