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

A sensitive immunosensor via Pd@Au0.85Pd0.15 in situ electrocatalysis generating H2O2 for quenching electrochemiluminescence of Ir(pbi)2(acac)@Ti3C2Tx MXene-PVA

The establishment of rapid target analysis methods for cytokeratin fragment antigen 21-1 (CYFRA 21-1) is urgently needed. [Ir(pbi)2(acac)] (pbi = 2-(4-bromophenyl)-1-hydrogen -benzimidazole, acac = acetylacetonate) as traditional electrochemiluminescence (ECL) luminophores has been confined due to its non-negligible dark toxicity and poor water solubility leading to poor biocompatibility and electrical conductivity as an organic molecule. Hence, to overcome this limitation, [Ir(pbi)2(acac)] can be effectively loaded on the polyvinyl alcohol hydrogel modified Ti3C2Tx MXene surface (Ir@Ti3C2Tx-PVA) as sensing platform which can emit high ECL signals. Then, a quenching strategy was proposed to fabricate an ECL sandwich immunosensor using H2O2 as quencher molecules which can generated by Pd@Au0.85Pd0.15. Especially, the generation of O2 to H2O2 can be achieved through a two-electron (2e-) reaction pathway by Pd@Au0.85Pd0.15, to overcome the restriction that the H2O2 was virtually impossible to label or immobilize on the non-enzyme nanomaterials. The proposed ECL assay achieves a response to CYFRA 21-1 within the range of 0.1 pg/mL-100 ng/mL, with a detection limit of 8.9 fg/mL (S/N = 3). This work provided a feasible tactic to seek superior-performance ECL luminophore and quencher consequently set up a novel means to makeup ultrasensitive ECL biosensor, which extended the utilization potential of Ir(pbi)2(acac) in ECL assays.

Efficient narrowband yellow organic light-emitting diodes based on iridium(III) complexes with the rigid indolo[3,2,1-jk]carbazole unit

Phosphorescent material with narrowband emission is crucial for advancing wide-color-gamut organic light-emitting diodes (OLEDs). In this work, two iridium(III) complexes, (PhthzICz)2Ir(tmd) and (thzICz)2Ir(tmd), using rigid 2-(benzothiazole-2-yl)indolo[3,2,1-jk]carbazole (PhthzICz) and 2-(thiazole-2-yl)indolo[3,2,1-jk]carbazole (thzICz) as cyclometalated ligands and 2,2,6,6-tetramethyl-3,5-heptanedione (tmd) as ancillary ligands, were synthesized. When these complexes were doped into the host material 3,3'-di(9H-carbazol-9-yl)-1,1'-biphenyl, the doped films exhibited yellow photoluminescence (PL) peaking at 537 and 531 nm, full width at half maximum (FWHM) bands of 35 and 60 nm, and PL quantum yields of 89.9% and 85.9%, respectively. OLEDs based on these two emitters display moderate performance characteristics with maximum external quantum efficiencies of 25.2% and 22.7%. Notably, the device based on (PhthzICz)2Ir(tmd) exhibits a narrow FWHM of 31 nm. Overall, the study highlights the practicality of incorporating rigid groups into the cyclometalated ligands of Ir(III) complexes as a viable strategy for achieving efficient Ir(III) complexes for OLEDs with narrow emission and high efficiency.

Site-Specific Anchoring a Luminescent Tag in a Protein with Non-Emissive Iridium(III) Complex

Site-specific modification of proteins with synthetic fluorescent tag effectively improves the resolution of imaging, and such a labeling method with negligible three-dimensional structural perturbations and minimal impact on the biological functions of proteins is of high interest to dissect the high-resolution activities of biomolecules in complex systems. To this end, several non-emissive iridium(III) complexes [Ir(C-N)2 (H2 O)2 ]+ OTF- (C-N denotes various cyclometalated ligands) were designed and synthesized. These complexes were tested for attaching a protein by coordinating to H/X (HisMet, HisHis, and HisCys) that are separated by i and i+4 in α-helix. Replacement of the two labile water ligands in the iridium(III) complex by a protein HisHis pair increases the luminescent intensity up to over 100 folds. This labeling approach has been demonstrated in a highly specific and efficient manner in a number of proteins, and it is also feasible for labeling target proteins in cell lysates.

Modular Imine Chelates with Variable Anionic Donors Promote Red Phosphorescence in Cyclometalated Iridium Complexes

The lack of red and deep-red emitting molecular phosphors with high photoluminescence quantum yields remains a significant fundamental challenge and has implications in optoelectronic technologies for color displays and other consumer products. In this work, we introduce a series of seven new red or deep-red emitting heteroleptic bis-cyclometalated iridium(III) complexes, supported by five different ancillary ligands (L^X) from the salicylaldimine and 2-picolinamide families. Previous work had shown that electron-rich anionic chelating "L^X" ligands can be effective in supporting efficient red phosphorescence, and the complementary approach described here, in addition to being synthetically simpler, offers two key advantages over the previous designs. First, the "L" and "X" functionalities can be independently tuned, providing excellent control over the electronic energy levels and excited-state dynamics. Second, these classes of L^X ligands can have beneficial impacts on the excited-state dynamics but do not significantly perturb the emission color profile. Cyclic voltammetry experiments show that the substituents on the L^X ligand impact the HOMO energy but have a minimal effect on the LUMO energy. Photoluminescence measurements reveal that all the compounds luminesce in the red or deep-red region as a function of the cyclometalating ligand and exhibit exceptionally high photoluminescence quantum yields (Φ_PL), comparable or superior to the best-performing red-emitting iridium complexes.

