Sample records for cyclometalated iridiumiii complexes

  1. Probing the mer- to fac-isomerization of tris-cyclometallated homo- and heteroleptic (C,N)3 iridium(III) complexes.

    PubMed

    McDonald, Aidan R; Lutz, Martin; von Chrzanowski, Lars S; van Klink, Gerard P M; Spek, Anthony L; van Koten, Gerard

    2008-08-04

    We have developed techniques which allow for covalent tethering, via a "hetero" cyclometallating ligand, of heteroleptic tris-cyclometallated iridium(III) complexes to polymeric supports (for application in light-emitting diode technologies). This involved the selective synthesis and thorough characterization of heteroleptic [Ir(C,N) 2(C',N')] tris-cyclometallated iridium(III) complexes. Furthermore, the synthesis and characterization of heteroleptic [Ir(C,N) 2OR] complexes is presented. Under standard thermal conditions for the synthesis of the facial ( fac) isomer of tris-cyclometallated complexes, it was not possible to synthesize pure heteroleptic complexes of the form [Ir(C,N) 2(C',N')]. Instead, a mixture of homo- and heteroleptic complexes was acquired. It was found that a stepwise procedure involving the synthesis of a pure meridonial ( mer) isomer followed by photochemical isomerization of this mer to the fac isomer was necessary to synthesize pure fac-[Ir(C,N) 2(C',N')] complexes. Under thermal isomerization conditions, the conversion of mer-[Ir(C,N) 2(C',N')] to fac-[Ir(C,N) 2(C',N')] was also not a clean reaction, with again a mixture of homo- and heteroleptic complexes acquired. An investigation into the thermal mer to fac isomerization of both homo- and heteroleptic tris-cyclometallated complexes is presented. It was found that the process is an alcohol-catalyzed reaction with the formation of an iridium alkoxide [Ir(C,N) 2OR] intermediate in the isomerization process. This catalyzed reaction can be carried out between 50 and 100 degrees C, the first such example of low-temperature mer-fac thermal isomerization. We have synthesized analogous complexes and have shown that they do indeed react so as to give fac-tris-cyclometallated products. A detailed explanation of the intermediates (and all of their stereoisomers, in particular when systems of the generic formula [M(a,b) 2(a',b')] are synthesized) formed in the mer to fac isomerization process is

  2. Phenyl substitution of cationic bis-cyclometalated iridium(iii) complexes for iTMC-LEECs.

    PubMed

    Suhr, Kristin J; Bastatas, Lyndon D; Shen, Yulong; Mitchell, Lauren A; Frazier, Gary A; Taylor, David W; Slinker, Jason D; Holliday, Bradley J

    2016-11-28

    A series of seven cationic bis-cyclometalated iridium(iii) complexes of the form [(C^N) 2 (N^N)Ir][PF 6 ] has been designed in order to examine the effect of bulky, hydrophobic phenyl substituents on the structure-property relationship of these ionic transition metal complexes (iTMCs) in light-emitting electrochemical cells (LEECs). Capping phenyl substituents on the cyclometalating and ancillary ligands allows for individual tuning of the HOMO and LUMO energy levels, respectively, yielding an emission range from yellow to red. The complexes in this series exhibit increased quantum yields, up to 70% higher than the unoptimized, archetypal [(2-phenylpyridine) 2 (2,2'-bipyridine)Ir][PF 6 ]. Among these, one complex, C3, was recently reported to produce devices with superior luminance and efficiency. Simultaneous measure of the series of complexes enabled the clear discernment of trends in device performance connected to fundamental structure-property relationships that elucidate the origin of enhanced luminance. In general, phenyl substitution of the 2-phenylpyridine ligands of the parent complex produced higher luminance and faster device response than phenyl substitution of the 2,2'-bipyridine ligand. Overall, complex design and device engineering produce competitive LEECs from simple, single-layer architectures. The synthesis, crystallographic, photophysical, and electrochemical properties of the iTMCs, along with the electroluminescence properties of the LEEC devices are reported herein.

  3. Identification of an iridium(III) complex with anti-bacterial and anti-cancer activity

    PubMed Central

    Lu, Lihua; Liu, Li-Juan; Chao, Wei-chieh; Zhong, Hai-Jing; Wang, Modi; Chen, Xiu-Ping; Lu, Jin-Jian; Li, Ruei-nian; Ma, Dik-Lung; Leung, Chung-Hang

    2015-01-01

    Group 9 transition metal complexes have been widely explored as therapeutic agents due to their unique geometry, their propensity to undergo ligand exchanges with biomolecules and their diverse steric and electronic properties. These metal complexes can offer distinct modes of action in living organisms compared to carbon-based molecules. In this study, we investigated the antimicrobial and anti-proliferative abilities of a series of cyclometallated iridium(III) complexes. The iridium(III) complex 1 inhibited the growth of S. aureus with MIC and MBC values of 3.60 and 7.19 μM, respectively, indicating its potent bactericidal activity. Moreover, complex 1 also exhibited cytotoxicity against a number of cancer cell lines, with particular potency against ovarian, cervical and melanoma cells. This cyclometallated iridium(III) complex is the first example of a substitutionally-inert, Group 9 organometallic compound utilized as a direct and selective inhibitor of S. aureus. PMID:26416333

  4. A direct access to heterobimetallic complexes by roll-over cyclometallation.

    PubMed

    Schön, F; Leist, M; Neuba, A; Lang, J; Braun, C; Sun, Y; Niedner-Schatteburg, G; Bräse, S; Thiel, W R

    2017-11-02

    Complexes of the type [Cp*Ir(N,N')Cl] + (N,N' = 2-(2-dialkylaminopyrimidin-4-yl)pyrimidine) can undergo roll-over cyclometallation leading to a novel N,N'-donor site. Following this strategy heterobimetallic complexes including iridium(iii) and a Group X metal centre in the oxidation state +II were achieved.

  5. Thermally induced defluorination during a mer to fac transformation of a blue-green phosphorescent cyclometalated iridium(III) complex.

    PubMed

    Zheng, Yonghao; Batsanov, Andrei S; Edkins, Robert M; Beeby, Andrew; Bryce, Martin R

    2012-01-02

    The new homoleptic tris-cyclometalated [Ir(C^N)(3)] complexes mer-8, fac-8, and fac-9 incorporating γ-carboline ligands are reported. Reaction of 3-(2,4-difluorophenyl)-5-(2-ethylhexyl)-pyrido[4,3-b]indole 6 with iridium(III) chloride under standard cyclometalating conditions gave the homoleptic complex mer-8 in 63% yield. The X-ray crystal structure of mer-8 is described. The Ir-C and Ir-N bonds show the expected bond length alternations for the differing trans influence of phenyl and pyridyl ligands. mer-8 quantitatively isomerized to fac-8 upon irradiation with UV light. However, heating mer-8 at 290 °C in glycerol led to an unusual regioselective loss of one fluorine atom from each of the ligands, yielding fac-9 in 58% yield. fac-8 is thermally very stable: no decomposition was observed when fac-8 was heated in glycerol at 290 °C for 48 h. The γ-carboline system of fac-8 enhances thermal stability compared to the pyridyl analogue fac-Ir(46dfppy)(3)10, which decomposes extensively upon being heated in glycerol at 290 °C for 2 h. Complexes mer-8, fac-8, and fac-9 are emitters of blue-green light (λ(max)(em) = 477, 476, and 494 nm, respectively). The triplet lifetimes for fac-8 and fac-9 are ~4.5 μs at room temperature; solution Φ(PL) values are 0.31 and 0.22, respectively.

  6. Accurate simulation of geometry, singlet-singlet and triplet-singlet excitation of cyclometalated iridium(III) complex.

    PubMed

    Wang, Jian; Bai, Fu-Quan; Xia, Bao-Hui; Zhang, Hong-Xing; Cui, Tian

    2014-03-01

    In the current contribution, we present a critical study of the theoretical protocol used for the determination of the electronic spectra properties of luminescent cyclometalated iridium(III) complex, [Ir(III)(ppy)₂H₂dcbpy]⁺ (where, ppy = 2-phenylpyridine, H₂dcbpy = 2,2'-bipyridine-4,4'-dicarboxylic acid), considered as a representative example of the various problems related to the prediction of electronic spectra of transition metal complex. The choice of the exchange-correlation functional is crucial for the validity of the conclusions that would be drawn from the numerical results. The influence of the exchange-correlation on geometry parameter and absorption/emission band, the role of solvent effects on time-dependent density function theory (TD-DFT) calculations, as well as the importance of the chosen proper procedure to optimize triplet excited geometry, have been thus examined in detail. From the obtained results, some general conclusions and guidelines are presented: i) PBE0 functional is the most accurate in prediction of ground state geometry; ii) the well-established B3LYP, B3P86, PBE0, and X3LYP have similar accuracy in calculation of absorption spectrum; and iii) the hybrid approach TD-DFT//CIS gives out excellent agreement in the evaluation of triplet excitation energy.

  7. Spectroscopic, Electrochemical and DFT Studies of Phosphorescent Homoleptic Cyclometalated Iridium(III) Complexes Based on Substituted 4-Fluorophenylvinyl- and 4-Methoxyphenylvinylquinolines.

    PubMed

    Adeloye, Adewale O; Mphahlele, Malose J; Adekunle, Abolanle S; Rhyman, Lydia; Ramasami, Ponnadurai

    2017-09-21

    This study reports the synthesis and comparative investigation of the substituent effects of a new series of highly luminescent homoleptic tris-cyclometalated iridium(III) complexes of the type [Ir(N ˄ C)₃]. These are based on two ligand type derivatives comprising of 4-fluorophenylvinylquinolines and 4-methoxyphenylvinylquinolines with electron-donating and/or electron-withdrawing groups as aryl substituents at 2-position. The structures of the ligands and their complexes were characterized by means of FT-IR, UV-Vis and NMR spectrometry complemented with photoluminescence and cyclic voltammetry. The photophysical properties of 2-aryl-4-(4-fluorophenylvinyl)quinoline and its corresponding complex were also studied using the density functional theory method. The photoluminescent properties of the ligands and the corresponding complexes showed high fluorescent intensities and quantum yields in solvents of different polarities. The photoluminescence spectra of the complexes in solid film, showed common transmission curves at longer wavelengths maximum (λ em = 697 nm) possibly originating from the interference of scattered light of higher-order transmission of monochromators.

  8. Spectroscopic, Electrochemical and DFT Studies of Phosphorescent Homoleptic Cyclometalated Iridium(III) Complexes Based on Substituted 4-Fluorophenylvinyl- and 4-Methoxyphenylvinylquinolines

    PubMed Central

    Adeloye, Adewale O.; Adekunle, Abolanle S.; Ramasami, Ponnadurai

    2017-01-01

    This study reports the synthesis and comparative investigation of the substituent effects of a new series of highly luminescent homoleptic tris-cyclometalated iridium(III) complexes of the type [Ir(N˄C)3]. These are based on two ligand type derivatives comprising of 4-fluorophenylvinylquinolines and 4-methoxyphenylvinylquinolines with electron-donating and/or electron-withdrawing groups as aryl substituents at 2-position. The structures of the ligands and their complexes were characterized by means of FT-IR, UV-Vis and NMR spectrometry complemented with photoluminescence and cyclic voltammetry. The photophysical properties of 2-aryl-4-(4-fluorophenylvinyl)quinoline and its corresponding complex were also studied using the density functional theory method. The photoluminescent properties of the ligands and the corresponding complexes showed high fluorescent intensities and quantum yields in solvents of different polarities. The photoluminescence spectra of the complexes in solid film, showed common transmission curves at longer wavelengths maximum (λem = 697 nm) possibly originating from the interference of scattered light of higher-order transmission of monochromators. PMID:28934145

  9. ARTICLES: Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

    NASA Astrophysics Data System (ADS)

    Wu, Qiu-hua; Wang, Chuan-hong; Song, Xi-ming; Zhang, Guo-lin

    2010-06-01

    A new cyclometalated iridium(III) complex Ir(DPP)3 (DPP = 2,3-diphenylpyrazine) was prepared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, 1H NMR, and mass spectroscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong 1MLCT (singlet metal to ligand charge-transfer) and 3MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respectively. The complex also shows strong photoluminescence at 573 nm at room temperature. These results suggest the complex to be a promising phosphorescent material.

  10. Colorimetric and luminescent bifunctional iridium(III) complexes for the sensitive recognition of cyanide ions

    NASA Astrophysics Data System (ADS)

    Chen, Xiudan; Wang, Huili; Li, Jing; Hu, Wenqin; Li, Mei-Jin

    2017-02-01

    Two new cyclometalated iridium(III) complexes [(ppy)2Irppz]Cl (1) and [(ppy)2Irbppz]Cl (2) (where ppy = 2-phenylpyridine, ppz = 4,7-phenanthrolino-5,6:5,6-pyrazine, bppz = 2.3-di-2-pyridylpyrazine), were designed and synthesized. The structure of [(ppy)2Irppz]Cl was determined by single crystal X-ray diffraction. Their photophysical properties were also studied. This kind of complexes could coordinate with Cu2 +, the photoluminescence (PL) of the complex was quenched, and the color changed from orange-red to green. The forming M-Cu (M: complexes 1 and 2) ensemble could be further utilized as a colorimetric and emission ;turn-on; bifunctional detection for CN-, especially for complex 1-Cu2 + showed a high sensitivity toward CN- with a limit of diction is 97 nM. Importantly, this kind of iridium(III) complexes shows a unique recognition of cyanide ions over other anions which makes it an eligible sensing probe for cyanide ions.

  11. Experimental and theoretical studies of structural and photophysical properties of a novel heteroleptic cyclometalated iridium(III) complex with 8-hydroxyquinoline-phenylazo ligand

    NASA Astrophysics Data System (ADS)

    Maity, Amit; Sinha, Debopam; Rajak, Kajal Krishna

    2018-04-01

    One novel heteroleptic iridium(III) complex with cyclometalated 2-phenylquinoline(2-phq) was synthesized by the stoichiometric reaction of [Ir(2-phq)2Cl]2, i.e, Bis-[μ-chlorodi-(2-phenylquinoline)iridium(III)] and HL ligand, where L- is deprotonated form of azo ligand prepared from 8-hydroxyquinoline and aniline in a 1:1 proportion of dichloromethane and ethanol solvent at argon atmosphere in presence of mild base triethylamine in stoichiometric ratio. The prepared complex was characterized by 1H NMR, ESI-mass spectrometry, IR spectroscopy and most accurately by X-ray single crystallography. The photo physical properties like absorption and emission, i.e, photoluminescence in liquid state as well as solid state were studied exclusively. The experimental electrochemical study was also done with cyclic voltammetry. The theoretical investigations of the photo physical properties were done by DFT and TDDFT calculations. The ground state excitation transitions of the complex arise from 1ILCT and 1MLCT transition. The UV-Vis and photoluminescence transition was also investigated by NTO analysis. The triplet state emission transition was characterized by 3MLCT and some portion of 3ILCT transition.

  12. Luminescent cyclometalated iridium(III) polypyridine indole complexes--synthesis, photophysics, electrochemistry, protein-binding properties, cytotoxicity, and cellular uptake.

    PubMed

    Lau, Jason Shing-Yip; Lee, Pui-Kei; Tsang, Keith Hing-Kit; Ng, Cyrus Ho-Cheong; Lam, Yun-Wah; Cheng, Shuk-Han; Lo, Kenneth Kam-Wing

    2009-01-19

    A series of luminescent cyclometalated iridium(III) polypyridine indole complexes, [Ir(N--C)(2)(N--N)](PF(6)) (HN--C = 2-phenylpyridine (Hppy), N--N = 4-((2-(indol-3-yl)ethyl)aminocarbonyl)-4'-methyl-2,2'-bipyridine (bpy-ind) (1a), N--N = 4-((5-((2-(indol-3-yl)ethyl)aminocarbonyl)pentyl)aminocarbonyl)-4'-methyl-2,2'-bipyridine (bpy-C6-ind) (1b); HN--C = 7,8-benzoquinoline (Hbzq), N--N = bpy-ind (2a), N--N = bpy-C6-ind (2b); and HN--C = 2-phenylquinoline (Hpq), N--N = bpy-ind (3a), N--N = bpy-C6-ind (3b)), have been synthesized, characterized, and their photophysical and electrochemical properties and lipophilicity 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 (lambda(em) = 540-616 nm, tau(o) = 0.13-5.15 mus). The emission of the complexes has been assigned to a triplet metal-to-ligand charge-transfer ((3)MLCT) (dpi(Ir) --> pi*(N--N)) excited state, probably with some mixing of triplet intraligand ((3)IL) (pi --> pi*) (pq) character for complexes 3a,b. Electrochemical measurements revealed that all the complexes showed an irreversible indole oxidation wave at ca. +1.1 V versus SCE, a quasi-reversible iridium(IV/III) couple at ca. +1.3 V, and a reversible diimine reduction couple at ca. -1.3 V. The interactions of these complexes with an indole-binding protein, bovine serum albumin (BSA), have been studied by emission titrations, and the K(a) values are on the order of 10(4) M(-1). Additionally, the cytotoxicity of the complexes toward human cervix epithelioid carcinoma (HeLa) cells has been examined by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. The IC(50) values of the complexes ranged from 1.1 to 6.3 microM, which are significantly smaller than that of cisplatin (30.7 microM) under the same experimental conditions. Furthermore, the cellular uptake of the complexes has been investigated by flow cytometry and laser

  13. A Luminescent Cocaine Detection Platform Using a Split G-Quadruplex-Selective Iridium(III) Complex and a Three-Way DNA Junction Architecture.

    PubMed

    Ma, Dik-Lung; Wang, Modi; He, Bingyong; Yang, Chao; Wang, Wanhe; Leung, Chung-Hang

    2015-09-02

    In this study, a series of 10 in-house cyclometalated iridium(III) complexes bearing different auxiliary ligands were tested for their selectivity toward split G-quadruplex in order to construct a label-free switch-on cocaine detection platform employing a three-way junction architecture and a G-quadruplex motif as a signal output unit. Through two rounds of screening, we discovered that the iridium(III) complex 7 exhibited excellent selectivity toward the intermolecular G-quadruplex motif. A detection limit as low as 30 nM for cocaine can be achieved by this sensing approach with a linear relationship between luminescence intensity and cocaine concentration established from 30 to 300 nM. Furthermore, this sensing approach could detect cocaine in diluted oral fluid. We hope that our simple, signal-on, label-free oligonucleotide-based sensing method for cocaine using a three-way DNA junction architecture could act as a useful platform in bioanalytical research.

  14. Singlet Oxygen Generation by Cyclometalated Complexes and Applications†

    PubMed Central

    Ashen-Garry, David; Selke, Matthias

    2014-01-01

    While cyclometalated complexes have been extensively studied for optoelectronic applications, these compounds also represent a relatively new class of photosensitizers for the production of singlet oxygen. Thus far, singlet oxygen generation from cyclometalated Ir and Pt complexes has been studied in detail. In this review, photophysical data for singlet oxygen generation from these complexes is presented, and the mechanism of 1O2 generation is discussed, including evidence for singlet oxygen generation via an electron transfer mechanism for some of cyclometalated Ir complexes. The period from the first report of singlet oxygen generation by a cyclometalated Ir complex in 2002 through August 2013 is covered in this review. This new class of singlet oxygen photosensitizers may prove to be rather versatile due to the ease of substitution of ancillary ligands without loss of activity. Several cyclometalated complexes have been tethered to zeolites, polystyrene, or quantum dots. Applications for photooxygenation of organic molecules, including “traditional” singlet oxygen reactions (ene reaction, [4+2] and [2+2] cycloadditions) as well as oxidative coupling of amines are presented. Potential biomedical applications are also reviewed. PMID:24344628

  15. A cyclometalated iridium(III) complex used as a conductor for the electrochemical sensing of IFN-γ

    NASA Astrophysics Data System (ADS)

    Miao, Xiangmin; Ko, Chung-Nga; Vellaisamy, Kasipandi; Li, Zongbing; Yang, Guanjun; Leung, Chung-Hang; Ma, Dik-Lung

    2017-02-01

    A novel iridium(III) complex was prepared and used as a conductor for sensitive and enzyme-free electrochemical detection of interferon gamma (IFN-γ). This assay is based on a dual signal amplification mechanism involving positively charged gold nanoparticles ((+)AuNPs) and hybridization chain reaction (HCR). To construct the sensor, nafion (Nf) and (+)AuNPs composite membrane was first immobilized onto the electrode surface. Subsequently, a loop-stem structured capture probe (CP) containing a special IFN-γ interact strand was modified onto the (+)AuNP surface via the formation of Au-S bonds. Upon addition of IFN-γ, the loop-stem structure of CP was opened, and the newly exposed “sticky” region of CP then hybridized with DNA hairpin-1 (H1), which in turn opened its hairpin structure for hybridizing with DNA hairpin-2 (H2). Happen of HCR between H1 and H2 thus generated a polymeric duplex DNA (dsDNA) chain. Meanwhile, the iridium(III) complex could interact with the grooves of the dsDNA polymer, producing a strong current signal that was proportional to IFN-γ concentration. Thus, sensitive detection of IFN-γ could be realized with a detection limit down to 16.3 fM. Moreover, satisfied results were achieved by using this method for the detection of IFN-γ in human serum samples.

  16. Singlet oxygen generation by cyclometalated complexes and applications.

    PubMed

    Ashen-Garry, David; Selke, Matthias

    2014-01-01

    While cyclometalated complexes have been extensively studied for optoelectronic applications, these compounds also represent a relatively new class of photosensitizers for the production of singlet oxygen. Thus far, singlet oxygen generation from cyclometalated Ir and Pt complexes has been studied in detail. In this review, photophysical data for singlet oxygen generation from these complexes are presented, and the mechanism of (1) O2 generation is discussed, including evidence for singlet oxygen generation via an electron-transfer mechanism for some of cyclometalated Ir complexes. The period from the first report of singlet oxygen generation by a cyclometalated Ir complex in 2002 through August 2013 is covered in this review. This new class of singlet oxygen photosensitizers may prove to be rather versatile due to the ease of substitution of ancillary ligands without loss of activity. Several cyclometalated complexes have been tethered to zeolites, polystyrene, or quantum dots. Applications for photooxygenation of organic molecules, including "traditional" singlet oxygen reactions (ene reaction, [4 + 2] and [2 + 2] cycloadditions) as well as oxidative coupling of amines are presented. Potential biomedical applications are also reviewed. © 2013 The American Society of Photobiology.

  17. Mitochondria-targeting cyclometalated iridium(III)-PEG complexes with tunable photodynamic activity.

    PubMed

    Li, Steve Po-Yam; Lau, Chris Tsan-Shing; Louie, Man-Wai; Lam, Yun-Wah; Cheng, Shuk Han; Lo, Kenneth Kam-Wing

    2013-10-01

    We present a new class of phosphorescent cyclometalated iridium(III) polypyridine poly(ethylene glycol) (PEG) complexes [Ir(N(^)C)2(bpy-CONH-PEG)](PF6) (bpy-CONH-PEG = 4-(N-(2-(ω-methoxypoly-(1-oxapropyl))ethyl)aminocarbonyl)-4'-methyl-2,2'-bipyridine, number average molecular weight (Mn) = 5272.23, weight average molecular weight (Mw) = 5317.38, polydispersity index (PDI) = 1.009; HN(^)C = 2-phenylpyridine, Hppy (1a), 2-((1,1'-biphenyl)-4-yl)pyridine, Hpppy (2a), 2-phenylquinoline, Hpq (3a), 2-phenylbenzothiazole, Hbt (4a), 2-(1-naphthyl)benzothiazole, Hbsn (5a)). The photophysical, photochemical, and biological properties of these complexes have been compared with those of their PEG-free counterparts [Ir(N(^)C)2(bpy-CONH-Et)](PF6) (bpy-CONH-Et = 4-(N-ethylaminocarbonyl)-4'-methyl-2,2'-bipyridine; HN(^)C = Hppy (1b), Hpppy (2b), Hpq (3b), Hbt (4b), Hbsn (5b)). Upon irradiation, all the complexes exhibited intense and long-lived green to orange-red emission under ambient conditions. The emission was phosphorescence in nature and can be quenched by O2 with the generation of singlet oxygen ((1)O2). The quantum yields for (1)O2 production of the complexes in aerated DMSO (0.24-0.83) were found to be dependent on the excited-state lifetimes of the complexes, which can be altered using different cyclometalating ligands (N(^)C). Cell-based assays indicated that the PEG complexes were noncytotoxic in the dark (IC50 > 300 μM); however, most of them became significantly cytotoxic upon irradiation (IC50 = 3.4 - 23.2 μM). Laser-scanning confocal microscopy images revealed localization of complex 3a in the mitochondrial region of HeLa cells and the induction of rapid necrotic cell death upon light activation. Additionally, the lack of dark toxicity and potential application of the PEG complexes as a visualizing reagent have been demonstrated using zebrafish (Danio rerio) as an animal model. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Luminescent Rhenium(I) and Iridium(III) Polypyridine Complexes as Biological Probes, Imaging Reagents, and Photocytotoxic Agents.

    PubMed

    Lo, Kenneth Kam-Wing

    2015-12-15

    Although the interactions of transition metal complexes with biological molecules have been extensively studied, the use of luminescent transition metal complexes as intracellular sensors and bioimaging reagents has not been a focus of research until recently. The main advantages of luminescent transition metal complexes are their high photostability, long-lived phosphorescence that allows time-resolved detection, and large Stokes shifts that can minimize the possible self-quenching effect. Also, by the use of transition metal complexes, the degree of cellular uptake can be readily determined using inductively coupled plasma mass spectrometry. For more than a decade, we have been interested in the development of luminescent transition metal complexes as covalent labels and noncovalent probes for biological molecules. We argue that many transition metal polypyridine complexes display triplet charge transfer ((3)CT) emission that is highly sensitive to the local environment of the complexes. Hence, the biological labeling and binding interactions can be readily reflected by changes in the photophysical properties of the complexes. In this laboratory, we have modified luminescent tricarbonylrhenium(I) and bis-cyclometalated iridium(III) polypyridine complexes of general formula [Re(bpy-R(1))(CO)3(py-R(2))](+) and [Ir(ppy-R(3))2(bpy-R(4))](+), respectively, with reactive functional groups and used them to label the amine and sulfhydryl groups of biomolecules such as oligonucleotides, amino acids, peptides, and proteins. Additionally, using a range of biological substrates such as biotin, estradiol, and indole, we have designed luminescent rhenium(I) and iridium(III) polypyridine complexes as noncovalent probes for biological receptors. The interesting results generated from these studies have prompted us to investigate the possible applications of luminescent transition metal complexes in intracellular systems. Thus, in the past few years, we have developed an interest

  19. Phosphorescent cyclometalated complexes for efficient blue organic light-emitting diodes

    PubMed Central

    Suzuri, Yoshiyuki; Oshiyama, Tomohiro; Ito, Hiroto; Hiyama, Kunihisa; Kita, Hiroshi

    2014-01-01

    Phosphorescent emitters are extremely important for efficient organic light-emitting diodes (OLEDs), which attract significant attention. Phosphorescent emitters, which have a high phosphorescence quantum yield at room temperature, typically contain a heavy metal such as iridium and have been reported to emit blue, green and red light. In particular, the blue cyclometalated complexes with high efficiency and high stability are being developed. In this review, we focus on blue cyclometalated complexes. Recent progress of computational analysis necessary to design a cyclometalated complex is introduced. The prediction of the radiative transition is indispensable to get an emissive cyclometalated complex. We summarize four methods to control phosphorescence peak of the cyclometalated complex: (i) substituent effect on ligands, (ii) effects of ancillary ligands on heteroleptic complexes, (iii) design of the ligand skeleton, and (iv) selection of the central metal. It is considered that novel ligand skeletons would be important to achieve both a high efficiency and long lifetime in the blue OLEDs. Moreover, the combination of an emitter and a host is important as well as the emitter itself. According to the dependences on the combination of an emitter and a host, the control of exciton density of the triplet is necessary to achieve both a high efficiency and a long lifetime, because the annihilations of the triplet state cause exciton quenching and material deterioration. PMID:27877712

  20. Phosphorescent cyclometalated complexes for efficient blue organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Suzuri, Yoshiyuki; Oshiyama, Tomohiro; Ito, Hiroto; Hiyama, Kunihisa; Kita, Hiroshi

    2014-10-01

    Phosphorescent emitters are extremely important for efficient organic light-emitting diodes (OLEDs), which attract significant attention. Phosphorescent emitters, which have a high phosphorescence quantum yield at room temperature, typically contain a heavy metal such as iridium and have been reported to emit blue, green and red light. In particular, the blue cyclometalated complexes with high efficiency and high stability are being developed. In this review, we focus on blue cyclometalated complexes. Recent progress of computational analysis necessary to design a cyclometalated complex is introduced. The prediction of the radiative transition is indispensable to get an emissive cyclometalated complex. We summarize four methods to control phosphorescence peak of the cyclometalated complex: (i) substituent effect on ligands, (ii) effects of ancillary ligands on heteroleptic complexes, (iii) design of the ligand skeleton, and (iv) selection of the central metal. It is considered that novel ligand skeletons would be important to achieve both a high efficiency and long lifetime in the blue OLEDs. Moreover, the combination of an emitter and a host is important as well as the emitter itself. According to the dependences on the combination of an emitter and a host, the control of exciton density of the triplet is necessary to achieve both a high efficiency and a long lifetime, because the annihilations of the triplet state cause exciton quenching and material deterioration.

  1. Synthesis and luminescence properties of iridium(III) azide- and triazole-bisterpyridine complexes.

    PubMed

    Goldstein, Daniel C; Peterson, Joshua R; Cheng, Yuen Yap; Clady, Raphael G C; Schmidt, Timothy W; Thordarson, Pall

    2013-07-26

    We describe here the synthesis of azide-functionalised iridium(III) bisterpyridines using the "chemistry on the complex" strategy. The resulting azide-complexes are then used in the copper(I)-catalysed azide-alkyne Huisgen 1,3-dipolar cycloaddition "click chemistry" reaction to from the corresponding triazole-functionalised iridium(III) bisterpyridines. The photophysical characteristics, including lifetimes, of these compounds were also investigated. Interestingly, oxygen appears to have very little effect on the lifetime of these complexes in aqueous solutions. Unexpectedly, sodium ascorbate acid appears to quench the luminescence of triazole-functionalised iridium(III) bisterpyridines, but this effect can be reversed by the addition of copper(II) sulfate, which is known to oxidize ascorbate under aerobic conditions. The results demonstrate that iridium(III) bisterpyridines can be functionalized for use in "click chemistry" facilitating the use of these photophysically interesting complexes in the modification of polymers or surfaces, to highlight just two possible applications.

  2. Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes.

    PubMed

    Lewis, David J; Dore, Valentina; Rogers, Nicola J; Mole, Thomas K; Nash, Gerard B; Angeli, Panagiota; Pikramenou, Zoe

    2013-11-26

    To establish highly luminescent nanoparticles for monitoring fluid flows, we examined the preparation of silica nanoparticles based on immobilization of a cyclometalated iridium(III) complex and an examination of the photophysical studies provided a good insight into the Ir(III) microenvironment in order to reveal the most suitable silica nanoparticles for micro particle imaging velocimetry (μ-PIV) studies. Iridium complexes covalently incorporated at the surface of preformed silica nanoparticles, [Ir-4]@Si500-Z, using a fluorinated polymer during their preparation, demonstrated better stability than those without the polymer, [Ir-4]@Si500, as well as an increase in steady state photoluminescence intensity (and therefore particle brightness) and lifetimes which are increased by 7-fold compared with nanoparticles with the same metal complex attached covalently throughout their core, [Ir-4]⊂Si500. Screening of the nanoparticles in fluid flows using epi-luminescence microscopy also confirm that the brightest, and therefore most suitable particles for microparticle imaging velocimetry (μ-PIV) measurements are those with the Ir(III) complex immobilized at the surface with fluorosurfactant, that is [Ir-4]@Si500-Z. μ-PIV studies demonstrate the suitability of these nanoparticles as nanotracers in microchannels.

  3. Derivatization of bichromic cyclometalated Ru(II) complexes with hydrophobic substituents.

    PubMed

    Robson, Kiyoshi C D; Koivisto, Bryan D; Berlinguette, Curtis P

    2012-02-06

    The syntheses and physical properties of cyclometalated Ru(II) complexes containing a triphenylamine (TPA) unit bearing aliphatic groups are reported. Each member of the series consists of an octahedral Ru(II) center coordinated by a tridentate polypyridyl ligand and a tridentate cyclometalating ligand. One of the chelating ligands contains electron-deficient methyl ester groups, while a TPA unit is attached to the central ring of the adjacent chelating ligand through a thiophene bridge. This study builds on our previous work (Inorg. Chem. 2011, 50, 6019-6028; Inorg. Chem. 2011, 50, 5494-5508) by (i) outlining a synthetic protocol for installing aliphatic groups on the TPA substituents, (ii) examining the role that terminal -O-hexyl and -S-hexyl groups situated on the TPA have on the electrochemical properties, and (iii) demonstrating the potential benefit of installing the TPA on the neutral chelating ligand rather than the anionic chelating ligand. The results reported herein provide important synthetic advances for our broader goal of developing bis-tridentate cyclometalated Ru(II) complexes for light-harvesting applications.

