Heteroleptic Ir(III) complexes containing both azolate chromophoric chelate and diphenylphosphinoaryl cyclometalates; reactivities, electronic properties and applications

The synthesis of a new family of octahedral Ir(III) complexes with dual cyclometalating phosphine chelates, namely: 1-(diphenylphosphino)naphthalene (dpnaH) and isoquinoline (dppiH), is reported. Two series of intermediate complexes, [Ir(dpna)(tht)(2)Cl(2)] (1), [Ir(dpna)(2)(OAc)] (2), [Ir(dppiH)(dppi)Cl(2)] (3) and [Ir(dppi)(2)(OAc)] (4), which can be classified by the coexistence of either a pair of cis-chlorides or a single acetate chelate, were obtained from treatment of phosphine with [IrCl(3)(tht)(3)] (tht = tetrahydrothiophene). The in situ generated acetate complexes 2 and 4 could react with azolate chelates, namely: 5-(2-pyridyl)-3-trifluoromethyl pyrazole (fppzH) and 5-(1-isoquinolyl)-3-tert-butyl-1,2,4-triazole (iqbtzH), to afford a new series of luminescent complexes [Ir(dpna)(2)(fppz)] (5a and 5b), [Ir(dpna)(2)(iqbtz)] (6a and 6b), [Ir(dppi)(2)(fppz)] (7a) and [Ir(dppi)(2)(iqbtz)] (8a). The phosphorescence lifetime (τ(obs)) fell in the range of a few tens of μs, showing possession of excessive ligand-centered ππ* mixed in part with MLCT character. A density functional theory (DFT) study was also conducted in order to shed light on the origin of the transitions in the absorption and emission spectra and to predict emission energies for these complexes. Organic light emitting diodes (OLEDs) displaying bright orange emission and with maximum η(ext) up to 17.1% were fabricated employing complexes 6a and 8a as the phosphorescent dopants.     

Theoretical study on the influence of ancillary and cyclometalated ligands on the electronic structures and optoelectronic properties of heteroleptic iridium(III) complexes

We report a theoretical analysis of a series of heteroleptic iridium(III) complexes (dox)(2)Ir(acac) [dox = 2,5-diphenyl-1,3,4-oxadiazolato-N,C(2), acac = acetylacetonate] (1a), (fox)(2)Ir(acac) [fox = 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazolato-N,C(2)] (1b), (fox)(2)Ir(Et(2)dtc) [Et(2)dtc = N,N'-diethyldithiocarbamate] (2), (fox)(2)Ir(Et(2)dtp) [Et(2)dtp = O,O'-diethyldithiophosphate] (3), (pypz)(2)Ir(acac) [pypz = 3,5-di(2-pyridyl)pyrazole] (4a), (O-pypz)(2)Ir(acac) (4b), (S-pypz)(2)Ir(acac) (4c) and (bptz)(2)Ir(acac) [bptz = 3-tert-butyl-5-(2-pyridyl)triazole] (5) by using the density functional theory (DFT) method to investigate their electronic structures and photophysical properties and obtain further insights into the phosphorescent efficiency mechanism. Meanwhile, we also investigate the influence of ancillary and cyclometalated ligands on the properties of the above complexes. The results reveal that the nature of the ancillary ligands can influence the electron density distributions of frontier molecular orbitals and their energies, resulting in change in transition character and emission color, while the different cyclometalated ligands have a large impact on the charge transfer performances of the studied complexes. The calculated absorption and luminescence properties of the four complexes 1a, 1b, 2 and 3 are compared with the available experimental data and a good agreement is obtained. Further, the assumed complexes 4a and 4b possess better charge transfer abilities and more balanced charge transfer rates, and they are potential candidates as blue-emitting materials.     