Amino group-driven distinguishing homocysteine from cysteine and glutathione in photoluminesecent signal of the iridium(III) complexes

In this work, six iridium(III) complexes have been designed, synthesized and characterized. The molecular structures of complex 1 ([(pba)₂Ir(bpy-2N(CH₃)₂)]PF₆), 2 ([(pba)₂Ir(bpy-2NH₂)]PF₆) and 3 ([(pba)₂Ir(bpy-2CH₃)]PF₆) were determined by single crystal X-ray diffraction. Upon addition of Hcy (homocysteine) to the solution of complex 1, a luminescent variation from orange red to green was observed by the naked eye, corresponding to a large blue shift from 604 nm to 498 nm (~106 nm). While the emission intensity of complex 1 was almost no change after addition of other common amino acids including Cys (cysteine) and GSH (glutathione). The aldehyde group of complex 1 formed a new thiazinane/thiazolidine ring with Hcy/Cys confirmed by ¹H NMR and high-resolution mass spectrometry. And the new product 1-Hcy had a higher quantum yield than 1-Cys. Theoretical calculations showed that the HOMO (highest occupied molecular orbital) of 1-Hcy was located on the newly formed six-membered thiazinane ring, which was different from the HOMO of 1-Cys. Compared with the other iridium(III) complexes, we can speculate that the large blue shift and enhancement of the emission intensity of the complex 1 were related to the strong electron donating ability of the modified amino groups on bipyridine ligand. This will provide an idea for the design of ratio-based luminescence probes for Hcy in future.

Simple Synthesis of Red Iridium(III) Complexes with Sulfur-Contained Four-Membered Ancillary Ligands for OLEDs

Phosphorescent iridium(III) complexes have been widely researched for the fabrication of efficient organic light-emitting diodes (OLEDs). In this work, three red Ir(III) complexes named Ir-1, Ir-2, and Ir-3, with Ir-S-C-S four-membered framework rings, were synthesized efficiently at room temperature within 5 min using sulfur-containing ancillary ligands with electron-donating groups of 9,10-dihydro-9,9-dimethylacridine, phenoxazine, and phenothiazine, respectively. Due to the same main ligand of 4-(4-(trifluoromethyl)phenyl)quinazoline, all Ir(III) complexes showed similar photoluminescence emissions at 622, 619, and 622 nm with phosphorescence quantum yields of 35.4%, 50.4%, and 52.8%, respectively. OLEDs employing these complexes as emitters with the structure of ITO (indium tin oxide)/HAT-CN (dipyra-zino[2,3-f,2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile, 5 nm)/TAPC (4,4'-cyclohexylidenebis[N,N-bis-(4-methylphenyl)aniline], 40 nm)/TCTA (4,4″,4″-tris(carbazol-9-yl)triphenylamine, 10 nm)/Ir(III) complex (10 wt%): 2,6DCzPPy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(mpyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) achieved good performance. In particular, the device based on complex Ir-3 with the phenothiazine unit showed the best performance with a maximum brightness of 22,480 cd m^-2, a maximum current efficiency of 23.71 cd A^-1, and a maximum external quantum efficiency of 18.1%. The research results suggest the Ir(III) complexes with a four-membered ring Ir-S-C-S backbone provide ideas for the rapid preparation of Ir(III) complexes for OLEDs.

Structure-Property Relationship in Amber Color Light-Emitting Electrochemical Cell with TFSI Counteranion: Enhancing Device Performance by Different Substituents on N∧N Ligand

Amber color emitting novel Ir(III) complexes were synthesized: [Ir(Meppy)₂(Fpbpy)][PF₆] (1bPF₆), [Ir(Meppy)₂(Fpbpy)][TFSI] (1bTFSI), [Ir(Meppy)₂(MeObpy)][PF₆] (2bPF₆) and [Ir(Meppy)₂(MeObpy)][TFSI] (2bTFSI), where Meppy = 2-(p-methylphenyl)-pyridine (b), Fpbpy = 4,4'-bis(4-fluorophenyl)-2,2'-bipyridine (1), and MeObpy = 4,4'-bis(4-methoxy)-2,2'-bipyridine (2). The photophysical and X-ray results showed that the complexes have aggregation-induced phosphorescent emission (AIPE) and a salt-induced polymorphism effect. The highest photoluminescence intensity was observed in complex 2bTFSI compared to other complexes in the solid state. Their theoretical absorption and phosphorescence emission transitions in acetonitrile were also investigated by using double- and triple-ζ basis sets with B3LYP and PBE0 hybrid functional. The best light-emitting electrochemical cell (LEC) performance was exhibited by complex 2bTFSI, and the data obtained were as follows: Luminance, current density, luminous efficiency, turn-on time, power efficiency, and external quantum efficiency were measured as 16 156 cd/m², 554 mA/cm², 8.49 cd/A, 17 s, 3.95 lm/W and 6.37%, respectively. The investigation of crystallographic characteristics have shown that the LEC performance of these complexes depends on cationic-anionic interaction which has a significant influence on molecular stacking of the molecules. Because, complex 2bTFSI, with weak cationic-anionic interactions, shows strong π···π stacking interactions between the adjacent molecules, it is the best lighting application candidate among the complexes.