  4. Stereoselective Synthesis of Cyclometalated Iridium (III) Complexes: Characterization and Photophysical Properties

    PubMed Central

    Yang, Liangru; von Zelewsky, Alex; Nguyen, Huong P.; Muller, Gilles; Labat, Gaël; Stoeckli-Evans, Helen

    2009-01-01

    The stereoselective synthesis of a highly luminescent neutral Ir(III) complex comprising two bidentate chiral, cyclometalating phenylpyridine derivatives, and one acetylacetonate as ligands is described. The final complex and some intermediates were characterized by X-ray structural analysis, NMR-, CD-, and CPL-spectroscopy. PMID:20161195

  5. A Colorimetric and Luminescent Dual-Modal Assay for Cu(II) Ion Detection Using an Iridium(III) Complex

    PubMed Central

    Ma, Dik-Lung; He, Hong-Zhang; Chan, Daniel Shiu-Hin; Wong, Chun-Yuen; Leung, Chung-Hang

    2014-01-01

    A novel iridium(III) complex-based chemosensor bearing the 5,6-bis(salicylideneimino)-1,10-phenanthroline ligand receptor was developed, which exhibited a highly sensitive and selective color change from colorless to yellow and a visible turn-off luminescence response upon the addition of Cu(II) ions. The interactions of this iridium(III) complex with Cu2+ ions and thirteen other cations have been investigated by UV-Vis absorption titration, emission titration, and 1H NMR titration. PMID:24927177

  6. Cyclometalated ruthenium(II) complexes with a bis-carbene CCC-pincer ligand.

    PubMed

    Zhang, You-Ming; Shao, Jiang-Yang; Yao, Chang-Jiang; Zhong, Yu-Wu

    2012-08-21

    The first series of cyclometalated ruthenium complexes with a CCC-pincer bis-carbene ligand have been obtained as bench-stable compounds. Single-crystal X-ray analysis of one of these complexes with 4'-di-p-anisylamino-2,2':6',2''-terpyridine is presented. The Ru(II/III) redox potentials and MLCT absorptions of these complexes can be varied by attaching an electron-donating or -withdrawing group on the noncyclometalating ligand.

  7. Photofunctional triplet excited states of cyclometalated Ir(III) complexes: beyond electroluminescence.

    PubMed

    You, Youngmin; Nam, Wonwoo

    2012-11-07

    The development of cyclometalated Ir(III) complexes has enabled important breakthroughs in electroluminescence because such complexes permit the efficient population of triplet excited states that give rise to luminescent transitions. The triplet states of Ir(III) complexes are advantageous over those of other transition metal complexes in that their electronic transitions and charge-transfer characteristics are tunable over wide ranges. These favorable properties suggest that Ir(III) complexes have significant potential in a variety of photofunctions other than electroluminescence. In this critical review, we describe recent photonic applications of novel Ir(III) complexes. Ir(III) complexes have been shown to affect the exciton statistics in the active layers of organic photovoltaic cells, thereby improving the photon-to-current conversion efficiencies. Nonlinear optical applications that take advantage of the strong charge-transfer properties of triplet transitions are also discussed. The tunability of the electrochemical potentials facilitates the development of efficient photocatalysis in the context of water photolysis or organic syntheses. The photoredox reactivities of Ir(III) complexes have been employed in studies of charge migration along DNA chains. The photoinduced cytotoxicity of Ir(III) complexes on live cells suggests that the complexes may be useful in photodynamic therapy. Potential biological applications of the complexes include phosphorescence labeling and sensing. Intriguing platforms based on cyclometalated Ir(III) complexes potentially provide novel protein tagging and ratiometric detection. We envision that future research into the photofunctionality of Ir(III) complexes will provide important breakthroughs in a variety of photonic applications.

  8. White-light phosphorescence emission from a single molecule: application to OLED.

    PubMed

    Bolink, Henk J; De Angelis, Filippo; Baranoff, Etienne; Klein, Cédric; Fantacci, Simona; Coronado, Eugenio; Sessolo, Michele; Kalyanasundaram, K; Grätzel, Michael; Nazeeruddin, Md K

    2009-08-21

    A simple mononuclear cyclometallated iridium(iii) complex exhibits white photo- and electro- luminescence in the wavelength range from 440 to 800 nm, which originates from a single emitting excited state of mixed character.

  9. Cyclometalated Iridium(III) Carbene Phosphors for Highly Efficient Blue Organic Light-Emitting Diodes.

    PubMed

    Chen, Zhao; Wang, Liqi; Su, Sikai; Zheng, Xingyu; Zhu, Nianyong; Ho, Cheuk-Lam; Chen, Shuming; Wong, Wai-Yeung

    2017-11-22

    Five deep blue carbene-based iridium(III) phosphors were synthesized and characterized. Interestingly, one of them can be fabricated into deep blue, sky blue and white organic light-emitting diodes (OLEDs) through changing the host materials and exciton blocking layers. These deep and sky blue devices exhibit Commission Internationale de l'Éclairage (CIE) coordinates of (0.145, 0.186) and (0.152, 0.277) with external quantum efficiency (EQE) of 15.2% and 9.6%, respectively. The EQE of the deep blue device can be further improved up to 19.0% by choosing a host with suitable energy level of its lowest unoccupied molecular orbital (LUMO).

  10. When two are better than one: bright phosphorescence from non-stereogenic dinuclear iridium(III) complexes.

    PubMed

    Daniels, Ruth E; Culham, Stacey; Hunter, Michael; Durrant, Marcus C; Probert, Michael R; Clegg, William; Williams, J A Gareth; Kozhevnikov, Valery N

    2016-04-28

    A new family of eight dinuclear iridium(iii) complexes has been prepared, featuring 4,6-diarylpyrimidines L(y) as bis-N^C-coordinating bridging ligands. The metal ions are also coordinated by a terminal N^C^N-cyclometallating ligand L(X) based on 1,3-di(2-pyridyl)benzene, and by a monodentate chloride or cyanide. The general formula of the compounds is {IrL(X)Z}2L(y) (Z = Cl or CN). The family comprises examples with three different L(X) ligands and five different diarylpyrimidines L(y), of which four are diphenylpyrimidines and one is a dithienylpyrimidine. The requisite proligands have been synthesised via standard cross-coupling methodology. The synthesis of the complexes involves a two-step procedure, in which L(X)H is reacted with IrCl3·3H2O to form dinuclear complexes of the form [IrL(X)Cl(μ-Cl)]2, followed by treatment with the diarylpyrimidine L(y)H2. Crucially, each complex is formed as a single compound only: the strong trans influence of the metallated rings dictates the relative disposition of the ligands, whilst the use of symmetrically substituted tridentate ligands eliminates the possibility of Λ and Δ enantiomers that are obtained when bis-bidentate units are linked through bridging ligands. The crystal structure of one member of the family has been obtained using a synchrotron X-ray source. All of the complexes are very brightly luminescent, with emission maxima in solution varying over the range 517-572 nm, according to the identity of the ligands. The highest-energy emitter is the cyanide derivative whilst the lowest is the complex with the dithienylpyrimidine. The trends in both the absorption and emission energies as a function of ligand substituent have been rationalised accurately with the aid of TD-DFT calculations. The lowest-excited singlet and triplet levels correlate with the trend in the HOMO-LUMO gap. All the complexes have quantum yields that are close to unity and phosphorescence lifetimes - of the order of 500 ns - that are

  11. Antagonizing STAT3 dimerization with a rhodium(III) complex.

    PubMed

    Ma, Dik-Lung; Liu, Li-Juan; Leung, Ka-Ho; Chen, Yen-Ting; Zhong, Hai-Jing; Chan, Daniel Shiu-Hin; Wang, Hui-Min David; Leung, Chung-Hang

    2014-08-25

    Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A bioaccumulative cyclometalated platinum(II) complex with two-photon-induced emission for live cell imaging.

    PubMed

    Koo, Chi-Kin; Wong, Ka-Leung; Man, Cornelia Wing-Yin; Lam, Yun-Wah; So, Leo King-Yan; Tam, Hoi-Lam; Tsao, Sai-Wah; Cheah, Kok-Wai; Lau, Kai-Chung; Yang, Yang-Yi; Chen, Jin-Can; Lam, Michael Hon-Wah

    2009-02-02

    The cyclometalated platinum(II) complex [Pt(L)Cl], where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine containing C(phenyl), N(pyridyl), and N(pyrazolyl) donor moieties, was found to possess two-photon-induced luminescent properties. The two-photon-absorption cross section of the complex in N,N-dimethylformamide at room temperature was measured to be 20.8 GM. Upon two-photon excitation at 730 nm from a Ti:sapphire laser, bright-green emission was observed. Besides its two-photon-induced luminescent properties, [Pt(L)Cl] was able to be rapidly accumulated in live HeLa and NIH3T3 cells. The two-photon-induced luminescence of the complex was retained after live cell internalization and can be observed by two-photon confocal microscopy. Its bioaccumulation properties enabled time-lapse imaging of the internalization process of the dye into living cells. Cytotoxicity of [Pt(L)Cl] to both tested cell lines was low, according to MTT assays, even at loadings as high as 20 times the dose concentration for imaging for 6 h.

  13. Cytotoxicity of Cyclometalated Platinum Complexes Based on Tridentate NCN and CNN-coordinating ligands: Remarkable Coordination Dependence

    PubMed Central

    Vezzu, Dileep A. k.; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

    2014-01-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the NʌCʌN-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the CʌNʌN-coordinated platinum complex based on 6-phenyl-2,2′-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by NʌCʌN- and CʌNʌN-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the NʌCʌN-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis was studied by western blot analysis and the activation of PARP via caspase 7 was observed. PMID:24531534

  14. Cyclometalated gold(III) trioxadiborrin complexes: studies of the bonding and excited states.

    PubMed

    Ayoub, Nicholas A; Browne, Amberle R; Anderson, Bryce L; Gray, Thomas G

    2016-03-07

    Trioxadiborrins are chelating ligands that assemble in dehydration reactions of boronic acids. They are structurally related to β-diketonate ligands, but have a 2-charge. Little is known of the bonding properties of trioxadiborrin ligands. Presented here are density-functional theory (DFT) studies of cyclometalated gold(III) trioxadiborrins. Substituent effects are evaluated, and comparison is made to the cyclometalating 2-(4-tolyl)pyridine (tpy) ligand on gold. The tpy ligand binds more strongly than any trioxadiborrin ligand considered here, and the two ligands bind competitively to gold. The 1,3-diphenyl trioxadiborrin ligand of 1 has a larger absolute binding enthalpy to gold than its β-diketonate analogue. Conjugation between boron and aryl substituents delocalizes charge and attenuates the trioxadiborrin's binding capacity. Steric effects that disrupt conjugation between boron and aryl substituents cause the trioxadiborrin to chelate more tightly. Fragment bond orders are divided into in-plane and out-of-plane contributions for square planar 1. In-plane bonding accounts for 88% of bond order between (tpy)Au2+ and the trioxadiborrin ligand. Cyclometalated gold(III) trioxadiborrin complexes were previously shown to be phosphorescent. Spin-unrestricted triplet-state geometry optimizations find that the ten largest excited-state distortions all occur on the tpy ligand. A plot of spin density in triplet 1 shows spin to reside predominantly on tpy. The 77 K luminescence spectrum of 1 is reported here. Time-dependent DFT and configuration interaction singles calculations (corrected for doubles excitations) overestimate the emission energy by ∼ 0.12 eV.

  15. Cytotoxicity of cyclometalated platinum complexes based on tridentate NCN and CNN-coordinating ligands: remarkable coordination dependence.

    PubMed

    Vezzu, Dileep A K; Lu, Qun; Chen, Yan-Hua; Huo, Shouquan

    2014-05-01

    A series of cyclometalated platinum complexes with diverse coordination patterns and geometries were screened for their anticancer activity. It was discovered that the N^C^N-coordinated platinum complex based on 1,3-di(pyridyl)benzene displayed much higher cytotoxicity against human lung cancer cells NCI-H522, HCC827, and NCI-H1299, and human prostate cancer cell RV1 than cisplatin. In a sharp contrast, the C^N^N-coordinated platinum complex based on 6-phenyl-2,2'-bipyridine was ineffective on these cancer cells. This remarkable difference in cytotoxicity displayed by N^C^N- and C^N^N-coordinated platinum complexes was related to the trans effect of the carbon donor in the cyclometalated platinum complexes, which played a crucial role in facilitating the dissociation of the chloride ligand to create an active binding site. The DNA binding was studied for the N^C^N-coordinated platinum complex using electrophoresis and emission titration. The cellular uptake observed by fluorescent microscope showed that the complex is largely concentrated in the cytoplasm. The possible pathways for the cell apoptosis were studied by western blot analysis and the activation of PARP via caspase 7 was observed. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Diarylethene-containing cyclometalated platinum(II) complexes: tunable photochromism via metal coordination and rational ligand design.

    PubMed

    Chan, Jacky Chi-Hung; Lam, Wai Han; Wong, Hok-Lai; Zhu, Nianyong; Wong, Wing-Tak; Yam, Vivian Wing-Wah

    2011-08-17

    The synthesis, characterization, electrochemistry, photophysics and photochromic behavior of a new class of cyclometalated platinum(II) complexes [Pt(C(∧)N)(O(∧)O)] (1a-5a and 1b-5b), where C(∧)N is a cyclometalating 2-(2'-thienyl)pyridyl (thpy) or 2-(2'-thienothienyl)pyridyl (tthpy) ligand containing the photochromic dithienylethene (DTE) unit and O(∧)O is a β-diketonato ligand of acetylacetonato (acac) or hexafluoroacetylacetonato (hfac), have been reported. The X-ray crystal structures of five of the complexes have also been determined. The electrochemical studies reveal that the first quasi-reversible reduction couple, and hence the nature of lowest unoccupied molecular orbital (LUMO) of the complexes, is sensitive to the nature of the ancillary O(∧)O ligands. Upon photoexcitation, complexes 1a-3a and 1b-3b exhibit drastic color changes, ascribed to the reversible photochromic behavior, which is found to be sensitive to the substituents on the pyridyl ring and the extent of π-conjugation of the C(∧)N ligand as well as the nature of the ancillary ligand. The thermal bleaching kinetics of complex 1a has been studied in toluene at various temperatures, and the activation barrier for the thermal cycloreversion of the complex has been determined. Density functional theory (DFT) calculations have been performed to provide an insight into the electrochemical, photophysical and photochromic properties.

  17. Blue phosphorescent nitrile containing C^C* cyclometalated NHC platinum(II) complexes.

    PubMed

    Tronnier, Alexander; Metz, Stefan; Wagenblast, Gerhard; Muenster, Ingo; Strassner, Thomas

    2014-02-28

    Since C^C* cyclometalated Pt(II) complexes with N-heterocyclic carbene (NHC) ligands have been identified as potential emitter materials in organic light-emitting devices (OLEDs), very promising results regarding quantum yields, colour and stability have been presented. Herein, we report on four nitrile substituted complexes with a chelating NHC ligand (1-(4-cyanophenyl)-3-isopropyl-1H-benzo[d]imidazole or 4-(tert-butyl)-1-(4-cyanophenyl)-3-methyl-1H-imidazole) and a bidentate monoanionic auxiliary ligand (acetylacetone or dimesitoylmethane). The complexes have been fully characterized including extensive 2D NMR studies (COSY, HSQC, HMBC, NOESY, (195)Pt NMR), three of them also by solid-state structures. Photophysical measurements in amorphous PMMA films and pure emitter films at room temperature reveal the impact of the mesityl groups in the auxiliary ligand, which led to a significant increase of the quantum yield, while the decay lifetimes decreased. The electron withdrawing nitrile groups shift the emission towards blue colour coordinates.

  18. A One-Pot Self-Assembly Reaction to Prepare a Supramolecular Palladium(II) Cyclometalated Complex: An Undergraduate Organometallic Laboratory Experiment

    ERIC Educational Resources Information Center

    Fernandez, Alberto; Lopez-Torres, Margarita; Fernandez, Jesus J.; Vazquez-Garcia, Digna; Vila, Jose M.

    2012-01-01

    A laboratory experiment for students in advanced inorganic chemistry is described. Students prepare palladium(II) cyclometalated complexes. A terdentate [C,N,O] Schiff base ligand is doubly deprotonated upon reaction with palladium(II) acetate in a self-assembly process to give a palladacycle with a characteristic tetranuclear structure. This…

  19. A G-quadruplex-selective luminescent iridium(III) complex and its application by long lifetime.

    PubMed

    Lin, Sheng; Lu, Lihua; Liu, Jin-Biao; Liu, Chenfu; Kang, Tian-Shu; Yang, Chao; Leung, Chung-Hang; Ma, Dik-Lung

    2017-05-01

    The G-quadruplex motif has been widely used for the construction of analytical detection platforms due to its rich structural polymorphism and flexibility. Luminescent assays are often limited due to the interference from endogenous fluorophores in biological samples. To address this challenge, a novel long lifetime iridium(III) complex 1 was synthesized and used to construct a G-quadruplex-based assay for detecting prostate specific antigen (PSA) in aqueous solution. PSA is a common biomarker in serum and used as a model for demonstration in this work. The PSA assay has achieved a detection limit of 40.8pg·mL -1 , and shows high selectivity towards PSA over other proteins. Additionally, the assay could function in diluted human serum by using time-resolved luminescent spectroscopy, with good linearity from 1 to 10ng·mL -1 of PSA, which is adequate to detect the PSA levels for physiological (<4ng·mL -1 ) and clinical (4-10ng·mL -1 ) applications. The assay was successfully constructed. As revealed from time-resolved method, the long lifetime property of iridium(III) complex 1 plays an important role in distinguishing phosphorescence signals from short-life auto-fluorescence of human serum. Luminescent transition metal complexes offer several advantages over other widely used organic fluorophores, such as long phosphorescence lifetime, large Stokes shift and modular syntheses. In addition, the assay could work effectively in diluted human serum using time-resolved luminescent spectroscopy, it therefore could be potentially developed to monitor PSA in biological samples. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. C^C* cyclometalated platinum(II) N-heterocyclic carbene complexes with a sterically demanding β-diketonato ligand – synthesis, characterization and photophysical properties.

    PubMed

    Tenne, M; Metz, S; Wagenblast, G; Münster, Ingo; Strassner, T

    2015-05-14

    Neutral cyclometalated platinum(ii) N-heterocyclic carbene complexes [Pt(C^C*)(O^O)] with C^C* ligands based on 1-phenyl-1,2,4-triazol-5-ylidene and 4-phenyl-1,2,4-triazol-5-ylidene, as well as acetylacetonato (O^O = acac) and 1,3-bis(2,4,6-trimethylphenyl)propan-1,3-dionato (O^O = mesacac) ancillary ligands were synthesized and characterized. All complexes are emissive at room temperature in a poly(methyl methacrylate) (PMMA) matrix with emission maxima in the blue region of the spectrum. High quantum efficiencies and short decay times were observed for all complexes with mesacac ancillary ligands. The sterically demanding mesityl groups of the mesacac ligand effectively prevent molecular stacking. The emission behavior of these emitters is in general independent of the position of the nitrogen in the backbone of the N-heterocyclic carbene (NHC) unit and a variety of substituents in 4-position of the phenyl unit, meta to the cyclometalating bond.

  1. Mitochondrial Dynamics Tracking with Two-Photon Phosphorescent Terpyridyl Iridium(III) Complexes

    NASA Astrophysics Data System (ADS)

    Huang, Huaiyi; Zhang, Pingyu; Qiu, Kangqiang; Huang, Juanjuan; Chen, Yu; Ji, Liangnian; Chao, Hui

    2016-02-01

    Mitochondrial dynamics, including fission and fusion, control the morphology and function of mitochondria, and disruption of mitochondrial dynamics leads to Parkinson’s disease, Alzheimer’s disease, metabolic diseases, and cancers. Currently, many types of commercial mitochondria probes are available, but high excitation energy and low photo-stability render them unsuitable for tracking mitochondrial dynamics in living cells. Therefore, mitochondrial targeting agents that exhibit superior anti-photo-bleaching ability, deep tissue penetration and intrinsically high three-dimensional resolutions are urgently needed. Two-photon-excited compounds that use low-energy near-infrared excitation lasers have emerged as non-invasive tools for cell imaging. In this work, terpyridyl cyclometalated Ir(III) complexes (Ir1-Ir3) are demonstrated as one- and two-photon phosphorescent probes for real-time imaging and tracking of mitochondrial morphology changes in living cells.

  2. Organometallic rhodium(III) and iridium(III) cyclopentadienyl complexes with curcumin and bisdemethoxycurcumin co-ligands.

    PubMed

    Pettinari, Riccardo; Marchetti, Fabio; Pettinari, Claudio; Condello, Francesca; Petrini, Agnese; Scopelliti, Rosario; Riedel, Tina; Dyson, Paul J

    2015-12-21

    A series of half-sandwich cyclopentadienyl rhodium(III) and iridium(III) complexes of the type [Cp*M(curc/bdcurc)Cl] and [Cp*M(curc/bdcurc)(PTA)][SO3CF3], in which Cp* = pentamethylcyclopentadienyl, curcH = curcumin and bdcurcH = bisdemethoxycurcumin as O^O-chelating ligands, and PTA = 1,3,5-triaza-7-phosphaadamantane, is described. The X-ray crystal structures of three of the complexes, i.e. [Cp*Rh(curc)(PTA)][SO3CF3] (5), [Cp*Rh(bdcurc)(PTA)][SO3CF3] (6) and [Cp*Ir(bdcurc)(PTA)][SO3CF3] (8), confirm the expected "piano-stool" geometry. With the exception of 5, the complexes are stable under pseudo-physiological conditions and are moderately cytotoxic to human ovarian carcinoma (A2780 and A2780cisR) cells and also to non-tumorigenic human embryonic kidney (HEK293) cells, but lack the cancer cell selectivity observed for related arene ruthenium(II) complexes.

  3. Transition-metal phosphors with cyclometalating ligands: fundamentals and applications.

    PubMed

    Chi, Yun; Chou, Pi-Tai

    2010-02-01

    One goal of this critical review is to provide advanced methodologies for systematic preparation of transition-metal based phosphors that show latent applications in the field of organic light emitting diodes (OLEDs). We are therefore reviewing various types of cyclometalating chelates for which the favorable metal-chelate bonding interaction, on the one hand, makes the resulting phosphorescent complexes highly emissive in both fluid and solid states at room temperature. On the other hand, fine adjustment of ligand-centered pi-pi* electronic transitions allows tuning of emission wavelength across the whole visible spectrum. The cyclometalating chelates are then classified according to types of cyclometalating groups, i.e. either aromatic C-H or azolic N-H fragment, and the adjacent donor fragment involved in the formation of metallacycles; the latter is an N-containing heterocycle, N-heterocyclic (NHC) carbene fragment or even diphenylphosphino group. These cyclometalating ligands are capable to react with heavy transition-metal elements, namely: Ru(II), Os(II), Ir(III) and Pt(II), to afford a variety of highly emissive phosphors, for which the photophysical properties as a function of chelate or metal characteristics are systematically discussed. Using Ir(III) complexes as examples, the C--N chelates possessing both C-H site and N-heterocyclic donor group are essential for obtaining phosphors with emission ranging from sky-blue to saturated red, while the N--N chelates such as 2-pyridyl-C-linked azolates are found useful for serving as true-blue chromophores due to their increased ligand-centered pi-pi* energy gap. Lastly, the remaining NHC carbene and benzyl phosphine chelates are highly desirable to serve as ancillary chelates in localizing the electronic transition between the metal and remaining lower energy chromophoric chelates. As for the potential opto-electronic applications, many of them exhibit remarkable performance data, which are convincing to pave a

  4. Installing an additional emission quenching pathway in the design of iridium(III)-based phosphorogenic biomaterials for bioorthogonal labelling and imaging.

    PubMed

    Li, Steve Po-Yam; Yip, Alex Man-Hei; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

    2016-10-01

    We report the synthesis, characterization, photophysical and electrochemical behaviour and biological labelling applications of new phosphorogenic bioorthogonal probes derived from iridium(III) polypyridine complexes containing a 1,2,4,5-tetrazine moiety. In contrast to common luminescent cyclometallated iridium(III) polypyridine complexes, these tetrazine complexes are almost non-emissive due to effective Förster resonance energy transfer (FRET) and/or photoinduced electron transfer (PET) from the excited iridium(III) polypyridine unit to the appended tetrazine moiety. However, they exhibited significant emission enhancement upon reacting with (1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN-OH) (ca. 19.5-121.9 fold) and BCN-modified bovine serum albumin (BCN-BSA) (ca. 140.8-1133.7 fold) as a result of the conversion of the tetrazine unit to a non-quenching pyridazine derivative. The complexes were applied to image azide-modified glycans in live cells using a homobifunctional crosslinker, 1,13-bis((1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethyloxycarbonylamino)-4,7,10-trioxatridecane (bis-BCN). Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Trifluoromethyl-Substituted Iridium(III) Complexes: From Photophysics to Photooxidation of a Biological Target.

    PubMed

    Bevernaegie, Robin; Marcélis, Lionel; Laramée-Milette, Baptiste; De Winter, Julien; Robeyns, Koen; Gerbaux, Pascal; Hanan, Garry S; Elias, Benjamin

    2018-02-05

    Photodynamic therapeutic agents are of key interest in developing new strategies to develop more specific and efficient anticancer treatments. In comparison to classical chemotherapeutic agents, the activity of photodynamic therapeutic compounds can be finely controlled thanks to the light triggering of their photoreactivity. The development of type I photosensitizing agents, which do not rely on the production of ROS, is highly desirable. In this context, we developed new iridium(III) complexes which are able to photoreact with biomolecules; namely, our Ir(III) complexes can oxidize guanine residues under visible light irradiation. We report the synthesis and extensive photophysical characterization of four new Ir(III) complexes, [Ir(ppyCF 3 ) 2 (N^N)] + [ppyCF 3 = 2-(3,5-bis(trifluoromethyl)phenyl)pyridine) and N^N = 2,2'-dipyridyl (bpy); 2-(pyridin-2-yl)pyrazine (pzpy); 2,2'-bipyrazine (bpz); 1,4,5,8-tetraazaphenanthrene (TAP)]. In addition to an extensive experimental and theoretical study of the photophysics of these complexes, we characterize their photoreactivity toward model redox-active targets and the relevant biological target, the guanine base. We demonstrate that photoinduced electron transfer takes place between the excited Ir(III) complex and guanine which leads to the formation of stable photoproducts, indicating that the targeted guanine is irreversibly damaged. These results pave the way to the elaboration of new type I photosensitizers for targeting cancerous cells.

  6. Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

    DOE PAGES

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    2015-11-02

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh 3 or P(OPh) 3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy) 2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh 3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ±more » 0.5 μs decay time is measured. For L = P(OPh) 3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.« less

  7. Efficient near-infrared emission of π-extended cyclometalated iridium complexes based on pyrene in solution-processed polymer light-emitting diode

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Hao, Zhaoran; Meng, Fanyuan; Wang, Pu; Yang, Liang; Wang, Yafei; Pei, Yong; Su, Shijian

    2018-05-01

    A novel iridium complex grafting hole-transporting triphenylamine (TPA) unit onto cyclometalated ligand, namely t-BuPyrPyTPA)2Ir(acac), was successfully synthesized and characterized. The photophysical, electrochemical and DFT/TD-DFT calculation, as well as electroluminescence properties of this iridium complex were fully investigated. Meanwhile, the PLEDs employing (t-BuPyrPyTPA)2Ir(acac) as dopant presented stable NIR emission peaked at 697 nm and a shoulder at 764 nm with a highest external quantum efficiency (EQE) of 0.56% at 4 wt% dopant concentration. These results demonstrate that expanding the conjugation length of the ligand is an effective way to achieve NIR emission.

  8. Light-emitting properties of cationic iridium complexes containing phenanthroline based ancillary ligand with blue-green and green emission colors

    NASA Astrophysics Data System (ADS)

    Kwon, Yiseul; Sunesh, Chozhidakath Damodharan; Choe, Youngson

    2015-01-01

    We report here two new cationic iridium(III) complexes with phenanthroline-based ancillary ligands, [Ir(dfppy)2(dibutyl-phen)]PF6 (Complex 1) and [Ir(ppz)2(dibutyl-phen)]PF6 (Complex 2) and their uses in light-emitting electrochemical cells (LECs). The design is based on 2-(2,4-difluorophenyl)pyridine (dfppy) and 1-phenylpyrazole (ppz) as the cyclometalating ligands and 2,9-dibutyl-1,10-phenanthroline (dibutyl-phen) as the ancillary ligand. The photophysical and electrochemical properties of the complexes were studied and the results obtained were corroborated with theoretical density functional theory (DFT) calculations. LECs were fabricated incorporating each complexes which resulted in blue-green light emission (502 nm) with Commission Internationale de l'Eclairage (CIE) coordinates of (0.26, 0.49) for Complex 1 and green (530 nm) electroluminescence with CIE coordinates of (0.33, 0.54) for Complex 2. The luminance and the current efficiency of the LECs based on Complex 1 are 947 cd m-2 and 0.25 cd A-1, respectively, which are relatively higher than that of Complex 2 with a maximum luminance of 773 cd m-2 and an efficiency of 0.16 cd A-1.

  9. New cyclometalated Iridium(III) beta-dicetone complex as phosphorescent dopant in Organic light emitting devices

    NASA Astrophysics Data System (ADS)

    Ivanov, P.; Petrova, P.; Stanimirov, S.; Tomova, R.

    2017-01-01

    A new Bis[4-(benzothiazolato-N,C2‧-2-yl)-N,N-dimethylaniline]Iridium(III) acetylacetonate (Me2N-bt) 2Ir(acac) was synthesized and identified by 1H NMR and elemental analysis. The application of the new compound as a dopant in the hole transporting layer (HTL) of Organic light emitting diode (OLED) structure: HTL/EL/ETL, where HTL was N,N’-bis(3-methylphenyl)-N,N’-diphenylbenzidine (TPD), incorporated in Poly(N-vinylcarbazole) (PVK) matrix, EL - electroluminescent layer of Bis(8-hydroxy-2-methylquinoline)-(4-phenylpheno-xy)aluminum (BAlq) and ETL - electron-transporting layer of Tris-(8-hydroxyquinoline) aluminum (Alq3) or Bis[2-(2-benzothiazoly) phenolato]zinc (Zn(btz)2). We established that the electroluminescent spectra of OLEDs at different concentrations of the dopant were basically the sum of the greenish-blue emission of BAlq and yellowish-green emission of Ir complex. It was found that with increasing of the dopant concentration the relative electroluminescent intensity of Iridium complex emission increased and this of BAlq decreased and as a result the fine tuning of OLED color was observed.

  10. Time-resolved EPR study on the photoexcited triplet state of the electron-donor-acceptor complex formed in the system of fac-tris[2-(4-octyl-phenyl) pyridine] iridium(III) and tetracene.

    PubMed

    Zhebin, Fu; Shuhei, Yoshioka; Hisao, Murai

    2014-01-09

    The physical properties of the phosphorescent organic light-emitting diode material fac-tris(phenylpyridine) iridium(III), Ir(ppy)3, have been reported with experimental and theoretical studies. Here, the photochemical properties of the excited triplet state of partially modified fac-tris[2-(4-octyl-phenyl) pyridine] iridium(III), Ir(C8ppy)3, were investigated using time-resolved electron paramagnetic resonance (tr-EPR) and optical methods by adding tetracene in the toluene solution. The tr-EPR observation at 77 K revealed the following two species: the excited triplet state of tetracene and another triplet species with zero field splitting parameters of |D| = 0.088 cm(-1) and |E| = 0.018 cm(-1) with characteristic spin polarization. The latter species was assigned to the electron-donor-acceptor (EDA) complex formed between Ir(C8ppy)3 and tetracene. The mechanism of formation and the properties of this EDA complex, including the information on the principal axes of (3)Ir(C8ppy)3*, are discussed.

  11. Synthesis and electrophosphorescence of iridium complexes containing benzothiazole-based ligands.

    PubMed

    Liu, Di; Ren, Huicai; Deng, Lijun; Zhang, Ting

    2013-06-12

    Four heteroleptic bis-cyclometalated iridium(III) complexes containing 2-aryl-benzothiazole ligands, in which the aryl is dibenzofuran-2-yl [Ir(O-bt)2(acac)], dibenzothiophene-2-yl [Ir(S-bt)2(acac)], dibenzothiophene-S,S-dioxide-2-yl [Ir(SO2-bt)2(acac)] and 4-(diphenylphosphoryl)phenyl [Ir(PO-bt)2(acac)], have been synthesized and characterized for use in organic light-emitting diodes (OLEDs). These complexes emit bright yellow (551 nm) to orange-red (598 nm) phosphorescence at room temperature, the peak wavelengths of which can be finely tuned depending upon the electronic properties of the aryl group in the 2-position of benzothiazole. The strong electron-withdrawing aryls such as dibenzothiophene-S,S-dioxide2-yl and 4-(diphenylphosphoryl)phenyl caused bathochromatic shift of the iridium complex phosphorescence. These iridium complexes were used as doped emitters to fabricate yellow to orange-red OLEDs and good performance was obtained. In particular, a maximum luminance efficiency of 58.4 cd A(-1) (corresponding to 30.6 lm W(-1) and 19%) with CIE coordinates of (0.45, 0.52) was achieved for Ir(O-bt)2(acac)-based yellow device. Furthermore, the yellow emitting Ir(S-bt)2(acac) was used to fabricate two-element white OLED that exhibited a high efficiency of 32.4 cd A(-1) with CIE coordinates of (0.28, 0.44).

