Red Phosphorescent Iridium Research Articles

A Pair of Deep Red Phosphorescent Responsive Emissive Cyclometalated Iridium (III) Complexes as Carbonic Anhydrase Inhibitor and Effective Theranostic Photosensitizer

ABSTRACTHerein, two deep red phosphorescent responsive emissive cyclometalated iridium (III) complexes with CAIX inhibition moiety was designed and synthesized; they can penetrate into living cells quickly and mainly located in the lysosome. They showed a strong binding affinity towards CAIX in vitro and effectively reduced cellular expression of CAIX. Moreover, the tethered CAIX‐inhibition moiety of benzene sulfonamide can decrease the inherent cytotoxicity of Ir(III) complex towards normal cells and improve killing selectivity towards cancer cells in dark; Ir3 and Ir4 exhibit approximately five to eight times higher killing selectivity than that of cisplatin; they exhibit satisfied photodynamic therapy effect under irradiation of 425 nm, ultimately resulting in apoptosis of cancer cell, which is accompanied with weakening of extracellular acidification, increased inhibition of cellular CAIX expression, significant loss of mitochondrial membrane potential, and elevated level of reactive oxygen. Herein, our work may demonstrate that combination of inhibition CAIX and metal photosensitizer may provide a promising strategy for constructing a novel theranostic platform.

Manipulating Förster and Dexter interactions between a thermally activated delayed fluorescence host and a phosphorescent dopant for highly efficient solution-processed red and white OLEDs

A blue TADF host with and without steric hindrances was utilized to manipulate Fӧrster and Dexter interactions with a red phosphorescent iridium complex, realizing the state-of-the-art PhOLEDs with a sufficiently high EQE of 22.2%.

Pure red phosphorescent iridium(iii) complexes containing phenylquinazoline ligands for highly efficient organic light-emitting diodes

By incorporating a methoxy group at the 6- and 7-sites of the quinazoline ring of phenylquinazoline cyclometalating ligands, the iridium complexes realize pure red phosphorescence. The PHOLED based on Ir2 achieves CIE of (0.65, 0.34) and a higher external quantum efficiency of 26.22%.

Naphthalene Benzimidazole Based Neutral Ir(III) Emitters for Deep Red Organic Light-Emitting Diodes.

Rigid naphthalene benzimidazole (NBI) based ligands (L1 and L2) are synthesized and utilized to make deep red phosphorescent cyclometalated iridium(III) complexes ([Ir(NBI)2(PyPzCF3)] (1) and [Ir(DPANBI)2(PyPzCF3)] (2)). Complexes 1 and 2 are prepared from the reaction of L1/L2 with the aid of ancillary ligands (PyPzCF3, 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine) in a two step method. The complexes are characterized by analytical and spectroscopic methods, as well as X-ray diffraction for 1. These complexes show a strong emission in the range of 635-700 nm that extends up to the near-infrared region (800 nm). The introduction of the diphenylamino (DPA) donor group on the naphthalene unit leads to a further red-shift in the emission. The complexes exhibit radiative quantum efficiency (ΦPL) of 0.27-0.29 in poly(methylmethacrylate) film and relatively short phosphorescence decay lifetimes (τ = 1.1-3.5 μs). The structural, electronic, and optical properties are investigated with the support of density functional theory (DFT) and time-dependent-DFT calculations. The calculation results indicate that the lowest-lying triplet (T1) excited state of 1 has a mixed metal-to-ligand charge transfer (3MLCT) and ligand-centered (3LC) character, while 2 shows a dominant 3LC character. Deep red-emitting organic light-emitting diodes fabricated using 1 as a dopant display a maximum external quantum efficiency of 10.9% with the CIE color coordinates of (0.690, 0.294), with an emission centered at 644 and 700 nm. Similarly, the emitter 2 also shows a maximum external quantum efficiency of 6.9% with emissions at 657 and 722 nm.

High performances red phosphorescent organic light-emitting diodes with low operation voltage

Abstract In this work, we demonstrated an efficient device design strategy in improving the electroluminescent performances of red phosphorescent emitter iridium(III) bis(2-phenylquinoly-N,C2′)dipivaloylmethane (PQ2Ir(dpm)) by constructing predominant and supplementary light-emitting layers (EMLs). 4,4′,4″-tris(carbazole-9-yl) triphenylamine (TcTa) and 4,7-dicarbazol-9-yl- [1,10]-phenanthroline (BUPH1) were selected as host materials of EMLs. Due to the well-designed double-EMLs device structure and the well-matched energy levels of selected materials, improved carriers’ balance and broadening recombination zone caused the low operation voltage and high device performances. Finally, the 4 wt% double-EMLs device obtained the highest brightness, external quantum efficiency, current efficiency, and power efficiency up to 29870 cd m−2, 12.18%, 19.74 cd A−1, and 25.84 lm W−1, respectively. At very low operation voltage of 3.4 V, this device realized the certain brightness of 1000 cd m−2 with power efficiency of 14.68 lm W−1.

