Novel nanostructured materials to develop oxygen-sensitive films for optical sensors

Novel nanostructured materials, such as aluminum oxide (AlOOH), silicon oxide (SiO₂) or zirconium oxide (ZrO₂) embedded into PVA, were investigated as potential matrices to incorporate organometallic compounds (OMCs) for the development of optical oxygen-sensitive sensors which make use of the principle of luminescence quenching.In order to assess the benefits and drawbacks of the nanoporous material, the luminescence quantum yield and the Stern-Volmer constants were investigated and compared with the values shown for the same OMCs solubilized in polymer films (polystyrene). Referred to polymer films, the incorporation of the dyes into nanoporous membranes increased the Stern-Volmer constant by more than a factor of 100. Their response time was less than 1 s and the optode membranes were stable at room temperature for at least 9 months. Sterilization by autoclavation and gamma irradiation resulted in a marginal loss in activity. The photostability and sterilizability of the oxygen-sensitive membranes and the performance of the optodes with respect to of different types of metal oxides are discussed in the paper, as well as the influence of the total pore volume (TPV), the pore diameter (PD), the transparency of the film and the geometry of the pores. The OMCs used in this work were: ETH^T-3003 (tris(4,7-bis(4-octylphenyl)-1,10-phenanthroline) ruthenium(II)), N-926 (bis(2-phenylpyridinyl)-N⁴,N⁴,N⁴′,N⁴′-tetramethyl-(4,4′-diamine-2,2′-bipyridine) iridium(III) chlorate), N-833 (tetrabutylammonium bis(isothiocyanate) bis(2-phenylpyridinyl)-iridium(III)) and N-837 (tetrabutylammonium bis(cyanate) bis(2-phenylpyridinyl)-iridium(III)).     

Highly efficient phosphorescent iridium (III) diazine complexes for OLEDs: Different photophysical property between iridium (III) pyrazine complex and iridium (III) pyrimidine complex

The synthesis and luminescence of four new iridium (III) diazine complexes (1-4) were investigated. HOMO and LUMO energy levels of the complexes were estimated according to the electrochemical performance and the UV-Vis absorption spectra, showing the pyrimidine complexes have a larger increase for the LUMO than the HOMO orbital in comparison with the pyrazine complexes. Several high-efficiency yellow and green OLEDs based on phosphorescent iridium (III) diazine complexes were obtained. The devices emitting yellow light based on 1 with turn-on voltage of 4.1 V exhibited an external quantum efficiency of 13.2% (power efficiency 20.3 lm/W), a maximum current efficiency of 37.3 cd/A. The electroluminescent performance for the green iridium pyrimidine complex of 3 is comparable to that of the iridium pyridine complex (PPY)₂Ir(acac) (PPY = 2-phenylpyridine), which is among the best reported.     

Efficient green-blue-light-emitting cationic iridium complex for light-emitting electrochemical cells

A highly luminescent novel cationic iridium complex [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 was synthesized and characterized using NMR, UV-visible absorption, and emission spectroscopy and electrochemical methods. This complex displays intense photoluminescence maxima in the green-blue region of the visible spectrum and exhibits unprecedented phosphorescence quantum yields, 80 +/- 10% with an excited-state lifetime of 2.2 mus in a dichloromethane solution at 298 K. Single-layer light-emitting electrochemical cells with the charged complex as conducting and electroluminescent material sandwiched between indium-tin oxide and Ag electrodes were fabricated, which emit green-blue light with an onset voltage as low as 2.5 V. Density functional theory calculations were performed to provide insight into the electronic structure of the [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 complex, comparing these results with those obtained for [iridium bis(2-phenylpyridine)(4,4'-tert-butyl-2,2'-bipyridine)]PF6.     

Novel phosphorescent neutral iridium(III) complex with the steric hindrance for highly efficient red organic light-emitting diodes

A novel and highly efficient thiophenquinolone-based red iridium(III) complex bearing a bulky fluorophenyl moiety is designed and synthesized. The complex shows intensive red phosphorescence (596 nm with shoulder at 642 nm), high photoluminescence efficiency (0.62) and broad full width at half maximum (81 nm). The bulky fluorophenyl moiety introduced into the complex could improve the efficiency of electroluminescence with the maximum current efficiency, power efficiency and the external quantum efficiency up to 29.0 cd/A, 30.4 lm/W and 17.6% due to the effective steric hindrance in solid states.     

Highly phosphorescent perfect green emitting iridium(iii) complex for application in OLEDs

A novel iridium complex, [bis-(2-phenylpyridine)(2-carboxy-4-dimethylaminopyridine)iridium(iii)] (N984), was synthesized and characterized using spectroscopic and electrochemical methods; a solution processable OLED device incorporating the N984 complex displays electroluminescence spectra with a narrow bandwidth of 70 nm at half of its intensity, with colour coordinates of x = 0.322; y = 0.529 that are very close to those suggested by the PAL standard for a green emitter.     

