Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo-and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers.

Luminescent organoboron complexes featuring substituted 8-quinolinolates as chelating ligands have been synthesized and characterized. Substitution of the quinolinolate has been achieved in the 5 and the 7 positions introducing phenyl, biphenyl, and 9,9′-dihexylfluorenyl substituents by reacting 8-benzyloxy-5,7-dibromoquinoline with the corresponding boronic acid derivatives in a Suzuki-type cross-coupling reaction. Upon deprotection, the 8-quinolinol derivatives have been transformed into the target compounds upon reaction with BPh 3 . (κ 2 -(N,O)-5,7-dibromo-8-quinolinolate)diphenylborane ( 9), (κ 2 -(N,O)-5,7diphenyl-8-quinolinolate)diphenylborane ( 10), (κ 2 -(N,O)-5,7-bis(biphenyl-4-yl)-8-quinolinolate)diphenylborane (11), and (κ 2 -(N,O)-5,7-bis(9,9-dihexylfluoren-2-yl)-8-quinolinolate)diphenylborane ( 12) have been investigated by nuclear magnetic resonance and infrared spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, thermal analysis, cyclic voltammetry, UV-vis absorption spectroscopy, and luminescence measurements in solution and in the solid state to retrieve a concise knowledge of the introduced compounds. Special emphasis has been placed on studying the consequences of extension of the conjugated π system of the quinolinolate ligand on materials properties. Small molecule organic light emitting devices (SMOLED) based on compounds 10, 11, and 12 give bright yellow to orange electroluminescence with low onset voltages (3.5-3.7 V) and continuous wave luminance intensities exceeding 1000 cd/m 2 , while devices based on 9 give poor results, proving 9 to be an unsuitable emissive material.

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A novel heteroleptic iridium(III) complex containing 5,7dibromoquinolinolate as co-ligand has been used to prepare main-chain iridium(III) polymers which produced white light emission when used as the active layer in polymeric lightemitting devices.