Abstract
The crystal structures of tris-[9,9-dihexyl-2-(5-meth-oxy-pyridin-2-yl-κN)-9H-fluoren-3-yl-κC 3]iridium pentane monosolvate, [Ir(C31H38NO)3]·C5H12, (I), di-μ2-chlorido-bis-{bis-[2-(5-fluoro-pyridin-2-yl)-9,9-dihexyl-9H-fluoren-3-yl]iridium} pentane 0.3-solvate, [Ir2(C30H35FN)4Cl2]·0.3C5H12, (II), di-μ2-cyanato-bis-{bis-[9,9-dihexyl-2-(5-meth-oxy-pyridin-2-yl)-9H-fluoren-1-yl]iridium} pentane monosolvate, [Ir2(C31H38NO)4(NCO)2(NCO)2]·C5H12, (III), and {μ-N,N'-bis-[3,5-bis-(tri-fluoro-meth-yl)phen-yl]oxamidato}bis(bis{2-[4-(2,4,6-trimethylphenyl)pyridin-2-yl]phenyl-κ2 C 1,N'}iridium)-chloro-benzene-pentane (1/2.3/0.4), [Ir2(C20H19N)4(C18H6F12N2O2)]·2.3C6H5Cl·0.4C5H12, (IV), synthesized in the quest for organic light-emitting devices, were determined. The bis-μ2-chloro and bis-μ2-cyanato complexes have ΔΔ and ΛΛ configurations of the distorted octa-hedral Ir centres in racemic crystals, whereas the oxamido complex has a centrosymmetric (meso) structure with the ΔΛ configuration. The bridging oxamido moiety has a nearly planar anti geometry. All structures show substantial disorder of both host mol-ecules and solvents of crystallization.
Highlights
Over the two decades since the pioneering work of Baldo et al (1998), cyclometalated IrIII complexes have been developed as emitters for organic light-emitting diodes (OLEDs) or light-emitting electrochemical cells (LECs) (Li et al, 2018; Adeloye, 2019)
The research focused on monoiridium species, because the di-iridium complexes known proved generally poor emitters because of their electron-withdrawing bridges; for example [Ir(ppy)2Cl]2 has a quantum yield 80 times lower than facIr(ppy)3 (King et al, 1985)
It is noteworthy that the optoelectronic properties of such complexes depend strongly on the position of the substituents in the pyridine ring
Summary
Over the two decades since the pioneering work of Baldo et al (1998), cyclometalated IrIII complexes have been developed as emitters (phosphorescent dopants) for organic light-emitting diodes (OLEDs) or light-emitting electrochemical cells (LECs) (Li et al, 2018; Adeloye, 2019) These complexes are structurally and synthetically versatile. It is noteworthy that the optoelectronic properties of such complexes depend strongly on the position of the substituents in the pyridine ring Whereas both electron-donating (OMe) or electron-withdrawing (F) substituents are known to lower the device efficiency of mono-iridium complexes – probably by perturbing the electron and hole mobilities and reducing the exiton formation (Al-Attar et al, 2011) – a substituent para to the N atom lowers the device efficiencies drastically (M’hamedi et al, 2012)
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