Saturated red phosphorescent Iridium(III) complexes containing phenylquinoline ligands for efficient organic light-emitting diodes

Saturated red iridium phosphors are strongly desired for application in organic light-emitting diodes (OLEDs). Most of the reported iridium complexes with 2-arylquinoline or its derivatives as cyclometalating ligands are orange-red phosphorescent with peak wavelength below 620 nm. Herein trifluoromethyl (CF3) or Fluorine (F) is introduced into the 6-site of quinoline ring to design and synthesize the cyclometalated ligands 2-phenyl-6-CF3/F-quinoline (CF3-phq or F-phq) and heteroleptic iridium complexes Ir(CF3-phq)2(acac) (Ir-1), Ir(CF3-phq)2(tmd) (Ir-2), Ir(F-phq)2(acac) (Ir-3) and Ir(F-phq)2(tmd) (Ir-4). Owing to the electron-deficient feature of CF3 and F, the electron affinity of these complexes are increased, the corresponding LUMOs are pulled downwards, and the phosphorescence of CF3-containing iridium complexes are saturated red with peaks at 627–632 nm in photoluminescence. At the same time, by varying the ancillary ligand from acetylacetonate (acac) to 2,2,6,6-tetrametylheptane-3,5-dionate (tmd), the emitting performance are dramatically improved. As a result, the Ir(CF3-phq)2(tmd) based red OLED realized pure red electroluminescence with Commision Internationale de L'Eclairage (CIE) coordinates of (0.67, 0.33) with a high brightness of 12695 cd m−2 and a maximum external quantum efficiency of 14.96%, respectively, which maintained as high as 9.62% at a practical luminance of 1000 cd m−2. This is the first example of saturated red iridium phosphors with structure modification at the 6-site of quinoline ring of 2-phenylquinoline ligand.

Synthesis and Characterization of High-Efficiency Red Phosphorescent Iridium(III) Complexes with 1-(4-(Trifluoromethyl)phenyl)isoquinoline Ligand

Two new tfmpiq-based bis-cyclometalated iridium(III) complexes, [(tfmpiq)2Ir(imdzppo)] (2a) and [(tfmpiq)2Ir(idzpo)] (2b) (where tfmpiq = 1-(4-(trifluoromethyl)phenyl)isoquinoline, imdzppo = 2-(imidazo[1,2-a]pyridin-2-yl)phenol, idzpo = 2-(2H-indazol-2-yl)phenol), have been synthesized and fully characterized. The single crystal structure of 2b has been determined. The relationship between the structures and photophysical properties of both complexes are considered, and the DFT calculations have been used to further support the deduction. These Ir(III) complexes emit red light with quantum yields of 39.9-51.9% in degassed CH2Cl2 solution at room temperature. Also, their emission originates from a hybrid 3MLCT/3LLCT/3LC excited state. All these results show that iridium(III) complexes 2a-2b are suitable for red-phosphorescent materials in OLEDs.

Ratiometric oxygen probes with a cell-penetrating peptide for imaging oxygen levels in living cells

We investigated the photophysical and intracellular properties of two newly designed molecule-based ratiometric oxygen probes, 7DEAC-R8-BTQphen (R8) and 7DEAC-R12-BTQphen (R12), to evaluate their suitability for intracellular O2 measurements. R8 and R12 consist of a blue fluorescent coumarin derivative (7DEAC) and a red phosphorescent iridium(III) complex (BTQphen) connected respectively by an octa- or dodecaarginine linker to promote intracellular delivery of the probes. The probes showed oxygen-sensitive dual emissions in acetonitrile, lipid bilayer membrane, and in living cells. Energy state diagrams showing the relaxation processes of R8 and R12 in the excited state were constructed using emission spectra, quantum yield, and lifetime data. Efficient photon absorption at 405 nm due to the 7DEAC chromophore is followed by intramolecular energy transfer to the BTQphen moiety, resulting in 7DEAC fluorescence and BTQphen phosphorescence with an intensity ratio and spectral separation suitable for ratiometric measurements. The validities of O2 concentrations derived from the ratios between the phosphorescence and fluorescence intensities of R8 and R12 were verified in lipid membranes, as well as in solution by phosphorescence lifetime measurements of the BTQphen moiety. The cellular uptake efficiencies of R8 and R12 were significantly enhanced due to their oligoarginine linkers compared to previous probes with oligoproline linkers. These ratiometric oxygen probes allowed visualization of the O2 gradient produced by placing a thin coverslip onto a HeLa cell monolayer.

