A comparative study of chemical modifiers in the determination of total arsenic in marine food by tungsten coil electrothermal atomic absorption spectrometry

Three platinum group elements (Pd, Ir and Rh) both in solution and in pre-reduced form, and also combined with Mg(NO₃)₂ or ascorbic acid, were assessed as possible chemical modifiers on the atomization of As in digest solutions of seafood matrices (clam and fish tissue) by tungsten coil electrothermal atomic absorption spectrometry (TCA-AAS) and compared without a modifier. Of 28 modifier alternatives in study including single form and binary mixtures, and based on maximum pyrolysis temperature without significant As loss and best As absorbance sensitivity during atomization, three modifiers: Rh (0.5 μg), Ir (1.0 μg) and Rh (0.5 μg) + ascorbic acid (0.5 μg), at optimum amounts were pre-selected and compared. The definitive modifier (rhodium (0.5 μg)) was selected by variance analysis. The mean within-day repeatability was 3% in consecutive measurements (25-300 μg l⁻¹) (three cycles, each of n = 6) and showed good short-term stability of the absorbance measurements. The mean reproducibility was 4% (n = 18 in a 3-day period) and the detection limit (3σ_blank/slope) was 42 pg (n = 16). Quantitation was by standard additions to compensate for matrix effects not corrected by the modifier. Three sample digestion procedures were compared in fish and clam tissue samples: microwave acid digestion alone (A) or combined with the addition of 2% (m/v) K₂S₂O₈ solution followed either by UV photo-oxidation (B) or re-digestion in a thermal block (C). The accuracy was established by determination of As in certified reference material of dogfish muscle (DORM-2). Procedures B and C showed good recoveries (102% (n = 4) and 103% (n = 7), respectively), whereas procedure A was not quantitative (85%). The methodology is simple, fast, reliable, of low cost and was applied to the determination of total As in lyophilized samples of clam and fish collected in the Chilean coast.     

Neutral and cationic cyclometallated Ir(III) complexes of anthra[1,2-d]imidazole-6,11-dione-derived ligands: Syntheses, structures and spectroscopic characterisation

The syntheses of two new ligands and five new heteroleptic cyclometallated Ir(III) complexes are reported. The ligands are based upon a functionalised anthra[1,2-d]imidazole-6,11-dione core giving LH¹⁻³ incorporating a pendant pyridine, quinoline or thiophene unit respectively. Neutrally charged, octahedral complexes [Ir(ppy)₂(L¹⁻³)] are chelated by two cyclometallated phenylpyridine (ppy) ligands and a third, ancillary deprotonated ligand L¹⁻³, whilst cationic analogues could only be isolated for [Ir(ppy)₂(LH¹⁻²)][PF₆]. X-ray crystal structures for [Ir(ppy)₂(L¹)], [Ir(ppy)₂(LH¹)][PF₆] and [Ir(ppy)₂(L²)] showed the complexes adopt a distorted octahedral coordination geometry, with the anthra[1,2-d]imidazole-6,11-dione ligands coordinating in a bidentate fashion. Preliminary DFT calculations revealed that for the complexes of LH¹ and LH² the LUMO is exclusively localized on the ancillary ligand, whereas the nature of the HOMO depends on the protonation state of the ancillary ligand, often being composed of both Ir(III) and phenylpyridine character. UV-vis. and luminescence data showed that the ligands absorb into the visible region ca. 400 nm and emit ca. 560 nm, both of which are attributed to an intra-ligand CT transition within the anthra[1,2-d]imidazole-6,11-dione core. The complexes display absorption bands attributed to overlapping ligand-centred and ¹MLCT-type electronic transitions, whilst only [Ir(ppy)₂(L²)] appeared to possess typical ³MLCT behaviour (λ_em = 616 nm; τ = 96 ns in aerated MeCN). The remaining complexes were generally visibly emissive (λ_em ≈ 560-570 nm; τ < 10 ns in aerated MeCN) with very oxygen-sensitive lifetimes more indicative of ligand-centred processes.     

