Syntheses, Photoluminescence, and Electroluminescence of a Series of Iridium Complexes with Trifluoromethyl-Substituted 2-Phenylpyridine as the Main Ligands and Tetraphenylimidodiphosphinate as the Ancillary Ligand

Controlling the sensitivity and selectivity for the detection of nitro-based explosives by modulating the electronic substituents on the ligand of AIPE-active cyclometalated iridium(III) complexes

Nitroaromatic compounds are extremely explosive materials that pose a national security risk and raise environmental concerns. The design and development of sensitive and selective compounds for explosive materials are highly desirable. 'Aggregation-Induced Emission' (AIE) active materials are best suited for sensing purposes because of their sensitivity, fast detection time, and easy operation. By rationally incorporating substituents on the cyclometalated (C^N) ligand, four different AIE active iridium(III) based monocyclometalated complexes with the general formula [Ir(PPh3)2(H)(Cl)(C^N)] were synthesized. The phenyl ring of the phenyl pyridine cyclometalated portion of an iridium(III) complex was substituted with the right substituents to adjust the FMO levels thus, leading to appropriate alignment of the energy levels. Each of the resulting complexes displayed a significant property known as 'Aggregation-Induced Phosphorescent Emission' (AIPE). The complexes were subjected to structural characterization, electrochemical analysis, and photophysical property studies. The synthesized complexes were employed for the detection of aromatic nitro explosive compounds such as trinitrophenol (TNP) and trinitrotoluene (TNT) in the aqueous phase with a high degree of sensitivity. The sensing capabilities of each complex were assessed for these nitro explosive compounds and compared to those of the unsubstituted iridium(III) complex (M). Notably, the best limits of detection for TNP and TNT have been achieved with iridium(III) complexes [M1 (489 pM) and M3 (3.6 nM)] within the literature reported until now. For detecting picric acid with M1, FRET was found to be the potential mechanism, and for TNT, PET was found to be the cause of emission quenching by M3. Furthermore, for low-cost detection, filter paper-based sensing was also found effective for each complex. Real-field sensing of PA in soil samples was also performed.

Theoretical Approach for the Luminescent Properties of Ir(III) Complexes to Produce Red-Green-Blue LEC Devices

With an appropriate mixture of cyclometalating and ancillary ligands, based on simple structures (commercial or easily synthesized), it has been possible to design a family of eight new Ir(III) complexes (1A, 1B, 2B, 2C, 3B, 3C, 3D and 3E) useful as luminescent materials in LEC devices. These complexes involved the use of phenylpyridines or fluorophenylpyridines as cyclometalating ligands and bipyridine or phenanthroline-type structures as ancillary ligands. The emitting properties have been evaluated from a theoretical approach through Density Functional Theory and Time-Dependent Density Functional Theory calculations, determining geometric parameters, frontier orbital energies, absorption and emission energies, injection and transport parameters of holes and electrons, and parameters associated with the radiative and non-radiative decays. With these complexes it was possible to obtain a wide range of emission colours, from deep red to blue (701-440 nm). Considering all the calculated parameters between all the complexes, it was identified that 1B was the best red, 2B was the best green, and 3D was the best blue emitter. Thus, with the mixture of these complexes, a dual host-guest system with 3D-1B and an RGB (red-green-blue) system with 3D-2B-1B are proposed, to produce white LECs.

Synthesis and luminescence properties of two Ir(iii) complexes containing styrene-modified phenylpyridine ligands

Two green-emitting iridium(iii) complexes containing styrene-modified phenylpyridine ligands have been synthesized for OLEDs.

Sky-blue iridium complexes with pyrimidine ligands for highly efficient phosphorescent organic light-emitting diodes

Three sky blue heteroleptic Ir(III) complexes with emission peaks at 457–459 nm, have been developed. A maximum quantum efficiency of 21.23% with CIE coordinates of (0.15, 0.26) is realized in their PhOLEDs, representing a higher efficiencies and improved color purities than FIrpic.

High stability and luminance efficiency thieno[2,3-d]pyridazine-based iridium complexes and their applications in high-performance yellow OLEDs

An OLED based on complex 1 shows promising efficiencies of 18.2%, 58.5 cd A⁻¹ and 45.9 lm W⁻¹ which are 40% higher than those of PO-01.