  12. The coordination chemistry of dipyridylbenzene: N-deficient terpyridine or panacea for brightly luminescent metal complexes?

    PubMed

    Williams, J A Gareth

    2009-06-01

    1,3-Di(2-pyridyl)benzene (dpybH) structurally resembles the widely-used ligand terpyridine (tpy), with which it is isoelectronic. In this critical review, following a brief overview of synthetic strategies for dpybH and derivatives, we survey the different types of complex that are possible with these ligands. Whilst metals such as ruthenium(ii), osmium(ii) and platinum(ii) give a terdentate N--C--N binding mode in which cyclometallation occurs at C(2), the ions iridium(iii), rhodium(iii) and palladium(ii) favour C(4) metallation. The latter process can be blocked by appropriate ligand modification, to allow the N--C--N mode to be accessed with these metal ions too. The luminescence properties of the complexes are discussed. A huge range of emission efficiencies are encountered amongst Ir(iii) complexes containing dpyb derivatives, according to the other ligands present. Trends can be rationalised with the aid of simple frontier-orbital considerations. The Pt(ii) complexes of dipyridylbenzenes are also intensely luminescent. Their application to contemporary organic light-emitting device (OLED) technology is discussed, including white light emitters exploiting excimer emission. Their potential as cell imaging agents amenable to time-resolved detection procedures on the microsecond timescale has also been demonstrated (118 references).

  13. Molecular organization of a water-insoluble iridium(III) complex in mixed monolayers.

    PubMed

    Giner-Casares, Juan J; Pérez-Morales, Marta; Bolink, Henk J; Muñoz, Eulogia; de Miguel, Gustavo; Martín-Romero, María T; Camacho, Luis

    2007-11-01

    In this work, organized mixed monolayers containing a cationic water-insoluble iridium(III) complex, Ir-dye, [Ir(ppy)(2)(tmphen)]PF(6), (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline, and ppy = 2-phenylpyridine), and an anionic lipid matrix, DMPA, dimyristoyl-phosphatidic acid, with different molar proportions, were formed by the co-spreading method at the air-water interface. The presence of the dye at the interface, as well as the molecular organization of the mixed films, is deduced from surface techniques such as pi-A isotherms, Brewster angle microscopy (BAM) and reflection spectroscopy. The results obtained remark the formation of an equimolar mixed film, Ir-dye/DMPA = 1:1. BAM images reveal a whole homogeneous monolayer, with gradually increasing reflectivity along the compression process up to reaching the collapse of this equimolecular monolayer at pi approximately equal to 37 mNm(-1). Increasing the molar ratio of DMPA in the mixture, the excess of lipid molecules organizes themselves forming dark flower-like domains of pure DMPA at high surface pressures, coexisting with the mixed Ir-dye/DMPA = 1:1 monolayer. On the other hand, unstable mixed monolayers are obtained by using an initial dye surface concentration higher than the equimolecular one. These mixed Langmuir monolayers have been successfully transferred onto solid substrates by the LB (Langmuir-Blodgett) technique.

  14. Synthesis and photophysical studies of blue phosphorescent Ir(III) complexes with dimethylphenylphospine.

    PubMed

    Ham, Ho-Wan; Jung, Kyung-Yoon; Kim, Young-Sik

    2012-02-01

    New blue emitting mixed ligand iridium(III) complexes comprising one cyclometalating, two phosphines trans to each other such as Ir{(CF3)2Meppy}(PPhMe3)2(H)(L) [L = CI, NCMe, CN] [(CF3)2Meppy = 2-(3', 5'-bis-trifluoromethylphenyl)-4-methylpyridine] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To achieve deep blue emission, the trifluoromethyl group substituted on the phenyl ring and the methyl group substituted on the pyridyl ring increased HOMO-LUMO gap and achieved the hypsochromic shift. To gain insight into the factors responsible for the emission color change and the different luminescence efficiency, we investigate the electron-withdrawing capabilities of ancillary ligands using the DFT and TD-DFT calculations on the ground and excited states of the complexes. From these results, we discuss how the ancillary ligand influences the emission peak as well as the metal to ligand charge transfer (MLCT) transition efficiency. The maximum emission spectra of Ir{(CF3)2Meppy}(PPhMe3)2(H)(Cl), [Ir{(CF3),Meppy)(PPhMe3),(H)(NCMe)]+ and Ir{(CF3)2Meppy}(PPhMe3)2(H)(CN) were in the ranges of 441, 435, 434 nm, respectively.

  15. The Photoluminescent Properties of New Cationic Iridium(III) Complexes Using Different Anions and Their Applications in White Light-Emitting Diodes.

    PubMed

    Yang, Hui; Meng, Guoyun; Zhou, Yayun; Tang, Huaijun; Zhao, Jishou; Wang, Zhengliang

    2015-09-14

    Three cationic iridium(III) complexes [Ir(ppy)₂(phen)][PF₆] (C1), [Ir(ppy)₂(phen)]₂SiF₆ (C2) and [Ir(ppy)₂(phen)]₂TiF₆ (C3) (ppy: 2-phenylpyridine, phen: 1, 10-phenanthroline) using different anions were synthesized and characterized by ¹H Nuclear magnetic resonance (¹HNMR), mass spectra (MS), Fourier transform infrared (FTIR) spectra and element analysis (EA). After the ultraviolet visible (UV-vis) absorption spectra, photoluminescent (PL) properties and thermal properties of the complexes were investigated, complex C1 and C3 with good optical properties and high thermal stability were used in white light-emitting diodes (WLEDs) as luminescence conversion materials by incorporation with 460 nm-emitting blue GaN chips. The integrative performances of the WLEDs fabricated with complex C1 and C3 are better than those fabricated with the widely used yellow phosphor Y₃Al₅O 12 :Ce 3+ (YAG). The color rendering indexes of the WLEDs with C1 and C3 are 82.0 and 82.6, the color temperatures of them are 5912 K and 3717 K, and the maximum power efficiencies of them are 10.61 Lm·W -1 and 11.41 Lm·W -1 , respectively.

  16. High Order in a Self-Assembled Iridium(III) Complex Gelator Towards Nanostructured IrO2 Thin Films.

    PubMed

    Scarpelli, Francesca; Ionescu, Andreea; Aiello, Iolinda; La Deda, Massimo; Crispini, Alessandra; Ghedini, Mauro; Brunelli, Elvira; Sesti, Settimio; Godbert, Nicolas

    2017-10-18

    The preparation and characterization of a new metallogelator based on the Ir III discrete cyclometalated complex [(ppy) 2 Ir(bpy)](CH 3 CH 2 OCH 2 CO 2 ) are reported, where H(ppy) is 2-phenylpiridine and bpy is 2,2'-bipyridine, which is used as an ancillary ligand. The compound is able to self-assemble in water in a range of concentrations between 3 % and 6 % w/w, creating a luminescent ordered supramolecular gel. The gel and xerogel architectures were investigated through polarized optical microscopy (POM), SEM and TEM microscopies coupled with powder X-ray diffraction. The gel supramolecular organization is characterized by columnar tetragonal strands, already present at high dilution conditions, of cations surrounded by counteranions. These strands, in turn, are self-assembled in an oblique columnar cell upon gelification. The xerogel thin films obtained upon complete dehydration maintained the gel supramolecular order and can be used as a precursor for the preparation of nanostructured IrO 2 thin films. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Long-lived room temperature deep-red/near-IR emissive intraligand triplet excited state (3IL) of naphthalimide in cyclometalated platinum(II) complexes and its application in upconversion.

    PubMed

    Wu, Wenting; Guo, Huimin; Wu, Wanhua; Ji, Shaomin; Zhao, Jianzhang

    2011-11-21

    [C(^)NPt(acac)] (C(^)N = cyclometalating ligand; acac = acetylacetonato) complexes in which the naphthalimide (NI) moiety is directly cyclometalated (NI as the C donor of the C-Pt bond) were synthesized. With 4-pyrazolylnaphthalimide, isomers with five-membered (Pt-2) and six-membered (Pt-3) chelate rings were obtained. With 4-pyridinylnaphthalimide, only the complex with a five-membered chelate ring (Pt-4) was isolated. A model complex with 1-phenylpyrazole as the C(^)N ligand was prepared (Pt-1). Strong absorption of visible light (ε = 21,900 M(-1) cm(-1) at 443 nm for Pt-3) and room temperature (RT) phosphorescence at 630 nm (Pt-2 and Pt-3) or 674 nm (Pt-4) were observed. Long-lived phosphorescences were observed for Pt-2 (τ(P) = 12.8 μs) and Pt-3 (τ(P) = 61.9 μs). Pt-1 is nonphosphorescent at RT in solution because of the acac-localized T(1) excited state [based on density functional theory (DFT) calculations and spin density analysis], but a structured emission band centered at 415 nm was observed at 77 K. Time-resolved transient absorption spectra and spin density analysis indicated a NI-localized intraligand triplet excited state ((3)IL) for complexes Pt-2, Pt-3, and Pt-4. DFT calculations on the transient absorption spectra (T(1) → T(n) transitions, n > 1) also support the (3)IL assignment of the T(1) excited states of Pt-2, Pt-3, and Pt-4. The complexes were used as triplet sensitizers for triplet-triplet-annihilation (TTA) based upconversion, and the results show that Pt-3 is an efficient sensitizer with an upconversion quantum yield of up to 14.1%, despite its low phosphorescence quantum yield of 5.2%. Thus, we propose that the sensitizer molecules at the triplet excited state that are otherwise nonphosphorescent were involved in the TTA upconversion process, indicating that weakly phosphorescent or nonphosphorescent transition-metal complexes can be used as triplet sensitizers for TTA upconversion.

  18. A Yellow-Emitting Homoleptic Iridium(III) Complex Constructed from a Multifunctional Spiro Ligand for Highly Efficient Phosphorescent Organic Light-Emitting Diodes.

    PubMed

    Ren, Bao-Yi; Guo, Run-Da; Zhong, Dao-Kun; Ou, Chang-Jin; Xiong, Gang; Zhao, Xiang-Hua; Sun, Ya-Guang; Jurow, Matthew; Kang, Jun; Zhao, Yi; Li, Sheng-Biao; You, Li-Xin; Wang, Lin-Wang; Liu, Yi; Huang, Wei

    2017-07-17

    To suppress concentration quenching and to improve charge-carrier injection/transport in the emission layer (EML) of phosphorescent organic light-emitting diodes (PhOLEDs), a facial homoleptic iridium(III) complex emitter with amorphous characteristics was designed and prepared in one step from a multifunctional spiro ligand containing spiro[fluorene-9,9'-xanthene] (SFX) unit. Single-crystal X-ray analysis of the resulting fac-Ir(SFXpy) 3 complex revealed an enlarged Ir···Ir distance and negligible intermolecular π-π interactions between the spiro ligands. The emitter exhibits yellow emission and almost equal energy levels compared to the commercial phosphor iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C 2 ')acetylacetonate (PO-01). Dry-processed devices using a common host, 4,4'-bis(N-carbazolyl)-1,1'-biphenyl, and the fac-Ir(SFXpy) 3 emitter at a doping concentration of 15 wt % exhibited a peak performance of 46.2 cd A -1 , 36.3 lm W -1 , and 12.1% for the current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE), respectively. Compared to control devices using PO-01 as the dopant, the fac-Ir(SFXpy) 3 -based devices remained superior in the doping range between 8 and 15 wt %. The current densities went up with increasing doping concentration at the same driving voltage, while the roll-offs remain relatively low even at high doping levels. The superior performance of the new emitter-based devices was ascribed to key roles of the spiro ligand for suppressing aggregation and assisting charge-carrier injection/transport. Benefiting from the amorphous stability of the emitter, the wet-processed device also exhibited respectful CE, PE, and EQE of 32.2 cd A -1 , 22.1 lm W -1 , and 11.3%, respectively, while the EQE roll-off was as low as 1.7% at the luminance of 1000 cd m -2 . The three-dimensional geometry and binary-conjugation features render SFX the ideal multifunctional module for suppressing concentration quenching

  19. Cyclometalated Iridium(III) Complexes as AIE Phosphorescent Probes for Real-Time Monitoring of Mitophagy in Living Cells

    NASA Astrophysics Data System (ADS)

    Jin, Chengzhi; Liu, Jiangping; Chen, Yu; Guan, Ruilin; Ouyang, Cheng; Zhu, Yanjiao; Ji, Liangnian; Chao, Hui

    2016-02-01

    Mitophagy, which is a special autophagy that removes damaging mitochondria to maintain sufficient healthy mitochondria, provides an alternative path for addressing dysfunctional mitochondria and avoiding cellular death. In the present study, by coupling the triphenylamine group with 2-phenylimidazo[4,5-f][1,10]phenanthroline derivatives, we synthesized five Ir(III) complexes with an AIE property that are expected to fulfill requirements for real-time monitoring of mitophagy. Ir1-Ir5 were exploited to image mitochondria with a short incubation time by confocal microscopy and inductive coupled plasma-mass spectrometry (ICP-MS). Due to aggregation-induced emission (AIE), Ir1-Ir5 exhibited excellent photostability compared to MitoTracker Green (MTG). Moreover, Ir1-Ir5 manifested satisfactory photostability in the mitochondrial physiological pH range. In addition, the uptake mechanism of Ir1 was investigated using confocal microscopy and flow cytometry analysis. Finally, using both Ir1 and LysoTracker Green, we were able to achieve real-time monitoring of mitophagy.

  20. [Au(pyb-H)(mnt)]: A novel gold(III) 1,2-dithiolene cyclometalated complex with antimicrobial activity (pyb-H=C-deprotonated 2-benzylpyridine; mnt=1,2-dicyanoethene-1,2-dithiolate).

    PubMed

    Pintus, Anna; Aragoni, M Carla; Cinellu, Maria A; Maiore, Laura; Isaia, Francesco; Lippolis, Vito; Orrù, Germano; Tuveri, Enrica; Zucca, Antonio; Arca, Massimiliano

    2017-05-01

    The novel heteroleptic cyclometalated complex [Au III (py b -H)(mnt)] (1; py b -H=C-deprotonated 2-benzylpyridine; mnt =1,2-dicyanoethene-1,2-dithiolate) was tested against a panel of ten Gram positive (belonging to the Staphylococcus, Streptococcus spp. and Bacillus clausii), Gram negative (E. coli, K. pneumoniae, P. aeruginosa) bacteria and three yeasts belonging to the Candida spp. Complex 1 showed a remarkable bacteriostatic antimicrobial activity against staphylococci, with Minimum Inhibitory Concentration (MIC) values of 1.56 and 3.13μg/mL for S. haemoliticus and S. aureus, respectively. Spectroscopic and electrochemical measurements, supported by Density Functional Theory (DFT) calculations, were exploited to fully investigate the electronic structure of complex 1 and its relationship with the antimicrobial activity. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Cyclometalated 6-phenyl-2,2'-bipyridyl (CNN) platinum(II) acetylide complexes: structure, electrochemistry, photophysics, and oxidative- and reductive-quenching studies.

    PubMed

    Schneider, Jacob; Du, Pingwu; Jarosz, Paul; Lazarides, Theodore; Wang, Xiaoyong; Brennessel, William W; Eisenberg, Richard

    2009-05-18

    Three cyclometalated 6-phenyl-4-(p-R-phenyl)-2,2'-bipyridyl (CNN-Ph-R) Pt(II) acetylide complexes, Pt(CNN-Ph-R)(CCPh), where R = Me (1), COOMe (2), and P(O)(OEt)(2) (3), have been synthesized and studied. Compounds 1 and 3 have been structurally characterized by single crystal X-ray crystallography and are found to exhibit distorted square planar geometries about the Pt(II) ions. The electrochemical properties of the compounds, as determined by cyclic voltammetry, have also been examined. Complexes 1-3 are brightly emissive in fluid CH(2)Cl(2) solution and in the solid state with lambda(em)(max) of ca. 600 nm and lifetimes on the order of ca. 500 ns in fluid solution. The emissions are assigned to a (3)MLCT transition. The complexes undergo oxidative quenching by MV(2+) with quenching rates near the diffusion-controlled limit (k(q) approximately 1.4 x 10(10) M(-1) s(-1)) in CH(2)Cl(2) solution. Reductive-quenching experiments of complexes 1-3 by the amine donors N,N,N',N'-tetramethylphenylenediamine (TMPD), phenothiazine (PTZ), and N,N,N',N'-tetramethylbenzidine (TMB) follow Stern-Volmer behavior, with very fast quenching rates on the order of 10(9)-10(10) M(-1) s(-1) in CH(2)Cl(2) solution. When the complexes are employed as the sensitizer in multiple component systems containing MV(2+), TEOA, and colloidal Pt in aqueous media, approximately one turnover of H(2) (TN vs mol of chromophore) is produced per hour upon irradiation with lambda > 410 nm but only after at least a 2 h induction period.

  2. Cyclometalated platinum(ii) complexes of 2,2'-bipyridine N-oxide containing a 1,1'-bis(diphenylphosphino)ferrocene ligand: structural, computational and electrochemical studies.

    PubMed

    Shahsavari, Hamid R; Fereidoonnezhad, Masood; Niazi, Maryam; Mosavi, S Talaat; Habib Kazemi, Sayed; Kia, Reza; Shirkhan, Shima; Abdollahi Aghdam, Siamak; Raithby, Paul R

    2017-02-14

    The preparation and characterization of new heteronuclear-platinum(ii) complexes containing a 1,1'-bis(diphenylphosphino)ferrocene (dppf) ligand are described. The reaction of the known starting complex [PtMe(κ 2 N,C-bipyO-H)(SMe 2 )], A, in which bipyO-H is a cyclometalated rollover 2,2'-bipyridine N-oxide, with the dppf ligand in a 2 : 1 ratio or an equimolar ratio led to the formation of the corresponding binuclear complex [Pt 2 Me 2 (κ 2 N,C-bipyO-H) 2 (μ-dppf)], 1, or the mononuclear complex [PtMe(κ 1 C-bipyO-H)(dppf)], 2, respectively. According to the reaction conditions, the dppf ligand in 1 and 2 behaves as either a bridging or chelating ligand. All complexes were characterized by NMR spectroscopy. The solid-state structure of 2 was determined by the single-crystal X-ray diffraction method and it was shown that the chelating dppf ligand in this complex was arranged in a "synclinal-staggered" conformation. Also, the occurrence of intermolecular C-H Cp O bipyO-H interactions in the solid-state gave rise to an extended 1-D network. The electronic absorption spectra and the electrochemical behavior of these complexes are discussed. Density functional theory (DFT) was used for geometry optimization of the singlet states in solution and for electronic structure calculations. The analysis of the molecular orbital (MO) compositions in terms of occupied and unoccupied fragment orbitals in 2 was performed.

  3. Judicious Design of Cationic, Cyclometalated Ir(III) Complexes for Photochemical Energy Conversion and Optoelectronics.

    PubMed

    Mills, Isaac N; Porras, Jonathan A; Bernhard, Stefan

    2018-02-20

    The exponential growth in published studies on phosphorescent metal complexes has been triggered by their utilization in optoelectronics, solar energy conversion, and biological labeling applications. Very recent breakthroughs in organic photoredox transformations have further increased the research efforts dedicated to discerning the inner workings and structure-property relationships of these chromophores. Initially, the principal focus was on the Ru(II)-tris-diimine complex family. However, the limited photostability and lack of luminescence tunability discovered in these complexes prompted a broadening of the research to include 5d transition metal ions. The resulting increase in ligand field splitting prevents the population of antibonding e g * orbitals and widens the energy range available for color tuning. Particular attention was given to Ir(III), and its cyclometalated, cationic complexes have now replaced Ru(II) in the vast majority of applications. At the start, this Account documents the initial efforts dedicated to the color tuning of these complexes for their application in light emitting electrochemical cells, an easy to fabricate single-layer organic light emitting device (OLED). Systematic modifications of the ligand sphere of [Ir(ppy) 2 bpy] + (ppy: 2-phenylpyridine, bpy: 2,2'-bipyridine) with electron withdrawing and donating substituents allowed access to complexes with luminescence emission maxima throughout the visible spectrum exhibiting room temperature excited state lifetimes ranging from nanoseconds to dozens of microseconds and quantum yields up to 15 times that of [Ru(bpy) 3 ] 2+ . The diverse photophysical properties were also beneficial when using these Ir(III) complexes for driving solar fuel-producing reactions. For instance, photocatalytic water-reduction systems were explored to gain access to efficient water splitting systems. For this purpose, a variety of water reduction catalysts were paired with libraries of Ir

  4. Carbon Dioxide Utilization by the Five-Membered Ring Products of Cyclometalation Reactions

    PubMed Central

    Omae, Iwao

    2016-01-01

    In carbon dioxide utilization by cyclometalated five-membered ring products, the following compounds are used in four types of applications: 1. 2-Phenylpyrazole iridium compounds, pincer phosphine iridium compounds and 2-phenylimidazoline iridium compounds are used as catalysts for both formic acid production from CO2 and H2, and hydrogen production from the formic acid. This formic acid can be a useful agent for H2 production and storage for fuel cell electric vehicles. 2. Other chemicals, e.g., dimethyl carbonate, methane, methanol and CO, are produced with dimethylaminomethylphenyltin compounds, pincer phosphine iridium compounds, pincer phosphine nickel compound and ruthenium carbene compound or 2-phenylpyridine iridium compounds, and phenylbenzothiazole iridium compounds as the catalysts for the reactions with CO2. 3. The five-membered ring intermediates of cyclometalation reactions with the conventional substrates react with carbon dioxide to afford their many types of carboxylic acid derivatives. 4. Carbon dioxide is easily immobilized at room temperature with immobilizing agents such as pincer phosphine nickel compounds, pincer phosphine palladium compounds, pincer N,N-dimethylaminomethyltin compounds and tris(2-pyridylthio)methane zinc compounds. PMID:28503084

  5. Carbon Dioxide Utilization by the Five-Membered Ring Products of Cyclometalation Reactions.

    PubMed

    Omae, Iwao

    2016-04-01

    In carbon dioxide utilization by cyclometalated five-membered ring products, the following compounds are used in four types of applications: 1. 2-Phenylpyrazole iridium compounds, pincer phosphine iridium compounds and 2-phenylimidazoline iridium compounds are used as catalysts for both formic acid production from CO 2 and H 2 , and hydrogen production from the formic acid. This formic acid can be a useful agent for H 2 production and storage for fuel cell electric vehicles. 2. Other chemicals, e.g. , dimethyl carbonate, methane, methanol and CO, are produced with dimethylaminomethylphenyltin compounds, pincer phosphine iridium compounds, pincer phosphine nickel compound and ruthenium carbene compound or 2-phenylpyridine iridium compounds, and phenylbenzothiazole iridium compounds as the catalysts for the reactions with CO 2 . 3. The five-membered ring intermediates of cyclometalation reactions with the conventional substrates react with carbon dioxide to afford their many types of carboxylic acid derivatives. 4. Carbon dioxide is easily immobilized at room temperature with immobilizing agents such as pincer phosphine nickel compounds, pincer phosphine palladium compounds, pincer N , N -dimethylaminomethyltin compounds and tris(2-pyridylthio)methane zinc compounds.

  6. Exceptionally long-lived light-emitting electrochemical cells: multiple intra-cation π-stacking interactions in [Ir(C^N)2(N^N)][PF6] emitters† †Electronic supplementary information (ESI) available: Experimental details. Fig. S1–S10: additional structural and NMR spectroscopic figures; voltage vs. time plots for LEC devices and electroluminescence spectra. CCDC 1019226–1019229. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4sc03942d

    PubMed Central

    Bünzli, Andreas M.; Constable, Edwin C.; Prescimone, Alessandro; Zampese, Jennifer A.; Longo, Giulia; Gil-Escrig, Lidón; Pertegás, Antonio; Ortí, Enrique

    2015-01-01

    A series of cyclometalated iridium(iii) complexes [Ir(C^N)2(N^N)][PF6] (N^N = 2,2′-bipyridine (1), 6-phenyl-2,2′-bipyridine (2), 4,4′-di-tert-butyl-2,2′-bipyridine (3), 4,4′-di-tert-butyl-6-phenyl-2,2′-bipyridine (4); HC^N = 2-(3-phenyl)phenylpyridine (HPhppy) or 2-(3,5-diphenyl)phenylpyridine (HPh2ppy)) are reported. They have been synthesized using solvento precursors so as to avoid the use of chlorido-dimer intermediates, chloride ion contaminant being detrimental to the performance of [Ir(C^N)2(N^N)][PF6] emitters in light-electrochemical cell (LEC) devices. Single crystal structure determinations and variable temperature solution 1H NMR spectroscopic data confirm that the pendant phenyl domains engage in multiple face-to-face π-interactions within the coordination sphere of the iridium(iii) centre. The series of [Ir(Phppy)2(N^N)]+ and [Ir(Ph2ppy)2(N^N)]+ complexes investigated include those with and without intra-cation face-to-face π-stacking. All the complexes display excellent luminescent properties, in particular when employed in thin solid films. The most important observation is that all the LECs using the [Ir(Phppy)2(N^N)]+ and [Ir(Ph2ppy)2(N^N)]+ emitters (i.e. with and without intra-cation π-stacking interactions) exhibit very stable luminance outputs over time, even when driven at elevated current densities. The most stable LEC had an extrapolated lifetime of more than 2500 hours under accelerated testing conditions. PMID:29142683

  7. Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex.

    PubMed

    Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

    2017-06-16

    A novel orange cationic iridium(III) complex [(TPTA)₂Ir(dPPOA)]PF₆ (TPTA: 3,4,5-triphenyl-4 H -1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)₂Ir(dPPOA)]PF₆ has high thermal stability with a decomposition temperature ( T d ) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)₂Ir(dPPOA)]PF₆ was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y₃Al₅O 12 :Ce 3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I'Eclairage ) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency ( η L ) was 128.5 lm∙W -1 . Such a cold white LED became a neutral white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and η L was 85.2 lm∙W -1 . It further became a warm white LED when [(TPTA)₂Ir(dPPOA)]PF₆ was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and η L was 46.1 lm∙W -1 . The results show that [(TPTA)₂Ir(dPPOA)]PF₆ is a promising phosphor candidate for fabricating warm white LEDs.

  8. Warm White Light-Emitting Diodes Based on a Novel Orange Cationic Iridium(III) Complex

    PubMed Central

    Tang, Huaijun; Meng, Guoyun; Chen, Zeyu; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

    2017-01-01

    A novel orange cationic iridium(III) complex [(TPTA)2Ir(dPPOA)]PF6 (TPTA: 3,4,5-triphenyl-4H-1,2,4-triazole, dPPOA: N,N-diphenyl-4-(5-(pyridin-2-yl)-1,3,4-oxadiazol-2-yl)aniline) was synthesized and used as a phosphor in light-emitting diodes (LEDs). [(TPTA)2Ir(dPPOA)]PF6 has high thermal stability with a decomposition temperature (Td) of 375 °C, and its relative emission intensity at 100 °C is 88.8% of that at 25°C. When only [(TPTA)2Ir(dPPOA)]PF6 was used as a phosphor at 6.0 wt % in silicone and excited by a blue GaN (GaN: gallium nitride) chip (450 nm), an orange LED was obtained. A white LED fabricated by a blue GaN chip (450 nm) and only yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) (1.0 wt % in silicone) emitted cold white light, its CIE (CIE: Commission International de I’Eclairage) value was (0.32, 0.33), color rendering index (CRI) was 72.2, correlated color temperature (CCT) was 6877 K, and luminous efficiency (ηL) was 128.5 lm∙W−1. Such a cold white LED became a neutral white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 0.5 wt %; its corresponding CIE value was (0.35, 0.33), CRI was 78.4, CCT was 4896 K, and ηL was 85.2 lm∙W−1. It further became a warm white LED when [(TPTA)2Ir(dPPOA)]PF6 was added at 1.0 wt %; its corresponding CIE value was (0.39, 0.36), CRI was 80.2, CCT was 3473 K, and ηL was 46.1 lm∙W−1. The results show that [(TPTA)2Ir(dPPOA)]PF6 is a promising phosphor candidate for fabricating warm white LEDs. PMID:28773020

  9. Theoretical characterization and design of highly efficient iridium (III) complexes bearing guanidinate ancillary ligand.

    PubMed

    Ren, Xin-Yao; Wu, Yong; Wang, Li; Zhao, Liang; Zhang, Min; Geng, Yun; Su, Zhong-Min

    2014-06-01

    A density functional theory/time-depended density functional theory was used to investigate the synthesized guanidinate-based iridium(III) complex [(ppy)2Ir{(N(i)Pr)2C(NPh2)}] (1) and two designed derivatives (2 and 3) to determine the influences of different cyclometalated ligands on photophysical properties. Except the conventional discussions on geometric relaxations, absorption and emission properties, many relevant parameters, including spin-orbital coupling (SOC) matrix elements, zero-field-splitting parameters, radiative rate constants (kr) and so on were quantitatively evaluated. The results reveal that the replacement of the pyridine ring in the 2-phenylpyridine ligand with different diazole rings cannot only enlarge the frontier molecular orbital energy gaps, resulting in a blue-shift of the absorption spectra for 2 and 3, but also enhance the absorption intensity of 3 in the lower-energy region. Furthermore, it is intriguing to note that the photoluminescence quantum efficiency (ΦPL) of 3 is significantly higher than that of 1. This can be explained by its large SOC value(n=3-4) and large transition electric dipole moment (μS3), which could significantly contribute to a larger kr. Besides, compared with 1, the higher emitting energy (ET1) and smaller (2) value for 3 may lead to a smaller non-radiative decay rate. Additionally, the detailed results also indicate that compared to 1 with pyridine ring, 3 with imidazole ring performs a better hole injection ability. Therefore, the designed complex 3 can be expected as a promising candidate for highly efficient guanidinate-based phosphorescence emitter for OLEDs applications. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Photophysical properties of the series fac- and mer-(1-phenylisoquinolinato-N∧C2')(x)(2-phenylpyridinato-N∧C2')(3-x)iridium(III) (x = 1-3).

    PubMed

    Deaton, Joseph C; Young, Ralph H; Lenhard, Jerome R; Rajeswaran, Manju; Huo, Shouquan

    2010-10-18

    The photophysical properties of tris-cyclometalated iridium(III) complexes have been probed by chemical and geometric variation through the series fac- and mer-Ir(piq)(x)(ppy)(3-x) (x = 1-3; piq = 1-phenylisoquinolinato-N(∧)C(2'), ppy = 2-phenylpyridinato-N(∧)C(2')). The phosphorescent decays were recorded in solution at 295 K and in polymer films from 2 to 295 K. In the heteroleptic complexes, emission occurs based solely on the piq ligand(s), at least by the nanosecond time scale, as its excited states are the lowest energy. Because fac-Ir(piq)(3) and fac-Ir(ppy)(3) possess practically the same oxidation potential, comparison of photophysical properties through the series fac-Ir(piq)(x)(ppy)(3-x) (x = 1-3) revealed the effects of having one, two, or three emissive piq ligands with no confounding effects from differences in electron withdrawing or donating properties between the spectator ppy ligands and the piq ligands. Effects of placement of piq ligands in different coordination geometries were elucidated by comparisons to the mer series.

  11. Sky-blue emitting bridged diiridium complexes: beneficial effects of intramolecular π-π stacking.

    PubMed

    Congrave, Daniel G; Hsu, Yu-Ting; Batsanov, Andrei S; Beeby, Andrew; Bryce, Martin R

    2018-02-06

    The potential of intramolecular π-π interactions to influence the photophysical properties of diiridium complexes is an unexplored topic, and provides the motivation for the present study. A series of diarylhydrazide-bridged diiridium complexes functionalised with phenylpyridine (ppy)-based cyclometalating ligands is reported. It is shown by NMR studies in solution and single crystal X-ray analysis that intramolecular π-π interactions between the bridging and cyclometalating ligands rigidify the complexes leading to high luminescence quantum efficiencies in solution and in doped films. Fluorine substituents on the phenyl rings of the bridge promote the intramolecular π-π interactions. Notably, these non-covalent interactions are harnessed in the rational design and synthesis of the first examples of highly emissive sky-blue diiridium complexes featuring conjugated bridging ligands, for which they play a vital role in the structural and photophysical properties. Experimental results are supported by computational studies.

  12. A new class of cyclometalated ruthenium sensitizers of the type ĈNN for efficient dye-sensitized solar cells.

    PubMed

    Kim, Jeum-Jong; Choi, Hyunbong; Paek, Sanghyun; Kim, Chulwoo; Lim, Kimin; Ju, Myung-Jong; Kang, Hong Seok; Kang, Moon-Sung; Ko, Jaejung

    2011-11-21

    A new class of cyclometalated ruthenium sensitizers incorporating a ĈNN ligand and conjugated 2,2'-bipyridine in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-206 using an electrolyte containing 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butylpyridine in CH(3)CN gave a short-circuit photocurrent density of 19.63 mA cm(-2), an open-circuit voltage of 0.74 V, and a fill factor of 0.72, affording an overall conversion efficiency of 10.39%. The efficiency is the highest one reported for dye-sensitized solar cells based on the cyclometalated ruthenium sensitizer of the type ĈNN. Moreover, the same device using a polymer gel electrolyte exhibited a remarkable stability under 1000 h of light soaking at 60 °C, retaining 91% of the initial efficiency of 7.14%.