Some phosphinite complexes of Rh and Ir, their intramolecular reactivity and DFT calculations about their application in biphenyl metathesis

Biphen(OPR₂) (with R: Ph, iPr, Cy) is reacted with [Rh(COE)₂Cl]₂. The corresponding μ-chloro-bridged dimers are received. An X-ray analysis of [Biphen(OPCy₂)RhCl]₂ is included. This compound shows a dynamic behaviour in solution, ascribed to a monomer/dimer equilibrium. The difference of the Biphen ligands to Milsteins PCP pincer-type ligand is shown. A catalytic cycle for biphenyl metathesis containing the coupling of oxidative addition and reductive elimination of the bridging C-C single bond in the biphenyl fragment using Rh^I/III complexes and the concept of chelating assistance was calculated using DFT (B3PW91/LANL2DZ). According to the calculations the activation energy of the oxidative addition is about 30 kcal/mol and for the reductive elimination about 19 kcal/mol. The fac-Rh^III complex is by far the most stable compound, but the formation of it is kinetically strongly disfavoured. Pre-catalysts (COD)M(Ph-O-PR₂) (M: Rh, Ir) were synthesized by pre-coordinating the phosphinite to the metal (X-ray structures of four such compounds included) followed by treatment with 2 equiv. of sec. BuLi (X-ray structures of two such compounds included). In case of Ir this synthesis is complicated by C-H activation (X-ray structure of (COD)Ir(H)(Cl)(2-Br-phenyl-O-(diisopropylphosphinite)) included) and fast oxidative addition of the Ph-C-Halide bond. For (COD)Ir(H)(Cl)(2-phenyl-O-(diisopropylphosphinite)) the C-H activation is reversible and thermodynamic parameters for the ring closure reaction were determined by VT-NMR measurement (ΔH = −21.1 ± 0.5 kJ/mol, ΔS = −62.8 ± 1.7 J/(mol K)). The pre-catalysts were reacted with Biphen(OPR₂) to enter the calculated catalytic cycle. With Rh as center metal this reaction works out cleanly to give new complexes with the three P-atoms coordinated to one Rh center. No hemi-labile character was found for these P-donors even at 105 °C in toluene. If (COD)Rh(2-phenyl-O-(diisopropylphosphinite)) is reacted with 2 equiv. of 2-iodo-phenyl-O-(diisopropylphosphinite) oxidative addition of one C-Iodo bond is observed and the corresponding mer-Rh^III complex is received. Upon treatment with 2 equiv. of sec. BuLi the resulting product is(Biphen(OPiPr₂))Rh^I(2-phenyl-O-(diisopropylphosphinite)) rather than mer-Rh^III(2-phenyl-O-(diisopropylphosphinite))₃. Reaction of [Rh(COD)Cl]₂ with 3 equiv. of 2-bromo-phenyl-O-(diphenylphosphinite) shows a fast scrambling of the chlorine into all possible ortho positions of the phenolate rings in the final Rh^III reaction product.     

Theoretical studies on structures and spectroscopic properties of bis-cyclometalated iridium complexes [Ir(ppy)2X2]

The electronic structures and spectroscopic properties of a series of mixed bis-cyclometalated iridium(III) complexes [Ir(ppy)₂X₂]⁻ (X = CN, 1; X = NCS, 2; X = NCO, 3; ppy = 2-phenylpyridl) were investigated at the B3LYP/LANL2DZ and CIS/LANL2DZ levels. The calculated geometry parameters in the ground state are well consistent with the corresponding experimental values. The HOMO of 1 is dominantly localized on Ir atom and ppy ligand, but the HOMO of 2 and 3 have significant X ligand composition. Under the TD-DFT level with PCM model, the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized geometries in the ground and excited states, respectively. The lowest-lying absorption of 1 at 403 nm is attributed to {[d_x²-y²(Ir)+d_xy(Ir)+π(ppy)]→[π^∗(ppy)]} transition with metal-to-ligand and intraligand charge transfer (MLCT/ILCT) transition characters, whereas those of 2 (449 nm) and 3 (475 nm) are related to {[d_x²-y²(Ir)+d_xy(Ir)+π(ppy)+π(NCS/NCO)]→[π^∗(ppy)]} transition with MLCT/ILCT and ligand-to-ligand charge transfer (LLCT) transition characters. The phosphorescence of 1 at 466 nm can be described as originating from ³{[d_x²-y²(Ir)+d_xy(Ir)+π(ppy)][π^∗(ppy)]} excited state, while those of 2 (487 nm) and 3 (516 nm) originate from ³{[d_x²-y²(Ir)+d_xy(Ir)+π(ppy)+π(NCS/NCO)][π^∗(ppy)]} excited states. The calculated results showed that the transition character of the absorption and emission can be changed by adjusting the π electron-accepting abilities of the X ligands and the phosphorescent color can be tuned by altering the X ligands.     

