RESUMO
A class of neutral tris-bidentate IrIII metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl3 ] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2'-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl2 ] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl2 ] (3). The reaction of 3 with the dianionic chelate precursor, 5,5'-di(trifluoromethyl)-3,3'-bipyrazole (bipzH2 ) or 5,5'-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH2 ), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexesâ 2-6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590-627â nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458â nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3 π-π* transition character in the blue-emitting 4-6. The dppBz does not participate in the radiative transitions in 4-6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral IrIII complexes containing phosphine chelates.
RESUMO
Emissive Ir(III) metal complexes possessing two tridentate chelates (bis-tridentate) are known to be more robust compared to those with three bidentate chelates (tris-bidentate). Here, the deep-blue-emitting, bis-tridentate Ir(III) metal phosphors bearing both the dicarbene pincer ancillary such as 2,6-diimidazolylidene benzene and the 6-pyrazolyl-2-phenoxylpyridine chromophoric chelate are synthesized. A deep-blue organic light-emitting diode from one phosphor exhibits Commission Internationale de l'Eclairage (CIE(x,y) ) coordinates of (0.15, 0.17) with maximum external quantum efficiency (max. EQE) of 20.7% and EQE = 14.6% at the practical brightness of 100 cd m-2 .