Iridium luminophore complexes for unimolecular oxygen sensors

In this study, a series of novel luminescent cyclometalated Ir(III) complexes has been synthesized and evaluated for use in unimolecular oxygen-sensing materials. The complexes Ir(C6)(2)(vacac), 1, Ir(ppy)(2)(vacac), 2, fac-Ir(ppy)(2)(vppy), 3, and mer-Ir(ppy)(2)(vppy), 4, where C6 = Coumarin 6, vacac = allylacetoacetate, ppy = 2-phenylpyridine, and vppy = 2-(4-vinylphenyl)pyridine, all have pendent vinyl or allyl groups for polymer attachment via the hydrosilation reaction. These luminophore complexes were characterized by NMR, absorption, and emission spectroscopy, luminescence lifetime and quantum yield measurements, elemental analysis, and cyclic voltammetry. Complex 1 was structurally characterized using X-ray crystallography, and a series of 1-D ((1)H, (13)C) and 2-D ((1)H-(1)H, (1)H-(13)C) NMR experiments were used to resolve the solution structure of 4. Complexes 1 and 3 displayed the longest luminescence lifetimes and largest quantum efficiencies in solution (tau = 6.0 micros, phi = 0.22 for 1; tau = 0.4 micros, phi = 0.2 for 3) and, as result, are the most promising candidates for future luminescence-quenching-based oxygen-sensing studies.     

Luminescent cyclometalated iridium(III) polypyridine di-2-picolylamine complexes: synthesis, photophysics, electrochemistry, cation binding, cellular internalization, and cytotoxic activity

A series of luminescent cyclometalated iridium(III) polypyridine complexes containing a di-2-picolylamine (DPA) moiety [Ir(N^C)(2)(phen-DPA)](PF(6)) (phen-DPA = 5-(di-2-picolylamino)-1,10-phenanthroline) (HN^C = 2-phenylpyridine, Hppy (1a), 2-(4-methylphenyl)pyridine, Hmppy (2a), 2-phenylquinoline, Hpq (3a), 4-(2-pyridyl)benzaldehyde, Hpba (4a)) and their DPA-free counterparts [Ir(N^C)(2)(phen-DMA)](PF(6)) (phen-DMA = 5-(dimethylamino)-1,10-phenanthroline) (HN^C = Hppy (1b), Hmppy (2b), Hpq (3b), Hpba (4b)) have been synthesized and characterized, and their photophysical and electrochemical properties investigated. Photoexcitation of the complexes in fluid solutions at 298 K and in alcohol glass at 77 K resulted in intense and long-lived luminescence. The emission of the complexes has been assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Ir) → π*(N^N)) or triplet intraligand ((3)IL) (π → π*) (N^C) excited state and with substantial mixing of triplet amine-to-ligand charge-transfer ((3)NLCT) (n → π*) (N^N) character, depending on the identity of the cyclometalating and diimine ligands. Electrochemical measurements revealed an irreversible amine oxidation wave at ca. +1.1 to +1.2 V vs saturated calomel electrode, a quasi-reversible iridium(IV/III) couple at ca. +1.2 to +1.6 V, and a reversible diimine reduction couple at ca. -1.4 to -1.5 V. The cation-binding properties of these complexes have been studied by emission spectroscopy. Upon binding of zinc ion, the iridium(III) DPA complexes displayed 1.2- to 5.4-fold emission enhancement, and the K(d) values determined were on the order of 10(-5) M. Job's plot analysis confirmed that the binding stoichiometry was 1:1. Additionally, selectivity studies showed that the iridium(III) DPA complexes were more sensitive toward zinc ion among various transition metal ions examined. Furthermore, the cytotoxicity of these complexes toward human cervix epithelioid carcinoma cells have been studied by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay and their cellular-uptake properties by inductively coupled plasma mass spectrometry and laser-scanning confocal microscopy.     