Synthesis and characterization of cyclometalated iridium(III) complexes containing benzoxazole derivatives and different ancillary ligands

The synthesis, structures, electrochemistry, and photophysics of a series of cyclometalated iridium(III) complexes based on benzoxazole derivatives and different β-diketonate ligands are reported. These complexes have a general formula C^∧N₂Ir(LL′) [where C^∧N is a monoanionic cyclometalating ligand; 2-phenylbenzoxazolato (pbo), 2-(4-chlorophenyl)benzoxazolato (cpbo), 2-phenyl-5-chlorobenzoxazolato (pcbo), 2-(3,5-difluorophenyl)benzoxazole (fpbo), or 2-(2-naphthyl)benzoxazolato (nbo), and LL′ is an ancillary ligand; acetylacetonate (acac), dibenzoylmethanate (dbm), or 1,1,1,5,5,5-hexafluoroacetylacetonate (hfacac)]. The complexes (pcbo)₂Ir(acac) (3), (dfpbo)₂Ir(acac) (4), (cpbo)₂Ir(dbm) (7), (dfpbo)₂Ir(dbm) (8), and (dfpbo)₂Ir(hfacac) (9) have been structurally characterized by X-ray crystallography. All of the complexes show reversible oxidation between 0.45 and 1.07 V, versus Fc/Fc⁺, and have short luminescence lifetime (τ = 0.1-1.3 μs) at room temperature. Except complex 9, the radiative decay rate (k_r) and nonradiative decay rate (k_nr) of the (C^∧N)₂Ir(LL′) complexes have been determined by using the lifetime and quantum efficiency. The k_r ranges between 2.0 × 10³ and 3.0 × 10⁵ s⁻¹ and k_nr spans a narrower range of values (5.0 × 10⁵ to 7.0 × 10⁶ s⁻¹).     

A novel series of iridium complexes with alkenylquinoline ligands: Theoretical study on electronic structure and spectroscopic property

The ground and the lowest-lying triplet excited state geometries, electronic structures, and spectroscopic properties of a novel series of neutral iridium(III) complexes with cyclometalated alkenylquinoline ligands [(C^N)₂Ir(acac)] (acac = acetoylacetonate; C^N = 2-[(E)-2-phenyl-1-ethenyl]pyridine (pep) 1; 2-[(E)-2-phenyl-1-ethenyl]quinoline (peq) 2; 1-[(E)-2-phenyl-1-ethenyl]isoquinoline (peiq) 3; 2-[(E)-1-propenyl]pyridine (pp) 4; 2-[(E)-1-fluoro-1-ethenyl]pyridine (fpp) 5) were investigated by DFT and CIS methods. The highest occupied molecular orbital is composed of d(Ir) and π(C^N) orbital, while the lowest unoccupied molecular orbital is dominantly localized on C^N ligand. Under the TD-DFT with PCM model level, the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground and triplet excited state geometries, respectively. The calculated lowest-lying absorptions at 437 nm (1), 481 nm (2), 487 nm (3), 422 nm (4), and 389 nm (5) are attributed to a {[d_x²-y²(Ir) + d_xz(Ir) + π(C^N)] → [π∗(C^N)]} transition with metal-to-ligand/intra-ligand charge transfer (MLCT/ILCT) characters, and the calculated phosphorescence at 582 nm (1), 607 nm (2), 634 nm (3), 515 nm (4), and 491 nm (5) can be described as originating from the ³{[d_x²-y²(Ir) + d_xz(Ir) + π (C^N)] [π∗(C^N)]} excited state with the ³MLCT/³ILCT characters. The calculated results revealed that the phosphorescent color of these new Ir(III) complexes can be tuned by changing the π-conjugation effect strength of the C^N ligand.     

