Synthesis and photophysical properties of gold(III) and Pt(II) complexes bearing persistent radicals

Organic Light Emitting Diodes (OLEDs) represent the next generation lighting technology. Transition metal complexes that exhibit luminescent properties have been investigated as triplet emitters for applications in OLED devices. Metal complexes bearing a persistent radical offer an interesting avenue to tune the excited-state properties, which could provide alternative emitter systems that has been only scarcely investigated. Presence of coordination sites at the radical ligands allows the metal centres to be coordinated, which is expected to modulate the photophysical and photochemical properties such as luminescence quantum yield, emission wavelength maxima and the stability in the photoexcited state. The organic radicals 2-(4-ethynylphenyl)-4,4,5,5-tetramethylimidazolidine-1,3-diol (nitronyl nitroxide) and (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)-methyl (PyBTM) were chosen as ligands due to their photo- and thermal stability. The present work reports the synthesis, characterization and detailed photophysical investigations of new cyclometalated Au(III) and Pt(II) complexes bearing nitronyl nitroxide and PyBTM as ligands, respectively. The resulting final complexes were stable to air and moisture. The photophysical investigations are strongly suggestive of an interplay between the radical spin and the triplet excited state. The outcomes of the thesis are expected to lead to an efficient strategy for altering the excited state properties of luminescent materials which could be applied for achieving efficient light emitting devices.