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We have developed a new process at high vacuum (5 x 10(-5) Torr) and high temperature (300 degrees C) to produce meridional iridium complexes from the dimer; interestingly, mer-Ir(m-ppy)(3) overthrows the concept of poor efficiency and shows excellent efficiency which is almost equal to that of fac-Ir(ppy)(3), fac-Ir(m-ppy)(3) and (ppy)(2)Ir(acac).

To examine the effects of coordination sites and the nature of ligands reported for color-tuning of a few cyclometalated Ir(III) complexes, a series of 3′-substituted (F, CH 3 , OCH 3 , and CF 3 ) phenylisoquinoline (piq) ligands were synthesized and successfully used to prepare iridium complexes, including bis[1-(5′-methyl)phenylisoquinolinato-N,, and bis[1-(5′-fluoro)phenylisoquinolinato-N,C 2′ ]iridium(III) (acetylacetonate) (6a4). Density functional theory results indicate that two conflicting effects, electronic and steric, can be applied to account for the substitution-sensitive coordination sites of piq: the methoxyl-or fluoro-substituted ligand generates both 2′-coordinated and 6′-coordinated isomers. Coordination of methoxy substitution prefers 6′-coordination of piq dominated by steric effects, while coordination of fluoro substitution prefers 2′-coordination, arising from better back-donation of the iridium center. Correlations of HOMO-LUMO gaps with electroluminescence (EL) data are discussed. More importantly, the EL data are well predicted by time-dependent density functional theory calculations.

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