Single-molecule magnet behavior in heterometallic M(II)-Mn(III)(2)-M(II) tetramers (M(II) = Cu, Ni) containing Mn(III) salen-type dinuclear core

The linear-type heterometallic tetramers, [Mn(III)(2)(5-MeOsaltmen)(2)M(II)(2)(L)(2)](CF(3)SO(3))(2) x 2H(2)O (MII = Cu, 1a; Ni, 2a), where 5-MeOsaltmen(2-) = N,N'-(1,1,2,2-tetramethylethylene) bis(5-methoxysalicylideneiminate), and H(2)L = 3-{2-[(2-hydroxy-benzylidene)-amino]-2-methyl-propylimino}-butan-2-one oxime, have been synthesized and characterized from structural and magnetic points of view. These two compounds are isostructural and crystallize in the same monoclinic P2(1)/n space group. The structure has a [M(II)-NO-Mn(III)-(O)(2)-Mn(III)-ON-M(II)] skeleton, where -NO- is a linking oximato group derived from the non-symmetrical Schiff-base complex [M(II)(L)] and -(O)(2)- is a biphenolato bridge in the out-of-plane [Mn(2)(5-MeOsaltmen)(2)](2+) dimer. The solvent-free compounds, 1b and 2b, have also been prepared by drying of the parent compounds, 1a and 2a, respectively, at 100 degrees C under dried nitrogen. After this treatment, the crystallinity is preserved, and 1b and 2b crystallize in a monoclinic P2(1)/c space group without significant changes in their structures in comparison to 1a and 2a. Magnetic measurements on 1a and 1b revealed antiferromagnetic Mn(III)---Cu(II) interactions via the oximato group and weak ferromagnetic Mn(III)---Mn(III) interactions via the biphenolato bridge leading to an S(T) = 3 ground state. On the other hand, the diamagnetic nature of the square planar Ni(II) center generates an S(T) = 4 ground state for 2a and 2b. At low temperature, these solvated (a) and desolvated (b) compounds display single-molecule magnet behavior modulated by their spin ground state.     

The preparation and characterisation of bimetallic iridium(II) complexes containing derivatised bridging naphthalene-1,8-disulfur or 4,5-dithiolato acephenanthrylene ligands

Oxidative addition of the disulfide compounds naphtho[1,8-cd][1,2]dithiole, 2-tert-butylnaptho[1,8-cd][1,2]dithiole, 2,7-di-tert-butylnaphtho[1,8-cd][1,2]dithiole, 4,5-dithiaacephenanthrylene and the thio/sulfinyl and thio/sulfonyl compounds naphtho[1,8-cd][1,2]dithiole 1-oxide, and naphtho[1,8-cd][1,2]dithiole 1,1-dioxide respectively to [[Ir(mu-Cl)(cod)](2)] give dinuclear Ir-Ir bonded Ir(II) compounds [[IrCl(cod)](2)(mu(2)-1,8-S(2)-nap)] 1, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2-(t)Bu-nap)] 2, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2,7-di-(t)Bu-nap)]] 3, [[IrCl(cod)](2)(mu(2)-4,5-S(2)-phenan)] 4, [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)]-nap)] 5 and [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)(2)]-nap)] 6 where the di-sulfur ligands act as bridges between the two Ir(II) metal centres. The compounds were obtained in moderate to good yields as orange or deep red powders or crystalline solids. Five of the new complexes have been structurally characterised and were found to have Ir-Ir bond lengths in the range 2.7630(8) to 2.8113(11) A.     

The time domain in co-stained cell imaging: time-resolved emission imaging microscopy using a protonatable luminescent iridium complex

The intense luminescence of the new complex Ir(ppy)(2)(pybz) (1) within the cytoplasm of live cells can be discriminated from the fluorescence of an organic stain, solely on the basis of the emission timescale {pybzH = 2-pyridyl-benzimidazole}. The protonated form of 1 displays red-shifted emission, and may be implicated in a superior uptake compared to Ir(ppy)(3).     

Intermolecular energy transfer involving an iridium complex studied by a combinatorial method

A recently developed combinatorial method utilizing angular dependence of evaporation rate was used to create compositional spread thin film libraries of Tris(2-pyridin-2-yl-indolizino[3,4,5-ab] isoindole-C(1), N('))iridium(III) [Ir(pin)(3)] and 4,4(')-N,N(')-dicarbazol-biphenyl (CBP) composite, with the molar fraction of Ir(pin)(3) complex varying in the 0.0003Ir(pin)(3) energy transfer proceeds by the Forster mechanism with the Forster radius of 30 A. The CBPxIr(pin)(3) composite has the highest photoluminescence quantum efficiency approximately 0.95, for chi(Ir(pin)(3) )=0.03 and is characterized by a structured green emission (lambda(max)=538 nm) originating from the ligand-centered (pi-pi(*))(3) state of the Ir(pin)(3) complex. On the contrary, the PL spectra of Ir(pin)(3) bulk are characterized by a weak red emission (lambda(max)=673 nm) attributed to the lowest metal-to-ligand charge transfer state. A statistical analysis based on a binomial distribution indicates that the emission from the (pi-pi(*))(3) state is quenched in Ir(pin)(3) molecules that are in a direct contact with each other.     

