|
| ||
|
|
||
Carbazole
Kinds of Carbazole Terms modified by Carbazole Selected AbstractsSelective Tuning of the HOMO,LUMO Gap of Carbazole-Based Donor,Acceptor,Donor Compounds toward Different Emission ColorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2010Huaqiang Zhang Abstract Carbazole-based donor,acceptor compounds with tunable HOMO,LUMO gaps were synthesized by Suzuki and Sonogashira cross-coupling reactions. Their optical and electrochemical properties were fully characterized. The results show that materials with different emission colors ranging from blue to green to orange could be obtained. The experimental results were also supported by theoretical calculations. [source] Synthesis and Characterization of Carbazole-Based Dendrimers with Porphyrin CoresEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006Ting Hua Xu Abstract A series of novel dendritic carbazole-based porphyrins [T(Cz-Gn)Ps] have been synthesized by a combination of Ullmann coupling and Adler condensation reactions and their intramolecular energy-transfer properties have been studied by absorption and steady-state fluorescence spectroscopy. It has been found that the light-harvesting capabilities of T(Cz-Gn)Ps increase with increasing generation, but that the efficiency of the energy transfer decreases from T(Cz-G0)P to T(Cz-G2)P due to the Förster energy-transfer process. In addition, these dendritic macromolecules can emit intense red light with high fluorescence quantum yields and so may find applications in photonic devices. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] New synthesis of highly potential efficient bluish-green electroluminescent materials based on 1,3,4-oxadiazole,triazolopyridinone,carbazole derivatives for single-layer devicesHETEROATOM CHEMISTRY, Issue 2 2006Ming-Hsiang Shin New potential bluish-green electroluminescent materials of 1,3,4-oxadiazole,triazolopyridin- one,carbazole derivatives were synthesized and characterized for single-layer devices. Carbazole, pyridine, and triazolopyridinone were completely introduced into 1,3,4-oxadiazole skeletal to play assistant roles in controlling fundamental photolytic process due to the electron-donating nature, excellent photoconductivity, and flexible structure properties. Following the spectroscopic studies and the measurements of cyclic voltammogram, 1,3,4-oxadiazole,triazolopyridinone,carbazole derivatives were highly efficient bluish-green electroluminescent materials. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:160,165, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20201 [source] Solution-Processable Carbazole-Based Conjugated Dendritic Hosts for Power-Efficient Blue-Electrophosphorescent DevicesADVANCED MATERIALS, Issue 48 2009Junqiao Ding A novel class of hosts suitable for solution processing has been developed based on a conjugated dendritic scaffold. By increasing the dendron generation, the highest occupied molecular orbital (HOMO) energy level can be tuned to facilitate hole injection, while the triplet energy remains at a high level, sufficient to host high-energy-triplet emitters. A power-efficient blue-electrophosphorescent device based on H2 (see figure) is presented. [source] Structural, electronic, and optical properties of 9-heterofluorenes: A quantum chemical studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007Run-Feng Chen Abstract Density-functional theory studies were applied to investigate the structural, electronic, and optical properties of 9-heterofluorenes achieved by substituting the carbon at 9 position of fluorene with silicon, germanium, nitrogen, phosphor, oxygen, sulfur, selenium, or boron. These heterofluorenes and their oligomers up to pentamers are highly aromatic and electrooptically active. The alkyl and aryl substituents of the heteroatom have limited influence, but the oxidation of the atom has significant influence on their molecular structures and properties. The highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) interaction theory was successfully applied to analyze the energy levels and the frontier wave functions of these heterofluorenes. Most heterofluorenes belong to type B of interaction with low-lying LUMO and have the second kind of wave function. Carbazole and selenafluorene have type C of interaction with high-lying HOMO and the third kind of wave function. Types C and D of heterofluorenes, such as carbazole, oxygafluorene, sulfurafluorene, and selenafluorene also have high triplet state energies. The extrapolated HOMO and LUMO for polyheterofluorenes indicate that polyselenonafluorene has the lowest LUMO; polycarbazole has the highest HOMO; polyselenafluorene has the highest bandgap (Eg); and polyborafluorene has the lowest Eg. Heterofluorenes and their oligomers and polymers are of great experimental interests, especially those having extraordinary properties revealed in this study. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Methacrylic Polymers Containing Optically Active Side-Chain Carbazole: Synthesis, Characterization and Photoconductive PropertiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2008Luigi Angiolini Abstract Two novel optically active polymethacrylates bearing in the side chain a cyclic chiral group of one prevailing absolute configuration linked to the carbazole chromophore, deriving from the related monomers (S)-(,)-3-methacryloyloxy- N -[3-(9-ethylcarbazolyl)]pyrrolidine [(S)-(,)-MECP] and (S)-(+)-2-methacryloyloxy- N -[3-(9-ethylcarbazolyl)]succinimide [(S)-(+)-MECSI], have been prepared and characterized with the aim to obtain materials suitable to photoconductive applications. Poly[(S)-(,)-MECP] and poly[(S)-(+)-MECSI] exhibit remarkable thermal stability, with glass transition temperature around 200,°C and decomposition temperatures in the range 330,350,°C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions among the side chain moieties and the presence of chiral conformation at least for chain segments of the macromolecules. The photoconductive properties are discussed in terms of extent of conjugation in the side chain based on the electron-acceptor or electron-donator properties of the optically active ring linked to the carbazole group. [source] Synthesis of Dendritic Oligo-Spiro(fluorene-9,9,-xanthene) Derivatives with Carbazole and Fluorene Pendants and their Thermal, Optical, and Electroluminescent PropertiesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2009Zengze Chu Abstract Two novel spiro-configured ter(arylene-ethynylene) derivatives, TSF-Cz and TSF-F, have been designed and synthesized using spiro(fluorene-9,9,-xanthene) (SFX) as building blocks, introducing a hole-transporting carbazole and a fluorene chromophore as the peripheral functional group into the backbone through an oxygen atom. The two well-defined oligomers possess good solubility, film-forming quality, and high Tg's at 140 and 126,°C, respectively. In addition, these oligomers exhibit blue photoluminescence (PL) emission both in solution and solid states. The double-layered devices fabricated using the two materials as the emitter show a sky-blue emission with a brightness and a current efficiency of 7,613,cd,·,m,2 and 1.11,cd,·,A,1 for TSF-Cz, and 1,507,cd,·,m,2 and 0.36,cd,·,A,1 for TSF-F, respectively. [source] Crystallization and preliminary X-ray diffraction studies of a ferredoxin reductase component of carbazole 1,9a-dioxygenase from Novosphingobium sp.ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010Carbazole 1,9a-dioxygenase (CARDO) is the initial enzyme of the carbazole-degradation pathway. The CARDO of Novosphingobium sp. KA1 consists of a terminal oxygenase, a putidaredoxin-type ferredoxin and a ferredoxin-NADH oxidoreductase (Red) and is classified as a class IIA Rieske oxygenase. Red from KA1 was crystallized at 278,K by the hanging-drop vapour-diffusion method using PEG 4000. The crystal diffracted to 1.58,Ĺ resolution and belonged to space group P32, with unit-cell parameters a = b = 92.2, c = 78.6,Ĺ, , = , = 90, , = 120°. Preliminary analysis of the X-ray diffraction data revealed that the asymmetric unit contained two Red monomers. The crystal appeared to be a merohedral twin, with a twin fraction of 0.32 and twin law (,h, ,k, l). [source] ChemInform Abstract: Synthesis of a Novel ,-Diketone Containing Carbazole and 2,5-Diphenyl-1,3,4-oxadiazole Fragments.CHEMINFORM, Issue 50 2009Huaijun Tang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Oxidative Pd(II)-Catalyzed C,H Bond Amination to Carbazole at Ambient Temperature.CHEMINFORM, Issue 17 2009James A. Jordan-Hore Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: One-Pot Synthesis of Carbazole via Tandem Suzuki,Miyaura and Amination Reaction.CHEMINFORM, Issue 22 2008Yuki Kitamura Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] N-Silatranylmethyl Derivatives of Pyrrole, Indole, and Carbazole.CHEMINFORM, Issue 19 2004M. G. Voronkov Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Alcoholysis of 2,2-Dichloropropyl Derivatives of Carbazole, Phenothiazine, and Phenoxazine.CHEMINFORM, Issue 39 2001V. A. Anfinogenov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Laser versus UV Photolysis: A Comparative Study with Carbazole.CHEMINFORM, Issue 17 2001Amitbodh Upadhyay Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Tris-Cyclometalated Iridium(III) Complexes of Carbazole(fluorenyl)pyridine Ligands: Synthesis, Redox and Photophysical Properties, and Electrophosphorescent