Synthesis and characterization of phosphorescent cyclometalated iridium complexes

The preparation, photophysics, and solid state structures of octahedral organometallic Ir complexes with several different cyclometalated ligands are reported. IrCl3.nH2O cleanly cyclometalates a number of different compounds (i.e., 2-phenylpyridine, 2-(p-tolyl)pyridine, benzoquinoline, 2-phenylbenzothiazole, 2-(1-naphthyl)benzothiazole, and 2-phenylquinoline), forming the corresponding chloride-bridged dimers, CwedgeN2Ir(mu-Cl)2IrCwedgeN2 (CwedgeNis a cyclometalated ligand) in good yield. These chloride-bridged dimers react with acetyl acetone (acacH) and other bidentate, monoanionic ligands such as picolinic acid (picH) and N-methylsalicylimine (salH), to give monomeric CwedgeN2Ir(LX) complexes (LX = acac, pic, sal). The emission spectra of these complexes are largely governed by the nature of the cyclometalating ligand, leading to lambda(max) values from 510 to 606 nm for the complexes reported here. The strong spin-orbit coupling of iridium mixes the formally forbidden 3MLCT and 3pi-pi* transitions with the allowed 1MLCT, leading to a strong phosphorescence with good quantum efficiencies (0.1-0.4) and room temperature lifetimes in the microsecond regime. The emission spectra of the CwedgeN2Ir(LX) complexes are surprisingly similar to the fac-IrCwedgeN3 complex of the same ligand, even though the structures of the two complexes are markedly different. The crystal structures of two of the CwedgeN2Ir(acac) complexes (i.e., CwedgeN = ppy and tpy) have been determined. Both complexes show cis-C,C', trans-N,N' disposition of the two cyclometalated ligands, similar to the structures reported for other complexes with a "CwedgeN2Ir" fragment. NMR data (1H and 13C) support a similar structure for all of the CwedgeN2Ir(LX) complexes. Close intermolecular contacts in both (ppy)2Ir(acac) and (tpy)2Ir(acac) lead to significantly red shifted emission spectra for crystalline samples of the ppy and tpy complexes relative to their solution spectra.     

A cationic iridium(III) complex showing aggregation-induced phosphorescent emission (AIPE) in the solid state: synthesis, characterization and properties

We report the synthesis and characterization of two cationic iridium(III) complexes with dendritic carbazole ligands as ancillary ligands, namely, [Ir(ppy)(2)L3]PF(6) (1) and [Ir(ppy)(2)L4]PF(6) (2), where L3 and L4 represent 3,8-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,10-phenanthroline and 3,8-bis(3',6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3,9'-bi(9H-carbazol)-9-yl)-1,10-phenanthroline, respectively. Their photophysical properties have been investigated and compared. The results have shown that complex 2 is aggregation-induced phosphorescent emission (AIPE) active and exhibits the highest photoluminescent quantum yield (PLQY) of 16.2% in neat film among the reported cationic Ir(III) complexes with AIPE activity. In addition, it also enjoys redox reversibility, good film-forming ability, excellent thermal stability as well as off/on luminescence switching properties, revealing its potential application as a candidate for light-emitting electrochemical cells and organic vapor sensing. To explore applications in biology, 2 was used to image cells.     

An iridium(III) complex of oximated 2,2'-bipyridine as a sensitive phosphorescent sensor for hypochlorite

The designed synthesis of a sensitive phosphorescent chemosensor [Ir(ppy)(2)(L1)](PF(6)) (1) (Hppy = 2-phenylpyridine, L1 = 4'-methyl-2,2'-bipyridyl-4-carbaldehyde oxime) was carried out for selective detection of hypochlorite (ClO(-)). Complex 1 is weakly emissive in solution at ambient temperature due likely to rapid isomerization of C=N-OH as an effective non-radiative decay process. When 1 reacts with ClO(-), however, the emission is remarkably enhanced, in which the oxime in L1 is converted to a carboxylic acid in L2 (4'-methyl-2,2'-bipyridine-4-carboxylic acid). The produced complex [Ir(ppy)(2)(L2)](PF(6)) (2) exhibits bright orange-yellow luminescence originating from [5d(Ir) → π*(bpy)] (3)MLCT and [π(ppy) → π*(bpy)] (3)LLCT triplet excited states as suggested from the DFT computational studies. The selective and competitive experiments reveal that complex 1 shows high sensing selectivity and sensitivity for ClO(-) over other reactive oxygen species (ROS) and metal ions.     