A cyclometalated iridium(III) complex with enhanced phosphorescence emission in the solid state (EPESS): synthesis, characterization and its application in bioimaging

Iridium(III) complexes with intense phosphorescence in solution have been widely applied in organic light-emitting diodes, chemosensors and bioimaging. However, little attention has been paid to iridium(III) complexes showing weak phosphorescence in solution and enhanced phosphorescence emission in the solid state (EPESS). In the present study, two β-diketonate ligands with different degrees of conjugation, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HL1) and 1-phenyl-3-methyl-4-phenylacetyl-5-pyrazolone (HL2), have been synthesized to be used as ancillary ligands for two iridium(III) complexes, Ir(ppy)(2)(L1) and Ir(ppy)(2)(L2) (Hppy = 2-phenylpyridine). The two complexes have been characterized by single-crystal X-ray crystallography, (1)H NMR and elemental analysis. Interestingly, Ir(ppy)(2)(L1) is EPESS-active whereas Ir(ppy)(2)(L2) exhibits moderately intense emission both in solution and as a neat film, indicating that the degree of conjugation of the β-diketone ligands determines the EPESS-activity. The single-crystal X-ray analysis has indicated that there are π-π interactions between the adjacent ppy ligands in Ir(ppy)(2)(L1) but not in Ir(ppy)(2)(L2). Finally, EPESS-active Ir(ppy)(2)(L1) has been successfully embedded in polymer nanoparticles and used as a luminescent label in bioimaging.     

Ligand effects on luminescence of new type blue light-emitting mono(2-phenylpyridinato)iridium(III) complexes

Newly prepared hydrido iridium(III) complexes [Ir(ppy)(PPh3)2(H)L](0,+) (ppy = bidentate 2-phenylpyridinato anionic ligand; L = MeCN (1b), CO (1c), CN(-) (1d); H being trans to the nitrogen of ppy ligand) emit blue light at the emission lambda(max) (452-457, 483-487 nm) significantly shorter than those (468, 495 nm) of the chloro complex Ir(ppy)(PPh3)2(H)(Cl) (1a). Replacing ppy of 1a-d with F2ppy (2,4-difluoro-2-phenylpyridinato anion) and F2Meppy (2,4-difluoro-2-phenyl-m-methylpyridinato anion) brings further blue-shifts down to the emission lambda(max) at 439-441 and 465-467 nm with CIE color coordinates being x = 0.16 and y = 0.18-0.20 to display a deep-blue photoemission. No significant blue shift is observed by replacing PPh3 of 1a with PPh2Me to produce Ir(ppy)(PPh2Me)2(H)(Cl) (1aPPh 2Me), which displays emission lambda max at 467 and 494 nm. The chloro complexes, [Ir(ppy)(PPh3)2(Cl)(L)](0,+) (L = MeCN (2b), CO (2c), CN(-) (2d)) having a chlorine ligand trans to the nitrogen of ppy also emit deep-blue light at emission lambda(max) 452-457 and 482-487 nm.     

