Synthesis, Structures and Photophysical Properties of Cationic Cyclometalated Iridium(III) Complexes Bearing N‐Phenylcarbazole Group

Abstract

Four cationic cyclometalated IrIII complexes [(MeOPCz)2Ir(bpy)]PF6 (3), [(MeOPCz)2Ir(dtb‐bpy)]PF6 (4), [(TFPCz)2Ir(bpy)]PF6 (5), and [(TFPCz)2Ir(dtb‐bpy)]PF6 (6) were successfully synthesized using two new cyclometalated ligands 9‐phenyl‐3‐(4‐methoxypyridin‐2‐yl)‐9H‐carbazole (MeOPCz) 1 and 9‐phenyl‐3‐(4‐trifluoromethylpyridin‐2‐yl)‐9H‐carbazole (TFPCz) 2 in combination with 2,2'‐bipyridine (bpy) and 4,4'‐di‐tert‐butyl‐2,2'‐bipyridine (dtb‐bpy) as ancillary ligands. These complexes adopt the distorted octahedral configuration, and the complexes 5 and 6 crystallize in the centrosymmetric space group C2/c. Emission wavelength of these complexes can be tuned from 583 nm to 628 nm by the substituents (methoxy, trifluoromethyl and tert‐butyl groups) in ligands. All of these complexes show relatively high emission efficiencies (0.28–0.41) and short lifetimes (0.242–0.461 μs).

Investigation on the photophysical properties of Cu(I) complexes supported by N‐heterocyclic carbene ligands with electron‐donating/withdrawing groups on imidazolylidene unit

“…[1][2] The traditional phosphorescence complexes (e. g. Ir(III) and Pt(II) complexes) usually show high electroluminescence performances, but these emitters are very expensive because of using noble metals as synthesis materials. [3][4][5][6][7] In past decade, researchers devoted to developing low-cost luminescent Cu(I) complexes as alternative to phosphorescent materials based on noble metals. [8] It has been proved that many Cu(I) complexes emit efficient TADF at ambient temperature due to their small energy gaps (ΔE ST ) between the lowest singlet state (S 1 ) and the lowest triplet states (T 1 ).…”

“…Transition metal complexes with efficient phosphorescence/ thermally activated delayed fluorescence (TADF) have been attracting much attention due to their application in electroluminescence devices, such as organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs), because these emitting materials are capable of harvesting both singlet and triplet excitons resulting in 100 % internal quantum efficiency [1–2] . The traditional phosphorescence complexes (e. g. Ir(III) and Pt(II) complexes) usually show high electroluminescence performances, but these emitters are very expensive because of using noble metals as synthesis materials [3–7] . In past decade, researchers devoted to developing low‐cost luminescent Cu(I) complexes as alternative to phosphorescent materials based on noble metals [8] .…”