Four-membered red iridium(iii) complexes with Ir-S-P-S structures: rapid room-temperature synthesis and application in OLEDs

In this work, with sulfur-containing ancillary ligands of triethylamine salts of bis(4-methoxyphenyl)-phosphinodithioic acid (omess) and bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphinodithioic acid (tbuss), two four-membered red iridium(iii) complexes (tfmpqz)₂Ir(omess) and (tfmpqz)₂Ir(tbuss) with Ir-S-P-S structures were synthesized rapidly at room temperature within 5 min, in which 4-(4-(trifluoromethyl)phenyl)quinazoline (tfmpqz) was used as the main ligand. The calculated Gibbs free energy changes of the complex formation reactions prove that they are exothermic and thermodynamically beneficial processes. Both Ir(iii) complexes show almost the same PL emissions at 624 and 623 nm with high phosphorescence quantum yields of 0.60 and 0.72, respectively. Using the two complexes as emitters, both organic light-emitting devices (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacabonitrile, 5 nm)/TAPC ((bis(4-(N,N-ditolylamino)phenyl)cyclohexane, 30 nm)/(tfmpqz)₂Ir(omess) or (tfmpqz)₂Ir(tbuss):26DCzppy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine) (12 wt%, 10 nm)/TmPyPB (1,3,5-tri((3-pyridyl)-phen-3-yl)benzene, 30 nm)/LiF (1 nm)/Al (100 nm) achieve good performances. Particularly, due to the introduction of tert-butyl groups into the (tfmpqz)₂Ir(tbuss) complex, its device exhibits better device properties with a maximum luminance of 26 184 cd m^-2, maximum current efficiency of 30.24 cd A^-1, maximum power efficiency of 22.61 lm W^-1 and maximum external quantum efficiency of 21.50% with CIE coordinates at (0.65, 0.34).

Fast Synthesis of Iridium(III) Complexes Incorporating a Bis(diphenylphorothioyl)amide Ligand for Efficient Pure Green OLEDs

Bis(diphenylphorothioyl)amide (Stpip) containing phosphor-sulfur (P═S) bonds was used as an ancillary ligand for three pure green iridium(III) emitters Ir1, Ir2, and Ir3, which were synthesized in few minutes at room temperature with high reaction yields above 70%. All these complexes show good thermal stability and excellent sublimation yields of around 80-90%, which are considered beneficial for industry practical production and organic light-emitting diode (OLED) fabrication. The emission profiles of these complexes meet the green standards of CIE1931 with coordinates of (0.33, 0.63), (0.33, 0.62), and (0.34, 0.62), respectively, and high photoluminescence quantum yields of up to 98% are achieved. Utilizing these complexes as emissive dopants, these OLEDs exhibited high current efficiency up to 91.94 cd A^-1, external quantum efficiency up to 26.52%, and power efficiency up to 92.60 lm W^-1 with very small efficiency roll-off, without adopting internal or external out-coupling methods. These results indicate that Stpip is a potentially suitable ligand scaffold for highly efficient phosphorescent Ir(III) emitters that endow corresponding OLEDs with high efficiency and small roll-off.

Two platinum(ii) complexes with a 4-phenyl-4H-1,2,4-triazole derivative as an ancillary ligand for efficient green OLEDs

Two new cyclometalated platinum(ii) complexes ((TN₃T)Pt(dptp), (4tfmppy)Pt(dptp)) with 2',6'-bis(trifluoromethyl)-2,3'-bipyridine (TN₃T) and 4-trifluoromethylphenylpyridine (4tfmppy) as the cyclometalated ligands and the nitrogen heterocycle 2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenol (dptp) as the ancillary ligand were developed. Both complexes are green phosphors with high photoluminescence quantum efficiency yields (λ_max = 532 nm, Φ_p = 65% for (TN₃T)Pt(dptp) and λ_max = 502 nm, Φ_p = 71% for (4tfmppy)Pt(dptp)) in CH₂Cl₂ solutions at room temperature, respectively. Organic light-emitting diodes (OLEDs) with single-emitting layer and double-emitting layer structures were fabricated with good performances. Particularly, the double-emitting layer device D2 based on the complex (4tfmppy)Pt(dptp) with 6 wt% doped concentration shows superior performances with a maximum EQE of 26.90% with mild efficiency roll-off. This study demonstrates that the ancillary ligand attached with a 4-phenyl-4H-1,2,4-triazole group could facilitate charge trapping across the bulk of the device for efficient OLEDs.