苯并咪唑基Ir(Ⅲ)配合物的合成、结构和发光行为的调控或转换

合成了2个新的铱配合物[Ir(ppy)(qbiH)]NO_3(1·NO_3)和[Ir(ppy)(qbi)](2)。晶体结构分析表明,配合物1·NO_3和2中的[Ir(ppy)2]+单元分别与苯并咪唑基的中性配体qbiH与阴离子配体qbi-螯合。在溶液以及在固态条件下,2个配合物表现出明显不同的发光行为。1·NO_3和2在CH_2Cl_2溶液中的磷光发射波长分别为581和574 nm。在固态,1·NO_3和2分别发红色(616 nm)与桔色(598 nm)的磷光。有趣的是,1·NO_3和2在Et3N或TFA蒸汽的作用下,表现出红光发射与桔光发射之间的转换,这是因为它们的配体qbiH和qbi-发生了酸碱诱导的结构转换。此外,还讨论了配合物1·NO_3和2的结构与发光行为之间的关系。     

Thermochromic luminescence of copper iodide clusters: the case of phosphine ligands

Three copper(I) iodide clusters coordinated by different phosphine ligands formulated [Cu(4)I(4)(PPh(3))(4)] (1), [Cu(4)I(4)(Pcpent(3))(4)] (2), and [Cu(4)I(4)(PPh(2)Pr)(4)] (3) (PPh(3) = triphenylphosphine, Pcpent(3) = tricyclopentylphosphine, and PPh(2)Pr = diphenylpropylphosphine) have been synthesized and characterized by (1)H and (31)P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa ?3, and tetragonal I ?42m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu-Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu-Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.     

Phosphorescent iridium(III) complex with an N^O ligand as a Hg(2+)-selective chemodosimeter and logic gate

Phosphorescent iridium(III) complexes have been attracting increasing attention in applications as luminescent chemosensors. However, no instance of an iridium(III) complex being used as a molecular logic gate has hitherto been reported. In the present study, two iridium(III) complexes, [Ir(ppy)(2)(PBT)] and [Ir(ppy)(2)(PBO)], have been synthesized (PBT, 2-(2-Hydroxyphenyl)-benzothiazole; PBO, 2-(2-hydroxyphenyl)-benzoxazole), and their chemical structures have been characterized by single-crystal X-ray analysis. Theoretical calculations and detailed studies of the photophysical and electrochemical properties of these two complexes have shown that the N^O ligands dominate their luminescence emission properties. Moreover, [Ir(ppy)(2)(PBT)], containing a sulfur atom in the N^O ligand, can serve as a highly selective chemodosimeter for Hg(2+) with ratiometric and naked-eye detection, which is associated with the dissociation of the N^O ligand PBT from the complex. Furthermore, complex [Ir(ppy)(2)(PBT)] has been further developed as an AND and INHIBIT logic gate with Hg(2+) and histidine as inputs.     

Inter- and intramolecular activation of aromatic C-H bonds by diphosphine and hydrido-bridged dinuclear iridium complexes

Reactions of [(Cp*Ir)2(mu-dmpm)(mu-H)2]2+ (1) with NaOtBu in aromatic solvent at room temperature give [(Cp*Ir)(H)(mu-dmpm)(mu-H)(Cp*Ir)(Ar)]+ [Ar = Ph (3), p-Tol (4a), m-Tol (4b), 2-furanyl (5a), 3-furanyl (5b)] via intermolecular aromatic C-H activation. Treatment of [(Cp*Ir)2(mu-dppm)(mu-H)2]2+ (2) with base (Et2NH) results in intramolecular C-H activation of the phenyl group in the dppm ligand to give [(Cp*Ir)(H){mu-PPh(C6H4)CH2PPh2}(mu-H)(Cp*Ir)]+ (6). The structures of 3, 5a, and 6 have been determined by X-ray diffraction methods.     

Mechanochromic luminescence switch of platinum(II) complexes with 5-trimethylsilylethynyl-2,2'-bipyridine

