Iridium(iii) phosphors with rigid fused-heterocyclic chelating architectures for efficient deep-red/near-infrared emissions in polymer light-emitting diodes

Abstract

Highly efficient deep-red/near-infrared emissions with maximum EQEs of 7.04% and 4.14%, respectively, are realized for Ir(iii) complexes by designing rigid fused-heterocyclic ligands.

Improved deep-red phosphorescence in cyclometalated iridium complexes via ancillary ligand modification

“…[35] Some recent improvements have been made by introducing new C^N ligands, sticking exclusively with acac or picolinate-supported bis-cyclometalated iridium structures. These include an Ir(C^N)2(acac) complex with phenazine-derived C^N ligands (λmax = 684 nm and ΦPL = 0.27), [36] an Ir(C^N)2(acac) compound with spirofluorenedibenzosuberene[d]quinoxaline C^N ligands (λmax = 686 nm and ΦPL = 0.51), and finally two picolinate-supported complexes with benzo[b]thiophen-2-yl)quinoline C^N ligands, π-extended versions of btp (λmax = 651 and 661 nm, and ΦPL = 0.48 and 0.37, respectively). [37] Clearly, there has been a surge of interest in preparing efficient deep-red iridium phosphors and applying them in optoelectronic devices, and the compounds described here offer a complementary approach to accessing deep-red emitters and have photoluminescence attributes that rival or exceed these recent breakthrough examples.…”

Near-infrared emitting iridium complexes: Molecular design, photophysical properties, and related applications

“…The substitution position is important for adjusting emission wavelength. Attaching these groups on the HOMOs localized part (usually the C part) is more effective to get redshift ( You et al., 2019 , 2020b ). Meanwhile, the flexible chains may bring extra vibration modes and lead to higher k nr ( Zhang et al., 2020 ).…”

“…Notably, Zhu et al. reported a series of complexes based on dibenzo[ a,c ]phenazine ligands, in which the N part, C part, and part of PS part were conjugated ( Figure 9 ) ( You et al., 2019 , 2020a , 2020b ). The rather rigid structure resulted in low Huang-Rhys factors and small k nr .…”

“…Sometimes, the product is a mixture of the binuclear Ir(III) dimer and facial homoleptic complexes, even the latter being the main product, which just reflect strong coordination ability of the ligands, and in this situation, synthesizing facial homoleptic complexes is the best choice ( Xue et al., 2017 ; Zhang et al., 2020 ). In some cases, the binuclear Ir(III) dimer cannot be synthesized by the most commonly used IrCl 3 ·nH 2 O, and in this situation, an iridium-containing starting material with higher activity than IrCl 3 ·nH 2 O is needed, such as the [Ir(COD)] 2 Cl 2 (COD = 1,5-cyclo-octadiene) ( You et al., 2019 , 2020a , 2020b ). Along with the improvement of reaction conditions, such as adding base, using different solvents, and adjusting the reaction temperature, the binuclear Ir(III) dimer might be successfully synthesized, then the synthesis of heteroleptic complexes is feasible, otherwise some modifications are needed to improve the coordination ability of ligands.…”

Recent Progress in the Development of Fluorescent Probes for Thiophenol

“…Luminescent heavy-metal complexes showed some favorable photophysical characteristics for sensing and bioimaging applications, such as a large Stokes shift and long emission lifetime, which are very helpful for eliminating autofluorescence in complicated biological and environmental samples [64,65,66,67,68,69,70]. Lu et al presented a cyclometalated iridium-based phosphorescent probe ( 11 ) (Figure 5) for sensing PhSH [71].…”