Light-Emitting DiodesCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2007Sylvia Bettington Dr. Abstract Using ligands synthesized by Suzuki cross-coupling methodology, new phosphorescent homoleptic tris-cyclometalated complexes have been obtained, namely fac -[Ir(Cz-2-FlnPy)3] (1,d,f) and fac -[Ir(Cz-3-FlnPy)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 (=0.14,V, versus Ag/AgNO3, CH2Cl2) is less positive (i.e. raised HOMO level) compared to that of the isomer 2,d (=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 =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 ,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 (,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. [source] Effects of eight polycyclic aromatic compounds on the survival and reproduction of the springtail Folsomia fimetaria L. (collembola, isotomidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2001Line E. Sverdrup Abstract The effects of eight polycyclic aromatic compounds on the survival and reproduction of the collembolan Folsomia fimetaria L. were investigated in a well-characterized Danish agricultural soil. With the exception of acridine, polycyclic aromatic hydrocarbons (PAHs) and neutral N-, S-, and O-monosubstituted analogues showed similar toxicities to soil collembolans when the results were expressed in relation to total soil concentrations (mg/kg). The estimated concentrations resulting in a 10% reduction of reproductive output (EC10 values) were based on measured initial concentrations and were for acridine 290 mg/kg, carbazole 10 mg/kg, dibenzofuran 19 mg/kg, dibenzothiophene 7.8 mg/kg, fluoranthene 37 mg/kg, fluorene 7.7 mg/kg, phenantrene 23 mg/kg, and pyrene 10 mg/kg. When the EC10 values were converted to soil pore-water concentrations, they showed a highly significant correlation (r2 = 0.71, p < 0.01) to no-observed-effect concentrations for the freshwater crustacean Daphnia magna, as estimated by a quantitative structure activity relation (QSAR) for baseline toxicity (nonpolar narcosis). Only carbazole and acridine were more than two times more toxic (4.9 and 3.1, respectively) than expected from the Daphnia QSAR data. The latter result indicates that the toxicity of the tested substances is close to that expected for compounds with nonpolar narcosis as the mode of action. However, the relatively large uncertainties in the extrapolation method prevent final conclusions from being drawn. [source] Activation of the aryl hydrocarbon receptor reveals distinct requirements for IL-22 and IL-17 production by human T helper cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2010Jean-Marie Ramirez Abstract Ligands of the aryl hydrocarbon receptor (AHR), a transcription factor mediating the effects of dioxin, favor Th17 differentiation and exacerbate autoimmunity in mice. We investigated how AHR ligands affected human T-cell polarization. We found that the high affinity and stable AHR-ligand dioxin as well as the natural AHR-ligand 6-formylinolo[3,2-b] carbazole induced the downstream AHR-target cytochrome P450A1, and without affecting IFN-,, they enhanced IL-22 while simultaneously decreasing IL-17A production by CD4+ T cells. The specific AHR-inhibitor CH-223191 abolished these effects. Furthermore, blockade of IL-23 and IL-1, important for Th17 expansion, profoundly decreased IL-17A but not IL-22 production. AHR agonists reduced the expression of the Th17 master transcription factor retinoic acid-related orphan receptor C (RORC), without affecting T-bet, GATA-3 and Foxp3. They also decreased the expression of the IL-23 receptor. Importantly, AHR-ligation did not only decrease the number of Th17 cells but also primed naďve CD4+ T cells to produce IL-22 without IL-17 and IFN-,. Furthermore, IL-22 single producers did not express CD161, which distinguished them from the CD161+ Th17 cells. Hence, our data provide compelling evidence that AHR activation participates in shaping human CD4+ T-cell polarization favoring the emergence of a distinct subset of IL-22-producing cells that are independent from the Th17 lineage. [source] Synthesis and Characterization of Carbazole-Based Dendrimers with Porphyrin CoresEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2006Ting Hua Xu Abstract A series of novel dendritic carbazole-based porphyrins [T(Cz-Gn)Ps] have been synthesized by a combination of Ullmann coupling and Adler condensation reactions and their intramolecular energy-transfer properties have been studied by absorption and steady-state fluorescence spectroscopy. It has been found that the light-harvesting capabilities of T(Cz-Gn)Ps increase with increasing generation, but that the efficiency of the energy transfer decreases from T(Cz-G0)P to T(Cz-G2)P due to the Förster energy-transfer process. In addition, these dendritic macromolecules can emit intense red light with high fluorescence quantum yields and so may find applications in photonic devices. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of Carrier-Transporting Dendrimers with Perylenebis(dicarboximide)s as a Luminescent CoreEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2006Jianfeng Pan Abstract Well-defined, modular dendrimers enable processing techniques and electronic properties to be tuned independently. Moreover, the dendritic topology can isolate the core chromophore, thus reducing or eliminating strong intermolecular interactions. This paper presents the synthesis of three series of flexible, dendron-functionalized dendrimers as red-light-emitting materials by a convergent approach: (1) carbazole (CZ) or oxadiazole (OXZ) terminated imide-type dendrimers, (2) cascade energy-transferring imide-type dendrimers, and (3) CZ-terminated perylene bay-type dendrimers. They all consist of the luminescent core of perylenebis(dicarboximide)s with specific functional groups of CZ or OXZ at the periphery and are constructed from flexible Fréchet-type poly(aryl ether) dendrons. The chemical structures of the dendrons and dendrimers were determined by standard spectroscopic techniques including 1H and 13C NMR spectroscopy and low/high-resolution mass spectrometry (ESI or MALDI-TOF). The dendrimers are designed on the basis of the following considerations: (1) dendron functionalization to incorporate CZ or OXZ units to realize the carrier-injection adjustment, (2) tuning or improving solubility, functionality, glass-transition temperature (Tg) with well-defined dendrons, and (3) avoiding luminescence quenching with the help of high site-isolation of dendrons to enhance core luminescence. DSC results indicate that the incorporation of Fréchet-type poly(aryl ether) dendrons can improve the amorphous properties and increase Tg. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Orientation Control of Linear-Shaped Molecules in Vacuum-Deposited Organic Amorphous Films and Its Effect on Carrier MobilitiesADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Daisuke Yokoyama Abstract The molecular orientation of linear-shaped molecules in organic amorphous films is demonstrated to be controllable by the substrate temperature. It is also shown that the molecular orientation affects the charge-transport characteristics of the films. Although linear-shaped 4,4,-bis[(N -carbazole)styryl]biphenyl molecules deposited on substrates at room temperature are horizontally oriented in amorphous films, their orientation when deposited on heated substrates with smooth surfaces becomes more random as the substrate temperature increases, even at temperatures under the glass transition temperature. Another factor dominating the orientation of the molecules deposited on heated substrates is the surface roughness of the substrate. Lower carrier mobilities are observed in films composed of randomly oriented molecules, demonstrating the significant effect of a horizontal molecular orientation on the charge-transport characteristics of organic amorphous films. [source] Synthesis and Characterization of Red-Emitting Iridium(III) Complexes for Solution-Processable Phosphorescent Organic Light-Emitting DiodesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Seung-Joon Lee Abstract A new series of highly efficient red-emitting phosphorescent Ir(III) complexes, (Et-CVz-PhQ)2Ir(pic-N-O), (Et-CVz-PhQ)2Ir(pic), (Et-CVz-PhQ)2Ir(acac), (EO-CVz-PhQ)2Ir(pic-N-O), (EO-CVz-PhQ)2Ir(pic), and (EO-CVz-PhQ)2Ir(acac), based on carbazole (CVz)-phenylquinoline (PhQ) main ligands and picolinic acid N-oxide (pic-N-O), picolinic acid (pic), and acetylacetone (acac) ancillary ligands, are synthesized for phosphorescent organic light-emitting diodes (PhOLEDs), and their photophysical, electrochemical, and electroluminescent (EL) properties are investigated. All of the Ir(III) complexes have high thermal stability and emit an intense red light with an excellent color purity at CIE coordinates of (0.65,0.34). Remarkably, high-performance solution-processable PhOLEDs were fabricated using Ir(III) complexes with a pic-N-O ancillary ligand with a maximum external quantum efficiency (5.53%) and luminance efficiency (8.89,cd,A,1). The novel use of pic-N-O ancillary ligand in the synthesis of phosphorescent materials is reported. The performance of PhOLEDs using these Ir(III) complexes correlates well with the results of density functional theory calculations. [source] Novel Heteroleptic CuI Complexes with Tunable Emission Color for Efficient Phosphorescent Light-Emitting