  13. Synthesis, Properties, and Light-Emitting Electrochemical Cell (LEEC) Device Fabrication of Cationic Ir(III) Complexes Bearing Electron-Withdrawing Groups on the Cyclometallating Ligands

    PubMed Central

    2016-01-01

    The structure–property relationship study of a series of cationic Ir(III) complexes in the form of [Ir(C^N)2(dtBubpy)]PF6 [where dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and C^N = cyclometallating ligand bearing an electron-withdrawing group (EWG) at C4 of the phenyl substituent, i.e., −CF3 (1), −OCF3 (2), −SCF3 (3), −SO2CF3 (4)] has been investigated. The physical and optoelectronic properties of the four complexes were comprehensively characterized, including by X-ray diffraction analysis. All the complexes exhibit quasireversible dtBubpy-based reductions from −1.29 to −1.34 V (vs SCE). The oxidation processes are likewise quasireversible (metal + C^N ligand) and are between 1.54 and 1.72 V (vs SCE). The relative oxidation potentials follow a general trend associated with the Hammett parameter (σ) of the EWGs. Surprisingly, complex 4 bearing the strongest EWG does not adhere to the expected Hammett behavior and was found to exhibit red-shifted absorption and emission maxima. Nevertheless, the concept of introducing EWGs was found to be generally useful in blue-shifting the emission maxima of the complexes (λem = 484–545 nm) compared to that of the prototype complex [Ir(ppy)2(dtBubpy)]PF6 (where ppy = 2-phenylpyridinato) (λem = 591 nm). The complexes were found to be bright emitters in solution at room temperature (ΦPL = 45–66%) with microsecond excited-state lifetimes (τe = 1.14–4.28 μs). The photophysical properties along with density functional theory (DFT) calculations suggest that the emission of these complexes originates from mixed contributions from ligand-centered (LC) transitions and mixed metal-to-ligand and ligand-to-ligand charge transfer (LLCT/MLCT) transitions, depending on the EWG. In complexes 1, 3, and 4 the 3LC character is prominent over the mixed 3CT character, while in complex 2, the mixed 3CT character is much more pronounced, as demonstrated by DFT calculations and the observed positive solvatochromism

  14. C-H activation in Ir(III) and N-demethylation in Pt(II) complexes with mesoionic carbene ligands: examples of monometallic, homobimetallic and heterobimetallic complexes.

    PubMed

    Maity, Ramananda; Tichter, Tim; van der Meer, Margarethe; Sarkar, Biprajit

    2015-11-14

    Mononuclear Pt(II) and the first dinuclear Pt(II) complexes along with a cyclometalated heterobimetallic Ir(III)/Pd(II) complex bearing mesoionic carbene donor ligands are presented starting from the same bis-triazolium salt. The mononuclear Pt(II) complex possesses a free triazole moiety which is generated from the corresponding triazolium salt through an N-demethylation reaction, whereas the mononuclear Ir(III) complex features an unreacted triazolium unit.

  15. Cycloruthenated complexes from imine-based heterocycles: synthesis, characterization, and reactivity toward alkynes.

    PubMed

    Cuesta, Luciano; Soler, Tatiana; Urriolabeitia, Esteban P

    2012-11-19

    Novel cycloruthenated complexes 2 a-c, 4 a-c, and 6 a, b based on heteroaromatic cores have been synthesized by reaction of a series of heterocycle-based imines with [{RuCl(η(6)-p-cymene)}(2)(μ-Cl)(2)] and Cu(OAc)(2). This approach has proved efficient for the cyclometalation of thiophene, benzothiophene, furan, benzofuran, pyrrole, and indole derivatives. In addition, even a double cyclometalation process over the same heterocyclic ring is possible, yielding unprecedented bimetallic complexes. These ruthenacycles react with 3-hexyne through an unexpected pathway, which involves the coupling of the original imino heterocycle and acetylene followed by dearomatization to afford fused hetero-hydropyridyl ligands bonded to the {Ru(p-cymene)} organometallic moiety (i.e., 7 a-c and 8 a-c). These complexes represent, as far as we know, the first examples of this type of compound within the context of cyclometalation, and an exhaustive analysis of their structure was carried out in solution and solid state. Furthermore, these unique species react with CuCl(2), which promotes the rearomatization and the release of highly valuable aromatic fused bis-heterocycles (i.e., 9 a-c, 10 a-c, 11 a, and 12 a/12 a'), providing a novel and appealing synthetic route to this extraordinary family of molecules. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Isomerization Reaction of mer- to fac-Tris(2-phenylpyridinato-N,C2')Iridium(III) Monitored by Using Surface-Enhanced Raman Spectroscopy.

    PubMed

    Wu, Bo-Han; Huang, Min-Jie; Lai, Cheng-Chang; Cheng, Chien-Hong; Chen, I-Chia

    2018-04-16

    We developed a new method by enclosing the complex tris(2-phenylpyridinato-N,C2')Iridium(III), Ir(ppy) 3 with surfactant cetyltrimethylammonium bromide (CATB), coated with a thin layer of silica then bonded to the surface of silver nanoparticle. These samples were used to acquire surface-enhanced Raman scattering (SERS) spectra. The thickness of silica layer was controlled to have efficient phosphorescence quenching and Raman enhancement by metal nanoparticle. The SERS spectra of fac- and mer-Ir(ppy) 3 , recorded at 633 nm excitation, display distinct ring breathing mode features because the total symmetric vibrational bands were enhanced. This provides a convenient means to differentiate these isomers with great sensitivity and to study their isomerization process. A direct conversion reaction of mer- to fac- isomerization is identified with time constant 3.1 min when mer was irradiated with Xe light. Via thermal activation, under moderate conditions (pH 5.5 and 343 K), we observed an intermediate particularly with new bands 320/662 cm -1 after heating for 17.5 h, and then those bands disappeared to form fac-Ir(ppy) 3 . On the basis of DFT calculations, the intermediate is proposed to contain octahedral N-N Ir(ppy) 3 -HO-silica structure; band at 320 cm -1 is assigned to iridium oxygen stretching mode ν Ir-O of this intermediate. Under acidic conditions, pH 1-2 catalyzed by silanol in silica, byproduct with band at 353 cm -1 was observed. According to the SERS bands and the calculation, this byproduct is assigned to be iridium(III) siloxide, and the new band is assigned to ν Ir-O .

  17. Neutral and ionic platinum compounds containing a cyclometallated chiral primary amine: synthesis, antitumor activity, DNA interaction and topoisomerase I-cathepsin B inhibition.

    PubMed

    Albert, Joan; Bosque, Ramon; Crespo, Margarita; Granell, Jaume; López, Concepción; Martín, Raquel; González, Asensio; Jayaraman, Anusha; Quirante, Josefina; Calvis, Carme; Badía, Josefa; Baldomà, Laura; Font-Bardia, Mercè; Cascante, Marta; Messeguer, Ramon

    2015-08-14

    The synthesis and preliminary biological evaluation of neutral and cationic platinum derivatives of chiral 1-(1-naphthyl)ethylamine are reported, namely cycloplatinated neutral complexes [PtCl{(R or S)-NH(2)CH(CH(3))C(10)H(6)}(L)] [L = SOMe(2) ( 1-R or 1-S ), L = PPh(3) (2-R or 2-S), L = P(4-FC(6)H(4))(3) (3-R), L = P(CH(2))(3)N(3)(CH(2))(3) (4-R)], cycloplatinated cationic complexes [Pt{(R)-NH(2)CH(CH(3))C(10)H(6)}{L}]Cl [L = Ph(2)PCH(2)CH(2)PPh(2) (5-R), L = (C(6)F(5))(2)PCH(2)CH(2)P(C(6)F(5))(2) (6-R)] and the Pt(ii) coordination compound trans-[PtCl(2){(R)-NH(2)CH(CH(3))C(10)H(6)}(2)] (7-R). The X-ray molecular structure of 7-R is reported. The cytotoxic activity against a panel of human adenocarcinoma cell lines (A-549 lung, MDA-MB-231 and MCF-7 breast, and HCT-116 colon), cell cycle arrest and apoptosis, DNA interaction, topoisomerase I and cathepsin B inhibition, and Pt cell uptake of the studied compounds are presented. Remarkable cytotoxicity was observed for most of the synthesized Pt(ii) compounds regardless of (i) the absolute configuration R or S, and (ii) the coordinated/cyclometallated (neutral or cationic) nature of the complexes. The most potent compound 2-R (IC(50) = 270 nM) showed a 148-fold increase in potency with regard to cisplatin in HCT-116 colon cancer cells. Preliminary biological results point out to different biomolecular targets for the investigated compounds. Neutral cyclometallated complexes 1-R and 2-R, modify the DNA migration as cisplatin, cationic platinacycle 5-R was able to inhibit topoisomerase I-promoted DNA supercoiling, and Pt(ii) coordination compound 7-R turned out to be the most potent inhibitor of cathepsin B. Induction of G-1 phase ( 2-R and 5-R ), and S and G-2 phases (6-R) arrests are related to the antiproliferative activity of some representative compounds upon A-549 cells. Induction of apoptosis is also observed for 2-R and 6-R.

  18. Cross-couplings in the elaboration of luminescent bis-terpyridyl iridium complexes: the effect of extended or inhibited conjugation on emission.

    PubMed

    Leslie, Wendy; Batsanov, Andrei S; Howard, Judith A K; Williams, J A Gareth

    2004-02-21

    The utility of Suzuki cross-coupling methodology for the in situ elaboration of bromo-functionalised bis-terpyridyl iridium(III) complexes has been explored. The complex [Ir(tpy)(tpy-phi-Br)]3+ [tpy-phi-Br = 4'-(4-bromophenyl)-2,2':6',2''-terpyridine] undergoes palladium-catalysed cross-coupling with aryl boronic acids to yield biaryl-substituted complexes directly. The biphenyl and 4-cyanobiphenyl-substituted products display relatively intense, long-lived (tau > 100 mus) yellow emission in degassed aqueous solution at room temperature, assigned to a 3pi-pi* state. A 4-aminobiphenyl-substituted analogue displays an additional low energy absorbance band, attributed to an intraligand charge-transfer (ILCT) excited state, and is scarcely emissive under the same conditions. The iridium(III) complex of 4'-mesityl-terpyridine is also reported. Its emission is much shorter-lived, with a spectral profile resembling that of unsubstituted [Ir(tpy)2]3+, confirming the need for the attainment of a roughly coplanar geometry for stabilisation of the 3pi-pi* excited state.

  19. Ligand-bridged dinuclear cyclometalated Ir(III) complexes: from metallamacrocycles to discrete dimers.

    PubMed

    Chandrasekhar, Vadapalli; Hajra, Tanima; Bera, Jitendra K; Rahaman, S M Wahidur; Satumtira, Nisa; Elbjeirami, Oussama; Omary, Mohammad A

    2012-02-06

    Metallamacrocycles 1, 2, and 3 of the general formula [{Ir(ppy)(2)}(2)(μ-BL)(2)](OTf)(2) (ppyH = 2-phenyl pyridine; BL = 1,2-bis(4-pyridyl)ethane (bpa) (1), 1,3-bis(4-pyridyl)propane (bpp) (2), and trans-1,2-bis(4-pyridyl)ethylene (bpe) (3)) have been synthesized by the reaction of [{(ppy)(2)Ir}(2)(μ-Cl)(2)], first with AgOTf to effect dechlorination and later with various bridging ligands. Open-frame dimers [{Ir(ppy)(2)}(2)(μ-BL)](OTf)(2) were obtained in a similar manner by utilizing N,N'-bis(2-pyridyl)methylene-hydrazine (abp) and N,N'-(bis(2-pyridyl)formylidene)ethane-1,2-diamine (bpfd) (for compounds 4 and 5, respectively) as bridging ligands. Molecular structures of 1, 3, 4, and 5 were established by X-ray crystallography. Cyclic voltammetry experiments reveal weakly interacting "Ir(ppy)(2)" units bridged by ethylene-linked bpe ligand in 3; on the contrary the metal centers are electronically isolated in 1 and 2 where the bridging ligands are based on ethane and propane linkers. The dimer 4 exhibits two accessible reversible reduction couples separated by 570 mV indicating the stability of the one-electron reduced species located on the diimine-based bridge abp. The "Ir(ppy)(2)" units in compound 5 are noninteracting as the electronic conduit is truncated by the ethane spacer in the bpfd bridge. The dinuclear compounds 1-5 show ligand centered (LC) transitions involving ppy ligands and mixed metal to ligand/ligand to ligand charge transfer (MLCT/LLCT) transitions involving both the cyclometalating ppy and bridging ligands (BL) in the UV-vis spectra. For the conjugated bridge bpe in compound 3 and abp in compound 4, the lowest-energy charge-transfer absorptions are red-shifted with enhanced intensity. In accordance with their similar electronic structures, compounds 1 and 2 exhibit identical emissions. The presence of vibronic structures in these compounds indicates a predominantly (3)LC excited states. On the contrary, broad and unstructured

  20. Synthesis and optoelectronic properties of a heterobimetallic Pt(II)-Ir(III) complex used as a single-component emitter in white PLEDs.

    PubMed

    Li, Xiaoshuang; Liu, Yu; Luo, Jian; Zhang, Zhiyong; Shi, Danyan; Chen, Qing; Wang, Yafei; He, Juan; Li, Jianming; Lei, Gangtie; Zhu, Weiguo

    2012-03-14

    To tune aggregation/excimer emission and obtain a single active emitter for white polymer light-emitting devices (PLEDs), a heterobimetallic Pt(II)-Ir(III) complex of FIr(pic)-C(6)DBC(6)-(pic)PtF was designed and synthesized, in which C(6)DBC(6) is a di(phenyloxyhexyloxy) bridging group, FIr(pic) is an iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore and FPt(pic) is a platinum(II) [(4,6-difluorophenyl)pyridinato-N,C(2)'] (picolinate) chromophore. Its physical and opto-electronic properties were investigated. Interestingly, the excimer emission was efficiently controlled by this heterobimetallic Pt(II)-Ir(III) complex compared to the PL profile of the mononuclear FPt(pic) complex in the solid state. Near-white emissions were obtained in the single emissive layer (SEL) PLEDs using this heterobimetallic Pt(II)-Ir(III) complex as a single dopant and poly(vinylcarbazole) as a host matrix at dopant concentrations from 0.5 wt% to 2 wt%. This work indicates that incorporating a non-planar iridium(III) complex into the planar platinum(II) complex can control aggregation/excimer emissions and a single phosphorescent emitter can be obtained to exhibit white emission in SEL devices.

  1. One-Electron Oxidation of [M(P(t) Bu3 )2 ] (M=Pd, Pt): Isolation of Monomeric [Pd(P(t) Bu3 )2 ](+) and Redox-Promoted C-H Bond Cyclometalation.

    PubMed

    Troadec, Thibault; Tan, Sze-Yin; Wedge, Christopher J; Rourke, Jonathan P; Unwin, Patrick R; Chaplin, Adrian B

    2016-03-07

    Oxidation of zero-valent phosphine complexes [M(P(t) Bu3 )2 ] (M=Pd, Pt) has been investigated in 1,2-difluorobenzene solution using cyclic voltammetry and subsequently using the ferrocenium cation as a chemical redox agent. In the case of palladium, a mononuclear paramagnetic Pd(I) derivative was readily isolated from solution and fully characterized (EPR, X-ray crystallography). While in situ electrochemical measurements are consistent with initial one-electron oxidation, the heavier congener undergoes C-H bond cyclometalation and ultimately affords the 14 valence-electron Pt(II) complex [Pt(κ(2) PC -P(t) Bu2 CMe2 CH2 )(P(t) Bu3 )](+) with concomitant formation of [Pt(P(t) Bu3 )2 H](+) . © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  2. Long-lived room-temperature deep-red-emissive intraligand triplet excited state of naphthalimide in cyclometalated Ir(III) complexes and its application in triplet-triplet annihilation-based upconversion.

    PubMed

    Sun, Jifu; Wu, Wanhua; Zhao, Jianzhang

    2012-06-25

    Cyclometalated Ir(III) complexes with acetylide ppy and bpy ligands were prepared (ppy = 2-phenylpyridine, bpy = 2,2'-bipyridine) in which naphthal (Ir-2) and naphthalimide (NI) were attached onto the ppy (Ir-3) and bpy ligands (Ir-4) through acetylide bonds. [Ir(ppy)(3)] (Ir-1) was also prepared as a model complex. Room-temperature phosphorescence was observed for the complexes; both neutral and cationic complexes Ir-3 and Ir-4 showed strong absorption in the visible range (ε=39,600  M(-1)  cm(-1) at 402 nm and ε=25,100  M(-1)  cm(-1) at 404 nm, respectively), long-lived triplet excited states (τ(T)=9.30 μs and 16.45 μs) and room-temperature red emission (λ(em)=640 nm, Φ(p)=1.4 % and λ(em)=627 nm, Φ(p)=0.3 %; cf. Ir-1: ε=16,600  M(-1)  cm(-1) at 382 nm, τ(em)=1.16 μs, Φ(p)=72.6 %). Ir-3 was strongly phosphorescent in non-polar solvent (i.e., toluene), but the emission was completely quenched in polar solvents (MeCN). Ir-4 gave an opposite response to the solvent polarity, that is, stronger phosphorescence in polar solvents than in non-polar solvents. Emission of Ir-1 and Ir-2 was not solvent-polarity-dependent. The T(1) excited states of Ir-2, Ir-3, and Ir-4 were identified as mainly intraligand triplet excited states ((3)IL) by their small thermally induced Stokes shifts (ΔE(s)), nanosecond time-resolved transient difference absorption spectroscopy, and spin-density analysis. The complexes were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion and quantum yields of 7.1 % and 14.4 % were observed for Ir-2 and Ir-3, respectively, whereas the upconversion was negligible for Ir-1 and Ir-4. These results will be useful for designing visible-light-harvesting transition-metal complexes and for their applications as triplet photosensitizers for photocatalysis, photovoltaics, TTA upconversion, etc. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. The Chameleonic Nature of Platinum(II) Imidazopyridine Complexes.

    PubMed

    Pinter, Piermaria; Pittkowski, Rebecca; Soellner, Johannes; Strassner, Thomas

    2017-10-12

    The synthesis and characterization of cyclometalated C^C* platinum(II) complexes with unique photophysical properties, aggregation induced enhancement of the quantum yields with a simultaneous decrease of phosphorescence lifetimes, is reported. Additionally, a change of emission color is induced by variation of the excitation wavelength. The aggregation behavior of these complexes is controlled by the steric demand of the substituents. The photophysical properties of these complexes are investigated through emission-excitation matrix analysis (EEM). The monomeric complexes are excellent room temperature phosphorescent blue emitters with emission maxima below 470 nm and quantum yields of up to 93 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Azobenzene Pd(II) complexes with N^N- and N^O-type ligands

    NASA Astrophysics Data System (ADS)

    Nikolaeva, M. V.; Puzyk, An. M.; Puzyk, M. V.

    2017-05-01

    Methods of synthesis of cyclometalated azobenzene palladium(II) complexes of [Pd(N^N)Azb]ClO4 and [Pd(N^O)Azb]ClO4 types (where Azb- is the deprotonated form of azobenzene; N^N is 2NH3, ethylenediamine, or 2,2'-bipyridine; and (N^O)- is the deprotonated form of amino acid (glycine, α-alanine, β-alanine, tyrosine, or tryptophan)) are developed. The electronic absorption and the electrochemical properties of these complexes are studied.

  5. Gram Scale Synthesis of Benzophenanthroline and Its Blue Phosphorescent Platinum Complex

    DOE PAGES

    Saris, Patrick J. G.; Thompson, Mark E.

    2016-08-04

    Here, the design, synthesis, and characterization of 12-phenylbenzo[f][1,7]phenanthroline, Bzp, is reported. Its use as a fluorine free ligand for sky blue phosphorescence is demonstrated in a cyclometallated platinum complex, BzpPtDpm. BzpPtDpm phosphoresces at the same wavelength as its analogous 4,6-difluorophenylpyridine complex at both room temperature (466 nm) and 77 kelvin (458 nm). Finally, production of a conformationally restricted derivative of BzpPtDpm with greatly increased quantum yield (46%) validates the versatility of the synthetic route.

  6. Gram Scale Synthesis of Benzophenanthroline and Its Blue Phosphorescent Platinum Complex

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saris, Patrick J. G.; Thompson, Mark E.

    Here, the design, synthesis, and characterization of 12-phenylbenzo[f][1,7]phenanthroline, Bzp, is reported. Its use as a fluorine free ligand for sky blue phosphorescence is demonstrated in a cyclometallated platinum complex, BzpPtDpm. BzpPtDpm phosphoresces at the same wavelength as its analogous 4,6-difluorophenylpyridine complex at both room temperature (466 nm) and 77 kelvin (458 nm). Finally, production of a conformationally restricted derivative of BzpPtDpm with greatly increased quantum yield (46%) validates the versatility of the synthetic route.

  7. Steering Asymmetric Lewis Acid Catalysis Exclusively with Octahedral Metal-Centered Chirality.

    PubMed

    Zhang, Lilu; Meggers, Eric

    2017-02-21

    Catalysts for asymmetric synthesis must be chiral. Metal-based asymmetric catalysts are typically constructed by assembling chiral ligands around a central metal. In this Account, a new class of effective chiral Lewis acid catalysts is introduced in which the octahedral metal center constitutes the exclusive source of chirality. Specifically, the here discussed class of catalysts are composed of configurationally stable, chiral-at-metal Λ-configured (left-handed propeller) or Δ-configured (right-handed propeller) iridium(III) or rhodium(III) complexes containing two bidentate cyclometalating 5-tert-butyl-2-phenylbenzoxazole (dubbed IrO and RhO) or 5-tert-butyl-2-phenylbenzothiazole (dubbed IrS and RhS) ligands in addition to two exchange-labile acetonitriles. They are synthetically accessible in an enantiomerically pure fashion through a convenient auxiliary-mediated synthesis. Such catalysts are of interest due to their intrinsic structural simplicity (only achiral ligands) and the prospect of an especially effective asymmetric induction due to the intimate contact between the chiral metal center and the metal-coordinated substrates or reagents. With respect to chiral Lewis acid catalysis, the bis-cyclometalated iridium and rhodium complexes provide excellent catalytic activities and asymmetric inductions for a variety of reactions including Michael additions, Friedel-Crafts reactions, cycloadditions, α-aminations, α-fluorinations, Mannich reactions, and a cross-dehydrogenative coupling. Mechanistically, substrates such as 2-acyl imidazoles are usually activated by two-point binding. Exceptions exist as for example for an efficient iridium-catalyzed enantioselective transfer hydrogenation of arylketones with ammonium formate, which putatively proceeds through an iridium-hydride intermediate. The bis-cyclometalated iridium complexes catalyze visible-light-induced asymmetric reactions by intertwining asymmetric catalysis and photoredox catalysis in a unique

  8. Mono- and bis-tolylterpyridine iridium(III) complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hinkle, Lindsay M.; Young, Jr., Victor G.; Mann, Kent R.

    The first structure report of trichlorido[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) dimethyl sulfoxide solvate, [IrCl{sub 3}(C{sub 22}H{sub 17}N{sub 3})] {center_dot} C{sub 2}H{sub 6}OS, (I), is presented, along with a higher-symmetry setting of previously reported bis[4'-(p-tolyl)-2,2':6',2{double_prime}-terpyridine]iridium(III) tris(hexafluoridophosphate) acetonitrile disolvate, [Ir(C{sub 22}H{sub 17}N{sub 3})2](PF{sub 6}){sub 3} {center_dot} 2C{sub 2}H{sub 3}N, (II) [Yoshikawa, Yamabe, Kanehisa, Kai, Takashima & Tsukahara (2007). Eur. J. Inorg. Chem. pp. 1911-1919]. For (I), the data were collected with synchrotron radiation and the dimethyl sulfoxide solvent molecule is disordered over three positions, one of which is an inversion center. The previously reported structure of (II) is presented in the more appropriate C2/c space group.more » The iridium complex and one PF{sub 6}{sup -} anion lie on twofold axes in this structure, making half of the molecule unique.« less

  9. Hydrogen storage and evolution catalysed by metal hydride complexes.

    PubMed

    Fukuzumi, Shunichi; Suenobu, Tomoyoshi

    2013-01-07

    The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-κN(2))benzoic acid-κC(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of β-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (λ > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes.

  10. Triplet-Triplet Annihilation Photon Upconversion in Polymer Thin Film: Sensitizer Design.

    PubMed

    Jiang, Xinpeng; Guo, Xinyan; Peng, Jiang; Zhao, Dahui; Ma, Yuguo

    2016-05-11

    Efficient visible-to-UV photon upconversion via triplet-triplet annihilation (TTA) is accomplished in polyurethane (PU) films by developing new, powerful photosensitizers fully functional in the solid-state matrix. These rationally designed triplet sensitizers feature a bichromophoric scaffold comprising a tris-cyclometalated iridium(III) complex covalently tethered to a suitable organic small molecule. The very rapid intramolecular triplet energy transfer from the former to the latter is pivotal for achieving the potent sensitizing ability, because this process out-competes the radiative and nonradiative decays inherent to the metal complex and produces long-lived triplet excitons localized with the acceptor moiety readily available for intermolecular transfer and TTA. Nonetheless, compared to the solution state, the molecular diffusion is greatly limited in solid matrices, which even creates difficulty for the Dexter-type intramolecular energy transfer. This is proven by the experimental results showing that the sensitizing performance of the bichromophoric molecules strongly depends on the spatial distance separating the donor (D) and acceptor (A) units and that incorporating a longer linker between the D and A evidently curbs the TTA upconversion efficiency in PU films. Using a rationally optimized sensitizer structure in combination with 2,7-di-tert-butylpyrene as the annihilator/emitter, the doped polyurethane (PU) films demonstrate effective visible-to-UV upconverted emission signal under noncoherent-light irradiation, attaining an upconversion quantum yield of 2.6%. Such quantum efficiency is the highest value so far reported for the visible-to-UV TTA systems in solid matrices.

  11. Photoinduced anticancer activity studies of iridium(III) complexes targeting mitochondria and tubules.

    PubMed

    Zhang, Wen-Yao; Yi, Qian-Yan; Wang, Yang-Jie; Du, Fan; He, Miao; Tang, Bing; Wan, Dan; Liu, Yun-Jun; Huang, Hong-Liang

    2018-05-10

    Three new iridium (III) complexes [Ir (ppy) 2 (ipbc)](PF 6 ) (1), [Ir (bzq) 2 (ipbc)](PF 6 ) (2) and [Ir (piq) 2 (ipbc)](PF 6 ) (3) were designed and synthesized. All the complexes were tested for anticancer activity using 3-(4,5-dimethylthiazole)-2,5-diphenyltetraazolium bromide (MTT) method. The complexes show no cytotoxic activity toward cancer BEL-7402, SGC-7901, Eca-109, A549, HeLa and HepG2 cells. However, upon irradiation with white light, the complexes display high cytotoxicity against BEL-7402 cells with an IC 50 value of 5.5 ± 0.8, 7.3 ± 1.3 and 11.5 ± 1.6 μM for 1, 2 and 3, respectively. AO/EB staining and comet assay show that the complexes can induce apoptosis in BEL-7402 cells. The complexes can increase intracellular ROS and Ca 2+ levels and cause a decrease in the mitochondrial membrane potential. Autophagic assays exhibit that the complexes can induce autophagy and regulate the expression of Beclin-1 and LC3 proteins. The cell cycle distribution in BEL-7402 cells was carried out by flow cytometry. The expression of Bcl-2 family proteins was studied by western blot. Additionally, the complexes can release cytochrome c and inhibit the polymerization of α-tubulin. Our study reveals that the complexes inhibit the cell growth in BEL-7402 cells through an ROS-mediated mitochondria dysfunction and targeting tubules pathways. These complexes are a promising new entity for the development of multi-target anticancer drugs. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

  12. Protonation of a lanthanum phosphide-alkyl occurs at the P-La not the C-La bond: isolation of a cationic lanthanum alkyl complex.

    PubMed

    Izod, Keith; Liddle, Stephen T; Clegg, William

    2004-08-07

    Protonation of the heteroleptic, cyclometalated lanthanum phosphide complex [((Me3Si)2CH)(C6H4-2-CH2NMe2)P]La(THF)[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))] with [Et3NH][BPh4] yields the cationic alkyllanthanum complex [(THF)4La[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))

  13. Rapid visual and spectrophotometric nitrite detection by cyclometalated ruthenium complex.

    PubMed

    Lo, Hoi-Shing; Lo, Ka-Wai; Yeung, Chi-Fung; Wong, Chun-Yuen

    2017-10-16

    Quantitative determination of nitrite ion (NO 2 - ) is of great importance in environmental and clinical investigations. A rapid visual and spectrophotometric assay for NO 2 - detection was developed based on a newly designed ruthenium complex, [Ru(npy)([9]aneS3)(CO)](ClO 4 ) (denoted as RuNPY; npy = 2-(1-naphthyl)pyridine, [9]aneS3 = 1,4,7-trithiacyclononane). This complex traps NO + produced in acidified NO 2 - solution, and yields observable color change within 1 min at room temperature. The assay features excellent dynamic range (1-840 μmol L -1 ) and high selectivity, and its limit of detection (0.39 μmol L -1 ) is also well below the guideline values for drinking water recommended by WHO and U.S. EPA. Practical use of this assay in tap water and human urine was successfully demonstrated. Overall, the rapidity and selectivity of this assay overcome the problems suffered by the commonly used modified Griess assays for nitrite determination. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Efficient Red-Emitting Platinum Complex with Long Operational Stability.

    PubMed

    Fleetham, Tyler; Li, Guijie; Li, Jian

    2015-08-05

    A tetradentate cyclometalated Pt(II) complex, PtN3N-ptb, was developed as an emissive dopant for stable and efficient red phosphorescent OLEDs. Devices employing PtN3N-ptb in electrochemically stable device architectures achieved long operational lifetimes with estimated LT97, of over 600 h at luminances of 1000 cd/m(2). Such long operational lifetimes were achieved utilizing only literature reported host, transporting and blocking materials with known molecular structures. Additionally, a thorough study of the effects of various host and transport materials on the efficiency, turn on voltage, and stability of the devices was carried out. Ultimately, maximum forward viewing EQEs as high as 21.5% were achieved, demonstrating that Pt(II) complexes can act as stable and efficient dopants with operational lifetimes comparable or superior to those of the best literature-reported Ir(III) complexes.

  15. Cyclometalated products of [(COE)(2)RhCl](2) and 1,3-(RSCH(2))(2)C(6)H(4) (R = (t)Bu, (i)Pr) Are Dimeric. Synthesis, molecular structures, and solution dynamics of [mu-ClRh(H)(RSCH(2))(2)C(6)H(3)-2,6](2).

    PubMed

    Evans, Daniel R; Huang, Mingsheng; Seganish, W Michael; Chege, Esther W; Lam, Yiu-Fai; Fettinger, James C; Williams, Tracie L

    2002-05-20

    Two tridentate thioether pincer ligands, 1,3-(RSCH(2))(2)C(6)H(4) (R = (t)()Bu, 1a; R = (i)()Pr, 1b) underwent cyclometalation using [(COE)(2)RhCl](2) in air/moisture-free benzene at room temperature. The resultant complexes, [mu-ClRh(H)(RSCH(2))(2)C(6)H(3)-2,6](2) (R = (t)Bu, 2a; R = (i)Pr, 2b) are dimeric both in the solid state and in solution. A battery of variable-temperature one- and two-dimensional (1)H NMR experiments showed conclusively that both complexes undergo dynamic exchange in solution. Exchange between two dimeric diastereomers of 2a in solution occurred via rotation about the Rh-C(ipso) bond. The dynamic exchange of 2b was significantly more complex as an additional exchange mechanism, sulfur inversion, occurred, which resulted in the exchange between several diastereomers in solution.

  16. Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes.

    PubMed

    Liao, Jia-Ling; Devereux, Leon R; Fox, Mark A; Yang, Chun-Chieh; Chiang, Yu-Cheng; Chang, Chih-Hao; Lee, Gene-Hsiang; Chi, Yun

    2018-01-12

    A class of neutral tris-bidentate Ir III metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl 3 ] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2'-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (3). The reaction of 3 with the dianionic chelate precursor, 5,5'-di(trifluoromethyl)-3,3'-bipyrazole (bipzH 2 ) or 5,5'-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH 2 ), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexes 2-6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3 π-π* transition character in the blue-emitting 4-6. The dppBz does not participate in the radiative transitions in 4-6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir III complexes containing phosphine chelates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Mono- and bis-tolyl­terpyridine iridium(III) complexes

    PubMed Central

    Hinkle, Lindsay M.; Young, Victor G.; Mann, Kent R.