Planar platinum(II) complexes Pt(bpyC≡CSiMe(3))(C≡CC(6)H(4)R-4)(2) (R = H (1), Bu(t) (2)) with 5-trimethylsilylethynyl-22'-bipyridine show an unusual, reversible, and reproducible mechanical stimuli-responsive color and luminescence switch. When crystalline 1 or 2 is ground, bright yellow-green emitting is immediately converted to red luminescence with an emission red shift of 121-155 nm for 1 or 53-89 nm for 2. Meanwhile, the crystalline state is transformed to an amorphous phase that can be reverted to the original crystalline state by organic vapor adsorbing or heating, along with red luminescence turning back to yellow-green emitting. The reversibility and reproducibility of luminescence mechanochromic properties have been dynamically monitored by the variations in emission spectra and X-ray diffraction patterns. The drastic grinding-triggered emission red shift is likely involved in the formation of a dimer or an aggregate through Pt-Pt interaction, resulting in a conversion of the (3)MLCT/(3)LLCT emissive state in the crystalline state into the (3)MMLCT triplet state in the amorphous phase. Compared with the drastic grinding-triggered emission red shift in 1 (121-155 nm), the corresponding response shift in 2 (53-89 nm) is much smaller since a bulky tert-butyl in C≡CC(6)H(4)bu(t)-4 induces the planar platinum(II) molecules to stack through a longer Pt-Pt distance and less intermetallic contact compared with that in 1, as suggested from EXAFS studies.     

Synthesis, Crystal Structure, and Photoluminescent and Semiconductive Properties of [La(C6NO2H5)3-(H2O)2]2n·(nH5O2)(nHgCl5)(2nHgCl4)·(2nH2O)

A new heterometallic 4f-5d inorganic-organic metal-isonicotinic acid complex [La(C6NO2H5)3(H2O)2]2n·(nH5O2)(nHgCl5)(2nHgCl4)·(2nH2O) 1 has been synthesized via hydro-thermal reaction and structurally characterized. Complex 1 crystallizes in the space group C2/c of monoclinic system with four formula units in a cell: α= 24.140(7), b = 20.884(7), c = 15.462(2) (A), β = 127.46(1)°,V = 6187(3) (A)3, C36H47Cl13Hg3La2N6O20, Mr = 2224.24, Dc = 2.388 g/cm3, Z = 4, T = 293(2) K, μ(MoKα) = 9.401 mm-1, F(000) = 4160 and R/wR = 0.0376/0.0636 for 4130 observed reflections (I > 2σ(I)) and 5617 unique reflections. Complex 1 is characteristic of a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that the title complex displays interesting emissions in violet and orange regions. The luminescence spectra show stronger orange emission than violet emission. Optical absorption spectra of 1 reveal the presence of a wide optical bandgap of 3.41 eV.     

Stereochemistry controlled by an asymmetric sulfur atom, and a rare example of a kryptoracemate

The ligands 4-methylthio-6-phenyl-2,2'-bipyridine (1) and the corresponding sulfoxide (2) and sulfone (3) have been synthesized and characterized in solution, and in the solid state by single crystal X-ray diffraction. Compounds 2 and 3 crystallize in the same space group (C2/c) with similar unit cell parameters; a small increase in the unit cell volume allows for the presence of the extra oxygen atom in 3. The sulfoxide and sulfone groups adopt conformations that permit intramolecular OHC(aryl) hydrogen bonds. The complexes [Ir(ppy)(2)L][PF(6)] with L = 1, 2 or 3 have been prepared and characterized. The asymmetric sulfur atom in ligand 2 gives rise to pairs of diastereoisomers of the complex which can be distinguished in the (1)H and (13)C NMR spectra. In solution, exchange of [PF(6)](-) by [Δ-TRISPHAT](-) gives rise to four diastereoisomers and we observed good dispersion of (1)H NMR resonances, especially for those assigned to protons close to the asymmetric sulfur atom. A single crystal X-ray diffraction study of 2{[Ir(ppy)(2)(3)][PF(6)]}·CHCl(3)·3H(2)O reveals that the complex crystallizes in the chiral space group P2(1)2(1)2(1), the asymmetric unit containing crystallographically independent Δ- and Λ-[Ir(ppy)(2)(3)](+) cations. This provides a rare example of a so-called kryptoracemate in the solid state. In MeCN solution, [Ir(ppy)(2)(1)][PF(6)], [Ir(ppy)(2)(2)][PF(6)] and [Ir(ppy)(2)(3)][PF(6)] are weakly emissive (λ(em) = 600, 647 and 672 nm, respectively) and preliminary studies of the electroluminescent properties of [Ir(ppy)(2)(2)][PF(6)] indicate that the complexes are not suitable candidates for LECs.     