Diodes,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007Q. Zhang Abstract A series of orange-red to red phosphorescent heteroleptic CuI complexes (the first ligand: 2,2,-biquinoline (bq), 4,4,-diphenyl-2,2,-biquinoline (dpbq) or 3,3,-methylen-4,4,-diphenyl-2,2,-biquinoline (mdpbq); the second ligand: triphenylphosphine or bis[2-(diphenylphosphino)phenyl]ether (DPEphos)) have been synthesized and fully characterized. With highly rigid bulky biquinoline-type ligands, complexes [Cu(mdpbq)(PPh3)2](BF4) and [Cu(mdpbq)(DPEphos)](BF4) emit efficiently in 20,wt,% PMMA films with photoluminescence quantum yield of 0.56 and 0.43 and emission maximum of 606,nm and 617,nm, respectively. By doping these complexes in poly(vinyl carbazole) (PVK) or N -(4-(carbazol-9-yl)phenyl)-3,6-bis(carbazol-9-yl) carbazole (TCCz), phosphorescent organic light-emitting diodes (OLEDs) were fabricated with various device structures. The complex [Cu(mdpbq)(DPEphos)](BF4) exhibits the best device performance. With the device structure of ITO/PEDOT/TCCz:[Cu(mdpbq)(DPEphos)](BF4) (15,wt,%)/TPBI/LiF/Al (III), a current efficiency up to 6.4,cd,A,1 with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.61, 0.39) has been realized. To our best knowledge, this is the first report of efficient mononuclear CuI complexes with red emission. [source] 2,7-Carbazolenevinylene-Based Oligomer Thin-Film Transistors: High Mobility Through Structural Ordering,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005N. Drolet Abstract We have fabricated organic field-effect transistors based on thin films of 2,7-carbazole oligomeric semiconductors 1,4-bis(vinylene-(N -hexyl-2-carbazole))phenylene (CPC), 1,4-bis(vinylene-(N,-methyl-7,-hexyl-2,-carbazole))benzene (RCPCR), N -hexyl-2,7-bis(vinylene-(N -hexyl-2-carbazole))carbazole (CCC), and N -methyl-2,7-bis(vinylene-(7-hexyl- N -methyl-2-carbazole))carbazole (RCCCR). The organic semiconductors are deposited by thermal evaporation on bare and chemically modified silicon dioxide surfaces (SiO2/Si) held at different temperatures varying from 25 to 200,°C during deposition. The resulting thin films have been characterized using UV-vis and Fourier-transform infrared spectroscopies, scanning electron microscopy, and X-ray diffraction, and the observed top-contact transistor performances have been correlated with thin-film properties. We found that these new ,-conjugated oligomers can form highly ordered structures and reach high hole mobilities. Devices using CPC as the active semiconductor have exhibited mobilities as high as 0.3,cm2,V,1,s,1 with on/off current ratios of up to 107. These features make CPC and 2,7-carbazolenevinylene-based oligomers attractive candidates for device applications. [source] Total Synthesis of Murrayanine Involving 4,5-Dimethyleneoxazolidin-2-ones and a Palladium(0)-Catalyzed Diaryl InsertionHELVETICA CHIMICA ACTA, Issue 8 2007Pablo Bernal Abstract A new total synthesis of the natural carbazole murrayanine (1) was developed by using the 4,5-dimethyleneoxazolidin-2-one 12 as starting material. The latter underwent a highly regioselective Diels,Alder cycloaddition with acrylaldehyde (=prop-2-enal; 13) to give adduct 14 (Scheme,3). Conversion of this adduct into diarylamine derivative 9 was carried out via hydrolysis and methylation (Scheme,4). Differing from our previous synthesis, in which such a diarylamine derivative was transformed into 1 by a PdII -stoichiometric cyclization, this new approach comprised an improved cyclization through a more efficient Pd0 -catalyzed intramolecular diaryl coupling which was applied to 9, thus obtaining the natural carbazole 1 in a higher overall yield. [source] One-Pot Three-Step Synthesis of Naphtho[2,3- a]carbazole- 5,13-diones using a Tandem Radical Alkylation,Cyclization, Aromatization Reaction SequenceADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Chunyong Ding Abstract A three-step, one-pot tandem reaction including radical nucleophilic alkylation/cyclization/aromatization was developed using 0.3 equivalents of silver(I) acetate (AgOAc) as the catalyst and 2 equivalents of ammonium persulfate [(NH4)2S2O8] as the oxidant. This strategy is highly efficient for the assembly of pentacyclic complex carbazoles from aryl-fused bromobenzoquinones and indol-3-ylpropanoic acid acids in 52,72% overall yields (three steps). This new approach provides a significant improvement over the previously reported methods and would greatly facilitate analog library construction of pentacyclic complex carbazoles and benefit further biological evaluation of these compounds. [source] Structural, electronic, and optical properties of 9-heterofluorenes: A quantum chemical studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007Run-Feng Chen