Determination of selenium in human milk by electrothermal atomic absorption spectrometry and chemical modification

A method was developed for the determination of selenium in human milk using electrothermal atomic absorption spectrometry. The use of chemical modifiers as well as their implications during the pyrolysis step was examined. The chemical modifiers that were studied were Zr, Ir as well as the mixed modifier Zr-Ir. The Ir modifier stabilized selenium at 1000 °C, Zr at 800 °C, while the mixed modifier at 1200 °C. The effect of modifier mass was studied and was found that better results are achieved with addition of 2 μg Zr and 2 μg Ir. The characteristic masses of selenium in the presence of Zr, Ir and the mixed modifier were found to be 73.3, 18.0 and 14.7 pg, respectively, while the corresponding limits of detection were found 2.0, 0.50 and 0.41 μg l⁻¹. Consequently better results were obtained with the mixed modifier. The developed method was applied for the determination of selenium in human milk, which was digested with a HNO₃ + H₂O₂ mixture in a microwave oven. The limit of detection of the method was 1.37 μg l⁻¹, the characteristic mass, m₀, was 48.8 pg and the repeatability was less than 5% as R.S.D.(%). Matrix matched calibration was used. Recoveries were estimated to be 93-105%. The method was applied to breast milk of Greek women (n = 9) and the Se content was found to be in the range 16.7-42.6 μg l⁻¹ with mean value 27.4 ± 5.5 μg l⁻¹.     

Application of heteroleptic iridium complexes with fluorenyl-modified 1-phenylisoquinoline ligand for high-efficiency red polymer light-emitting devices

A series of new heteroleptic iridium complexes bearing fluorenyl-modified 1-phenylisoquinoline as the first ligand and different ancillary ligands has been prepared and characterized. These complexes bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)acetylacetonate(Ir(DMFPQ)₂acac)), bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)(3-(pyridin-2-yl)-1,2,4-triazolate)(Ir(DMFPQ)₂pt) and bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)(2-(2-pyridyl)benzimidazolate)(Ir(DMFPQ)₂pbi) showed red phosphorescent emissions of 615-630 nm in dichloromethane solution. The device fabricated with these complexes doped into a host polyfluorene (PFO) blend with 30% of an electron transport material 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) showed high device efficiencies. Ir(DMFPQ)₂acac exhibited red emission with an external quantum efficiency(η_ext) of 14.3% and luminous efficiency(η_c) of 7.8 cd/A at 1.2 mA/cm² and the maximum brightness reached 10 006 cd/m² (Commission Internationale de I’Eclairage(CIE) chromaticity coordinates: (0.67, 0.32)) at 412 mA/cm². Ir(DMFPQ)₂pt showed a η_ext of 13.0% and η_c of 9.2 cd/A at 17 mA/cm², 1532 cd/m², and the maximum brightness reached 15085 cd/m² (CIE: 0.64, 0.34) at 360 mA/cm².     

Synthesis, characterization and reactivity of tribenzylphosphine rhodium and iridium complexes

New rhodium and iridium complexes, with the formula [MCl(PBz₃)(cod)] [M = Rh (1), Ir (2)] and [M(PBz₃)₂(cod)]PF₆ [M = Rh (3), Ir (4)] (cod = 1,5-cyclooctadiene), stabilized by the tribenzylphosphine ligand (PBz₃) were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The addition of pyridine to a methanol solution of 1or 2, followed by metathetical reaction with NH₄PF₆, gave the corresponding derivatives [M(py)(PBz₃)(cod)]PF₆ [M = Rh (5), Ir (6)]. At room temperature in CHCl₃ solution, 4 converted spontaneously to the ortho-metallated complex [IrH(PBz₃)(cod){η²-P,C-(C₆H₄CH₂)PBz₂}]PF₆ (7) as a mixture of cis/trans isomers via intramolecular C-H activation of a benzylic phenyl ring. The reaction of 3 or 4 with hydrogen in coordinating solvents gave the dihydrido bis(solvento) derivative [M(H)₂(S)₂(PBz₃)₂]PF₆ (M = Rh, Ir; S = acetone, acetonitrile, THF), that transformed into the corresponding dicarbonyls [M(H)₂(CO)₂(PBz₃)₂]PF₆ by treatment with CO. Analogous cis-dihydrido complexes [M(H)₂(THF)₂(py)(PBz₃)₂]PF₆ (M = Rh, Ir) were observed by reaction of the py derivatives 5 and 6 with H₂.     