    2010-01-01

    The first structure report of trichlorido[4′-(p-tolyl)-2,2′:6′,2′′-terpyridine]iridium(III) dimethyl sulfoxide solvate, [IrCl3(C22H17N3)]·C2H6OS, (I), is presented, along with a higher-symmetry setting of previously reported bis­[4′-(p-tolyl)-2,2′:6′,2′′-terpyridine]iridium(III) tris­(hexa­fluorido­phosphate) acetonitrile disolvate, [Ir(C22H17N3)2](PF6)3·2C2H3N, (II) [Yoshikawa, Yamabe, Kanehisa, Kai, Takashima & Tsukahara (2007 ▶). Eur. J. Inorg. Chem. pp. 1911–1919]. For (I), the data were collected with synchrotron radiation and the dimethyl sulfoxide solvent mol­ecule is disordered over three positions, one of which is an inversion center. The previously reported structure of (II) is presented in the more appropriate C2/c space group. The iridium complex and one PF6 − anion lie on twofold axes in this structure, making half of the mol­ecule unique. PMID:20203396

  18. Photodynamic killing of cancer cells by a Platinum(II) complex with cyclometallating ligand

    NASA Astrophysics Data System (ADS)

    Doherty, Rachel E.; Sazanovich, Igor V.; McKenzie, Luke K.; Stasheuski, Alexander S.; Coyle, Rachel; Baggaley, Elizabeth; Bottomley, Sarah; Weinstein, Julia A.; Bryant, Helen E.

    2016-03-01

    Photodynamic therapy that uses photosensitizers which only become toxic upon light-irradiation provides a strong alternative to conventional cancer treatment due to its ability to selectively target tumour material without affecting healthy tissue. Transition metal complexes are highly promising PDT agents due to intense visible light absorption, yet the majority are toxic even without light. This study introduces a small, photostable, charge-neutral platinum-based compound, Pt(II) 2,6-dipyrido-4-methyl-benzenechloride, complex 1, as a photosensitizer, which works under visible light. Activation of the new photosensitizer at low concentrations (0.1-1 μM) by comparatively low dose of 405 nm light (3.6 J cm-2) causes significant cell death of cervical, colorectal and bladder cancer cell lines, and, importantly, a cisplatin resistant cell line EJ-R. The photo-index of the complex is 8. We demonstrate that complex 1 induces irreversible DNA single strand breaks following irradiation, and that oxygen is essential for the photoinduced action. Neither light, nor compound alone led to cell death. The key advantages of the new drug include a remarkably fast accumulation time (diffusion-controlled, minutes), and photostability. This study demonstrates a highly promising new agent for photodynamic therapy, and attracts attention to photostable metal complexes as viable alternatives to conventional chemotherapeutics, such as cisplatin.

  19. A rhodium(III) complex inhibits LPS-induced nitric oxide production and angiogenic activity in cellulo.

    PubMed

    Liu, Li-Juan; Lin, Sheng; Chan, Daniel Shiu-Hin; Vong, Chi Teng; Hoi, Pui Man; Wong, Chun-Yuen; Ma, Dik-Lung; Leung, Chung-Hang

    2014-11-01

    Metal-containing complexes have arisen as viable alternatives to organic molecules as therapeutic agents. Metal complexes possess a number of advantages compared to conventional carbon-based compounds, such as distinct geometries, interesting electronic properties, variable oxidation states and the ability to arrange different ligands around the metal centre in a precise fashion. Meanwhile, nitric oxide (NO) plays key roles in the regulation of angiogenesis, vascular permeability and inflammation. We herein report a novel cyclometalated rhodium(III) complex as an inhibitor of lipopolysaccharides (LPS)-induced NO production in RAW264.7 macrophages. Experiments suggested that the inhibition of NO production in cells by complex 1 was mediated through the down-regulation of nuclear factor-κB (NF-κB) activity. Furthermore, complex 1 inhibited angiogenesis in human umbilical vein endothelial cells (HUVECs) as revealed by an endothelial tube formation assay. This study demonstrates that kinetically inert rhodium(III) complexes may be potentially developed as effective anti-angiogenic agents. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Diaryl-1,2,3-Triazolylidene Platinum(II) Complexes.

    PubMed

    Soellner, Johannes; Strassner, Thomas

    2018-04-11

    Control of the excited state geometry by rational ligand design leads to a new class of phosphorescent emitters with extraordinary photophysical properties. Extension of the π-system in the triplet state leading to a significant bathochromic shift of the emission was avoided by introduction of additional steric demand. We report the synthesis, characterization and photophysical properties of novel platinum(II) complexes bearing C^C* cyclometalated mesoionic carbene (MIC) with different β-diketonate ligands. The MIC ligand precursors were prepared from 1-phenyl-1,2,3-triazole using arylation protocols, introducing phenyl or mesityl functionalities. A solid state structure confirming the NMR assignments is presented. The emission properties were investigated in detail at room temperature and 77 K and are supported by DFT calculations and cyclic voltammetry. All complexes, with emission maxima between 502-534 nm, emit with quantum efficiencies ranging from 70-84 % in PMMA films. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy

    PubMed Central

    Zhao, Qiang; Zhang, Chuanqi; Liu, Shujuan; Liu, Yahong; Zhang, Kenneth Yin; Zhou, Xiaobo; Jiang, Jiayang; Xu, Wenjuan; Yang, Tianshe; Huang, Wei

    2015-01-01

    It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F- is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F--responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F− with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F− in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F−-sensitive red phosphorescence from iridium(III) complex to the F−-insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F− also changes its emission lifetime, and the lifetime-based detection of F− in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe’s concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications. PMID:26552859

  2. DFT/TDDFT investigation on the photophysical properties of a series of phosphorescent cyclometalated complexes based on the benchmark complex FIrpic

    NASA Astrophysics Data System (ADS)

    Han, Deming; Gong, Ping; Lv, Shuhui; Zhao, Lihui; Zhao, Henan

    2018-05-01

    The photophysical properties of four Ir(III) complexes have been investigated by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). The effect of the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption and phosphorescent properties has been studied. The theoretical calculation shows that the lowest-lying singlet absorptions for complexes 1-4 are located at 387, 385, 418 and 386 nm, respectively. For 1-4, the phosphorescence at 465, 485, 494 and 478 nm is mainly attributed to the LUMO → HOMO and LUMO → HOMO-1 transition configurations characteristics. In addition, ionisation potential (IP), electron affinities (EAs) and reorganisation energy have been investigated to evaluate the charge transfer and balance properties between hole and electron. The balance of the reorganisation energies for complex 3 is better than others. The difference between hole transport and electron transport for complex 3 is the smallest among these complexes, which is beneficial to achieve the hole and electron transfer balance in emitting layer.

  3. Unexpected formation of chiral pincer CNN nickel complexes with β-diketiminato type ligands via C-H activation: synthesis, properties, structures, and computational studies.

    PubMed

    Lu, Zhengliang; Abbina, Srinivas; Sabin, Jared R; Nemykin, Victor N; Du, Guodong

    2013-02-04

    Reaction of lithiated chiral, unsymmetric β-diketimine type ligands HL(2a-e) containing oxazoline moiety (HL(2a-e) = 2-(2'-R(1)NH)-phenyl-4-R(2)-oxazoline) with trans-NiCl(Ph)(PPh(3))(2) afforded a series of new chiral CNN pincer type nickel complexes (3a-3e) via an unexpected cyclometalation at benzylic or aryl C-H positions. Single crystal X-ray diffraction analysis established the pincer coordination mode and the strained conformation. Chirality, and in one case, racemization of the target nickel complexes were confirmed by circular dichroism (CD) spectroscopy. Electronic structure and band assignments in experimental UV-vis and CD spectra were discussed on the basis of Density Functional Theory (DFT) and time-dependent (TD) DFT calculations.

  4. Rigid biimidazole ancillary ligands as an avenue to bright deep blue cationic iridium(iii) complexes.

    PubMed

    Henwood, Adam F; Evariste, Sloane; Slawin, Alexandra M Z; Zysman-Colman, Eli

    2014-01-01

    Herein we report the synthesis and optoelectronic characterisation of three deep blue-emitting cationic iridium complexes, of the form [Ir(dFppy)(2)(N^N)]PF(6), bearing biimidazole-type N^N ancillary ligands (dFppyH = 2-(2,4-difluorophenyl)pyridine). Complex 1 contains the parent biimidazole, biim, while 2 contains a dimethylated analog, dMebiim, and 3 contains an ortho-xylyl-tethered biimidzole, o-xylbiim. We explore a strategy of tethering the biimidazole in order to rigidify the complex and increase the photoluminescent quantum yield, culminating in deep blue (λ(max): 457 nm in MeOH at 298 K) ligand-centered emission with a very high photoluminescent quantum yield of 68% and microsecond emission lifetime. Density functional theory calculations elucidate the origin of such disparate excited state kinetics across this series, especially in light of virtually identical optoelectronic properties observed for these compounds.

  5. The Use of Cyclometalated NHCs and Pyrazoles for the Development of Fully Efficient Blue PtII Emitters and Pt/Ag Clusters.

    PubMed

    Arnal, Lorenzo; Fuertes, Sara; Martín, Antonio; Sicilia, Violeta

    2018-05-15

    New bis-pyrazole complexes [Pt(C^C*)(RpzH) 2 ]X, containing a cyclometalated N-heterocyclic carbene ligand (HC^C*=1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene) were prepared as chloride (X=Cl - , RpzH: 3,5-Me 2 pzH 1 a, 4-MepzH 2 a, pzH 3 a), perchlorate (X=ClO 4 - , 1 b-3 b), or hexafluorophosphate (X=PF 6 - , RpzH: 3,5-Me 2 pzH 1 c) salts. The X-ray structure of 1 a showed that the Cl - anion is trapped by the cation through two N-H⋅⋅⋅Cl bonds. In solution of methanol, acetone and THF at RT, 1 a-3 a coexist in equilibrium with the corresponding [PtCl(C^C*)(RpzH)] (B) and RpzH species. In CH 2 Cl 2 , this equilibrium takes place just for 2 a and 3 a, but it is completely shifted to the left at 243 and 223 K for 2 a and 3 a, respectively. The low-lying absorption and emission bands were assigned to intraligand (ILCT) charge transfer on the NHC group. Quantum yield measurements in PMMA films revealed that 1 b, 2 b and 1 c are amongst the most efficient blue-light emitters, with values up to 100 %. Proton abstraction from the coordinated 3,5-Me 2 pzH in 1 b by NEt 3 and replacement by Ag + afforded a neutral [Pt 2 Ag 2 ] cluster containing Pt→Ag dative bonds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Iridium complexes containing mesoionic C donors: selective C(sp3)-H versus C(sp2)-H bond activation, reactivity towards acids and bases, and catalytic oxidation of silanes and water.

    PubMed

    Petronilho, Ana; Woods, James A; Mueller-Bunz, Helge; Bernhard, Stefan; Albrecht, Martin

    2014-11-24

    Metalation of a C2-methylated pyridylimidazolium salt with [IrCp*Cl2]2 affords either an ylidic complex, resulting from C(sp(3))-H bond activation of the C2-bound CH3 group if the metalation is performed in the presence of a base, such as AgO2 or Na2CO3, or a mesoionic complex via cyclometalation and thermally induced heterocyclic C(sp(2))-H bond activation, if the reaction is performed in the absence of a base. Similar cyclometalation and complex formation via C(sp(2))-H bond activation is observed when the heterocyclic ligand precursor consists of the analogous pyridyltriazolium salt, that is, when the metal bonding at the C2 position is blocked by a nitrogen rather than a methyl substituent. Despite the strongly mesoionic character of both the imidazolylidene and the triazolylidene, the former reacts rapidly with D(+) and undergoes isotope exchange at the heterocyclic C5 position, whereas the triazolylidene ligand is stable and only undergoes H/D exchange under basic conditions, where the imidazolylidene is essentially unreactive. The high stability of the Ir-C bond in aqueous solution over a broad pH range was exploited in catalytic water oxidation and silane oxidation. The catalytic hydrosilylation of ketones proceeds with turnover frequencies as high as 6,000 h(-1) with both the imidazolylidene and the triazolylidene system, whereas water oxidation is enhanced by the stronger donor properties of the imidazol-4-ylidene ligands and is more than three times faster than with the triazolylidene analogue. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Mechanistic investigations of imine hydrogenation catalyzed by cationic iridium complexes.

    PubMed

    Martín, Marta; Sola, Eduardo; Tejero, Santiago; Andrés, José L; Oro, Luis A

    2006-05-15

    Complexes [IrH2(eta6-C6H6)(PiPr3)]BF4 (1) and [IrH2(NCMe)3(PiPr3)]BF4 (2) are catalyst precursors for homogeneous hydrogenation of N-benzylideneaniline under mild conditions. Precursor 1 generates the resting state [IrH2{eta5-(C6H5)NHCH2Ph}(PiPr3)]BF4 (3), while 2 gives rise to a mixture of [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)2(PiPr3)]BF4 (4) and [IrH{PhN=CH(C6H4)-kappaN,C}(NCMe)(NH2Ph)(PiPr3)]BF4 (5), in which the aniline ligand is derived from hydrolysis of the imine. The less hindered benzophenone imine forms the catalytically inactive, doubly cyclometalated compound [Ir{HN=CPh(C6H4)-kappaN,C}2(NH2CHPh2)(PiPr3)]BF4 (6). Hydrogenations with precursor 1 are fast and their reaction profiles are strongly dependent on solvent, concentrations, and temperature. Significant induction periods, minimized by addition of the amine hydrogenation product, are commonly observed. The catalytic rate law (THF) is rate = k[1][PhN=CHPh]p(H2). The results of selected stoichiometric reactions of potential catalytic intermediates exclude participation of the cyclometalated compounds [IrH{PhN=CH(C6H4)-kappaN,C}(S)2(PiPr3)]BF4 [S = acetonitrile (4), [D6]acetone (7), [D4]methanol (8)] in catalysis. Reactions between resting state 3 and D2 reveal a selective sequence of deuterium incorporation into the complex which is accelerated by the amine product. Hydrogen bonding among the components of the catalytic reaction was examined by MP2 calculations on model compounds. The calculations allow formulation of an ionic, outer-sphere, bifunctional hydrogenation mechanism comprising 1) amine-assisted oxidative addition of H2 to 3, the result of which is equivalent to heterolytic splitting of dihydrogen, 2) replacement of a hydrogen-bonded amine by imine, and 3) simultaneous H delta+/H delta- transfer to the imine substrate from the NH moiety of an arene-coordinated amine ligand and the metal, respectively.

  8. Cyclometalation and coupling of a rigid 4,5-bis(imino)acridanide pincer ligand on yttrium.

    PubMed

    Wong, Edwin W Y; Emslie, David J H

    2015-07-07

    An extremely rigid NNN-donor proligand, 4,5-bis{(diphenylmethylene)amino}-2,7,9,9-tetramethylacridan, H[AIm2] was prepared in five steps starting from 5-methyl-2-aminobenzoic acid and 4-bromotoluene. Reaction of intensely orange H[AIm2] with LiCH2SiMe3 formed deep blue Li(x)[AIm2]x (x = 2 in the solid state), while reaction with [Y(CH2SiMe3)3(THF)2] (0.5 equiv.) afforded deep blue [Y(AIm2)(AIm)] (1; AIm = an AIm2 ligand cyclometalated at the ortho-position of one of the phenyl rings). Compound 1 slowly isomerizes to form green-brown 2, which contains a single trianionic, hexadentate ligand that features one amine, two imine, and three amido donors. The acridanide backbone and one imine group in each of the original AIm2 ligands is intact, but the two acridanide backbones are now linked by an isoindoline heterocycle. Yttrium in 2 is coordinated to six nitrogen donors and the ortho carbon of an isoindoline phenyl substituent. The intense colours of H[AIm2], Li(x)[AIm2]x and 1 were shown by TD-DFT calculations to arise from charge transfer transitions from the HOMO, which is localized on the acridanide ligand backbone, to the LUMO and LUMO+1, which are localized on the imine substituents. The conversion of 1 to 2 was studied by UV-Visible absorption spectroscopy and is first-order with a half-life of 7.8 hours at room temperature.

  9. Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal-Ligand Induced Catalytic Dehydrogenation of Amines.

    PubMed

    Valencia, Marta; Pereira, Ana; Müller-Bunz, Helge; Belderraín, Tomás R; Pérez, Pedro J; Albrecht, Martin

    2017-07-03

    Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such N pyr ⋅⋅⋅H-N interactions are demonstrated by X-ray diffraction analysis, 1 H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand-metal cooperative substrate activation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Mitochondrial imaging in live or fixed tissues using a luminescent iridium complex.

    PubMed

    Sorvina, Alexandra; Bader, Christie A; Darby, Jack R T; Lock, Mitchell C; Soo, Jia Yin; Johnson, Ian R D; Caporale, Chiara; Voelcker, Nicolas H; Stagni, Stefano; Massi, Massimiliano; Morrison, Janna L; Plush, Sally E; Brooks, Douglas A

    2018-05-29

    Mitochondrial morphology is important for the function of this critical organelle and, accordingly, altered mitochondrial structure is exhibited in many pathologies. Imaging of mitochondria can therefore provide important information about disease presence and progression. However, mitochondrial imaging is currently limited by the availability of agents that have the capacity to image mitochondrial morphology in both live and fixed samples. This can be particularly problematic in clinical studies or large, multi-centre cohort studies, where tissue archiving by fixation is often more practical. We previously reported the synthesis of an iridium coordination complex [Ir(ppy) 2 (MeTzPyPhCN)] + ; where ppy is a cyclometalated 2-phenylpyridine and TzPyPhCN is the 5-(5-(4-cyanophen-1-yl)pyrid-2-yl)tetrazolate ligand; and showed that this complex (herein referred to as IraZolve-Mito) has a high specificity for mitochondria in live cells. Here we demonstrate that IraZolve-Mito can also effectively stain mitochondria in both live and fixed tissue samples. The staining protocol proposed is versatile, providing a universal procedure for cell biologists and pathologists to visualise mitochondria.

  11. Phosphorescent binuclear iridium complexes based on terpyridine-carboxylate: an experimental and theoretical study.

    PubMed

    Andreiadis, Eugen S; Imbert, Daniel; Pécaut, Jacques; Calborean, Adrian; Ciofini, Ilaria; Adamo, Carlo; Demadrille, Renaud; Mazzanti, Marinella

    2011-09-05

    The phosphorescent binuclear iridium(III) complexes tetrakis(2-phenylpyridine)μ-(2,2':6',2''-terpyridine-6,6''-dicarboxylic acid)diiridium (Ir1) and tetrakis(2-(2,4-difluorophenyl) pyridine))μ-(2,2':6',2''-terpyridine-6,6''-dicarboxylic acid)diiridium (Ir2) were synthesized in a straightforward manner and characterized using X-ray diffraction, NMR, UV-vis absorption, and emission spectroscopy. The complexes have similar solution structures in which the two iridium centers are equivalent. This is further confirmed by the solid state structure of Ir2. The newly reported complexes display intense luminescence in dichloromethane solutions with maxima at 538 (Ir1) and 477 nm (Ir2) at 298 K (496 and 468 nm at 77 K, respectively) and emission quantum yields reaching ~18% for Ir1. The emission quantum yield for Ir1 is among the highest values reported for dinuclear iridium complexes. It shows only a 11% decrease with respect to the emission quantum yield reported for its mononuclear analogue, while the molar extinction coefficient is roughly doubled. This suggests that such architectures are of potential interest for the development of polymetallic assemblies showing improved optical properties. DFT and time-dependent-DFT calculations were performed on the ground and excited states of the complexes to provide insights into their structural, electronic, and photophysical properties.

  12. A theoretical study on the mechanistic highlights behind the Brønsted-acid dependent mer-fac isomerization of homoleptic carbenic iridium complexes for PhOLEDs.

    PubMed

    Setzer, Tobias; Lennartz, Christian; Dreuw, Andreas

    2017-06-06

    Recently, a successful Brønsted-acid mediated geometric isomerization of the meridional homoleptic carbenic iridium(iii) complexes tris-(N-phenyl,N-methyl-benzimidazol-2-yl)iridium(iii) (1) and tris-(N-phenyl,N-benzyl-benzimidazol-2-yl)iridium(iii) (2) into their facial form has been reported. In the present work the pronounced acid-dependency of this particular isomerization procedure is revisited and additional mechanistic pathways are taken into account. Moreover, the acid-induced material decomposition is addressed. All calculations are carried out using density functional theory (DFT) while the environmental effects in solution are accounted for by the COSMO-RS model. The simulated results clearly reveal the outstanding importance of the complex interplay between acid strength, coordinating power of the corresponding base and the steric influence of the ligand system in contrast to the plain calculation of minimum energy pathways for selected complexes. Eventually, general rules to enhance the material-specific reaction yields are provided.

  13. A kinetico-mechanistic study on the C-H bond activation of primary benzylamines; cooperative and solid-state cyclopalladation on dimeric complexes.

    PubMed

    Font, Helena; Font-Bardia, Mercè; Gómez, Kerman; González, Gabriel; Granell, Jaume; Macho, Israel; Martínez, Manuel

    2014-09-28

    The cyclometallation reactions of dinuclear μ-acetato complexes of the type [Pd(AcO)(μ-AcO)L]2 (L = 4-RC6H4CH2NH2, R = H, Cl, F, CF3), a process found to occur readily even in the solid state, have been studied from a kinetico-mechanistic perspective. Data indicate that the dinuclear acetato bridged derivatives are excellent starting materials to activate carbon-hydrogen bonds in a facile way. In all cases the established concerted ambiphilic proton abstraction by a coordinated acetato ligand has been proved. The metallation has also been found to occur in a cooperative manner, with the metallation of the first palladium unit of the dimeric complex being rate determining; no intermediate mono-metallated compounds are observed in any of the processes. The kinetically favoured bis-cyclopalladated compound obtained after complete C-H bond activation does not correspond to the final isolated XRD-characterized complexes. This species, bearing the classical open-book dimeric form, has a much more complex structure than the final isolated compound, with different types of acetato ligands.

  14. Pincer-CNC mononuclear, dinuclear and heterodinuclear Au(III) and Pt(II) complexes supported by mono- and poly-N-heterocyclic carbenes: synthesis and photophysical properties.

    PubMed

    Gonell, S; Poyatos, M; Peris, E

    2016-04-07

    A family of cyclometallated Au(iii) and Pt(ii) complexes containing a CNC-pincer ligand (CNC = 2,6-diphenylpyridine) supported by pyrene-based mono- or bis-NHC ligands have been synthesized and characterized, together with the preparation of a Pt-Au hetero-dimetallic complex based on a Y-shaped tris-NHC ligand. The photophysical properties of all the new species and of two related Ru(ii)-arene complexes were studied and compared. Whereas the pyrene-based complexes only exhibit emission in solution, those containing the Y-shaped tris-NHC ligand are only luminescent when dispersed in poly(methyl methacrylate) (PMMA). In particular, the pyrene-based complexes were found to be emissive in the range of 373-440 nm, with quantum yields ranging from 3.1 to 6.3%, and their emission spectra were found to be almost superimposable, pointing to the fluorescent pyrene-centered nature of the emission. This observation suggests that the emission properties of the pyrene fragment may be combined with some of the numerous applications of NHCs as supporting ligands allowing, for instance, the design of biological luminescent agents.

  15. η(6) -Arene-Zirconium-PNP-Pincer Complexes: Mechanism of Their Hydrogenolytic Formation and Their Reactivity as Zirconium(II) Synthons.

    PubMed

    Plundrich, Gudrun T; Wadepohl, Hubert; Clot, Eric; Gade, Lutz H

    2016-06-27

    The cyclometalated monobenzyl complexes [(Cbzdiphos(R) -CH)ZrBnX] 1 (iPr) Cl and 1 (Ph) I reacted with dihydrogen (10 bar) to yield the η(6) -toluene complexes [(Cbzdiphos(R) )Zr(η(6) -tol)X] 2 (iPr) Cl and 2 (Ph) I (cbzdiphos=1,8-bis(phosphino)-3,6-di-tert-butyl-9H-carbazole). The arene complexes were also found to be directly accessible from the triiodide [(Cbzdiphos(Ph) )ZrI3 ] through an in situ reaction with a dibenzylmagnesium reagent and subsequent hydrogenolysis, as exemplified for the η(6) -mesitylene complex [(Cbzdiphos(Ph) )Zr(η(6) -mes)I] (3 (Ph) I). The tolyl-ring in 2 (iPr) Cl adopts a puckered arrangement (fold angle 23.3°) indicating significant arene-1,4-diido character. Deuterium labeling experiments were consistent with an intramolecular reaction sequence after the initial hydrogenolysis of a Zr-C bond by a σ-bond metathesis. A DFT study of the reaction sequence indicates that hydrogenolysis by σ-bond metathesis first occurs at the cyclometalated ancillary ligand giving a hydrido-benzyl intermediate, which subsequently reductively eliminates toluene that then coordinates to the Zr atom as the reduced arene ligand. Complex 2 (Ph) I was reacted with 2,6-diisopropylphenyl isocyanide giving the deep blue, diamagnetic Zr(II) -diisocyanide complex [(Cbzdiphos(Ph) )Zr(CNDipp)2 I] (4 (Ph) I). DFT modeling of 4 (Ph) I demonstrated that the HOMO of the complex is primarily located as a "lone pair on zirconium", with some degree of back-bonding into the C≡N π* bond, and the complex is thus most appropriately described as a zirconium(II) species. Reaction of 2 (Ph) I with trimethylsilylazide (N3 TMS) and 2 (iPr) Cl with 1-azidoadamantane (N3 Ad) resulted in the formation of the imido complexes [(Cbzdiphos(R) )Zr=NR'(X)] 5 (iPr) Cl-NAd and 5 (Ph) I-NTMS, respectively. Reaction of 2 (iPr) Cl with azobenzene led to N-N bond scission giving 6 (iPr) Cl, in which one of the NPh-fragments is coupled with the carbazole

  16. Sequential double second-order nonlinear optical switch by an acido-triggered photochromic cyclometallated platinum(II) complex.

    PubMed

    Boixel, Julien; Guerchais, Véronique; Le Bozec, Hubert; Chantzis, Agisilaos; Jacquemin, Denis; Colombo, Alessia; Dragonetti, Claudia; Marinotto, Daniele; Roberto, Dominique

    2015-05-07

    An unprecedented DTE-based Pt(II) complex, 2(o), which stands as the first example of a sequential double nonlinear optical switch, induced first by protonation and next upon irradiation with UV light is presented.

  17. Visible Light Photocatalysis of [2+2] Styrene Cycloadditions via Energy Transfer

    PubMed Central

    Lu, Zhan; Yoon, Tehshik P.

    2012-01-01

    Hip to be square: Styrenes participate in [2+2] cycloadditions upon irradiation with visible light in the presence of an iridium(III) polypyridyl complex. In contrast to previous reports of visible light photoredox catalysis, the mechanism of this process involves photosensitization by energy transfer and not electron transfer. PMID:22965321

  18. Photophysical properties of ortho-metalated monomeric and dimeric complexes containing rhodium(III) and iridium(III) metal centers

    NASA Astrophysics Data System (ADS)

    Marshall, Jason Alexander

    Photophysical properties of dichloro-bridged dimers and monomeric tris complexes of the type [M(NC)2Cl]2 and M(NC)3, where NC refers to the ortho-metalating ligands 2-phenylpyridine (ppy), benzo[h]quinoline (bzq), or 2-(p-tolyl)pyridine (ptpy) and M is Rh(III) or Ir(III), were investigated. Excited-state emission of Rh(III) complexes are highly structured and independent of temperature from 4--100 K in glassy media, with long lifetimes (102 mus to ms). Emission is not observed from the pale yellow, fluid solutions of Rh(III) complexes at room temperature. Below 7K, decay kinetics are sensitive to temperature and are complicated, requiring multi-exponential fits in 4:1 EtOH/MeOH. The spectroscopic properties are consistent with the assignment of a lowest 3pipi* excited-state manifold perturbed by an admixture of higher-lying states possessing strong spin-orbit interactions. The complicated decays are attributed to spin-relaxation-limited behavior between spin-levels in the 3pipi* manifold. Deep yellow solutions of Ir(III) complexes in 4:1 EtOH/MeOH are observed to emit in both glassy media and in fluid solution, displaying severe changes in spectral shape as the glass softens which are not attributable to rigidochromic shifts. Low-temperature spectra are structured with emission origins in the range 496--520 nm whereas room-temperature emission of complexes in fluid solution are characteristically broad structureless bands with maxima redshifted from spectra measured in rigid media. Both the emission and the excited-state lifetimes display temperature dependence, with lifetimes in the microsecond to tens of microseconds range at 77 K, increasing by more than an order of magnitude as the temperature is decreased to 4 K. Each of these characteristic band shapes arises from separate components of the emission which have been time-resolved from the low-temperature spectrum. A long-lived, structured component of the emission, only observed in rigid media, has been

  19. Enhanced CO2 electroreduction efficiency through secondary coordination effects on a pincer iridium catalyst.

    PubMed

    Ahn, Steven T; Bielinski, Elizabeth A; Lane, Elizabeth M; Chen, Yanqiao; Bernskoetter, Wesley H; Hazari, Nilay; Palmore, G Tayhas R

    2015-04-07

    An iridium(III) trihydride complex supported by a pincer ligand with a hydrogen bond donor in the secondary coordination sphere promotes the electrocatalytic reduction of CO2 to formate in water/acetonitrile with excellent Faradaic efficiency and low overpotential. Preliminary mechanistic experiments indicate formate formation is facile while product release is a kinetically difficult step.

  20. Application of a novel red-emitting cationic iridium(III) coordination polymer in warm white light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Chen, Mingxian; Sun, Riyong; Ye, Yanchun; Tang, Huaijun; Dong, Xueyan; Yan, Jialun; Wang, Kaimin; Zhou, Qiang; Wang, Zhengliang

    2018-02-01

    A novel red-emitting cationic iridium(III) coordination polymer using 2-(9-(2-ethylhexyl)-9H-carbazol-3-yl)benzo[d]thiazole as main ligands, 4,4‧-bipyridine as bridging auxiliary ligands and Clˉ as anions was synthesized. It had high thermal stability with a thermal decomposition temperature (Td) of 345 °C and low thermal quenching with an activation energy (Ea) of 0.2760 eV, with the temperature increasing from 20 °C to 100 °C, its photoluminescent intensity decreased to 76.7%. It can be efficiently excited by blue light of GaN chips, the cold white light of GaN-based LEDs using only Y3Al5O12:Ce3+ (YAG:Ce, 7.0 wt% in silicone) as phosphors can become warmer when it was blended in. When blending concentrations were 0.1 wt% and 0.2 wt%, the cold white light became neutral white light, the correlated color temperature (CCT) decreased from 6157 K to 5240 K, then to 4043 K, the color rendering index (CRI) changed from 72.7 to 81.3, then to 78.6, the luminous efficiency (ηL) changed from 134.1 lm·w-1 to 61.9 lm·w-1, then to 46.3 lm·w-1, the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates changed from (0.32, 0.33) to (0.34, 0.33), then to (0.38, 0.36). At 0.3 wt%, the light became warm white light, the corresponding CCT was 3475 K, CRI was 75.6, ηL was 36.9 lm·w-1, and CIE value was (0.41, 0.40). The results suggest the coordination polymer is a promising red-emitting phosphor candidate for neutral and warm white LEDs, especially for warm white LEDs.

  1. Long term stable deep red light-emitting electrochemical cells based on an emissive, rigid cationic Ir(iii) complex

    DOE PAGES

    Namanga, Jude E.; Ruhr-Univ. Bochum, Bochum; Gerlitzki, Niels; ...

    2017-02-17

    Here, the new cationic iridium complex [Ir(bzq) 2(biq)][PF 6] (bzq = benzo[ h]quinolinato and biq = 2,2'-biquinoline) has been synthesized for application as an emitter in light emitting electrochemical cells (LECs). The molecular structure and crystal packing of this complex were established by single X-ray diffraction (SXRD). The electrochemical and photophysical properties of the complex were examined to determine the frontier orbital energies as well as the optical transitions that led to photoemission. The complex was found to emit at 644 nm and 662 nm for powder and thin films, respectively. A high powder photoluminescence quantum yield of 25% wasmore » determined, which is attributed to a reduction in vibrational modes of the complex due to the use of the rigid cyclometalated (C^N) bzq ligand. A LEC with [Ir(bzq) 2(biq)][PF 6] as the emitter was fabricated which showed a deep red emission (662 nm) with a luminance of 33.65 cd m –2, yielding a current efficiency of 0.33 cd A –1 and a power efficiency of 0.2 lm W –1. Most importantly, the LEC based on [Ir(bzq) 2(biq)][PF 6] demonstrated a lifetime of 280 hours which is among the longest device lifetimes reported for any deep red light emitting LEC.« less

  2. Long term stable deep red light-emitting electrochemical cells based on an emissive, rigid cationic Ir(iii) complex

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Namanga, Jude E.; Ruhr-Univ. Bochum, Bochum; Gerlitzki, Niels

    Here, the new cationic iridium complex [Ir(bzq) 2(biq)][PF 6] (bzq = benzo[ h]quinolinato and biq = 2,2'-biquinoline) has been synthesized for application as an emitter in light emitting electrochemical cells (LECs). The molecular structure and crystal packing of this complex were established by single X-ray diffraction (SXRD). The electrochemical and photophysical properties of the complex were examined to determine the frontier orbital energies as well as the optical transitions that led to photoemission. The complex was found to emit at 644 nm and 662 nm for powder and thin films, respectively. A high powder photoluminescence quantum yield of 25% wasmore » determined, which is attributed to a reduction in vibrational modes of the complex due to the use of the rigid cyclometalated (C^N) bzq ligand. A LEC with [Ir(bzq) 2(biq)][PF 6] as the emitter was fabricated which showed a deep red emission (662 nm) with a luminance of 33.65 cd m –2, yielding a current efficiency of 0.33 cd A –1 and a power efficiency of 0.2 lm W –1. Most importantly, the LEC based on [Ir(bzq) 2(biq)][PF 6] demonstrated a lifetime of 280 hours which is among the longest device lifetimes reported for any deep red light emitting LEC.« less

  3. Binuclear cyclometalated organoplatinum complexes containing 1,1'-bis(diphenylphosphino)ferrocene as spacer ligand: kinetics and mechanism of MeI oxidative addition.