Effects of the Methyl Group on the Emission Efficiency of the Red Phosphorescent Iridium(III) Complexes for OLEDs

Novel red phosphorescent iridium(III) complexes, namely (MN-Q)2Ir(tmd), (MN-MQ)2Ir(tmd), (PT-P)2Ir(tmd) and (PT-MP)2Ir(tmd) were synthesized for the red phosphorescent organic lightemitting diodes (phOLEDs). The ligands have sites of both the electron donor and acceptor in a molecule. The main ligands were synthesized by the Suzuki coupling reaction, and comprised an electron donor and an electron acceptor group. Subsequently, the iridium(III) complexes were synthesized by the Nonoyama reaction and their photochemical luminescence properties were investigated by ultraviolet-visible and photoluminescence spectroscopy. The manufactured devices were characterized by current density-voltage-luminance, power efficiency, external quantum efficiency, as well as their electroluminescence spectra. Finally, the effects of the trifluoromethyl group on the emission efficiency of the organic light-emitting diodes were investigated by comparing the energy levels and luminescence efficiency of the three iridium complexes.

Effects of the Trifluoromethyl Group on the Emission Efficiency of Red Phosphorescent Iridium(III) Complexes.

In this work, three novel phosphorescent iridium(III) complexes, namely (PT-TFP)2Ir(tmd), (PT-P)2Ir(tmd), and (MN-TFP)2Ir(tmd), were synthesized. All three complexes were phosphorescent red-emitting diode materials. The main ligands were synthesized by the Suzuki coupling reaction, and comprised an electron donor and an electron acceptor group. Subsequently, the iridium(III) complexes were synthesized by the Nonoyama reaction and their photochemical luminescence properties were investigated by ultraviolet-visible and photoluminescence spectroscopy. The manufactured devices were characterized by current density-voltage-luminance, power efficiency, external quantum efficiency, as well as their electroluminescence spectra. Finally, the effects of the trifluoromethyl group on the emission efficiency of the organic light-emitting diodes were investigated by comparing the energy levels and luminescence efficiency of the three iridium complexes.

Deep Blue Phosphorescent Organic Light-Emitting Diodes with CIEy Value of 0.11 and External Quantum Efficiency up to 22.5.

Organic light-emitting diodes (OLEDs) based on red and green phosphorescent iridium complexes are successfully commercialized in displays and solid-state lighting. However, blue ones still remain a challenge on account of their relatively dissatisfactory Commission International de L'Eclairage (CIE) coordinates and low efficiency. After analyzing the reported blue iridium complexes in the literature, a new deep-blue-emitting iridium complex with improved photoluminescence quantum yield is designed and synthesized. By rational screening host materials showing high triplet energy level in neat film as well as the OLED architecture to balance electron and hole recombination, highly efficient deep-blue-emission OLEDs with a CIE at (0.15, 0.11) and maximum external quantum efficiency (EQE) up to 22.5% are demonstrated. Based on the transition dipole moment vector measurement with a variable-angle spectroscopic ellipsometry method, the ultrahigh EQE is assigned to a preferred horizontal dipole orientation of the iridium complex in doped film, which is beneficial for light extraction from the OLEDs.

Synthesis and photophysical studies of red phosphorescent Ir(III) complexes chelated with a thienopyridyl ligand for white organic light-emitting diodes

ABSTRACTFor efficient white organic light-emitting diodes (OLEDs), it is necessary for luminescence to cover a wide range of visible light area. According to these needs, we synthesized new types of red phosphorescent iridium(III) complexes and compared their luminescent properties with the previously reported iridium complexes. The iridium complexes that we investigated and compared herein have 2-phenylquinoline (pq) as main ligands and 4-(1-Naphtyl)thieno[3,2-c]pyridine (1-NTP), 4-(2-Naphthyl)thieno[3,2-c]pyridine (2-NTP) and 4-(p-biphenyl)thieno[3,2-c]pyridine (BTP) as ancillary ligand, respectively. We characterized the complexes with 1H NMR and mass spectrometer. The photoluminescence (PL) spectra of the resulting iridium complexes, (1-NTP)Ir(pq)2, (2-NTP)Ir(pq)2 and (BTP)Ir(pq)2 exhibited red shift about 15 to 20 nm compared to a well-known red complex, (acac)Ir(pq)2. The bathochromic shift in luminescence seems to be caused by a thienopyridyl derivative in the ancillary ligands. Furthermore, the PL spectra of the complexes prepared in this study exhibited wide range phosphorescence with the full-width at half maximum (FWHM) of ∼100 nm. We also measured their bandgaps with cyclic voltammetry (CV) and studied their relationships with the corresponding UV-Vis spectra.