Comparison of different permanent chemical modifiers for lead determination in Orujo spirits by electrothermal atomic absorption spectrometry

Different analytical methods for the determination of lead in Orujo spirits by electrothermal atomic absorption spectrometry (ETAAS) were developed using permanent modifiers (W, Ir, Ru, W-Ir and W-Ru) thermally deposited on platforms inserted in pyrolitic graphite tubes and Pd-Mg(NO₃)₂ conventional modifier mixture. In all cases, the Pb determination was performed without any sample pretreatment or preconcentration steps. The comparison between the chemical modifiers employed has been made in terms of pyrolysis and atomization temperatures, characteristic masses, detection limits, and atomization and background signal shapes. The limits of detection obtained were 0.375, 0.387, 0.109, 0.251 and 0.267 ng mL⁻¹ for W, Ir, Ru, W-Ir and W-Ru, respectively and 0.710 ng mL⁻¹ for Pd-Mg(NO₃)₂. The characteristic masses were 14.1, 11.2, 5.6, 8.3 and 9.3 pg for W, Ir, Ru, W-Ir and W-Ru, respectively and 22.2 pg for Pd-Mg(NO₃)₂. For all the developed procedures using the different modification systems, the relative standard deviations (<10%) and the analytical recoveries (95-103%) were acceptable. The more suitable methods for Pb determination in distillate spirits were those using permanent modifiers in contrast with classical Pd-Mg(NO₃)₂. The best analytical performance was achieved for W, Ir and W-Ir methods, which were applied to lead determination in Orujo spirit samples from Galicia (NW Spain). The Pb concentrations found in the analyzed samples were comprised in the range (<LOD to 1.5 μg mL⁻¹).     

Synthesis, characterization, photophysical and electrochemical properties of new phosphorescent dopants for OLEDs

New heteroleptic iridium(III) complexes of 2-(p-substituted-phenyl)-pyridine were synthesized and characterized. These complexes have two cyclometalated ligands (C^∧N) and a bidentate ancillary ligand (LX), that is, (C^∧N)₂Ir(LX). LX was either acetylacetonate or 5-nitro-8-hydroxy quinolate. Substitution on the p-phenyl of C^∧N ligands was used to alter the electronic properties of these complexes. The (C^∧N)₂Ir(acac) complexes show phosphorescence with good quantum yields and microsecond lifetimes and also show photoluminescence over a wide visible range (λ_max = 503-620 nm). The HOMO level and triplet energy level of these complexes were also determined. These data indicate their potential use as emitting materials for organic light emitting diodes, OLEDs.     

Carbazole-oxadiazole containing polyurethanes as phosphorescent host for organic light emitting diodes

New types of polyurethanes (PUs) were prepared from condensation polymerization of isophorone diisocyanate (IPDI) with various combination of 9-butyl-3,6-bis(4-hydroxyphenyl)carbazole (Cz) and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), and end-capped with 4-tert-butyl phenol. The Cz-OXD PUs can also be used as host for phosphorescent dye. Red EL emission was obtained when Ir(btp)₂(acac) or Ir(2-phq)₂(acac) was used as the phosphorescent dyes in Cz-OXD (3:1) PU. Maximum brightness of 394 cd/m² and EL efficiency of 1 cd/A were achieved for the Ir(2-phq)₂(acac) base device. In addition, white light PLED was demonstrated when co-dopant of Ir(btp)₂(acac) and Firpic were used.     

Color tuning of iridium complexes for organic light-emitting diodes: The electronegative effect and π-conjugation effect

Novel red phosphorescent emitter bis(4-phenylquinazolinato-N,C^2′) iridium(acetylacetonate) [(pqz)₂Ir(acac)], bis(1-(1′-naphthyl)-5-methylisoquinolinato-N,C^2′)iridium(acetylacetonate) [(1-mniq)₂Ir(acac)] and bis(1-(2′-naphthyl)-5-methylisoquinolinato-N,C^2′)iridium(acetylacetonate) [(2-mniq)₂Ir(acac)] have been synthesized and fully characterized. The electronegative effect of (pqz)₂Ir(acac) ligand shows almost the same influence as the extended π-conjugation effect of (2-mniq)₂Ir(acac). Density functional theory (DFT) was applied to calculate the Kohn-Sham orbitals of HOMOs and LUMOs in the iridium complexes to illustrate the N(1) electronegative atom effect. Finally, lowest triplet state (T₁) energies calculated by time-dependent DFT (TDDFT) were compared with the experimental electroluminescent data. The calculated data for the iridium complexes agreed fairly well with experimental data. Electroluminescent devices with a configuration of ITO/NPB/CBP:dopant/BCP/AlQ₃/LiF/Al were fabricated. The device using (pqz)₂Ir(acac) as a dopant showed deep-red emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates x = 0.70, y = 0.30.     