    PubMed

    Jamali, Sirous; Nabavizadeh, S Masoud; Rashidi, Mehdi

    2008-06-16

    The binuclear complex [Pt2Me2(ppy)2(mu-dppf)], 1, in which ppy = deprotonated 2-phenylpyridyl and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was synthesized by the reaction of [PtMe(SMe2)(ppy)] with 0.5 equiv of dppf at room temperature. In this reaction when 1 equiv of dppf was used, the dppf chelating complex 2, [PtMe(dppf)(ppy-kappa1C)], was obtained. The reaction of Pt(II)-Pt(II) complex 1 with excess MeI gave the Pt(IV)-Pt(IV) complex [Pt2I2Me4(ppy)2(mu-dppf)], 3. When the reaction was performed with 1 equiv of MeI, a mixture containing unreacted complex 1, a mixed-valence Pt(II)-Pt(IV) complex [PtMe(ppy)(mu-dppf)PtIMe2(ppy)], 4, and complex 3 was obtained. In a comparative study, the reaction of [PtMe(SMe2)(ppy)] with 1 equiv of monodentate phosphine PPh3 gave [PtMe(ppy)(PPh3)], A. MeI was reacted with A to give the platinum(IV) complex [PtMe2I(ppy)(PPh3)], C. All the complexes were fully characterized using multinuclear (1H, 31P, 13C, and 195Pt) NMR spectroscopy, and complex 2 was further identified by single crystal X-ray structure determination. The reaction of binuclear Pt(II)-Pt(II) complex 1 with excess MeI was monitored by low temperature 31P NMR spectroscopy and further by 1H NMR spectroscopy, and the kinetics of the reaction was studied by UV-vis spectroscopy. On the basis of the data, a mechanism has been suggested for the reaction which overall involved stepwise oxidative addition of MeI to the two Pt(II) centers. In this suggested mechanism, the reaction proceeded through a number of Pt(II)-Pt(IV) and Pt(IV)-Pt(IV) intermediates. Although MeI in each step was trans oxidatively added to one of the Pt(II) centers, further trans to cis isomerizations of Me and I groups were also identified. A comparative kinetic study of the reaction of monomeric platinum(II) complex A with MeI was also performed. The rate of reaction of MeI with complex 1 was some 3.5 times faster than that with complex A, indicating that dppf in the complex 1, as compared with

  4. Photophysical properties of a new series of water soluble iridium bisterpyridine complexes functionalised at the 4' position.

    PubMed

    Goldstein, Daniel C; Cheng, Yuen Yap; Schmidt, Timothy W; Bhadbhade, Mohan; Thordarson, Pall

    2011-03-07

    Four new hetero- and homo-leptic iridium(III) bisterpyridine complexes have been prepared which incorporate aniline (tpy-φ-NH(2)), benzoic acid (tpy-φ-COOH), and benzyl alcohol (tpy-φ-CH(2)OH) substituents at the 4' positions of the tpy ligands (tpy = 2,2':6',2''-terpyridine, φ = phenylene). The electrochemical behaviour and ground and excited state spectroscopic properties of the complexes are reported, and the X-ray crystal structures of a homoleptic benzyl alcohol [Ir(tpy-φ-CH(2)OH)(2)](PF(6))(3), homoleptic aniline [Ir(tpy-φ-NH(2))(2)](PF(6))(3), and heteroleptic benzyl alcohol/aniline substituted complex [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))](PF(6))(3) have been solved. Complexes with aniline substituents were found to display absorption bands at around 430 nm corresponding to intraligand charge transfer (ILCT) that are sensitive to changes in solvent and pH. Strong emission in the visible region involving the ILCT state is observed in two of the complexes (Φ(e) = 0.7% and 2.6%) in acetonitrile. In the heteroleptic aniline/benzyl alcohol complex the Stokes shift is shown to be linearly related to solvent polarisability according to the Lippert equation, but only for solvents with weak hydrogen bonding interactions. Additionally, in water, emission from the ILCT state is quenched and only weak ligand centred (LC) emission is observed. The long lifetimes and quantum yields of these complexes make them interesting candidates for probes in sensing applications, especially [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))(2)](PF(6))(3) due to its unusual sensitivity to the solvent environment.

  5. Phosphorescent Iridium(III) Complexes Bearing Fluorinated Aromatic Sulfonyl Group with Nearly Unity Phosphorescent Quantum Yields and Outstanding Electroluminescent Properties.

    PubMed

    Zhao, Jiang; Yu, Yue; Yang, Xiaolong; Yan, Xiaogang; Zhang, Huiming; Xu, Xianbin; Zhou, Guijiang; Wu, Zhaoxin; Ren, Yixia; Wong, Wai-Yeung

    2015-11-11

    A series of heteroleptic functional Ir(III) complexes bearing different fluorinated aromatic sulfonyl groups has been synthesized. Their photophysical features, electrochemical behaviors, and electroluminescent (EL) properties have been characterized in detail. These complexes emit intense yellow phosphorescence with exceptionally high quantum yields (ΦP > 0.9) at room temperature, and the emission maxima of these complexes can be finely tuned depending upon the number of the fluorine substituents on the pendant phenyl ring of the sulfonyl group. Furthermore, the electrochemical properties and electron injection/transporting (EI/ET) abilities of these Ir(III) phosphors can also be effectively tuned by the fluorinated aromatic sulfonyl group to furnish some desired characters for enhancing the EL performance. Hence, the maximum luminance efficiency (ηL) of 81.2 cd A(-1), corresponding to power efficiency (ηP) of 64.5 lm W(-1) and external quantum efficiency (ηext) of 19.3%, has been achieved, indicating the great potential of these novel phosphors in the field of organic light-emitting diodes (OLEDs). Furthermore, a clear picture has been drawn for the relationship between their optoelectronic properties and chemical structures. These results should provide important information for developing highly efficient phosphors.

  6. Strong ligand field effects of blue phosphorescent Ir(III) complexes with phenylpyrazole and phosphines.

    PubMed

    Park, Se Won; Ham, Ho Wan; Kim, Young Sik

    2012-04-01

    In the paper, we describe new Ir complexes for achieving efficient blue phosphorescence. New blue-emitting mixed-ligand Ir complexes comprising one cyclometalating, two phosphines trans to each other such as Ir(dppz)(PPh3)2(H)(L) (Ll= Cl, NCMe+, CN), [dppz = 3,5-Diphenylpyrazole] were synthesized and studied to tune the phosphorescence wavelength to the deep blue region and to enhance the luminescence efficiencies. To gain insight into the factors responsible for the emission color change and the variation of luminescence efficiency, we investigate the electron-withdrawing capabilities of ancillary ligands using DFT and TD-DFT calculations on the ground and excited states of the complexes. To achieve deep blue emission and increase the emission efficiency, (1) we substitute the phenyl group on the 3-position of the pyrazole ring that lowers the triplet energy enough that the quenching channel is not thermally accessible and (2) change the ancillary ligands coordinated to iridium atom to phosphine and cyano groups known as very strong field ligands. Their inclusion in the coordination sphere can increase the HOMO-LUMO gap to achieve the hypsochromic shift in emission color and lower the HOMO and LUMO energy level, which causes a large d-orbital energy splitting and avoids the quenching effect to improve the luminescence efficiency. The maximum emission spectra of Ir(dppz)(PPh3)2(H)(CI) and Ir(dppz)(PPh3)2(H)(CN) were in the ranges of 439, 432 nm, respectively.

  7. Multistate Redox Switching and Near-Infrared Electrochromism Based on a Star-Shaped Triruthenium Complex with a Triarylamine Core

    NASA Astrophysics Data System (ADS)

    Tang, Jian-Hong; He, Yan-Qin; Shao, Jiang-Yang; Gong, Zhong-Liang; Zhong, Yu-Wu

    2016-10-01

    A star-shaped cyclometalated triruthenium complex 2(PF6)n (n = 3 and 4) with a triarylamine core was synthesized, which functions as a molecular switch with five well-separated redox states in both solution and film states. The single-crystal X-ray structure of 2(PF6)3 is presented. This complex displays four consecutive one-electron redox waves at +0.082, +0.31, +0.74, and +1.07 V vs Ag/AgCl. In each redox state, it shows significantly different NIR absorptions with λmax of 1590 nm for 24+, 1400 nm for 25+, 1060 nm for 26+, and 740 nm for 27+, respectively. Complex 24+ shows a single-line EPR signal at g = 2.060, while other redox states are all EPR inactive. The spin density distributions and NIR absorptions in different redox states were rationalized by DFT and TDDFT calculations. A vinyl-substituted triruthenium analogous 3(PF6)4 was prepared, which was successfully polymerized on ITO glass electrode surfaces by reductive electropolymerization. The obtained poly-3n+/ITO film was characterized by FTIR, AFM, and SEM analysis. It shows four well-defined redox couples and reversible multistate NIR electrochromism. In particular, a contrast ratio (ΔT%) up to 63% was achieved at the optic telecommunication wavelength (1550 nm).

  8. Phosphorescent heterobimetallic complexes involving platinum(iv) and rhenium(vii) centers connected by an unsupported μ-oxido bridge.

    PubMed

    Molaee, Hajar; Nabavizadeh, S Masoud; Jamshidi, Mahboubeh; Vilsmeier, Max; Pfitzner, Arno; Samandar Sangari, Mozhgan

    2017-11-28

    Heterobimetallic compounds [(C^N)LMe 2 Pt(μ-O)ReO 3 ] (C^N = ppy, L = PPh 3 , 2a; C^N = ppy, L = PMePh 2 , 2b; C^N = bhq, L = PPh 3 , 2c; C^N = bhq, L = PMePh 2 , 2d) containing a discrete unsupported Pt(iv)-O-Re(vii) bridge have been synthesized through a targeted synthesis route. The compounds have been prepared by a single-pot synthesis in which the Pt(iv) precursor [PtMe 2 I(C^N)L] complexes are allowed to react easily with AgReO 4 in which the iodide ligand of the starting Pt(iv) complex is replaced by an ReO 4 - anion. In these Pt-O-Re complexes, the Pt(iv) centers have an octahedral geometry, completed by a cyclometalated bidentate ligand (C^N), two methyl groups and a phosphine ligand, while the Re(vii) centers have a tetrahedral geometry. Elemental analysis, single crystal X-ray diffraction analysis and multinuclear NMR spectroscopy are used to establish their identities. The new complexes exhibit phosphorescence emission in the solid and solution states at 298 and 77 K, which is an uncommon property of platinum complexes with an oxidation state of +4. According to DFT calculations, we found that this emission behavior in the new complexes originates from ligand centered 3 LC (C^N) character with a slight amount of metal to ligand charge transfer ( 3 MLCT). The solid-state emission data of the corresponding cycloplatinated(iv) precursor complexes [PtMe 2 I(C^N)L], 1a-1d, pointed out that the replacement of I - by an ReO 4 - anion helps enhancing the emission efficiency besides shifting the emission wavelengths.

  9. Iridium(iii) phosphorescent complexes with dual stereogenic centers: single crystal, electronic circular dichroism evidence and circularly polarized luminescence properties.

    PubMed

    Li, Tian-Yi; Zheng, You-Xuan; Zhou, Yong-Hui

    2016-12-06

    Iridium complexes with a chiral metal center and chiral carbons, Λ/Δ-(dfppy) 2 Ir(chty-R) and Λ/Δ-(dfppy) 2 Ir(chty-S), were synthesized and characterized. These isomers have the same steady-state photophysical properties, and obvious offsets in ECD spectra highlight both the chiral sources. Each enantiomeric couple shows mirror-image CPL bands with a dissymmetry factor in the order of 10 -3 .

  10. Structural and luminescence studies on pi...pi and Pt...Pt interactions in mixed chloro-isocyanide cyclometalated platinum(II) complexes.

    PubMed

    Díez, Alvaro; Forniés, Juan; Larraz, Carmen; Lalinde, Elena; López, José A; Martín, Antonio; Moreno, M Teresa; Sicilia, Violeta

    2010-04-05

    [Pt(bzq)Cl(CNR)] [bzq = benzoquinolinate; R = tert-butyl ((t)Bu 1), 2-6-dimethylphenyl (Xyl 2), 2-naphthyl (2-Np 3)] complexes have been synthesized and structurally and photophysically characterized. 1 was found to co-crystallize in two distinct pseudopolymorphs: a red form, which exhibits an infinite 1D-chain ([1](infinity)) and a yellow form, which contains discrete dimers ([1](2)), both stabilized by interplanar pi...pi (bzq) and short Pt...Pt bonding interactions. Complex 3, generated through the unexpected garnet-red double salt isomer [Pt(bzq)(CN-2-Np)(2)][Pt(bzq)Cl(2)] 4, crystallizes as yellow Pt...Pt dimers ([3](2)), while 2 only forms pi...pi (bzq) contacting dimers. Their electronic absorption and luminescence behaviors have been investigated. According to Time-Dependent Density Functional Theory (TD-DFT) calculations, the lowest-lying absorption (CH(2)Cl(2)) has been attributed to combined (1)ILCT and (1)MLCT/(1)ML'CT (L = bzq, L' = CNR) transitions, the latter increasing from 1 to 3. In solid state, while the yellow form [1](2) exhibits a green (3)MLCT unstructured emission only at 77 K, the 1-D form [1](infinity) displays a characteristic low-energy red emission (672 nm, 298 K; 744 nm, 77 K) attributed to a mixed (3)MMCT [d(sigma*)-->p(sigma)]/(3)MMLCT [dsigma*(M(2))-->sigma(pi*)(bzq)] excited state. However, upon exposure to standard atmospheric conditions, [1](infinity) shows an irreversible change to an orange-ochre solid, whose emissive properties are similar to those of the crude 1. Complexes 2 and 3 (77 K) exhibit a structured emission from discrete fragments ((3)LC/(3)MLCT), whereas the luminescence of the garnet-red salt 4 is dominated by a low energy emission (680 nm, 298 K; 730 nm, 77 K) arising from a (3)MMLCT excited state. Solvent (CH(2)Cl(2), toluene, 2-MeTHF and CH(3)CN) and concentration-dependent emission studies at 298 K and at 77 K are also reported for 1-3. In CH(2)Cl(2) solution, the low phosphorescent emission band is ascribed

  11. Impact of various lipophilic substituents on ruthenium(II), rhodium(III) and iridium(III) salicylaldimine-based complexes: synthesis, in vitro cytotoxicity studies and DNA interactions.

    PubMed

    Cassells, Irwin; Stringer, Tameryn; Hutton, Alan T; Prince, Sharon; Smith, Gregory S

    2018-05-30

    A series of bidentate salicylaldimine ligands was prepared and reacted with either [RuCl(µ-Cl)(p-cymene)] 2 , [RhCl(µ-Cl)(Cp*)] 2 or [IrCl(µ-Cl)(Cp*)] 2 . All of the compounds were characterised using an array of spectroscopic and analytical techniques, namely, nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and mass spectrometry. Single crystal X-ray diffraction (XRD) was used to confirm the bidentate coordination mode of the salicylaldimine ligand to the metal centre. The platinum group metal (PGM) complexes were screened against the MCF7 breast cancer cell line. The ruthenium and iridium salicylaldimine complexes showed comparable or greater cytotoxicity than cisplatin against the MCF7 cancer cells, as well as greater cytotoxicity than their rhodium counterparts. Three of the salicylaldimine complexes showed potent activity in the range 18-21 µM. Two of these complexes had a greater affinity for cancerous cells than for CHO non-cancerous cells (SI > 4). Preliminary mechanistic studies suggest that the ruthenium complexes undergo solvation prior to 5'-GMP binding, whereas the iridium complexes were inert to the solvation process.

  12. Asymmetric Iridium Catalyzed C-C Coupling of Chiral Diols via Site-Selective Redox-Triggered Carbonyl Addition

    PubMed Central

    Shin, Inji; Krische, Michael J.

    2015-01-01

    Cyclometalated π-allyliridium C,O-benzoate complexes modified by axially chiral chelating phosphine ligands display a pronounced kinetic preference for primary alcohol dehydrogenation, enabling highly site-selective redox-triggered carbonyl additions of chiral primary-secondary 1,3-diols with exceptional levels of catalyst-directed diastereoselectivity. Unlike conventional methods for carbonyl allylation, the present redox-triggered alcohol C-H functionalizations bypass the use of protecting groups, premetalated reagents, and discrete alcohol-to-aldehyde redox reactions. PMID:26187028

  13. Serendipitous preparation of fac-(aceto-nitrile-κN)tri-chlorido-[(1,2,5,6-η)-cyclo-octa-1,5-diene]iridium(III).

    PubMed

    Morris, David M; Merola, Joseph S

    2015-04-01

    A reaction between [(COD)IrCl]2 (COD is cyclo-octa-1,5-diene), HCl and indene failed to provide the hoped for chlorido-indenyliridium dimer, but instead produced the title compound, [IrCl3(CH3CN)(C8H12)], which is an octa-hedral complex of iridium(III) with a chelating cyclo-octa-1,5-diene ligand, three chloride ligands in a fac arrangement, and one aceto-nitrile ligand. Attempts to devise a rational synthesis for the title compound were unsuccessful.

  14. Novel thiophene-based cycloruthenated compounds: synthesis, characterization, and reactivity.

    PubMed

    Cuesta, Luciano; Maluenda, Irene; Soler, Tatiana; Navarro, Rafael; Urriolabeitia, Esteban P

    2011-01-03

    The reactions between a series of thiophene-based imines with [(η(6)-C(6)H(6))RuCl(μ-Cl)](2), in a basic medium, and in MeCN give a family of ruthenacycles of stoichiometry [Ru(C^N)(NCMe)(4)]PF(6) (C^N = orthometalated thiopheneimine). In these species, the C-H activation process is produced in most cases at the thiophene ring. When two C-H bonds are competing (thiophene vs aryl), the cyclometalation can be driven regioselectively to the thiophene unit or to the aryl ring as a function of the location of the iminic C=N bond. Cyclometalation can also be oriented to positions 2 or 3 of the thiophene depending on the situation of the imine in the heterocycle (3 or 2, respectively). In all studied cases, the η(6)-C(6)H(6) ligand was substituted by acetonitrile. The X-ray structures of two representative complexes have been determined. These thiophene-based metallacycles react with iodine under very mild conditions affording, after hydrolysis, substituted 3-iodo-2-formyl(benzo)thiophenes or substituted 2-iodo-3-formyl(benzo)thiophenes, as a function of the organometallic precursor.

  15. A new synthetic route to the preparation of a series of strong photoreducing agents: fac Tris-ortho-metalated complexes of iridium(III) with substituted 2-phenylpyridines

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Y.; Baer, C.D.; Camaioni-Neto, C.

    1991-04-17

    A new procedure is reported for the high-yield synthesis of fac-tris-ortho-metalated complexes of Ir(III) with 2-phenylpyridine (Hppy) and with substituted 2-phenylpyridine (R-Hppy) ligands. The reported procedure uses the Ir(III) starting material Ir(acac){sub 3} (acac = 2,4-pentanedionate) and typically produces the fac-tris-ortho-metalated complexes in yields of 40-75%. Each of the complexes formed with substituted phenylpyridines exhibited a luminescence lifetime of approximately 2-5 microseconds in nitrogen-saturated acetonitrile at room temperature, and each complex is characterized by a reversible oxidative wave in cyclic voltammetry in acetonitrile. 42 refs., 1 fig., 1 tab.

  16. Theoretical studies on the photophysical properties of luminescent pincer gold(iii) arylacetylide complexes: the role of π-conjugation at the C-deprotonated [C^N^C] ligand† †Electronic supplementary information (ESI) available: Experimental details of synthesis, characterization, and photophysical properties of complex 3-endo, additional computational details, and the Cartesian coordinates of the optimized structures. CCDC 1034529. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4sc03697b

    PubMed Central

    Chan, Kaai Tung; Chang, Xiaoyong

    2015-01-01

    We have performed theoretical analyses of the photophysical properties of a series of cyclometalated gold(iii) arylacetylide complexes, [(C^N^C)AuIIIC 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 CPh-4-OMe], with different extents of π-conjugation at the doubly C-deprotonated [C^N^C] ligand via replacement of one of the phenyl moieties in the non-conjugated CH^N^C ligand (1) by a naphthalenyl (2) or a fluorenyl moiety (3-exo and 3-endo; HCH^N^CH = 2,6-diphenylpyridine). Conforming to the conventional wisdom that extended π-conjugation imposes rigidity on the structure of the 3IL(ππ*(C^N^C)) excited state (IL = intraligand), the calculated Huang–Rhys factors for the 3IL → S0 transition follow the order: 1 > 2 > 3-exo ∼ 3-endo, which corroborates qualitatively the experimental non-radiative decay rate constants, knr: 1 ≫ 2 > 3-exo

  17. Small molecular glasses based on multiposition encapsulated phenyl benzimidazole iridium(III) complexes: toward efficient solution-processable host-free electrophosphorescent diodes.

    PubMed

    Xu, Hui; Yu, Dong-Hui; Liu, Le-Le; Yan, Peng-Fei; Jia, Li-Wei; Li, Guang-Ming; Yue, Zheng-Yu

    2010-01-14

    Three electrophosphorescent small molecular Ir(3+) complexes, Ir(HexPhBI)(3) 1 (HexPhBI = 1-Hexyl-2-phenyl-1H-benzo[d]imidazole), Ir(CzPhBI)(3) 2 (CzPhBI = 9-(6-(2-phenyl-1H-benzo[d]imidazol-1-yl)hexyl)-9H-carbazole), and Ir(Cz(2)PhBI)(3) 3 (Cz(2)PhBI = 9-(6-(4-(1-(6-(9H-carbazol-9-yl)hexyl)-1H-benzo[d]imidazol-2-yl)phenoxy)hexyl)-9H-carbazole), were synthesized in which 3 was designed with the structure of multiposition encapsulation. Compared to the hexyl-substituted 1, 2 and 3 end-capped with the conjugated carbazole moieties have improved thermal stability. X-ray diffraction analysis proved the amorphous state of 2 and 3. High-photoluminescent efficiencies of 3 are achieved as 72% in solution and 61% in solid. It indicates that the peripheral carbazoles not only facilitate the separation of triplet-emission cores and reduce the intermolecular aggregation but also supply a routine for the intermolecular energy transfer. Electrochemical analysis showed the more oxidation states of 3, which might be anticipated to make it superior to 1 and 2 in hole injection and transporting. The important role of the peripheral carbazole moieties in carrier injection/transporting and the optical properties of the complexes were further investigated by Gaussian simulation. A dramatic electroluminescent (EL) performance, including external quantum efficiency of nearly 6%, low turn-on voltage of 2.5 V, and high brightness over 6000 cd m(-2), from the host-free spin-coated device of 3 was achieved. The superiority of multiencapsulation in EL was proved by comparing the EL performance of 2 and 3. By making comparison between the host-free and phosphor-doping devices, it indicated that the combined modification of the aliphatic chains and functional groups in multipositions is a feasible approach to realize the high-efficiency small molecular phosphorescent materials.

  18. Cyclopalladation of dimesityl selenide: synthesis, reactivity, structural characterization, isolation of an intermediate complex with C-H···Pd intra-molecular interaction and computational studies.

    PubMed

    Kolay, Siddhartha; Wadawale, Amey; Das, Dasarathi; Kisan, Hemanta K; Sunoj, Raghavan B; Jain, Vimal K

    2013-08-14

    The reaction of dimesityl selenide (Mes2Se) with either PdCl2(PhCN)2 in toluene or PdCl2 in toluene-acetonitrile yields a chloro-bridged binuclear palladium complex, [Pd2Cl2(μ-Cl)2(Mes2Se)2] (1), whereas with Na2PdCl4 in refluxing ethanol, a cyclometallated palladium complex, [Pd2(μ-Cl)2{MesSeC6H2(Me2)CH2}2] (2) is afforded. 2 can also be obtained when 1 is refluxed in ethanol. On treatment with Pb(Epy)2 in dichloromethane, 2 afforded the Epy-bridged binuclear complexes, [Pd2(μ-Epy)2{MesSeC6H2(Me2)CH2}2] (3; E = S (3a) or Se (3b)). Treatment of 2 with PPh3 yields a bridge-cleaved monomeric complex, [PdCl{MesSeC6H2(Me2)CH2}(PPh3)]. The molecular structures of 1-3 were established by X-ray diffraction analyses. All the complexes are dimeric, with the palladium atoms acquiring a distorted square planar configuration. There are intra-molecular C-H···Pd interactions (d(M-H): 2.75 Å and

  19. Dynamic NMR study of ethene exchange in cationic CNN-type platinum(II) complexes.

    PubMed

    Plutino, M Rosaria; Fenech, Lucia; Stoccoro, Sergio; Rizzato, Silvia; Castellano, Carlo; Albinati, Alberto

    2010-01-18

    Cationic ethylene platinum(II) complexes of the type [Pt(CNN)(C(2)H(4))](+), containing a methyl fragment and different diimines (NN), or terdentate (kappaC-kappa(2)NN') anionic ligands, were synthesized and fully characterized both as solids and in solution [NN = 2,2'-dipyridylamine, 1; 2,2'-dipyridylsulfide, 2; 1,10-phenanthroline, 3; 4,7-diphenyl-1,10-phenanthroline, 4; 3,4,7,8-tetramethyl-1,10-phenanthroline, 5; 2,2'-bipyridine, 6; HC-NN = 6-tert-butyl-2,2'-bipyridine, 7; 6-neo-pentyl-2,2'-bipyridine, 8; 6-phenyl-2,2'-bipyridine, 9; 6-(alpha-methyl)benzyl-2,2'-bipyridine, 10; 6-(alpha-ethyl)benzyl-2,2'-bipyridine, 11; 6-(alpha,alpha-dimethyl)benzyl-2,2'-bipyridine, 12]. Crystals suitable for X-ray analysis of complexes 5 and 7 were obtained. Ethene exchange at the cyclometalated platinum(II) complexes 7, 8, and 10-12 was studied by (1)H NMR line-broadening experiments in chloroform-d, as a function of both temperature and olefin concentrations. For the other prepared complexes the process was too fast to be monitored on the NMR time scale even at the lowest temperature. The ethylene exchange rates show a linear dependence on the concentration of the free ligand, with a negligible k(1) term indicating that either a solvolytic or a dissociative pathway to the products is absent or negligible. The values of the second-order rate constants k(exc), as obtained by linear regression analysis of the experimental data at 298 K, are in a range of ca. 10(4)-10(5) s(-1) m(-1). The activation entropies are negative, ranging between -129 and -112 J K(-1) mol(-1), as expected for associative processes. The activation process is largely entropy controlled: the TDeltaS()() contribution to the free energy of activation is extremely large, amounting to more than 80% for all complexes, with a smaller enthalpy contribution. All the experimental findings evidence that the mechanism takes place via an associative attack by the entering olefin, through a well-ordered, stable

  20. Cyclometalated Iminophosphorane Gold(III) and Platinum(II) Complexes. A Highly Permeable Cationic Platinum(II) Compound with Promising Anticancer Properties

    PubMed Central

    2015-01-01

    New organometallic gold(III) and platinum(II) complexes containing iminophosphorane ligands are described. Most of them are more cytotoxic to a number of human cancer cell lines than cisplatin. Cationic Pt(II) derivatives 4 and 5, which differ only in the anion, Hg2Cl62– or PF6– respectively, display almost identical IC50 values in the sub-micromolar range (25–335-fold more active than cisplatin on these cell lines). The gold compounds induced mainly caspase-independent cell death, as previously reported for related cycloaurated compounds containing IM ligands. Cycloplatinated compounds 3, 4, and 5 can also activate alternative caspase-independent mechanisms of death. However, at short incubation times cell death seems to be mainly caspase dependent, suggesting that the main mechanism of cell death for these compounds is apoptosis. Mercury-free compound 5 does not interact with plasmid (pBR322) DNA or with calf thymus DNA. Permeability studies of 5 by two different assays, in vitro Caco-2 monolayers and a rat perfusion model, have revealed a high permeability profile for this compound (comparable to that of metoprolol or caffeine) and an estimated oral fraction absorbed of 100%, which potentially makes it a good candidate for oral administration. PMID:26147404

  1. Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its palladium(II), platinum(II), ruthenium(III) and iridium(III) complexes.

    PubMed

    Rani, Soni; Kumar, Sumit; Chandra, Sulekh

    2014-01-24

    A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,0(7-12)] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and (1)H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its Palladium(II), Platinum(II), Ruthenium(III) and Iridium(III) complexes

    NASA Astrophysics Data System (ADS)

    Rani, Soni; Kumar, Sumit; Chandra, Sulekh

    2014-01-01

    A novel, tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 3,5,14,16-tetramethyl-2,6,13,17-tetraazatricyclo[12,0,07-12] cosa-1(22),2,5,7,9,11,13,16,18,20-decaene(L), has been synthesized and characterized by elemental analyses, IR, Mass, and 1H NMR spectral studies. Complexes of Pd(II), Pt(II), Ru(III) and Ir(III) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral and thermal studies. On the basis of molar conductance the complexes may be formulated as [PdL]Cl2, [PtL]Cl2, [Ru(L)Cl2]Cl and [Ir(L)Cl2]Cl. The complexes are insoluble in most common solvents, including water, ethanol, carbon tetrachloride and acetonitrile, but soluble in DMF/DMSO. The value of magnetic moment indicates that all the complexes are diamagnetic except Ru(III) complex which shows magnetic moment corresponding to one unpaired electron. The magnetic moment of Ru(III) complex is 1.73 B.M. at room temperature. The antimicrobial activities of ligand and its complexes have been screened in vitro, as growth inhibiting agents. The antifungal and antibacterial screening were carried out using Food Poison and Disc Diffusion Method against plant pathogenic fungi and bacteria Alternaria porri, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa respectively. The compounds were dissolved in DMSO to get the required solutions. The required medium used for these activities was PDA and nutrient agar.

  3. Solid-state phosphorescence-to-fluorescence switching in a cyclometalated Ir(III) complex containing an acid-labile chromophoric ancillary ligand: implication for multimodal security printing.

    PubMed

    Whang, Dong Ryeol; You, Youngmin; Chae, Weon-Sik; Heo, Jeongyun; Kim, Sehoon; Park, Soo Young

    2012-11-06

    In this study, we have demonstrated the reconstruction of encrypted information by employing photoluminescence spectra and lifetimes of a phosphorescent Ir(III) complex (IrHBT). IrHBT was constructed on the basis of a heteroleptic structure comprising a fluorescent N^O ancillary ligand. From the viewpoint of information security, the transformation of the Ir(III) complex between phosphorescent and fluorescent states can be encoded with chemical/photoirradiation methods. Thin polymer films (poly(methylmethacrylate), PMMA) doped with IrHBT display long-lived emission typical of phosphorescence (λ(max) = 586 nm, τ(obs) = 2.90 μs). Meanwhile, exposure to HCl vapor switches the emission to fluorescence (λ(max) = 514 nm, τ(obs) = 1.53 ns) with drastic changes in both the photoluminescence color and lifetime. Security printing on paper impregnated with IrHBT or on a PMMA film containing IrHBT and photoacid generator (triphenylsulfonium triflate) enables the bimodal readout of photoluminescence color and lifetime.

  4. Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral-at-Rhodium Lewis Acid.

    PubMed

    Huang, Yong; Song, Liangliang; Gong, Lei; Meggers, Eric

    2015-12-01

    A bis-cyclometalated chiral-at-metal rhodium complex catalyzes the Diels-Alder reaction between N-Boc-protected 3-vinylindoles (Boc = tert-butyloxycarbonyl) and β-carboxylic ester-substituted α,β-unsaturated 2-acyl imidazoles with good-to-excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92-99% ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2-acyl imidazole dienophile by two-point binding and overrules the preferred regioselectivity of the uncatalyzed reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A new class of transition metal pincer ligand: tantalum complexes that feature a [CCC] X3-donor array derived from a terphenyl ligand.