Design of pyridinylphosphinate-based blue iridium phosphors for high-efficiency organic light-emitting diodes

At present, cyclometalated iridium (Ir)(iii) complexes are the most promising emitters for OLEDs. Contrary to well-developed Ir(iii)-based red and green phosphorescent complexes, the efficient blue emitters are limited and the performances of blue OLEDs are still not satisfactory. Inspired by this, we designed two novel blue Ir(iii) complexes employing 2-(2,4-difluoropyridyl)pyridine (dfpypy) and 2,6-difluoro-3-(pyridin-2-yl)benzonitrile (FCN) as the main ligands, respectively, and phenyl(pyridin-2-yl)phosphinate (ppp) as the ancillary ligand. The rational design of the molecular structure makes the two complexes achieve blue emission and possess good electron mobility simultaneously. The devices based on the Ir(iii) phosphors exhibited good electroluminescence performances with low turn-on voltages, a peak current efficiency of 24.51 cd A^-1, a maximum external quantum efficiency of 12.4%, a peak power efficiency of 21.99 lm W^-1 and low efficiency roll-off. These results provide an effective strategy for the future molecular design of blue Ir(iii) complexes with good electron transport property for OLEDs.

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.

Synthesis and luminescence properties of two cross-linkable Ir(iii) complexes

The EL performances of the vacuum- and solution-processed devices of two cross-linkable iridium(iii) complexes were investigated.

Cu(I) Complexes of Multidentate N,C,N- and P,C,P-Carbodiphosphorane Ligands and Their Photoluminescence

A series of dinuclear copper(I) N,C,N- and P,C,P-carbodiphosphorane (CDP) complexes using multidentate ligands CDP(Py)2 (1) and (CDP(CH2PPh2)2 (13) have been isolated and characterized. Detailed structural information was gained by single-crystal XRD analyses of nine representative examples. The common structural motive is the central double ylidic carbon atom with its characteristic two lone pairs involved in the binding of two geminal L-Cu(I) fragments at Cu-Cu distances in the range 2.55-2.67 Å. In order to enhance conformational rigidity within the characteristic Cu-C-Cu triangle, two types of chelating side arms were symmetrically attached to each phosphorus atom: two 2-pyridyl functions in ligand CDP(Py)2 (1) and its dinuclear copper complexes 2-9 and 11, as well as two diphenylphosphinomethylene functions in ligand CDP(CH2PPh2)2 (13) and its di- and mononuclear complexes 14-18. Neutral complexes were typically obtained via the reaction of 1 with Cu(I) species CuCl, CuI, and CuSPh or via the salt elimination reaction of [(CuCl)2(CDP(Py)2] (2) with sodium carbazolate. Cationic Cu(I) complexes were prepared upon treating 1 with two equivalents of [Cu(NCMe)4]PF6, followed by the addition of either two equivalents of an aryl phosphine (PPh3, P(C6H4OMe)3) or one equivalent of bisphosphine ligands bis[(2-diphenylphosphino)phenyl] ether (DPEPhos), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (XantPhos), or 1,1'-bis(diphenyl-phosphino) ferrocene (dppf). For the first time, carbodiphosphorane CDP(CH2PPh2)2 (13) could be isolated upon treating its precursor [CH(dppm)2]Cl (12) with NaNH2 in liquid NH3. A protonated and a deprotonated derivative of ligand 13 were prepared, and their coordination was compared to neutral CDP ligand 13. NMR analysis and DFT calculations reveal that the most stable tautomer of 13 does not show a CDP (or carbone) structure in its uncoordinated base form. For most of the prepared complexes, photoluminescence upon irradiation with UV light at room temperature was observed. Quantum yields (ΦPL) were determined to be 36% for dicationic [(CuPPh3)2(CDP(Py)2)](PF6)2 (4) and 60% for neutral [(CuSPh)2(CDP(CH2PPh2)2] (16).

Efficient blue, green and red iridium(iii) complexes with noncovalently-linked pyrazole/pyrazolide rings for organic light-emitting diodes

Blue, green and red iridium(iii) complexes using a new pyrazole/pyrazolide ancillary ligand system, and their application in OLEDs with EQEs of up to 21.0% and low efficiency roll-off.

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).