Synthesis of a highly phosphorescent emitting iridium(III) complex and its application in OLEDs

A rigid ligand benzo[de]benzo[4,5]imidazo[2,1-α]isoquinolin-7-one (biio) was designed and conveniently synthesized, and the corresponding bis-cyclometalated iridium complex (biio)₂Ir(acac) (acac = acetylacetone) was prepared. The light emitting and electrochemical properties of this complex were studied. The complex has the characters of simply synthetic procedure and strong phosphorescence. The electroluminescent device using this complex as dopant was fabricated. The device had the structure of ITO/NPB (40 nm)/Ir complex:CBP (7%, 30 nm)/BCP (15 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (100 nm). The maximum emission of the device was at 496 nm. The maximum brightness of the device can reach 79640 cd m⁻² with an external quantum efficiency of 12.1% and a maximum current efficiency of 31.7 cd A⁻¹.     

Multisignaling detection of Hg2+ based on a phosphorescent iridium(III) complex

A multisignaling chemosensor for Hg(2+) based on the iridium(III) complex Ir(thq)(2)(acac) was realized through UV-Vis absorption, phosphorescent emission and electrochemical measurements. Upon addition of Hg(2+), an obvious blue-shift in absorption spectra and a strong decrease of emission intensity were measured for Ir(thq)(2)(acac), which could be observed by the naked eye. Hg(2+) is coordinated to Ir(thq)(2)(acac), forming a 1 : 1 complex. Because Hg(2+) is a thiophilic metal ion, the interaction between Hg(2+) and the sulfur atom of cyclometalated ligands is responsible for the significant variations in optical and electrochemical signals.     

Highly selective phosphorescent chemosensor for fluoride based on an iridium(III) complex containing arylborane units

A new phosphorescent iridium(III) complex [Ir(Bpq)2(bpy)](+)PF6(-) based on cyclometalated ligands (Bpq) containing a dimesitylboryl group was synthesized and characterized by photophysical and electrochemical studies. The excited-state properties of Bpq and [Ir(Bpq)2(bpy)](+)PF6(-) were investigated using molecular orbital calculations. Importantly, both Bpq and [Ir(Bpq)2(bpy)](+)PF6(-) could be used as highly selective chemosensors for a fluoride anion (F(-)) detected by the naked eye, owing to the interaction of the dimesitylboryl group (BMes2) with F(-). For the Bpq ligand, a red shift of the emission spectrum was observed upon the addition of F(-), which could be attributed to an excited-state switch from a pi-pi* transition to a charge-transfer transition upon complexation with F(-). The addition of F(-) to a solution of [Ir(Bpq)2(bpy)](+)PF6(-) induced a change in the solution color from yellow to orange-red and phosphorescent quenching, indicating that [Ir(Bpq)2(bpy)](+)PF6(-) could act as an excellent ON-OFF-type phosphorescent chemosensor for F(-).     

新型铱配合物化学发光探针测定亚硫酸盐的研究

研究发现酸性条件下,亚硫酸根对自制的新型环金属铱配合物[ (dpci)2Ir(pca)])(dpci=3,4-二苯基邻二氮杂萘,pca=吡啶-2-羧酸)-硫酸铈体系的化学发光有显著的增强作用,据此建立了检测亚硫酸根的新方法.在最佳条件下,亚硫酸根浓度与化学发光强度在5.0×10-7 ～3.0×10-4 mol/L范围内...     

A yellow-emitting iridium complex for use in phosphorescent multiple-emissive-layer white organic light-emitting diodes with high color quality and efficiency

A cyclometalated iridium(III) complex containing 2-(9,9-diethylfluoren-2-yl)pyridine [Ir(Flpy)₃] was prepared and used in the fabrication of both yellow and white organic light-emitting diodes (OLEDs). A hole-blocking material has been used as a hole barrier layer in-between different emission layers, helping the formation of the hole limitation region. With the proper position of a hole barrier layer and the construction of a four-emission-layer structure involving the use of [Ir(Flpy)₃], the resulting WOLED shows sound device performance as well as very stable color even at high luminances. Such WOLEDs have been demonstrated to reveal superior white light color stability/efficiency trade-off optimization. The Commission Internationale de L’Eclairage (CIE) coordinate differences Δx and Δy are confined to ±0.015 when the luminance increases from 13 to 14806 cd/m². The color rendering index (CRI) of the device is also very good, which varies only from 86 to 87 by changing from the normal direction to 80° off-normal at 12 V. The peak electrophosphorescence efficiency can reach as high as 24.6 cd/A at 168 cd/m²and it can still be kept at 17.2 cd/A at 10834 cd/m². Such outstanding performance renders this all-phosphor WOLED very attractive as a white light source for illumination applications, which typically demand high efficiency, high CRI, and stable color in high brightness work conditions.     