Study of the characteristics of phosphorescent red organic light emitting diode using new iridium(III) complex with thiophene as dopant material

ABSTRACTNew red phosphorescent iridium(III) complex, (TP-MQ)2Ir(tmd) was synthesized for red emitter of the phosphorescent organic light-emitting diodes (phOLEDs). The ligands have sites of both the electron donor and acceptor in a molecule. The main ligands consisted of electron-donors Thiophene and electron-acceptor 4-methylquinoline were synthesized by Suzuki coupling reaction. The iridium(III) complexes based on main ligands and 2,2,6,6-tetramethyl-3,5-heptanedione(tmd) ancillary ligand were synthesized by Nonoyama reaction. Their luminescence property was investigated by UV-visible spectroscopy and photoluminescence (PL) spectroscopy. The manufactured OLED were characterized by investigation of electroluminescence spectrum, current density-voltage-luminance, power efficiency, external quantum efficiency and life time.

Highly efficient and spectrally stable white organic light-emitting diodes using new red heteroleptic Iridium(III) complexes

Highly efficient red phosphorescent iridium(III) complexes, (MPQ)2Ir(Pppy) and (MPQ)2Ir(TMSppy) based on 4-methyl-2-phenylquinoline (MPQ) as a cyclometalated main ligand and 2-[(1,1′-biphenyl)4-yl]pyridine (Pppy) or 2-[4-(trimethylsilyl)phenyl]pyridine (TMSppy) as a second cyclometalated ligand were synthesized for use in organic light-emitting diodes (OLEDs). The iridium(III) complex with MPQ and acetylacetone (acac) as an ancillary ligand, (MPQ)2Ir(acac), was also synthesized for comparison. The geometrical configuration of the heteroleptic complex (MPQ)2Ir(acac)is N,N-trans, whereas (MPQ)2Ir(Pppy) and (MPQ)2Ir(TMSppy)show all-facial geometries. Among the iridium(III) complexes, red OLEDs using the (MPQ)2Ir(Pppy) exhibited significantly more improved luminance and external quantum efficiency with markedly prevented concentration self-quenching at high doping concentration by introduction of Pppy. Moreover, a high maximum external quantum efficiency (EQEmax) of 28.0% with a high color-rendering index (CRI) of 81 was achieved in the white OLEDs (WOLED) fabricated using the bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) [FIrpic], tris(2-phenylpyridine)iridium(III) [Ir(ppy)3], and (MPQ)2Ir(Pppy), and it is one of the highest values among the reported three primary color component WOLED. Also, the WOLED fabricated using the (MPQ)2Ir(Pppy) showed excellent spectral stability at different voltages.

High-color-rendering-index white polymer light-emitting electrochemical cells based on ionic host-guest systems: Utilization of blend films of blue-fluorescent cationic polyfluorenes and red-phosphorescent cationic iridium complexes

Abstract The authors present high-color-rendering-index (CRI) white polymer light-emitting electrochemical cells (PLECs) based on ionic host-guest systems. PLECs were fabricated with blend films composed of a blue fluorescent cationic π-conjugated polymer, poly(9,9-bis[6′-(N,N,N,-trimethylammonium)hexyl]fluorine-co-alt-1,4-phenylene)bromide (PFN+Br−), used as a host, and a red phosphorescent cationic iridium complex, [Ir(ppy)2(biq)]+(PF6)− (where (ppy)− = 2-phenylpyridinate and biq = 2,2′-biquinoline), used as a guest. By optimizing the composition of PFN+Br− and [Ir(ppy)2(biq)]+(PF6)− in the active layers, white light emission with Commission Internationale de l'Eclairage (CIE) coordinates of (x = 0.28, y = 0.31) and a very high CRI of 95.8 was achieved through mixing of blue and red light at an applied voltage of 4.0 V. The white light emissions were obtained at a low [Ir(ppy)2(biq)]+(PF6)− concentration (PFN+Br−:[Ir(ppy)2(biq)]+(PF6)− = 1:0.01 (mass ratio)), showing that [Ir(ppy)2(biq)]+(PF6)− acts as a suitable energy acceptor. The emission mechanism of the ionic host-guest PLECs can be explained by Forster resonance energy transfer (FRET) and Dexter energy transfer (DET) from the excited PFN+Br− to [Ir(ppy)2(biq)]+(PF6)−. Utilization of ionic host-guest PLECs is a very promising method for realizing white light-emitting devices with very high CRI.