Tris-cyclometalated iridium(III) complexes of carbazole(fluorenyl)pyridine ligands: synthesis, redox and photophysical properties, and electrophosphorescent light-emitting diodes

Using ligands synthesized by Suzuki cross-coupling methodology, new phosphorescent homoleptic tris-cyclometalated complexes have been obtained, namely fac-[Ir(Cz-2-Fl(n)Py)(3)] (1 d-f) and fac-[Ir(Cz-3-Fl(n)Py)(3)] (2 d-f), which are solution-processible triplet emitters (Cz denotes N-hexylcarbazole, n is the number of 9,9'-dihexylfluorene (Fl) units (n=0,1,2) and Py is pyridine). In all cases, Py and Fl are substituted at the 2- and 2,7-positions, respectively, and Cz moieties are substituted by either Py or Fl at the 2- or 3-positions, in series 1 and 2, respectively. The oxidation potential of 1 d studied by cyclic voltammetry ({E{{{\rm ox}\hfill \atop 1/2\hfill}}}=0.14 V, versus Ag/AgNO(3), CH(2)Cl(2)) is less positive (i.e. raised HOMO level) compared to that of the isomer 2 d ({E{{{\rm ox}\hfill \atop 1/2\hfill}}}=0.30 V), where the Cz-nitrogen is meta to the Ir center. Ligand-centered oxidations occur at more positive potentials, leading to 7+ oxidation states with good chemical reversibility and electrochemical quasi-reversibility, for example, for 2 f {E{{{\rm ox}\hfill \atop {\rm pa}\hfill}}} =0.45 (1e), 0.95 (3e), 1.24 V (3e). Striking differences are seen in the solution-state photophysical data between complexes [Ir(Cz-2-Py)(3)] (1 d) and [Ir(Cz-3-Py)(3)] (2 d), in which the Cz moiety is bonded directly to the metal center: for the latter there is an 85 nm blue-shift in emission, a decrease in the luminescence lifetime and an increase in the PLQY value. Organic light emitting devices were made by spin-coating using polyspirobifluorene:bis(triphenyl)diamine (PSBF:TAD) copolymer as host and the complexes 1 d or 2 d as dopants. Turn-on voltages are low (3-4 V). With 1 d orange light is emitted at lambda(max)=590 nm with an EQE of 1.3 % (at 7.5 mA cm(-2)) and an emission intensity (luminance) of 4354 cd m(-2) (at 267 mA m(-2)). The green emission from 2 d devices (lambda(max)=500 nm) is due to the reduced electron-donating ability of the carbazole unit in 2 d. Recording the EL spectra of the 1 d device at 6 V (current density, 100 mA cm(-2)) established that the time to half brightness was about 9 h under continuous operation with no change in the spectral profile, confirming the high chemical stability of the complex.     

Synthesis,Crystal Structure,and Photoluminescent and Semiconductive Properties of [La(C_6NO_2H_5)_3-(H_2O)_2]_(2n)·(nH_5O_2)(nHgCl_5)(2nHgCl_4)·(2nH_2O)

A new heterometallic 4f-5d inorganic-organic metal-isonicotinic acid complex [La(C6NO2H5)3(H2O)2]2n·(nH5O2)(nHgCl5)(2nHgCl4)·(2nH2O) 1 has been synthesized via hydro-thermal reaction and structurally characterized. Complex 1 crystallizes in the space group C2/c of monoclinic system with four formula units in a cell:a =24.140(7),b=20.884(7),c=15.462(2),β=127.46(1)°,V=6187(3)3,C36H47Cl13Hg3La2N6O20,Mr=2224.24,Dc=2.388 g/cm3,Z=4,T=293(2) K,μ(MoKα)=9.401 mm-1,F(000)=4160 and R/wR=0.0376/0.0636 for 4130 observed reflections (I > 2σ(I)) and 5617 unique reflections. Complex 1 is characteristic of a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that the title complex displays interesting emissions in violet and orange regions. The luminescence spectra show stronger orange emission than violet emission. Optical absorption spectra of 1 reveal the presence of a wide optical bandgap of 3.41 eV.