Abstract Density-functional theory studies were applied to investigate the structural, electronic, and optical properties of 9-heterofluorenes achieved by substituting the carbon at 9 position of fluorene with silicon, germanium, nitrogen, phosphor, oxygen, sulfur, selenium, or boron. These heterofluorenes and their oligomers up to pentamers are highly aromatic and electrooptically active. The alkyl and aryl substituents of the heteroatom have limited influence, but the oxidation of the atom has significant influence on their molecular structures and properties. The highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) interaction theory was successfully applied to analyze the energy levels and the frontier wave functions of these heterofluorenes. Most heterofluorenes belong to type B of interaction with low-lying LUMO and have the second kind of wave function. Carbazole and selenafluorene have type C of interaction with high-lying HOMO and the third kind of wave function. Types C and D of heterofluorenes, such as carbazole, oxygafluorene, sulfurafluorene, and selenafluorene also have high triplet state energies. The extrapolated HOMO and LUMO for polyheterofluorenes indicate that polyselenonafluorene has the lowest LUMO; polycarbazole has the highest HOMO; polyselenafluorene has the highest bandgap (Eg); and polyborafluorene has the lowest Eg. Heterofluorenes and their oligomers and polymers are of great experimental interests, especially those having extraordinary properties revealed in this study. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2005Li Yang Abstract Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)- co - alt -2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (,H-L), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (Egs) and the maximal absorption wavelength ,abs of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as ,H-L, Eg, IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)n series. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 969,979, 2005 [source] N -Arylation of N-H heterocycles with aryl bromides and aryl iodides using cui and kf/Al2O3JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2008Rahman Hosseinzadeh Copper-catalyzed system for N -arylation of N-H group in heterocycles such as indole, pyrrole and carbazole with aryl iodides and aryl bromides using potassium fluoride supported on alumina as a base is described. This is a simple and efficient method for the coupling of aryl iodides and bromides with N-H heterocycles. Different functionalized iodo and bromo arenes were coupled with N-H heterocycles using this system. [source] Synthesis and characterization of tritium labeled 2,3,4,9-tetrahydro-1H -carbazoles as potent DP receptor antagonistsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2004Carl Berthelette Abstract Tritium labeled 2,3,4,9-tetrahydro-1H -carbazole 1a and 2a were prepared in good yields with a specific activity of 7.0 Ci/mmol (214 GBq/mmol) and 4.2 Ci/mmol (155 GBq/mmol), respectively. Both compounds have been synthesized in high radiochemical purity by catalytic tritium,bromine exchange of the corresponding aryl bromide precursors. The 6-bromocarbazole precursors 7 and 8 were prepared as a mixture by a three step process, involving regioselective bromination of 3c with pyridinium tribromide, oxidation of thioether 4c using m -CPBA and hydrolysis of acylsultamcarbazole 5c. Finally, HPLC separation of the enantiomers afforded the 6-bromo precursors 7 and 8 in high diastereomeric ratio (dr 99% and dr 93% respectively). Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis and characterization of a thiadiazole/benzoimidazole-based copolymer for solar cell applicationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010Guan-yu Chen Abstract In this study, we synthesized a new polymer, PCTDBI, containing alternating carbazole and thiadiazole-benzoimidazole (TDBI) units. This polymer (number-average molecular weight = 25,600 g mol,1), which features a planar imidazole structure into the polymeric main chain, possesses reasonably good thermal properties (Tg = 105 °C; Td = 396 °C) and an optical band gap of 1.75 eV that matches the maximum photon flux of sunlight. Electrochemical measurements revealed an appropriate energy band offset between the polymer's lowest unoccupied molecular orbital and that of PCBM, thereby allowing efficient electron transfer between the two species. A solar cell device incorporating PCTDBI and PCBM at a blend ratio of 1:2 (w/w) exhibited a power conversion efficiency of 1.20%; the corresponding device incorporating PCTDBI and PC71BM (1:2, w/w) exhibited a PCE of 1.84%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] | ||||||||||||||||||||||||||||||||||