Heterobimetallic complexes as oxygen donor bidentate ligands: synthesis of early-late trinuclear complexes

The early-late heterometallic complexes [TiCp^∗((OCH₂)₂Py)(μ-O)M(COD)] (M = Rh, Ir) behave as four-electron donor ligands yielding the polynuclear cationic complexes [TiCp^∗(OCH₂)₂ Py(μ-O){M(COD)}₂]OTf (M = Rh (1), Ir (2)). The molecular structure of complex 1 has been established through an X-ray diffraction study.     

Theoretical design of phosphorescence parameters for organic electro-luminescence devices based on iridium complexes

Time-dependent density functional theory with quadratic response methodology is used in order to calculate and compare spin–orbit coupling effects and the main mechanism of phosphorescence of the neutral Ir(ppy)₃ and cationic [Ir(bpy)₃]³⁺ tris-iridium compounds, [Ir(ppy)₂(bpy)]⁺ and [Ir(2-phenylpyridine)₂(4,4′-tert-butyl-2,2′-bipyridine]⁺ complexes, including also the recently synthesised [Ir(2-phenylpyridine)₂(4,4′-dimethylamino-2,2′-bipyridine]⁺ and [Ir(2,4-difluorophenylpyridine)₂(4,4′-dimethylamino-2,2′-bipyridine]⁺ dyes, where ppy = 2-phenylpyridine and bpy = 2,2′-bipyridine ligands. Comparison with the symmetric, lighter and more studied [Ru(bpy)₃]²⁺ and [Rh(bpy)₃]³⁺ complexes is also presented. Variations in phosphorescence lifetimes for Ir(ppy)₃ and [Ir(bpy)₃]³⁺ dyes as well as for the mixed cationic complexes are well reproduced by the quadratic response method. All the ortho-metalated iridium compounds exhibit strong phosphorescence, which is used in organic light-emitting diodes (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. The results from the first principle theoretical analysis of phosphorescence have helped to clarify the connections between the main features of electronic structure and the photo-physical properties of the studied heavy organometallic OLED materials.     

Sano-Tachiya-Noolandi-Hong versus Onsager modelling of charge photogeneration in organic solids

We have studied the electric field dependence of charge photogeneration efficiency in organic solids for various radial distribution functions (Dirac delta, Gaussian, exponential) of initial e-h pairs in the framework of Sano-Tachiya-Noolandi-Hong (STNH) theory assuming that the final recombination (capture reaction) proceeds on a sphere of finite radius (a) with a finite velocity (κ). We compare the STNH results with the conventional Onsager theory assuming a = 0. We show that charge photogeneration is more enhanced, especially in low-electric field range, for broader initial pair distributions and for smaller final recombination velocities. We compare theoretical results with experimental data taken from electromodulation of photoluminescence (EML) for two archetypical organic photoconductors, Alq₃ and Ir(ppy)₃, commonly used as emitters in organic LEDs. From analysis of our results we infer the lower limit of final recombination velocity, κ = 0.2-2 cm/s, in vacuum evaporated films of Alq₃ and Ir(ppy)₃ which compares favorably with an evaluation of this quantity in amorphous solids.     