Synthesis and properties of a series of iridium complexes with imidazolo[2,1-b]thiazole derivatives as primary ligands

Ten novel phosphorescent iridium complexes based on imidazolo[2,1-b]thiazole derivatives as primary ligands with luminescent nearly full colors.

Towards blue emitting monocyclometalated gold(iii) complexes – synthesis, characterization and photophysical investigations

The electronic properties of cyclometalating ligands and ancillary ligands were successfully tailored to achieve blue emission in monocyclometalated gold(iii) complexes.

Polypyridyl ligands as a versatile platform for solid-state light-emitting devices

A comprehensive review of tuneable polypyridine complexes as the emissive components of OLED and LEC devices is presented, with a view to bridging the gap between molecular design and commercialization.

Highly efficient bluish green organic light-emitting diodes of iridium(iii) complexes with low efficiency roll-off

Two novel iridium(iii) complexes Ir(BTBP)2mepzpy and Ir(BTBP)2phpzpy were successfully synthesized, in which 2',6'-bis(trifluoromethyl)-2,4'-bipyridine (BTBP) was used as the main ligand, and 2-(3-methyl-1H-pyrazol-5-yl)pyridine (mepzpy) and 2-(3-2-(3-phenyl-1H-pyrazol-5-yl))pyridine (phpzpy) were introduced as the ancillary ligands, respectively. Both Ir(iii) complexes displayed bluish green emission peaks at 486 and 487 nm with high quantum efficiencies of 0.73 and 0.69, respectively. The organic light-emitting diodes (OLEDs) with the structure of ITO/HATCN (hexaazatriphenylenehexacarbonitrile, 5 nm)/TAPC (bis[4-(N,N-ditolylamino)-phenyl]cyclohexane, 40 nm)/Ir(BTBP)2mepzpy or Ir(BTBP)2phpzpy (10 wt%): 2,6-DCzPPy (2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 30 nm)/LiF (1 nm)/Al (100 nm) exhibited high efficiencies with low efficiency roll-off. Especially, the device based on the Ir(BTBP)2mepzpy complex achieved a maximum current efficiency of 58.17 cd A-1 and a maximum external quantum efficiency of 25.33% with Commission Internationale de 1'Eclairage coordinates of (0.19, 0.43). These results indicate that novel cyclometalated Ir(iii) complexes for high efficiency OLEDs with low efficiency roll-off were obtained by our rational design.

Iridium(iii) phosphorescent complexes with dual stereogenic centers: single crystal, electronic circular dichroism evidence and circularly polarized luminescence properties

Iridium complexes with a chiral metal center and chiral carbons, Λ/Δ-(dfppy)₂Ir(chty-R) and Λ/Δ-(dfppy)₂Ir(chty-S), were synthesized and characterized. These isomers have the same steady-state photophysical properties, and obvious offsets in ECD spectra highlight both the chiral sources. Each enantiomeric couple shows mirror-image CPL bands with a dissymmetry factor in the order of 10^-3.

Efficient yellow electroluminescence of four iridium(iii) complexes with benzo[d]thiazole derivatives as main ligands

Four yellow iridium(iii) complexes with benzo[d]thiazole derivatives as the main ligands display good device performances with a maximum current efficiency of up to 69.8 cd A⁻¹ and a maximum external quantum efficiency of up to 24.3%.

Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)2(N^N)]+A- type and their selected electroluminescent properties

Iridium C,N-cyclometalated complexes with an ionic structure are considered to be promising candidates for application in host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility of reducing their concentration in organic matrices as well as allows obtaining organic light emitting devices (OLEDs) with interesting emission parameters. We report herein a methodology enabling the synthesis of cyclometalated ionic iridium(iii) complexes of the type [Ir(C^N)₂(N^N)]⁺A^- according to a three-component one-pot strategy involving the acceleration of the reaction via microwave irradiation. The developed protocol allowed efficient synthesis of a series of new cationic iridium(iii) coordination derivatives, which were isolated and spectroscopically characterized, while the structures of two of them were determined by the X-ray method. Moreover, the iridium(iii) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme that was used to predict HOMO-LUMO gaps for the studied Ir(iii) complexes showed a good correlation between the experimental and calculated values. In order to determine the influence of the structure and nature of the ancillary ligand on the location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on a poly(N-vinylcarbazole)/2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (PVK/PBD) matrix. The highest luminance, above 10 000 cd m^-2, was recorded for the device containing only 1.0 wt% of [Ir(bzq)₂(1,10-phenanthroline)]⁺PF₆^- in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range of 1.0 to 2.2 cd A^-1.

