posted on 2023-11-21, 20:20authored byJuan C. Babón, Pierre-Luc T. Boudreault, Miguel A. Esteruelas, Miguel A. Gaona, Susana Izquierdo, Montserrat Oliván, Enrique Oñate, Jui-Yi Tsai, Andrea Vélez
Two
complementary procedures are presented to prepare cis-pyridyl-iridium(III) emitters of the class [3b+3b+3b′] with two orthometalated ligands
of the 2-phenylpyridine type (3b) and a third ligand
(3b′). They allowed to obtain four emitters of
this class and to compare their properties with those of the trans-pyridyl isomers. The finding starts from IrH5(PiPr3)2, which reacts with 2-(p-tolyl)pyridine to give fac-[Ir{κ2-C,N-[C6MeH3-py]}3] with an almost quantitative yield. Stirring the latter in
the appropriate amount of a saturated solution of HCl in toluene results
in the cis-pyridyl adduct IrCl{κ2-C,N-[C6MeH3-py]}2{κ1-Cl-[Cl–H-py-C6MeH4]} stabilized with p-tolylpyridinium
chloride, which can also be transformed into dimer cis-[Ir(μ-OH){κ2-C,N-[C6MeH3-py]}2]2. Adduct IrCl{κ2-C,N-[C6MeH3-py]}2{κ1-Cl-[Cl–H-py-C6MeH4]} directly generates cis-[Ir{κ2-C,N-[C6MeH3-py]}2{κ2-C,N-[C6H4–Isoqui]}] and cis-[Ir{κ2-C,N-[C6MeH3-py]}2{κ2-C,N-[C6H4-py]}] by transmetalation from Li[2-(isoquinolin-1-yl)-C6H4] and Li[py-2-C6H4]. Dimer cis-[Ir(μ-OH){κ2-C,N-[C6MeH3-py]}2]2 is also
a useful starting complex when the precursor molecule of 3b′ has a fairly acidic hydrogen atom, suitable for removal by hydroxide
groups. Thus, its reactions with 2-picolinic acid and acetylacetone
(Hacac) lead to cis-Ir{κ2-C,N-[C6MeH3-py]}2{κ2-O,N-[OC(O)-py]} and cis-Ir{κ2-C,N-[C6MeH3-py]}2{κ2-O,O-[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.