Synthesis, opto-physics, and electroluminescence of cyclometalated iridium (III) complex with alkyltrifluorene picolinic acid

To improve the opto-physics, electroluminescence, and dispersibility of iridium (III) complexes in polymer light-emitting devices, we synthesized and characterized two red-emitting heteroleptic cyclometalated iridium (III) complexes of (Piq)₂Ir(Tfl-pic) and (Piq)₂Ir(Brfl-pic), in which Piq is 1-phenylisoquinoline, Tfl-pic and Brfl-pic are alkyltrifluorene- and dibromoalkylfluorene-containing picolinic acid derivatives bridged with alkoxy chain, respectively. Compared to (Piq)₂Ir(pic) and (Piq)₂Ir(Brfl-pic), (Piq)₂Ir(Tfl-pic) exhibited higher thermal stability, better dispersibility and excellent quantum efficiency. High-efficiency red emission with a maximum current efficiency of 6.28 cdA⁻¹ and a maximum EL peak at 608 nm was obtained in the (Piq)₂Ir(Tfl-pic)-doped devices using a blend of poly(9,9-dioctylfluorene) and 2-(4-biphenyl)-5-(4-tert -butylphenyl)-1,3,4-oxadiazole as a host matrix.     

Insertion of nitrene and chalcogenolate groups into the Ir-C σ bond in a cyclometalated iridium(III) complex

Treatment of [Cp∗Ir(ppy)Cl] (Cp∗ = η⁵-C₅Me₅, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTf⁻ = triflate) in MeOH and MeCN gave the solvento complexes [Cp∗Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN (2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs (Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion of the NTs group into the Ir-C(ppy) bond and formation of [Cp∗Ir(η²-ppy-NTs)(MeCN)][OTf] (3). Treatment of 1 with R₂E₂ afforded [Cp∗Ir(ppy)(η¹-R₂E₂)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5 with Ag(OTf) resulted in cleavage of the E-E bond and insertion of an ER group into the Ir-C(ppy) bond. The crystal structures of complexes 2-6 and [Cp∗Ir(η²-ppy-S-p-tol)(H₂O)][OTf]₂ have been determined.     

Synthesis,characterization and antimalarial activity of new iridium–chloroquine complexes

Chloroquine base (CQ) reacts with [Ir(COD)Cl]₂ and IrCl₃ · 3H₂O to yield of Ir(CQ)Cl(COD) (1) and Ir₂Cl₆(CQ) · 3H₂O (2), respectively. Reaction of [Ir(COD)Cl]₂ with CQ in the presence of NH₄PF₆ leaded to [Ir(CQ)(Solv)₂]PF₆ (3). The three new iridium–CQ complexes were characterized by a combination of elemental analysis, IR and NMR spectroscopies and evaluated in vitro against Plasmodium beghei. Comparison of the IC₅₀ values obtained with the experimental compounds with that determined for chloroquine diphosphate indicated a higher activity for complex 2, while complexes 1 and 3 showed a similar and lower activity, respectively.     

Direct functionalization of the cyclometalated 2-(2′-pyridyl)phenyl ligand bound to iridium(III)

Treatment of [Ir(ppy)₂(μ-Cl)]₂ and [Ir(ppy)₂(dtbpy)][OTf] (ppy = 2-(2′-pyridyl)phenyl; dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridine; OTf = triflate) with pyridinium tribromide in the presence of Fe powder led to isolation of [Ir(4-Br-ppy)(μ-Br)]₂ (1) and [Ir(4-Br-ppy)₂(dtbpy)][OTf] (2), respectively. Pd-catalyzed cross-coupling of 2 with RB(OH)₂ afforded [Ir(4-R-ppy)₂(dtbpy)][OTf] (R = 4′-FC₆H₄ (3)), 4′-PhC₆H₄ (4), 2′-thienyl (5), 4′-C₆H₄CH₂OH (6). Treatment of 4 with B₂(pin)₂ (pin = pinacolate) afforded [Ir{4-(pin)B-ppy}₂(dtbpy)][OTf] (7). The alkynyl complexes [Ir(4-PhCC-ppy)₂(dtbpy)][OTf] (8) and [Ir{4-Me₂(OH)CC-ppy}(4-Br-ppy)(dtbpy)][OTf] (9) were prepared by cross-coupling of 2 with PhCCSnMe₃ and Me₂C(OH)CCH, respectively. Ethynylation of [Ir(fppy)₂(dtbpy)][OTf] (fppy = 5-formyl-2-(2′-pyridyl)phenyl) with Ohira’s reagent MeCOC(N₂)P(O)(OEt)₂ afforded [Ir{5-HCC-ppy}₂(dtbpy)][OTf] (10). The solid-state structures of 2, 5, 7, and 10 have been determined.