Synthesis and electroluminescent property of highly efficient phosphorescent red dopants based on modulated main ligands

ABSTRACTNovel red phosphorescent iridium(III) complexes, (DPAP-MQ)2Ir(tmd), (DMAP-MQ)2Ir(tmd), (PN-MQ)2Ir(tmd) were synthesized for red emitter of the phosphorescent organic light-emitting diodes (phOLEDs). The ligands have sites of both the electron donor and acceptor in a molecule. The main ligands consisted of electron-donors ((dimethylamino)phenyl, (diphenylamino)phenyl, (dimethylamino)naphthalene) and electron-acceptor methyl quinoline were synthesized by suzuki coupling reaction. The iridium(III) complexes based on main ligands and 2,2,6,6-tetramethyl-3,5-heptanedione(tmd) ancillary ligand were synthesized by Nonoyama reaction. Their luminescence property was investigated by UV-visible spectroscopy and photoluminescence (PL) spectroscopy. The manufactured PHOLEDs were characterized by investigation of current density-voltage-luminance, luminance efficiency, external quantum efficiency, electroluminescence spectrum. These phosphorescent iridium complexes will be promising candidates for highly efficient red emitters.

Synthesis and Electroluminescent Characteristics of Red Phosphorescent Iridium(III) Complexes for Highly Efficient Organic Light-Emitting Diodes

Synthesis and Electroluminescent Characteristics of Red Phosphorescent Iridium(III) Complexes for Highly Efficient Organic Light-Emitting Diodes

English

English

New red phosphorescent iridium(III) complex with 4-tert-Butylphenyl-boronic acid of organic borane

ABSTRACTA new phosphorescent (CQ-BP)2Ir(acac), (CMQ-BP)2Ir(acac), (BQ-BP)2Ir(acac) was synthesized for organic light-emitting diodes (OLEDs). OLEDs using phosphorescent iridium(III) complexes attract enormous attention because they allow highly efficient electro phosphorescence. The donor-acceptor type ligands for the Iridium(III) complexes were synthesized by Suzuki coupling reaction. The ligands through changes in oxidative addition materials (electron-acceptor) and organic borane (electron-donor) to get the red color were to study the appropriate Iridium(III) complexes. Oxidative addition materials were used such as 2-chloro-4-methylquinoline, 1-chloroisoquinoline and 2-bromoquinoline. 4-tert-Butylphenyl-boronic acid was used as organic borane. The dopant was synthesized by Nonoyama reaction. Red dopants were observed with an emission peak at approximately 600 nm. Iridium(III) complexes were measured by nuclear magnetic resonance (NMR), UV-visible spectroscopy and photoluminescence (PL). The phosphorescence emission maxima were dependent on the electron density of donor and acceptor moiety of the ligands.

Synthesis and characterization of red phosphorescent iridium(Ⅲ) complexes based on electron-acceptor modulation of main ligand for high efficiency organic light-emitting diodes

ABSTRACTA new series of red phosphorescent iridium(Ⅲ) complexes, (PT-TFP)2Ir(tmd), (PT-P)2Ir(tmd), and (PT-MP)2Ir(tmd) were synthesized for highly efficient red emitter of the organic light-emitting diodes (OLEDs). The main ligands consisted of electron-donor (phenanthren) and electron-acceptor (trifluoromethyl pyridine, pyridine, and methyl pyridine) were synthesized by Suzuki coupling reaction. The iridium(Ⅲ) complexes based on main ligands and 2,2,6,6-tetramethyl-3,5-heptanedione(tmd) ancillary ligand were synthesized by Nonoyama reaction. Their luminescence properties were investigated by UV-visible spectroscopy and photoluminescence (PL) spectroscopy. The OLEDs devices were manufactured by vacuum deposition and These OLEDs devices were characterized by investigation of current density-voltage-luminance (J-V-L), current efficiency, power efficiency, external quantum efficiency (EQE), EL spectrum. The Ir(Ⅲ) complexes will be used as a solution process dopant for the hybrid OLED devices.