    PubMed

    Sattler, Aaron; Parkin, Gerard

    2012-02-01

    A new class of [CCC] X(3)-donor pincer ligand for transition metals has been constructed via cyclometalation of a 2,6-di-p-tolylphenyl ([Ar(Tol(2))]) derivative. Specifically, addition of PMe(3) to [Ar(Tol(2))]TaMe(3)Cl induces elimination of methane and formation of the pincer complex, [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl (Tol' = C(6)H(3)Me), which may also be obtained by treatment of Ta(PMe(3))(2)Me(3)Cl(2) with [Ar(Tol(2))]Li. Solutions of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl undergo ligand redistribution with the formation of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Me(2)and [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Cl(2), which may also be synthesized by the reactions of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl with MeMgBr and ZnCl(2), respectively. Reduction of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Cl(2) with KC(8) in benzene gives the benzene complex [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)(η(6)-C(6)H(6)) that is better described as a 1,4-cyclohexadienediyl derivative. Deuterium labeling employing Ta(PMe(3))(2)(CD(3))(3)Cl(2) demonstrates that the pincer ligand is created by a pair of Ar-H/Ta-Me sigma-bond metathesis transformations, rather than by a mechanism that involves α-H abstraction by a tantalum methyl ligand. © 2012 American Chemical Society

  6. C-H activations at iridium(I) square-planar complexes promoted by a fifth ligand.

    PubMed

    Martín, Marta; Torres, Olga; Oñate, Enrique; Sola, Eduardo; Oro, Luis A

    2005-12-28

    In the presence of ligands such as acetonitrile, ethylene, or propylene, the Ir(I) complex [Ir(1,2,5,6-eta-C8H12)(NCMe)(PMe3)]BF4 (1) transforms into the Ir(III) derivatives [Ir(1-kappa-4,5,6-eta-C8H12)(NCMe)(L)(PMe3)]BF4 (L = NCMe, 2; eta2-C2H4, 3; eta2-C3H6, 4), respectively, through a sequence of C-H oxidative addition and insertion elementary steps. The rate of this transformation depends on the nature of L and, in the case of NCMe, the pseudo-first-order rate constants display a dependence upon ligand concentration suggesting the formation of five-coordinate reaction intermediates. A similar reaction between 1 and vinyl acetate affords the Ir(III) complex [Ir(1-kappa-4,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (7) via the isolable five-coordinate Ir(I) compound [Ir(1,2,5,6-eta-C8H12){kappa-O-eta2-OC(Me)OC2H3}(PMe3)]BF4 (6). DFT (B3LYP) calculations in model complexes show that reactions initiated by acetonitrile or ethylene five-coordinate adducts involve C-H oxidative addition transition states of lower energy than that found in the absence of these ligands. Key species in these ligand-assisted transformations are the distorted (nonsquare-planar) intermediates preceding the intramolecular C-H oxidative addition step, which are generated after release of one cyclooctadiene double bond from the five-coordinate species. The feasibility of this mechanism is also investigated for complexes [IrCl(L)(PiPr3)2] (L = eta2-C2H4, 27; eta2-C3H6, 28). In the presence of NCMe, these complexes afford the C-H activation products [IrClH(CH=CHR)(NCMe)(PiPr3)2] (R = H, 29; Me, 30) via the common cyclometalated intermediate [IrClH{kappa-P,C-P(iPr)2CH(CH3)CH2}(NCMe)(PiPr3)] (31). The most effective C-H oxidative addition mechanism seems to involve three-coordinate intermediates generated by photochemical release of the alkene ligand. However, in the absence of light, the reaction rates display dependences upon NCMe concentration again indicating the intermediacy of five

  7. Near-infrared-emitting heteroleptic cationic iridium complexes derived from 2,3-diphenylbenzo[g]quinoxaline as in vitro theranostic photodynamic therapy agents

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Li; Yin, Huimin; Cui, Peng

    Five heteroleptic cationic iridium complexes with a π-expansive cyclometalating 2,3-diphenylbenzo[g] quinoxaline (dpbq) ligand (C^N ligand) and different diimine ligands (N^N ligands) (i.e. 2,2’-bipyridine (bpy, 1), phenanthroline (phen, 2), 2-(2-pyridinyl)quinoline (pqu, 3), 2,2’-bisquinoline (bqu, 4), and 2-(quinolin-2-yl)quinoxaline (quqo, 5)) were synthesized and characterized. The lowest-energy singlet electronic transitions (S1 states) were mainly dpbq ligand-centred 1ILCT (intraligand charge transfer)/1MLCT (metal to ligand charge transfer) transitions mixed with some 1π,π* transitions for complexes 1–4 with increased contributions from 1LLCT (ligand to ligand charge transfer) in 3 and 4. For complex 5, the S1 state was switched to the 1LLCT/1MLCT transitions. All five complexesmore » displayed weak near-infrared (NIR) phosphorescence, with maximal emission output spanning 700–1400 nm and quantum yields being on the order of 10-3. The triplet state absorptions of 1–4 all resembled that of the [Ir(dpbq)2Cl]2 dimer with lifetimes of ca. 400 ns, while the TA spectrum of 5 possessed the characteristics of both the quqo ligand and the [Ir(dpbq)2Cl]2 dimer with a bi-exponential decay of ca. 5 μs and 400 ns. While the photophysics of these complexes differ slightly, their theranostic photodynamic therapy (PDT) effects varied drastically. All of the complexes were biologically active toward melanoma cells. Complexes 2 and 3 were the most cytotoxic, with 230–340 nM activity and selectivity factors for melanoma cells over normal skin fibroblasts of 34 to 40 fold. Complexes 2, 3, and 5 became very potent cytotoxins with light activation, with EC50 values as low as 12–18 nM. This potent nanomolar light-triggered activity combined with a lower dark toxicity resulted in 5 having a phototherapeutic index (PI) margin of almost 275. The bpy coligand led to the least amount of dark toxicity of 1, while phen and pqu produced cytotoxic but selective

  8. Interplay of Zero-Field Splitting and Excited State Geometry Relaxation in fac-Ir(ppy)3.

    PubMed

    Gonzalez-Vazquez, José P; Burn, Paul L; Powell, Benjamin J

    2015-11-02

    The lowest energy triplet state, T1, of organometallic complexes based on iridium(III) is of fundamental interest, as the behavior of molecules in this state determines the suitability of the complex for use in many applications, e.g., organic light-emitting diodes. Previous characterization of T1 in fac-Ir(ppy)3 suggests that the trigonal symmetry of the complex is weakly broken in the excited state. Here we report relativistic time dependent density functional calculations of the zero-field splitting (ZFS) of fac-Ir(ppy)3 in the ground state (S0) and lowest energy triplet (T1) geometries and at intermediate geometries. We show that the energy scale of the geometry relaxation in the T1 state is large compared to the ZFS. Thus, the natural analysis of the ZFS and the radiative decay rates, based on the assumption that the structural distortion is a small perturbation, fails dramatically. In contrast, our calculations of these quantities are in good agreement with experiment.

  9. Ruthenium complexes containing 2-(2-nitrosoaryl)pyridine: structural, spectroscopic, and theoretical studies.

    PubMed

    Chan, Siu-Chung; Cheung, Ho-Yuen; Wong, Chun-Yuen

    2011-11-21

    Ruthenium complexes containing 2-(2-nitrosoaryl)pyridine (ON(^)N) and tetradentate thioether 1,4,8,11-tetrathiacyclotetradecane ([14]aneS4), [Ru(ON(^)N)([14]aneS4)](2+) [ON(^)N = 2-(2-nitrosophenyl)pyridine (2a), 10-nitrosobenzo[h]quinoline (2b), 2-(2-nitroso-4-methylphenyl)pyridine, (2c), 2-(2-nitrosophenyl)-5-(trifluoromethyl)pyridine (2d)] and analogues with the 1,4,7-trithiacyclononane ([9]aneS3)/tert-butylisocyanide ligand set, [Ru(ON(^)N)([9]aneS3)(C≡N(t)Bu)](2+) (4a and 4b), have been prepared by insertion of a nitrosonium ion (NO(+)) into the Ru-aryl bond of cyclometalated ruthenium(II) complexes. The molecular structures of the ON(^)N-ligated complexes 2a and 2b reveal that (i) the ON(^)N ligands behave as bidentate chelates via the two N atoms and the bite angles are 86.84(18)-87.83(16)° and (ii) the Ru-N(NO) and N-O distances are 1.942(5)-1.948(4) and 1.235(6)-1.244(5) Å, respectively. The Ru-N(NO) and N-O distances, together with ν(N═O), suggest that the coordinated ON(^)N ligands in this work are neutral moiety (ArNO)(0) rather than monoanionic radical (ArNO)(•-) or dianion (ArNO)(2-) species. The nitrosated complexes 2a-2d show moderately intense absorptions centered at 463-484 nm [ε(max) = (5-6) × 10(3) dm(3) mol(-1) cm(-1)] and a clearly discriminable absorption shoulder around 620 nm (ε(max) = (6-9) × 10(2) dm(3) mol(-1) cm(-1)), which tails up to 800 nm. These visible absorptions are assigned as a mixing of d(Ru) → ON(^)N metal-to-ligand charge-transfer and ON(^)N intraligand transitions on the basis of time-dependent density functional theory (TD-DFT) calculations. The first reduction couples of the nitrosated complexes range from -0.53 to -0.62 V vs Cp(2)Fe(+/0), which are 1.1-1.2 V less negative than that for [Ru(bpy)([14]aneS4)](2+) (bpy = 2,2'-bipyridine). Both electrochemical data and DFT calculations suggest that the lowest unoccupied molecular orbitals of the nitrosated complexes are ON(^)N-centered. Natural population

  10. Theoretical study on phosphorescence efficiency and color tuning from orange to blue-green of Ir(III) complexes based on substituted 2-phenylimidazo[1,2-a]pyridine ligand.

    PubMed

    Li, Xiao-Na; Wu, Zhi-Jian; Li, Xi-Yan; Zhang, Hong-Jie; Liu, Xiao-Juan

    2011-04-30

    The geometrical structures, phosphorescence quantum yields, and electroluminescence (EL) efficiency of six iridium(III) complexes containing 2-phenylimidazo[1,2-a]pyridine ligand are investigated by density functional theory (DFT), which show a wide color tuning of photoluminescence from orange (λ(em) = 550 nm) to blue-green (λ(em) = 490 nm). The calculated results shed some light on the reasons of the remarkably manipulated excited-state and EL properties through substitution effect. The Mulliken charge calculation reveals that attached -CF(3) groups on phenyl and imidazo[1,2-a]pyridine (impy) moieties (4) can make both of them as electron-deficient region, which will lead to the contraction of the whole coordination sphere and strengthen the metal-ligand interaction. While attaching two -CF(3) groups on phenyl ring can make it more electron-deficient, which will induce electron transferring from acac and impy fragment to phenyl ring, and also result in the contracted structure. The largest metal-to-ligand charge transfer ((3)MLCT) character and the smaller S(1)-T(1) energy gap (ΔE(S(1)-T(1))) value increase the emission quantum yields of 4 and 6 than other complexes. For EL efficiency, because of the similar highest occupied molecular orbital (HOMO) levels of 4 and 6 to that of holes injection material poly(N-vinylcarbazole) (PVK) and the larger dipole moments, majority hole will be accumulated on the HOMO of 4 and 6. Combination with the lower lowest unoccupied molecular orbital energy levels compared with PVK, the recombination zones of 4 and 6 can be well confined within emitting material layer (EML) and lead to the higher EL efficiency. Copyright © 2010 Wiley Periodicals, Inc.

  11. Yellow emitting Iridium (III) phenyl-benzothiazole complexes with different β-diketone ancillary ligands as dopants in white organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Ivanov, P.; Petrova, P.; Tomova, R.

    2018-03-01

    We discuss the influence of the type of β-diketone ancillary ligand in Iridium (III) bis phenyl-benzothiazole complexes ((bt)2Ir(β-diketone)) on their photophysical and electroluminescent properties when they are used as dopants in white organic light-emitting diodes (WOLED). For this purpose, we investigated four novel yellow cyclometalated complexes: (bt)2Ir(dbm), (bt)2Ir(fmtdbm), (bt)2Ir(tta) and (bt)2Ir(bsm), where dbm = 1,3-diphenylpropane-1,3-dionate; fmtdbm = 1-(4-fluorophenyl)-3-(4-methoxyphenyl)propane-1,3-dionate; tta = 4,4,4-trifluoro-1-(thiophene-2-yl)butane-1,3-dionate; and bsm = 1-phenylicosane-1,3-dionate). To obtain white light by mixing emissions of two complementary colors (yellow emitted by the dopant and blue, by another emitter), we chose the following OLED structure: ITO/doped HTL/ElL/ETL/M, where ITO was a transparent anode of In2O3:SnO2; M, a metallic Al cathode; HTL, 4,4’-Bis(9H-carbazol-9-yl)biphenyl (CBP) involved in a poly(N-vinylcarbazole) (PVK) matrix; ElL, an electroluminescent layer of aluminum(III)bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq); and ETL, an electron-transporting layer of zinc(II)bis(2-2-hydroxyphenyl)benzothiazole. We found that all complexes are suitable candidates for fabrication of WOLED. The best results were demonstrated by the device doped with 2 wt % of (bt)2Ir(bsm), which had twice as high luminescence (1100 cd/m2) and one-and-a-half as high current efficiency (5 cd/A) as the device doped with 1.25 wt % of the known (bt)2Ir(acac), with its 580 cd/m2 and 3.4 cd/A at approximately the same CIE (Commission Internationale de L’Eclairage) (x/y) coordinates of the warm white light emitted by the two devices.

  12. A Highly Reactive Dicationic Iridium(III) Catalyst for Polarized Nazarov Cyclization

    PubMed Central

    Vaidya, Tulaza; Atesin, Abdurrahman C.; Herrick, Ildiko R.; Frontier, Alison J.; Eisenberg, Richard

    2010-01-01

    Pushing the Nazarov Envelope A new electrophilic complex [IrBr(CO)(diethylisopropylidene malonate)((R)-(+)-BINAP)](SbF6)2 (2) exhibits unusual activity in the catalysis of polarized Nazarov cyclization. Aryl vinyl ketones that show poor reactivity with well-known catalysts such as [Ir(CH3)(CO)(1,2-diiodobenzene)(dppe)](B(Arf)4−)2 (1), Sc(OTf)3 + LiClO4 and Cu(ClO4)2, can be cyclized with 2 + AgSbF6 (1:1) under mild conditions with concurrent AgBr precipitation. PMID:20358570

  13. Complete Monitoring of Coherent and Incoherent Spin Flip Domains in the Recombination of Charge-Separated States of Donor-Iridium Complex-Acceptor Triads.

    PubMed

    Klein, Johannes H; Schmidt, David; Steiner, Ulrich E; Lambert, Christoph

    2015-09-02

    The spin chemistry of photoinduced charge-separated (CS) states of three triads comprising one or two triarylamine donors, a cyclometalated iridium complex sensitizer and a naphthalene diimide (NDI) acceptor, was investigated by transient absorption spectroscopy in the ns-μs time regime. Strong magnetic-field effects (MFE) were observed for two triads with a phenylene bridge between iridium complex sensitizer and NDI acceptor. For these triads, the lifetimes of the CS states increased from 0.6 μs at zero field to 40 μs at about 2 T. Substituting the phenylene by a biphenyl bridge causes the lifetime of the CS state at zero field to increase by more than 2 orders of magnitude (τ = 79 μs) and the MFE to disappear almost completely. The kinetic MFE was analyzed in the framework of a generalized Hayashi-Nagakura scheme describing coherent (S, T0 ↔ T±) as well as incoherent (S, T0 ⇌ T±) processes by a single rate constant k±. The magnetic-field dependence of k± of the triads with phenylene bridge spans 2 orders of magnitude and exhibits a biphasic behavior characterized by a superposition of two Lorentzians. This biphasic MFE is observed for the first time and is clearly attributable to the coherent (B < 10 mT) and incoherent (10 mT < B < 2 T) domains of spin motion induced by isotropic and anisotropic hyperfine coupling. The parameters of both domains are well understood in terms of the structural properties of the two triads, including the effect of electron hopping in the triad with two donor moieties. The kinetic model also accounts for the reduction of the MFE on reducing the rate constant of charge recombination in the triad with the biphenyl bridge.

  14. Mixing of phosphorescent and exciplex emission in efficient organic electroluminescent devices.

    PubMed

    Cherpak, Vladyslav; Stakhira, Pavlo; Minaev, Boris; Baryshnikov, Gleb; Stromylo, Evgeniy; Helzhynskyy, Igor; Chapran, Marian; Volyniuk, Dmytro; Hotra, Zenon; Dabuliene, Asta; Tomkeviciene, Ausra; Voznyak, Lesya; Grazulevicius, Juozas Vidas

    2015-01-21

    We fabricated a yellow organic light-emitting diode (OLED) based on the star-shaped donor compound tri(9-hexylcarbazol-3-yl)amine, which provides formation of the interface exciplexes with the iridium(III) bis[4,6-difluorophenyl]-pyridinato-N,C2']picolinate (FIrpic). The exciplex emission is characterized by a broad band and provides a condition to realize the highly effective white OLED. It consists of a combination of the blue phosphorescent emission from the FIrpic complex and a broad efficient delayed fluorescence induced by thermal activation with additional direct phosphorescence from the triplet exciplex formed at the interface. The fabricated exciplex-type device exhibits a high brightness of 38 000 cd/m(2) and a high external quantum efficiency.

  15. Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

    PubMed Central

    Kappaun, Stefan; Slugovc, Christian; List, Emil J. W.

    2008-01-01

    Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo- and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers. PMID:19325819

  16. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh 3 or P(OPh) 3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy) 2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh 3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ±more » 0.5 μs decay time is measured. For L = P(OPh) 3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.« less

  17. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Göries, D., E-mail: dennis.goeries@desy.de; Roedig, P.; Stübe, N.

    We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy){sub 3}. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our resultsmore » further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of ∼103 ps full width at half maximum (FWHM).« less

  18. Blue-to-Green Emitting Neutral Ir(III) Complexes Bearing Pentafluorosulfanyl Groups: A Combined Experimental and Theoretical Study

    PubMed Central

    2017-01-01

    A structure–property relationship study of neutral heteroleptic (1 and 2, [Ir(C∧N)2(L∧X)]) and homoleptic (3 and 4, fac-[Ir(C∧N)3]) Ir(III) complexes (where L∧X = anionic 2,2,6,6-tetramethylheptane-3,5-dionato-κO3,κO6 (thd) and C∧N = a cyclometalating ligand bearing a pentafluorosulfanyl (−SF5) electron-withdrawing group (EWG) at the C4 (HL1) and C3 (HL2) positions of the phenyl moiety) is presented. These complexes have been fully structurally characterized, including by single-crystal X-ray diffraction, and their electrochemical and optical properties have also been extensively studied. While complexes 1 ([Ir(L1)2(thd)]), 3 (Ir(L1)3), and 4 (Ir(L2)3) exhibit irreversible first reduction waves based on the pentafluorosulfanyl substituent in the range of −1.71 to −1.88 V (vs SCE), complex 2 ([Ir(L2)2(thd)]) exhibits a quasi-reversible pyridineC∧N-based first reduction wave that is anodically shifted at −1.38 V. The metal + C∧N ligand oxidation waves are all quasi-reversible in the range of 1.08–1.54 V (vs SCE). The optical gap, determined from the lowest energy absorption maxima, decreases from 4 to 2 to 3 to 1, and this trend is consistent with the Hammett behavior (σm/σp with respect to the metal–carbon bond) of the −SF5 EWG. In degassed acetonitrile, for complexes 2–4, introduction of the −SF5 group produced a blue-shifted emission (λem 484–506 nm) in comparison to reference complexes [Ir(ppy)2(acac)] (R1, where acac = acetylacetonato) (λem 528 nm in MeCN), [Ir(CF3-ppy) (acac)] (R3, where CF3-ppyH = 2-(4-(trifluoromethyl)phenyl)pyridine) (λem 522 nm in DCM), and [Ir(CF3-ppy)3] (R8) (λem 507 nm in MeCN). The emission of complex 1, in contrast, was modestly red shifted (λem 534 nm). Complexes 2 and 4, where the −SF5 EWG is substituted para to the Ir–CC∧N bond, are efficient phosphorescent emitters, with high photoluminescence quantum yields (ΦPL = 58–79% in degassed MeCN solution) and microsecond emission

  19. At the Borderline between Metal-Metal Mixed Valency and a Radical Bridge Situation: Four Charge States of a Diruthenium Complex with a Redox-Active Bis( mer-tridentate) Ligand.

    PubMed

    Mondal, Sudipta; Schwederski, Brigitte; Frey, Wolfgang; Fiedler, Jan; Záliš, Stanislav; Kaim, Wolfgang

    2018-04-02

    The complex ions [L 3 Ru(μ,η 3 :η 3 -BL)RuL 3 ] n+ (1 n+ , L 3 = 4,4',4″-tri- tert-butyl-2,6,2',6″-terpyridine and H 2 BL 2- = 1,2-bis(salicyloyl)hydrazide(2-)) were isolated with PF 6 - or ClO 4 - counterions ( n = 1) and as bis(hexafluorophosphate) ( n = 2). Structural, electrochemical, and spectroscopic characterization reveals the monocation as intermediate ( K c = 10 8.2 ) in the three-step reversible redox system 1 0/+/2+/3+ . The 1 + ion has the molecule-bridged (Ru- - -Ru 4.727 Å) ruthenium centers involved in five- and six-membered chelate rings, and it exhibits long-wavelength absorptions at λ max 2240, 1660, and 1530 nm (ε max = 1000, 3000, and 8000 M -1 cm -1 , respectively), which would be compatible with a Ru III Ru II mixed-valent situation or with a coordinated radical ion bridge. In fact, EPR and DFT analysis of 1 + reveals that the spin is equally distributed over the ligand bridge and over both metals. The oxidized paramagnetic ions 1 2+ and 1 3+ have been studied by 1 H NMR and EPR and by TD-DFT supported UV-vis-NIR and MIR (mid-IR) spectroelectrochemistry. The capacity of various kinds of bis( mer-tridentate) bridging ligands (π donors or π acceptors, cyclometalated or noncyclometalated) for mediating metal-metal interactions is discussed.

  20. Formation of a Ruthenium-Arene Complex, Cyclometallation with a Substituted Benzylamine, and Insertion of an Alkyne

    ERIC Educational Resources Information Center

    Chetcuti, Michael J.; Ritleng, Vincent

    2007-01-01

    The three step synthesis is presented to allow the functionalization of an aromatic amine by forming new C-C and C-N bonds via an intramolecular C-H activation under mild conditions. The reactions are stoichiometric and allow the students to isolate the different organometallic intermediates.

  1. Room-Temperature C-H Functionalization Sequence under Benchtop Conditions for the Undergraduate Chemistry Laboratory

    ERIC Educational Resources Information Center

    Chen, Shuming

    2018-01-01

    An iridium(III)-mediated C-H functionalization sequence involving a concerted cyclometalation-deprotonation/migratory insertion pathway is reported for the undergraduate chemistry laboratory. The air- and water-stable iridacycle intermediates are readily isolated and characterized by NMR spectroscopy. Both steps of the experiment are performed at…

  2. Highly efficient hydrogenation of carbon dioxide to formate catalyzed by iridium(iii) complexes of imine-diphosphine ligands.

    PubMed

    Liu, Chong; Xie, Jian-Hua; Tian, Gui-Long; Li, Wei; Zhou, Qi-Lin

    2015-05-01

    A new iridium catalyst containing an imine-diphosphine ligand has been developed, which showed high efficiency for the hydrogenation of CO 2 to formate (yield up to 99%, TON up to 450 000). A possible catalytic mechanism is proposed, in which the imine group of the catalyst plays a key role in the cleavage of H 2 and the activation of CO 2 .

  3. Optimising the synthesis, polymer membrane encapsulation and photoreduction performance of Ru(II)- and Ir(III)-bis(terpyridine) cytochrome c bioconjugates.

    PubMed

    Hvasanov, David; Mason, Alexander F; Goldstein, Daniel C; Bhadbhade, Mohan; Thordarson, Pall

    2013-07-28

    Ruthenium(II) and iridium(III) bis(terpyridine) complexes were prepared with maleimide functionalities in order to site-specifically modify yeast iso-1 cytochrome c possessing a single cysteine residue available for modification (CYS102). Single X-ray crystal structures were solved for aniline and maleimide Ru(II) 3 and Ru(II) 4, respectively, providing detailed structural detail of the complexes. Light-activated bioconjugates prepared from Ru(II) 4 in the presence of tris(2-carboxyethyl)-phosphine (TCEP) significantly improved yields from 6% to 27%. Photoinduced electron transfer studies of Ru(II)-cyt c in bulk solution and polymer membrane encapsulated specimens were performed using EDTA as a sacrificial electron donor. It was found that membrane encapsulation of Ru(II)-cyt c in PS140-b-PAA48 resulted in a quantum efficiency of 1.1 ± 0.3 × 10(-3), which was a two-fold increase relative to the bulk. Moreover, Ir(III)-cyt c bioconjugates showed a quantum efficiency of 3.8 ± 1.9 × 10(-1), equivalent to a ∼640-fold increase relative to bulk Ru(II)-cyt c.

  4. White polymer light-emitting diodes based on star-shaped polymers with an orange dendritic phosphorescent core.

    PubMed

    Zhu, Minrong; Li, Yanhu; Cao, Xiaosong; Jiang, Bei; Wu, Hongbin; Qin, Jingui; Cao, Yong; Yang, Chuluo

    2014-12-01

    A series of new star-shaped polymers with a triphenylamine-based iridium(III) dendritic complex as the orange-emitting core and poly(9,9-dihexylfluorene) (PFH) chains as the blue-emitting arms is developed towards white polymer light-emitting diodes (WPLEDs). By fine-tuning the content of the orange phosphor, partial energy transfer and charge trapping from the blue backbone to the orange core is realized to achieve white light emission. Single-layer WPLEDs with the configuration of ITO (indium-tin oxide)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/polymer/CsF/Al exhibit a maximum current efficiency of 1.69 cd A(-1) and CIE coordinates of (0.35, 0.33), which is very close to the pure white-light point of (0.33, 0.33). To the best of our knowledge, this is the first report on star-shaped white-emitting single polymers that simultaneously consist of fluorescent and phosphorescent species. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Silylene extrusion from organosilanes via double geminal Si-H bond activation by a Cp*Ru(kappa2-P,N)+ complex: observation of a key stoichiometric step in the glaser-tilley alkene hydrosilylation mechanism.

    PubMed

    Rankin, Matthew A; MacLean, Darren F; Schatte, Gabriele; McDonald, Robert; Stradiotto, Mark

    2007-12-26

    Treatment of Cp*RuCl(kappa2-P,N-2b) (2b = 2-NMe2-3-PiPr2-indene) with TlSO3CF3 produced the cyclometalated complex [4]+SO3CF3- in 94% isolated yield. Exposure of [4]+X- (X = B(C6F5)4 or SO3CF3) to Ph2SiH2 (10 equiv) or PhSiH3 afforded the corresponding [Cp*(mu-P,N-2b)(H)2Ru=SiRPh]+X- complexes, [5]+X- (R = Ph; X = B(C6F5)4, 82%; X = SO3CF3, 39%) and [6]+X- (R = H; X = B(C6F5)4, 94%; X = SO3CF3, 95%). Notably, these transformations represent the first documented examples of Ru-mediated silylene extrusion via double geminal Si-H bond activation of an organosilane-a key step in the recently proposed Glaser-Tilley (G-T) alkene hydrosilylation mechanism. Treatment of [5]+B(C6F5)4- with KN(SiMe3)2 or [6]+SO3CF3- with NaN(SiMe3)2 afforded the corresponding zwitterionic Cp*(mu-2-NMe2-3-PiPr2-indenide)(H)2Ru=SiRPh complex in 69% (R = Ph, 7) or 86% (R = H, 8) isolated yield. Both [6]+X- and 8 proved unreactive toward 1-hexene and styrene and provided negligible catalytic turnover in the attempted metal-mediated hydrosilylation of these substrates with PhSiH3, thereby providing further empirical evidence for the required intermediacy of base-free Ru=Si species in the G-T mechanism. Isomerization of the P,N-indene ligand backbone in [6]+X-, giving rise to [Cp*(mu-1-PiPr2-2-NMe2-indene)(H)2Ru=SiHPh]+X- ([9]+X-), was observed. In the case of [9]+SO3CF3-, net intramolecular addition of the Ru=Si-H group across the styrene-like C=C unit within the ligand backbone to give 10 (96% isolated yield) was observed. Crystallographic characterization data are provided for [4]+X-, [5]+X-, [6]+X-, 8, and 10.

  6. Two-photon luminescence from polar bis-terpyridyl-stilbene derivatives of Ir(III) and Ru(II).

    PubMed

    Natrajan, Louise S; Toulmin, Anita; Chew, Alex; Magennis, Steven W

    2010-12-07

    Four structurally related iridium(III) and ruthenium(II) complexes bearing two polar terpyridyl-stilbene derived chromophores 4-(4-{2-[4-(methoxy)phenyl]ethenyl}phenyl)-2,2'-6',2''-terpyridine (ttpyeneanisole) and 4-(4-{2-[phenyl]ethenyl}phenyl)-2,2'-6',2''-terpyridine (tpystilbene) have been synthesised and characterised in the solid state and in solution. In the solid state, the dihedral angle subtending the pyridyl and tolyl groups of 27.1° in the Ir(III) complex [Ir(ttpyeneanisole)(2)]·3PF(6) is more acute than in the Ru(II) derivative [Ru(tpystilbene)(2)]·2PF(6) (35.5°), indicating the presence of a greater degree of π-delocalisation across the terpyridine unit in the former compound. Their luminescence properties in fluid solution have been investigated following both resonant and non-resonant excitation. We have shown that each of the complexes undergoes two-photon excitation when excited in the near infrared (740 to 820 nm), with two-photon absorption cross sections in the range 11-67 × 10(-50) cm(4) s photon(-1). The larger cross sections for the Ir(III) complexes reflect the differences observed in the solid state. This work therefore demonstrates that such complexes are promising as luminescent markers for 3D imaging and illustrates that simple functionalisation of the chromophores and the choice of metal can lead to marked enhancements in the two-photon cross sections (σ(2)) compared to those of simpler heteroleptic polypyridyl based derivatives.

  7. Fast reductive amination by transfer hydrogenation "on water".

    PubMed

    Lei, Qian; Wei, Yawen; Talwar, Dinesh; Wang, Chao; Xue, Dong; Xiao, Jianliang

    2013-03-18

    Reductive amination of various ketones and aldehydes by transfer hydrogenation under aqueous conditions has been developed, by using cyclometallated iridium complexes as catalysts and formate as hydrogen source. The pH value of the solution is shown to be critical for a high catalytic chemoselectivity and activity, with the best pH value being 4.8. In comparison with that in organic solvents, the reductive amination in an aqueous phase is faster, and the molar ratio of the substrate to the catalyst (S/C) can be set as high as 1×10(5) , the highest S/C value ever reported in reductive amination reactions. The catalyst is easy to access and the reaction is operationally simple, allowing a wide range of ketones and aldehydes to react with various amines in high yields. The protocol provides a practical and environmental friendly new method for the synthesis of amine compounds. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. A rhodium(III)-based inhibitor of autotaxin with antiproliferative activity.

    PubMed

    Kang, Tian-Shu; Wang, Wanhe; Zhong, Hai-Jing; Liang, Jia-Xin; Ko, Chung-Nga; Lu, Jin-Jian; Chen, Xiu-Ping; Ma, Dik-Lung; Leung, Chung-Hang

    2017-02-01

    Cancer of the skin is by far the most common of all cancers. Melanoma accounts for only about 1% of skin cancers but causes a large majority of skin cancer deaths. Autotaxin (ATX), also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), regulates physiological and pathological functions of lysophosphatidic acid (LPA), and is thus an important therapeutic target. We synthesized ten metal-based complexes and a novel cyclometalated rhodium(III) complex 1 was identified as an ATX enzymatic inhibitor using multiple methods, including ATX enzymatic assay, thermal shift assay, western immunoblotting and so on. Protein thermal shift assays showed that 1 increased the melting temperature (T m ) of ATX by 3.5°C. 1 also reduced ATX-LPA mediated downstream survival signal pathway proteins such as ERK and AKT, and inhibited the activation of the transcription factor nuclear factor κB (NF-κB) and signal transducer and activator of transcription 3 (STAT3). 1 also exhibited strong anti-proliferative activity against A2058 melanoma cells (IC 50 =0.58μM). Structure-activity relationship indicated that both the rhodium(III) center and the auxiliary ligands of complex 1 are important for bioactivity. 1 represents a promising scaffold for the development of small-molecule ATX inhibitors for anti-tumor applications. To our knowledge, complex 1 is the first metal-based ATX inhibitor reported to date. Rhodium complexes will have the increased attention in therapeutic and bioanalytical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Highly Efficient Solution-Processed Deep-Red Organic Light-Emitting Diodes Based on an Exciplex Host Composed of a Hole Transporter and a Bipolar Host.

