Saturated red iridium(iii) complexes containing a unique four-membered Ir–S–C–N backbone: mild synthesis and application in OLEDs†
A series of new iridium(III) cyclometalated complexes (4tfmpiq)2Ir(tiptha), (4tfmpiq)2Ir(phdiptha), (4tfmpiq)2Ir(fphdiptha) and (4tfmpiq)2Ir(ipdptha) (4tfmpiq = 4-(4-(trifluoromethyl)phenyl)isoquinoline, tiptha = 1,1,3-triisopropylthiourea, phdiptha = 1,1-diisopropyl-3-phenylthiourea, fphdiptha = 3-(4-fluorophenyl)-1,1-diisopropylthiourea, ipdptha = 3-isopropyl-1,1-diphenylthiourea) containing a unique four-membered ring Ir–S–C–N backbone were facilely synthesized under mild conditions. By introducing different substituents such as isopropyl, phenyl, 4-fluorophenyl, diisopropylamine and diphenylamine on the thiourea ancillary ligands, not only the S–C–N ligands can be extensively derived, but also the emission colors (λpeak = 627–636 nm) and photoluminescence quantum efficiencies (ΦP = 38.0–42.0%) can be regulated. Employing these complexes as emitters, the organic light emitting diodes (OLEDs) exhibited good performances with a maximum external quantum efficiency (EQEmax) of 13.1% for saturated red emission with CIE coordinates of (0.68, 0.32). These results demonstrate the great potential of the S–C–N ancillary ligands for developing new Ir(III) complexes towards OLED applications.