A promising phosphorescent iridium complex with fluorine substituents: synthesis, crystal structure, photo- and electro-luminescence performance

In this paper, we report a phosphorescent Ir(III) emitter of Ir(acac-F6)(F-BT)₂, where acac-F6 = 1,1,1,5,5,5-hexafluoropentane-2,4-dione and F-BT = 2-(2-fluorophenyl)benzo[d]thiazole, including its crystal structure, electronic nature, photophysical characteristics, thermal and electrochemical properties. Data suggest that Ir(acac-F6)(F-BT)₂ is a promising emitter with high quantum yield of 0.19 and good thermal stability, along with its proper energy levels for charge carrier transportation. Electroluminescence (EL) devices using Ir(acac-F6)(F-BT)₂ as emitter are also fabricated, and their electroluminescence performances are investigated in detail. The optimal EL device shows a maximum luminance of 27,000 cd/cm² and a peak current efficiency of 8.7 cd/A.     

Solution-processable high-efficiency bis(trifluoromethyl)phenyl functionalized phosphorescent neutral iridium(III) complex for greenish yellow electroluminescence

A novel and highly efficient bis(trifluoromethyl)phenyl functionalized iridium(III) complex is designed and synthesized. The complex shows intensive greenish yellow phosphorescence (525?nm with 563?nm as shoulder), high photoluminescence efficiency (0.90) and moderate full width at half maximum (72?nm). The bulky bis(trifluoromethyl)phenyl moiety introduced into the complex provides the excellent solubility and effective steric hindrance for solution-processed organic light-emitting diodes. The maximum power efficiency and current efficiency of electroluminescence are 4.13?lm/W and 9.54?cd/A, respectively.     

Synthesis and optical properties of white phosphorescent carbazole - iridium copolymers

A series of novel carbazole-iridium copolymers have been designed and synthesized by the combination of blue-emitting acrylate carbazole M1 with hole transporting property and yellow-emitting cyclometalated iridium complex M2 containing 2-phenylpyridine as main ligand and acrylic acid as auxiliary ligand. The results showed that the blue carbazole host resulted in an efficient energy transfer to the yellow iridium complex guest, and when the feed molar ratio of M1 to M2 was 99:1, the emission spectrum of the copolymer presented a broad peak emission which can cover the whole visible range from 400 to 700 nm to obtain a nearly white copolymer material with the CIE coordinates of (0.30, 0.31), as a consequence of polymerized units luminescence, host-guest energy transfer and conjugation degree. Nevertheless, the host-guest energy transfer resulted in green emission about 524 nm of copolymer as the proportion of iridium complex monomer increased. The fluorescence quantum yields of the copolymers were significantly improved compared to the iridium complex monomer.     

Cationic iridium complex is a new and efficient Lewis acid catalyst for aldol and Mannich reactions

A cationic iridium complex [Ir(cod)₂]SbF₆ was found to be a new and efficient Lewis acid catalyst for Mukaiyama aldol and Mannich reactions. Aldehydes react smoothly with silyl enol ethers to give β-siloxy ketones in the presence of 0.5 mol % of [Ir(cod)₂]SbF₆. The reaction of N-alkyl arylaldimines with ketene silyl acetals in the presence of 5 mol % [Ir(cod)₂]SbF₆/P(OPh)₃ gave β-amino esters. After Mannich reaction was complete, stirring of the reaction mixture for 24 h led to cyclization to give β-lactam. The reaction of N-aryl benzaldimine with silyl enol ether derived from acetophenone gave a tetrahydroquinoline derivative as a single diastereomer.     

Polyvinylpolypyrrolidone-bromine complex: Mild and efficient polymeric reagent for bromination of activated aromatic compounds

Mild and efficient method for bromination of electron-rich aromatic compounds is described using polyvinylpolypyrrolidone-bromine complex（PVPP-Br₂）.The reaction proceeded smoothly with phenols and N,N-alkylated amines to afford the corresponding monobrominated product in good yields at ambient temperature.     

Engineering biodegradable polymeric network for the efficient removal of organo‐amphiphilic toxicants

Motivated with the continued demand for developing quality material showing better response for the efficient removal of organo‐amphiphilic toxicants, we have demonstrated the growth of three‐dimensional polymer organic framework—a covalent crosslinked polymer C2B derived via photon triggered thiol‐alkene click reaction. Instrumentation techniques such as nuclear magnetic resonance, thermogravimetric analysis, and fourier transform infrared spectroscopy were used for the characterization. FESEM and Cryo‐SEM analysis were done to analyze the morphology of the resin. The adsorption and release experiments were done with ultraviolet‐visible spectroscopic technique. The polymer C2B derived from polyolefin and tetrathiol via thiol‐alkene photoclick reaction showed efficiency toward adsorption of organo‐amphiphilic contaminants such as dioxane, dimethylformamide, fluorescein, and rhodamine B (RH). Even the material selectively showed the efficient release of toxicant—RH. Moreover, it can be reused over cycles. This makes the polymer C2B as potential candidate to be commercially viable for textile industries.