Syntheses, photoluminescence and electroluminescence of two novel platinum(ii) complexes

Highly efficient green OLEDs based on two platinum complexes showed a peak current efficiency of 48.3 cd A⁻¹ with low efficiency roll-off; and even at a brightness of 1000 cd m⁻², a current efficiency of 47.0 cd A⁻¹ could still be obtained.

Novel Design of Iridium Phosphors with Pyridinylphosphinate Ligands for High-Efficiency Blue Organic Light-emitting Diodes

Due to the high quantum efficiency and wide scope of emission colors, iridium (Ir) (III) complexes have been widely applied as guest materials for OLEDs (organic light-emitting diodes). Contrary to well-developed Ir(III)-based red and green phosphorescent complexes, the efficient blue emitters are rare reported. Like the development of the LED, the absence of efficient and stable blue materials hinders the widely practical application of the OLEDs. Inspired by this, we designed two novel ancillary ligands of phenyl(pyridin-2-yl)phosphinate (ppp) and dipyridinylphosphinate (dpp) for efficient blue phosphorescent iridium complexes (dfppy)₂Ir(ppp) and (dfppy)₂Ir(dpp) (dfppy = 2-(2,4-difluorophenyl)pyridine) with good electron transport property. The devices using the new iridium phosphors display excellent electroluminescence (EL) performances with a peak current efficiency of 58.78 cd/A, a maximum external quantum efficiency of 28.3%, a peak power efficiency of 52.74 lm/W and negligible efficiency roll-off ratios. The results demonstrated that iridium complexes with pyridinylphosphinate ligands are potential blue phosphorescent materials for OLEDs.

Regioisomerism in cationic sulfonyl-substituted [Ir(C^N)2(N^N)]+ complexes: its influence on photophysical properties and LEC performance

In a series of regioisomeric [Ir(C^N)₂(bpy)]⁺ complexes containing methylsulfonyl groups on the cyclometallating ligands, the influence of the substitution position on photophysical, electrochemical and LEC device properties is investigated.

Crystal structure, photoluminescence and electroluminescence of three bluish green light-emitting iridium complexes

Three iridium(iii) complexes were applied in efficient OLEDs showing a maximum current efficiency (η_c) value of 37.61 cd A⁻¹ with low efficiency roll-off.

Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices

Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(III), platinum(II), gold(III), ruthenium(II), copper(I) and osmium(II) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure-property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs.

Colour tuning by the ring roundabout: [Ir(C^N)2(N^N)]+ emitters with sulfonyl-substituted cyclometallating ligands

A series of fluorine-free blue and green emitting iridium complexes containing sulfone-substituted cyclometallating and pyrazolyl-pyridine ancillary ligands has been synthesized and their properties investigated.

Two blue iridium complexes for efficient electroluminescence with low efficiency roll-off

Two blue iridium(iii) complexes were applied in efficient OLEDs (η_c,max of 22.83 cd A⁻¹ for (dfpypy)₂Ir(tpip); η_c,max of 20.79 cd A⁻¹ for (dfpypy)₂Ir(Ftpip)) with low efficiency roll-off.

Four highly efficient cuprous complexes and their applications in solution-processed organic light-emitting diodes

Four novel highly emissive cuprous complexes were prepared. The OLEDs from these complexes had a peak current efficiency of 17.8 cd A⁻¹ and an EQE of 6.4%.

Highly phosphorescent iridium(iii) complexes based on 2-(biphenyl-4-yl)benzo[d]oxazole derivatives: synthesis, structures, properties and DFT calculations

A series of new 2-(biphenyl-4-yl)benzo[d]oxazole based bis-cyclometalated iridium(iii) complexes have been synthesized, and their high quantum efficiency are presented.

Novel phosphorescent iridium(iii) complexes containing 2-thienyl quinazoline ligands: synthesis, photophysical properties and theoretical calculations

Highly efficient phosphorescent iridium complexes based on 2-thienyl quinazoline derivatives with various substituents are successfully prepared and fully characterized.