Two Synthetic Tools to Deepen the Understanding of the Influence of Stereochemistry on the Properties of Iridium(III) Heteroleptic Emitters.

Two complementary procedures are presented to prepare -pyridyl-iridium(III) emitters of the class [++] with two orthometalated ligands of the 2-phenylpyridine type () and a third ligand (). They allowed to obtain four emitters of this class and to compare their properties with those of the -pyridyl isomers. The finding starts from IrH(PPr), which reacts with 2-(-tolyl)pyridine to give -[Ir{κ--[CMeH-py]}] with an almost quantitative yield. Stirring the latter in the appropriate amount of a saturated solution of HCl in toluene results in the -pyridyl adduct IrCl{κ--[CMeH-py]}{κ--[Cl-H-py-CMeH]} stabilized with -tolylpyridinium chloride, which can also be transformed into dimer -[Ir(μ-OH){κ--[CMeH-py]}]. Adduct IrCl{κ--[CMeH-py]}{κ--[Cl-H-py-CMeH]} directly generates -[Ir{κ--[CMeH-py]}{κ--[CH-Isoqui]}] and -[Ir{κ--[CMeH-py]}{κ--[CH-py]}] by transmetalation from Li[2-(isoquinolin-1-yl)-CH] and Li[py-2-CH]. Dimer -[Ir(μ-OH){κ--[CMeH-py]}] is also a useful starting complex when the precursor molecule of has a fairly acidic hydrogen atom, suitable for removal by hydroxide groups. Thus, its reactions with 2-picolinic acid and acetylacetone (Hacac) lead to -Ir{κ--[CMeH-py]}{κ--[OC(O)-py]} and -Ir{κ--[CMeH-py]}{κ--[acac]}. The stereochemistry of the emitter does not significantly influence the emission wavelengths. On the contrary, its efficiency is highly dependent on and associated with the stability of the isomer. The more stable isomer shows a higher quantum yield and color purity.