    PubMed

    Huang, Manli; Jiang, Bei; Xie, Guohua; Yang, Chuluo

    2017-10-19

    With the aim to achieve highly efficient deep-red emission, we introduced an exciplex forming cohost, 4,4',4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA): 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) (1:1). Due to the efficient triplet up-conversion processes upon the exciplex forming cohost, excellent performances of the devices were achieved with deep-red emission. Using the heteroleptic iridium complexes as the guest dopants, the solution-processed deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with the iridium(III) bis(6-(4-(tert-butyl)phenyl)phenanthridine)acetylacetonate [(TP-BQ) 2 Ir(acac)]-based phosphorescent emitter exhibited an electroluminescent peak at 656 nm and a maximum external quantum efficiency (EQE) of 11.9%, which is 6.6 times that of the device based on the guest emitter doped in the polymer-based cohost. The unique exciplex with a typical hole transporter and a bipolar material is ideal and universal for hosting the red PhOLEDs and tremendously improves the device performances.

  10. High-efficiency emitting materials based on phenylquinoline/carbazole-based compounds for organic light emitting diode applications

    NASA Astrophysics Data System (ADS)

    Jin, Sung-Ho

    2009-08-01

    Highly efficient light-emitting materials based on phenylquinoline-carbazole derivative has been synthesized for organic-light emitting diodes (OLEDs). The materials form high quality amorphous thin films by thermal evaporation and the energy levels can be easily adjusted by the introduction of different electron donating and electron withdrawing groups on carbazoylphenylquinoline. Non-doped deep-blue OLEDs using Et-CVz-PhQ as the emitter show bright emission (CIE coordinates, x=0.156, y=0.093) with an external quantum efficiency of 2.45 %. Furthermore, the material works as an excellent host material for BCzVBi to get high-performance OLEDs with excellent deep-blue CIE coordinates (x=0.155, y=0.157), high power efficiency (5.98 lm/W), and high external quantum efficiency (5.22 %). Cyclometalated Ir(III) μ-chloride bridged dimers were synthesized by iridium trichloride hydrate with an excess of our developed deep-blue emitter, Et-CVz-PhQ. The Ir(III) complexes were prepared by the dimers with the corresponding ancillary ligands. The chloride bridged diiridium complexes can be easily converted to mononuclear Ir(III) complexes by replacing the two bridging chlorides with bidentate monoanionic ancillary ligands. Among the various types of ancillary ligands, we firstly used picolinic acid N-oxide, including picolinic acid and acetylacetone as an ancillary ligands for Ir(III) complexes. The PhOLEDs also shows reasonably high brightness and good luminance efficiency of 20,000 cd/m2 and 12 cd/A, respectively.

  11. Communication complexity and information complexity

    NASA Astrophysics Data System (ADS)

    Pankratov, Denis

    Information complexity enables the use of information-theoretic tools in communication complexity theory. Prior to the results presented in this thesis, information complexity was mainly used for proving lower bounds and direct-sum theorems in the setting of communication complexity. We present three results that demonstrate new connections between information complexity and communication complexity. In the first contribution we thoroughly study the information complexity of the smallest nontrivial two-party function: the AND function. While computing the communication complexity of AND is trivial, computing its exact information complexity presents a major technical challenge. In overcoming this challenge, we reveal that information complexity gives rise to rich geometrical structures. Our analysis of information complexity relies on new analytic techniques and new characterizations of communication protocols. We also uncover a connection of information complexity to the theory of elliptic partial differential equations. Once we compute the exact information complexity of AND, we can compute exact communication complexity of several related functions on n-bit inputs with some additional technical work. Previous combinatorial and algebraic techniques could only prove bounds of the form theta( n). Interestingly, this level of precision is typical in the area of information theory, so our result demonstrates that this meta-property of precise bounds carries over to information complexity and in certain cases even to communication complexity. Our result does not only strengthen the lower bound on communication complexity of disjointness by making it more exact, but it also shows that information complexity provides the exact upper bound on communication complexity. In fact, this result is more general and applies to a whole class of communication problems. In the second contribution, we use self-reduction methods to prove strong lower bounds on the information

  12. Conformation-induced remote meta-C-H activation of amines

    NASA Astrophysics Data System (ADS)

    Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

    2014-03-01

    Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

  13. Conformation-induced remote meta-C-H activation of amines.

    PubMed

    Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

    2014-03-13

    Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

  14. Triplet exciton diffusion in fac-tris(2-phenylpyridine) iridium(III)-cored electroluminescent dendrimers

    NASA Astrophysics Data System (ADS)

    Namdas, Ebinazar B.; Ruseckas, Arvydas; Samuel, Ifor D. W.; Lo, Shih-Chun; Burn, Paul L.

    2005-02-01

    We have studied triplet-triplet annihilation in neat films of electrophosphorescent fac-tris(2-phenylpyridine) iridium(III) [Ir(ppy)3]-cored dendrimers containing phenylene- and carbazole-based dendrons with 2-ethylhexyloxy surface groups using time-resolved photoluminescence. From measured annihilation rates, the limiting current densities above which annihilation would dominate in dendrimer light-emitting devices are found to be >1A/cm2. The triplet exciton diffusion length varies in the range of 2-10 nm depending on the dendron size. The distance dependence of the nearest-neighbor hopping rate shows that energy transfer is dominated by the exchange mechanism.

  15. Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1 O 2 generation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu, Wenting; Han, Congcong; Zhang, Qinhua

    advanced photosensitizers for singlet oxygen (1O2) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the 1O2 generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (DEST) and hence generate 1O2 effectively. Due to its significant and selectivity for 1O2 generation, the as-prepared carbon nitride-based photosensitizer shows a high selectivemore » photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated PtII complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization.« less

  16. An integrated micro-volume fiber-optic sensor for oxygen determination in exhaled breath based on iridium(III) complexes immobilized in fluorinated xerogels.

    PubMed

    Xiong, Yan; Ye, Zhongbin; Xu, Jing; Zhu, Yuanqiang; Chen, Chen; Guan, Yafeng

    2013-03-21

    A novel integrated fiber-optic sensor with micro detection volume is developed and evaluated for O(2) determination on a breath-by-breath basis in human health monitoring applications. The sensing element was fabricated by dip-coating an uncladded optical fiber with [Ir(piq)(2)(acac)]-doped hybrid fluorinated ORMOSIL (organically modified silicate) film, which was prepared from 3,3,3-trifluoropropyltrimethoxysilane (TFP-TriMOS) and n-propyltrimethoxysilane (n-propyl-TriMOS). The sensor was then constructed by inserting the prepared optical fiber into a transparent capillary. A microchannel formed between the optical fiber and the capillary inner wall acted as a flow cell for the sample flowing through. The evanescent wave (EW) field produced on the fiber core surface can excite the O(2)-sensitive fluorophores of [Ir(piq)(2)(acac)] to produce emission fluorescence. O(2) can be sensed by its quenching effect on the emission fluorescence intensity. Spectroscopic properties have been characterized by FTIR and fluorescence measurements. Stern-Volmer and Demas models were both employed to analyse the sensor sensitivity, which is 13.0 with the LOD = 0.009% (3σ) and the response time is about 1 s. By integrating the sensing and detection elements on the optical fiber, the novel configuration showed advantages of easy fabrication and low cost. Parameters of sensitivity, response time, repeatability, humidity effect and temperature effect were discussed in detail. The proposed sensor showed potential for practical in-breath O(2) analysis application due to its advantages of easy fabrication, low cost, fast response, excellent hydrophobicity, negligible temperature interference and suitable sensitivity.

  17. On State Complexes and Special Cube Complexes

    ERIC Educational Resources Information Center

    Peterson, Valerie J.

    2009-01-01

    This thesis presents the first steps toward a classification of non-positively curved cube complexes called state complexes. A "state complex" is a configuration space for a "reconfigurable system," i.e., an abstract system in which local movements occur in some discrete manner. Reconfigurable systems can be used to describe, for example,…

  18. Synthesis and oxidation of CpIrIII compounds: functionalization of a Cp methyl group.

    PubMed

    Park-Gehrke, Lisa S; Freudenthal, John; Kaminsky, Werner; Dipasquale, Antonio G; Mayer, James M

    2009-03-21

    [CpIrCl(2)](2) () and new CpIr(III)(L-L)X complexes (L-L = N-O or C-N chelating ligands; X = Cl, I, Me) have been prepared and their reactivity with two-electron chemical oxidants explored. Reaction of with PhI(OAc)(2) in wet solvents yields a new chloro-bridged dimer in which each of the Cp ligands has been singly acetoxylated to form [Cp(OAc)Ir(III)Cl(2)](2) () (Cp(OAc) = eta(5)-C(5)Me(4)CH(2)OAc). Complex and related carboxy- and alkoxy-functionalized Cp(OR) complexes can also be prepared from plus (PhIO)(n) and ROH. [Cp(OAc)Ir(III)Cl(2)](2) () and the methoxy analogue [Cp(OMe)Ir(III)Cl(2)](2) () have been structurally characterized. Treatment of [CpIrCl(2)](2) () with 2-phenylpyridine yields CpIr(III)(ppy)Cl () (ppy = cyclometallated 2-phenylpyridyl) which is readily converted to its iodide and methyl analogues CpIr(III)(ppy)I and CpIr(III)(ppy)Me (). CpIr(III) complexes were also prepared with N-O chelating ligands derived from anthranilic acid (2-aminobenzoic acid) and alpha-aminoisobutyric acid (H(2)NCMe(2)COOH), ligands chosen to be relatively oxidation resistant. These complexes and were reacted with potential two-electron oxidants including PhI(OAc)(2), hexachlorocyclohexadienone (C(6)Cl(6)O), N-fluoro-2,4,6-trimethylpyridinium (Me(3)pyF(+)), [Me(3)O]BF(4) and MeOTf (OTf = triflate, CF(3)SO(3)). Iridium(V) complexes were not observed or implicated in these reactions, despite the similarity of the potential products to known CpIr(V) species. The carbon electrophiles [Me(3)O]BF(4) and MeOTf appear to react preferentially at the N-O ligands, to give methyl esters in some cases. Overall, the results indicate that Cp is not inert under oxidizing conditions and is therefore not a good supporting ligand for oxidizing organometallic complexes.

  19. Synchronization in node of complex networks consist of complex chaotic system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wei, Qiang, E-mail: qiangweibeihua@163.com; Digital Images Processing Institute of Beihua University, BeiHua University, Jilin, 132011, Jilin; Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian, 116024

    2014-07-15

    A new synchronization method is investigated for node of complex networks consists of complex chaotic system. When complex networks realize synchronization, different component of complex state variable synchronize up to different scaling complex function by a designed complex feedback controller. This paper change synchronization scaling function from real field to complex field for synchronization in node of complex networks with complex chaotic system. Synchronization in constant delay and time-varying coupling delay complex networks are investigated, respectively. Numerical simulations are provided to show the effectiveness of the proposed method.

  20. A robust yellow-emitting metallophosphor with electron-injection/-transporting traits for highly efficient white organic light-emitting diodes.

    PubMed

    Zhou, Guijiang; Yang, Xiaolong; Wong, Wai-Yeung; Wang, Qi; Suo, Si; Ma, Dongge; Feng, Jikang; Wang, Lixiang

    2011-10-24

    With the aim of endowing triplet emitters in the development of organic light-emitting devices (OLEDs) with electron-injection/-transporting (EI/ET) features, the phenylsulfonyl moiety was introduced into the phenyl ring of a 2-phenylpyridine (Hppy) ligand and the yellow phosphorescent heteroleptic iridium(III) complex 1 was developed. It was shown that the SO(2)Ph unit could provide EI/ET character to 1, as indicated from both electrochemical and computational data. Complex 1 is a promising yellow-emitting material for both monochromatic OLEDs and white OLEDs (WOLEDs). The outstanding electronic traits associated with 1, coupled with careful device design, afforded very attractive electroluminescent performances for two-element WOLEDs, including a low turn-on voltage of less than 3.7 V, a maximum brightness of 48,000 cd m(-2), an external quantum efficiency of 13.0%, a luminance efficiency of 34.7 cd A(-1), and a power efficiency of 24.3 Lm W(-1). In addition, a good color rendering index (CRI) of about 74, a stable white color with a Commission Internationale de L'Eclairage (CIE(x,y)) variation of Δ(x, y) < ±(0.02, 0.02), and a correlated color temperature higher than 5130 K were obtained. These encouraging results indicate the potential of these WOLEDs as good candidates for warm indoor lighting sources, as well as the critical contribution of such key EI/ET properties to triplet emitters to advance new OLED research. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Not so Complex: Iteration in the Complex Plane

    ERIC Educational Resources Information Center

    O'Dell, Robin S.

    2014-01-01

    The simple process of iteration can produce complex and beautiful figures. In this article, Robin O'Dell presents a set of tasks requiring students to use the geometric interpretation of complex number multiplication to construct linear iteration rules. When the outputs are plotted in the complex plane, the graphs trace pleasing designs…

  2. Syntactic Complexity as an Aspect of Text Complexity

    ERIC Educational Resources Information Center

    Frantz, Roger S.; Starr, Laura E.; Bailey, Alison L.

    2015-01-01

    Students' ability to read complex texts is emphasized in the Common Core State Standards (CCSS) for English Language Arts and Literacy. The standards propose a three-part model for measuring text complexity. Although the model presents a robust means for determining text complexity based on a variety of features inherent to a text as well as…

  3. Complex Fuzzy Set-Valued Complex Fuzzy Measures and Their Properties

    PubMed Central

    Ma, Shengquan; Li, Shenggang

    2014-01-01

    Let F*(K) be the set of all fuzzy complex numbers. In this paper some classical and measure-theoretical notions are extended to the case of complex fuzzy sets. They are fuzzy complex number-valued distance on F*(K), fuzzy complex number-valued measure on F*(K), and some related notions, such as null-additivity, pseudo-null-additivity, null-subtraction, pseudo-null-subtraction, autocontionuous from above, autocontionuous from below, and autocontinuity of the defined fuzzy complex number-valued measures. Properties of fuzzy complex number-valued measures are studied in detail. PMID:25093202

  4. Food-web complexity, meta-community complexity and community stability.

    PubMed

    Mougi, A; Kondoh, M

    2016-04-13

    What allows interacting, diverse species to coexist in nature has been a central question in ecology, ever since the theoretical prediction that a complex community should be inherently unstable. Although the role of spatiality in species coexistence has been recognized, its application to more complex systems has been less explored. Here, using a meta-community model of food web, we show that meta-community complexity, measured by the number of local food webs and their connectedness, elicits a self-regulating, negative-feedback mechanism and thus stabilizes food-web dynamics. Moreover, the presence of meta-community complexity can give rise to a positive food-web complexity-stability effect. Spatiality may play a more important role in stabilizing dynamics of complex, real food webs than expected from ecological theory based on the models of simpler food webs.

  5. Representation of complex probabilities and complex Gibbs sampling

    NASA Astrophysics Data System (ADS)

    Salcedo, Lorenzo Luis

    2018-03-01

    Complex weights appear in Physics which are beyond a straightforward importance sampling treatment, as required in Monte Carlo calculations. This is the wellknown sign problem. The complex Langevin approach amounts to effectively construct a positive distribution on the complexified manifold reproducing the expectation values of the observables through their analytical extension. Here we discuss the direct construction of such positive distributions paying attention to their localization on the complexified manifold. Explicit localized representations are obtained for complex probabilities defined on Abelian and non Abelian groups. The viability and performance of a complex version of the heat bath method, based on such representations, is analyzed.

  6. Complexity: an internet resource for analysis of DNA sequence complexity

    PubMed Central

    Orlov, Y. L.; Potapov, V. N.

    2004-01-01

    The search for DNA regions with low complexity is one of the pivotal tasks of modern structural analysis of complete genomes. The low complexity may be preconditioned by strong inequality in nucleotide content (biased composition), by tandem or dispersed repeats or by palindrome-hairpin structures, as well as by a combination of all these factors. Several numerical measures of textual complexity, including combinatorial and linguistic ones, together with complexity estimation using a modified Lempel–Ziv algorithm, have been implemented in a software tool called ‘Complexity’ (http://wwwmgs.bionet.nsc.ru/mgs/programs/low_complexity/). The software enables a user to search for low-complexity regions in long sequences, e.g. complete bacterial genomes or eukaryotic chromosomes. In addition, it estimates the complexity of groups of aligned sequences. PMID:15215465

  7. Reverse saturable absorption (RSA) in fluorinated iridium derivatives

    NASA Astrophysics Data System (ADS)

    Ferry, Michael J.; O'Donnell, Ryan M.; Bambha, Neal; Ensley, Trenton R.; Shensky, William M.; Shi, Jianmin

    2017-08-01

    The photophysical properties of cyclometallated iridium compounds are beneficial for nonlinear optical (NLO) applications, such as the design of reverse saturable absorption (RSA) materials. We report on the NLO characterization of a family of compounds of the form [Ir(pbt)2(LX)], where pbt is 2-phenylbenzothiazole and LX is a beta-diketonate ligand. In particular, we investigate the effects of trifluoromethylation on compound solubility and photophysics compared to the parent acetylacetonate (acac) version. The NLO properties, such as the singlet and triplet excited-state cross sections, of these compounds were measured using the Z-scan technique. The excited-state lifetimes were determined from visible transient absorption spectroscopy.

  8. Complexity Survey.

    ERIC Educational Resources Information Center

    Gordon, Sandra L.; Anderson, Beth C.

    To determine whether consensus existed among teachers about the complexity of common classroom materials, a survey was administered to 66 pre-service and in-service kindergarten and prekindergarten teachers. Participants were asked to rate 14 common classroom materials as simple, complex, or super-complex. Simple materials have one obvious part,…

  9. Dynamic complexity: plant receptor complexes at the plasma membrane.

    PubMed

    Burkart, Rebecca C; Stahl, Yvonne

    2017-12-01

    Plant receptor complexes at the cell surface perceive many different external and internal signalling molecules and relay these signals into the cell to regulate development, growth and immunity. Recent progress in the analyses of receptor complexes using different live cell imaging approaches have shown that receptor complex formation and composition are dynamic and take place at specific microdomains at the plasma membrane. In this review we focus on three prominent examples of Arabidopsis thaliana receptor complexes and how their dynamic spatio-temporal distribution at the PM has been studied recently. We will elaborate on the newly emerging concept of plasma membrane microdomains as potential hubs for specific receptor complex assembly and signalling outputs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Radioisotope trithiol complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jurisson, Silvia S.; Cutler, Cathy S.; Degraffenreid, Anthony J.

    The present invention is directed to a series of stable radioisotope trithiol complexes that provide a simplified route for the direct complexation of radioisotopes present in low concentrations. In certain embodiments, the complex contains a linking domain configured to conjugate the radioisotope trithiol complex to a targeting vector. The invention is also directed to a novel method of linking the radioisotope to a trithiol compound to form the radioisotope trithiol complex. The inventive radioisotope trithiol complexes may be utilized for a variety of applications, including diagnostics and/or treatment in nuclear medicine.

  11. Energy-Complexity Relations by Structural Complexity Methods

    NASA Astrophysics Data System (ADS)

    Ricca, Renzo L.

    2011-09-01

    In this paper we shall review some of the most recent developments and results on work on energy-complexity relations and, if time will allow it, we shall provide an analytical proof of eq. (3) below, a fundamental relation between energy and complexity established by numerical experiments.

  12. Revitalizing Complex Analysis: A Transition-to-Proof Course Centered on Complex Topics

    ERIC Educational Resources Information Center

    Sachs, Robert

    2017-01-01

    A new transition course centered on complex topics would help in revitalizing complex analysis in two ways: first, provide early exposure to complex functions, sparking greater interest in the complex analysis course; second, create extra time in the complex analysis course by eliminating the "complex precalculus" part of the course. In…

  13. 3D Complex: A Structural Classification of Protein Complexes

    PubMed Central

    Levy, Emmanuel D; Pereira-Leal, Jose B; Chothia, Cyrus; Teichmann, Sarah A

    2006-01-01

    Most of the proteins in a cell assemble into complexes to carry out their function. It is therefore crucial to understand the physicochemical properties as well as the evolution of interactions between proteins. The Protein Data Bank represents an important source of information for such studies, because more than half of the structures are homo- or heteromeric protein complexes. Here we propose the first hierarchical classification of whole protein complexes of known 3-D structure, based on representing their fundamental structural features as a graph. This classification provides the first overview of all the complexes in the Protein Data Bank and allows nonredundant sets to be derived at different levels of detail. This reveals that between one-half and two-thirds of known structures are multimeric, depending on the level of redundancy accepted. We also analyse the structures in terms of the topological arrangement of their subunits and find that they form a small number of arrangements compared with all theoretically possible ones. This is because most complexes contain four subunits or less, and the large majority are homomeric. In addition, there is a strong tendency for symmetry in complexes, even for heteromeric complexes. Finally, through comparison of Biological Units in the Protein Data Bank with the Protein Quaternary Structure database, we identified many possible errors in quaternary structure assignments. Our classification, available as a database and Web server at http://www.3Dcomplex.org, will be a starting point for future work aimed at understanding the structure and evolution of protein complexes. PMID:17112313

  14. Social complexity as a proximate and ultimate factor in communicative complexity

    PubMed Central

    Freeberg, Todd M.; Dunbar, Robin I. M.; Ord, Terry J.

    2012-01-01

    The ‘social complexity hypothesis’ for communication posits that groups with complex social systems require more complex communicative systems to regulate interactions and relations among group members. Complex social systems, compared with simple social systems, are those in which individuals frequently interact in many different contexts with many different individuals, and often repeatedly interact with many of the same individuals in networks over time. Complex communicative systems, compared with simple communicative systems, are those that contain a large number of structurally and functionally distinct elements or possess a high amount of bits of information. Here, we describe some of the historical arguments that led to the social complexity hypothesis, and review evidence in support of the hypothesis. We discuss social complexity as a driver of communication and possible causal factor in human language origins. Finally, we discuss some of the key current limitations to the social complexity hypothesis—the lack of tests against alternative hypotheses for communicative complexity and evidence corroborating the hypothesis from modalities other than the vocal signalling channel. PMID:22641818

  15. Surface Organometallic Chemistry of Supported Iridium(III) as a Probe for Organotransition Metal–Support Interactions in C–H Activation

    DOE PAGES

    Kaphan, David M.; Klet, Rachel C.; Perras, Frederic A.; ...

    2018-05-11

    Systematic study of the interactions between organometallic catalysts and metal oxide support materials is essential for the realization of rational design in heterogeneous catalysis. Herein we describe the stoichiometric and catalytic chemistry of a [Cp*(PMe 3)Ir(III)] complex chemisorbed on a variety of acidic metal oxides as a multifaceted probe for stereoelectronic communication between the support and organometallic center. Electrophilic bond activation was explored in the context of stoichiometric hydrogenolysis as well as catalytic H/D exchange. Further information was obtained from the observation of processes related to dynamic exchange between grafted organometallic species and those in solution. The supported organometallic speciesmore » were characterized by a variety of spectroscopic techniques including dynamic nuclear polarization-enhanced solid-state NMR spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption spectroscopy. Finally, strongly acidic modified metal oxides such as sulfated zirconia engender high levels of activity toward electrophilic bond activation of both sp 2 and sp 3 C–H bonds, including the rapid deuteration of methane at room temperature; however, the global trend for the supports studied here does not suggest a direct correlation between activity and surface Brønsted acidity.« less

  16. Surface Organometallic Chemistry of Supported Iridium(III) as a Probe for Organotransition Metal–Support Interactions in C–H Activation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaphan, David M.; Klet, Rachel C.; Perras, Frederic A.

    Systematic study of the interactions between organometallic catalysts and metal oxide support materials is essential for the realization of rational design in heterogeneous catalysis. Herein we describe the stoichiometric and catalytic chemistry of a [Cp*(PMe 3)Ir(III)] complex chemisorbed on a variety of acidic metal oxides as a multifaceted probe for stereoelectronic communication between the support and organometallic center. Electrophilic bond activation was explored in the context of stoichiometric hydrogenolysis as well as catalytic H/D exchange. Further information was obtained from the observation of processes related to dynamic exchange between grafted organometallic species and those in solution. The supported organometallic speciesmore » were characterized by a variety of spectroscopic techniques including dynamic nuclear polarization-enhanced solid-state NMR spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption spectroscopy. Finally, strongly acidic modified metal oxides such as sulfated zirconia engender high levels of activity toward electrophilic bond activation of both sp 2 and sp 3 C–H bonds, including the rapid deuteration of methane at room temperature; however, the global trend for the supports studied here does not suggest a direct correlation between activity and surface Brønsted acidity.« less

  17. Complex Light

    NASA Astrophysics Data System (ADS)

    Secor, Jeff; Alfano, Robert; Ashrafi, Solyman

    2017-01-01

    The emerging field of complex light-the study and application of custom light beams with tailored intensity, polarization or phase-is a focal point for fundamental breakthroughs in optical science. As this review will show, those advances in fundamental understanding, coupled with the latest developments in complex light generation, are translating into a range of diverse and cross-disciplinary applications that span microscopy, high-data-rate communications, optical trapping and quantum optics. We can expect more twists along the way, too, as researchers seek to manipulate and control the propagation speed of complex light beams, while others push the more exotic possibilities afforded by complex light in quantum-entanglement experiments.

  18. Unraveling chaotic attractors by complex networks and measurements of stock market complexity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cao, Hongduo; Li, Ying, E-mail: mnsliy@mail.sysu.edu.cn

    2014-03-15

    We present a novel method for measuring the complexity of a time series by unraveling a chaotic attractor modeled on complex networks. The complexity index R, which can potentially be exploited for prediction, has a similar meaning to the Kolmogorov complexity (calculated from the Lempel–Ziv complexity), and is an appropriate measure of a series' complexity. The proposed method is used to research the complexity of the world's major capital markets. None of these markets are completely random, and they have different degrees of complexity, both over the entire length of their time series and at a level of detail. However,more » developing markets differ significantly from mature markets. Specifically, the complexity of mature stock markets is stronger and more stable over time, whereas developing markets exhibit relatively low and unstable complexity over certain time periods, implying a stronger long-term price memory process.« less

  19. Clinical Complexity in Medicine: A Measurement Model of Task and Patient Complexity.

    PubMed

    Islam, R; Weir, C; Del Fiol, G

    2016-01-01

    Complexity in medicine needs to be reduced to simple components in a way that is comprehensible to researchers and clinicians. Few studies in the current literature propose a measurement model that addresses both task and patient complexity in medicine. The objective of this paper is to develop an integrated approach to understand and measure clinical complexity by incorporating both task and patient complexity components focusing on the infectious disease domain. The measurement model was adapted and modified for the healthcare domain. Three clinical infectious disease teams were observed, audio-recorded and transcribed. Each team included an infectious diseases expert, one infectious diseases fellow, one physician assistant and one pharmacy resident fellow. The transcripts were parsed and the authors independently coded complexity attributes. This baseline measurement model of clinical complexity was modified in an initial set of coding processes and further validated in a consensus-based iterative process that included several meetings and email discussions by three clinical experts from diverse backgrounds from the Department of Biomedical Informatics at the University of Utah. Inter-rater reliability was calculated using Cohen's kappa. The proposed clinical complexity model consists of two separate components. The first is a clinical task complexity model with 13 clinical complexity-contributing factors and 7 dimensions. The second is the patient complexity model with 11 complexity-contributing factors and 5 dimensions. The measurement model for complexity encompassing both task and patient complexity will be a valuable resource for future researchers and industry to measure and understand complexity in healthcare.

  20. Thinking Forbidden Thoughts: The Oedipus Complex as a Complex of Knowing.

    PubMed

    Schein, Michael

    2016-04-01

    The Oedipus complex, considered by Freud the "nuclear complex of development," played a central role in the evolution of psychoanalytic thought. This paper returns to the point of transition from the seduction theory, Freud's initial theorem, to the oedipal model, and suggests that the Oedipus complex is first and foremost a text and as such contains a multiplicity of narratives. In particular, the author articulates the close relation between the Oedipus complex and the subject of knowing, postulating that underlying its surface level, the deep-level structure of this complex is one of knowing. As a complex of knowing it is of dual quality, both promoting and impeding the ability to know.

  1. Nucleoprotein Complexes Containing Replicating Simian Virus 40 DNA: Comparison with Polyoma Nucleoprotein Complexes

    PubMed Central

    Hall, Mark R.; Meinke, William; Goldstein, David A.

    1973-01-01

    Procedures for isolating nucleoprotein complexes containing replicating polyoma DNA from infected mouse cells were used to prepare short-lived nucleoprotein complexes (r-SV40 complexes) containing replicating simian virus 40 (SV40) DNA from infected monkey cells. Like the polyoma complexes, r-SV40 complexes were only partially released from nuclei by cell lysis but could be extracted from nuclei by prolonged treatment with solutions containing Triton X-100. r-SV40 complexes sedimented faster than complexes containing SV40 supercoiled DNA (SV40 complex) in sucrose gradients, and both types of SV40 nucleoprotein complexes sedimented ahead of polyoma complexes containing supercoiled polyoma DNA (py complex). The sedimentation rates of py complex and SV40 complex were 56 and 61S, respectively, based on the sedimentation rate of the mouse large ribosomal subunit as a marker. r-SV40 complexes sedimented as multiple peaks between 56 and 75S. Sedimentation and buoyant density measurements indicated that protein is bound to all forms of SV40 DNA at about the same ratio of protein to DNA (1-2/1) as was reported for polyoma nucleoproteins. PMID:4359958

  2. Comparison of dye doping and ultrathin emissive layer in white organic light-emitting devices with dual emissive layers

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Qi, Yige; Yu, Junsheng

    2014-09-01

    White organic light-emitting devices (WOLEDs) with combined doping emissive layer (EML) and ultrathin EML have been fabricated to investigate the effect of each EML on the electroluminescent (EL) performance of the WOLEDs. Through tailoring doping concentration of bis[(4,6-difluorophenyl)-pyridinato-N,C2'](picolinate) iridium(III) (FIrpic) and thickness of ultrathin bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate) [(tbt)2Ir(acac)] EML, it is found that the change in the doping ratio of FIrpic significantly influenced the EL efficiencies and spectra, while the alteration of ultrathin EML thickness had much milder effect on the EL performance. The results indicated that ultrathin EML is in favor of reproducibility in mass production compared with doping method.

  3. Effects of Task Complexity on L2 Writing Behaviors and Linguistic Complexity

    ERIC Educational Resources Information Center

    Révész, Andrea; Kourtali, Nektaria-Efstathia; Mazgutova, Diana

    2017-01-01

    This study investigated whether task complexity influences second language (L2) writers' fluency, pausing, and revision behaviors and the cognitive processes underlying these behaviors; whether task complexity affects linguistic complexity of written output; and whether relationships between writing behaviors and linguistic complexity are…

  4. Controlling site selectivity in Pd-catalyzed oxidative cross-coupling reactions.

    PubMed

    Lyons, Thomas W; Hull, Kami L; Sanford, Melanie S

    2011-03-30

    This paper presents a detailed investigation of the factors controlling site selectivity in the Pd-mediated oxidative coupling of 1,3-disubstituted and 1,2,3-trisubstituted arenes (aryl-H) with cyclometalating substrates (L~C-H). The influence of both the concentration and the steric/electronic properties of the quinone promoter are studied in detail. In addition, the effect of steric/electronic modulation of the carboxylate ligand is discussed. Finally, we demonstrate that substitution of the carboxylate for a carbonate X-type ligand leads to a complete reversal in site selectivity for many arene substrates. The origins of these trends in site selectivity are discussed in the context of the mechanism of Pd-catalyzed oxidative cross-coupling.

  5. Complexity and dynamics of topological and community structure in complex networks

    NASA Astrophysics Data System (ADS)

    Berec, Vesna

    2017-07-01

    Complexity is highly susceptible to variations in the network dynamics, reflected on its underlying architecture where topological organization of cohesive subsets into clusters, system's modular structure and resulting hierarchical patterns, are cross-linked with functional dynamics of the system. Here we study connection between hierarchical topological scales of the simplicial complexes and the organization of functional clusters - communities in complex networks. The analysis reveals the full dynamics of different combinatorial structures of q-th-dimensional simplicial complexes and their Laplacian spectra, presenting spectral properties of resulting symmetric and positive semidefinite matrices. The emergence of system's collective behavior from inhomogeneous statistical distribution is induced by hierarchically ordered topological structure, which is mapped to simplicial complex where local interactions between the nodes clustered into subcomplexes generate flow of information that characterizes complexity and dynamics of the full system.

  6. Complexity Theory

    USGS Publications Warehouse

    Lee, William H K.

    2016-01-01

    A complex system consists of many interacting parts, generates new collective behavior through self organization, and adaptively evolves through time. Many theories have been developed to study complex systems, including chaos, fractals, cellular automata, self organization, stochastic processes, turbulence, and genetic algorithms.

  7. Evolution of biological complexity

    PubMed Central

    Adami, Christoph; Ofria, Charles; Collier, Travis C.

    2000-01-01

    To make a case for or against a trend in the evolution of complexity in biological evolution, complexity needs to be both rigorously defined and measurable. A recent information-theoretic (but intuitively evident) definition identifies genomic complexity with the amount of information a sequence stores about its environment. We investigate the evolution of genomic complexity in populations of digital organisms and monitor in detail the evolutionary transitions that increase complexity. We show that, because natural selection forces genomes to behave as a natural “Maxwell Demon,” within a fixed environment, genomic complexity is forced to increase. PMID:10781045

  8. Asteroidal-meteoric complexes.

    NASA Astrophysics Data System (ADS)

    Shestaka, I. S.

    1994-12-01

    Fourteen asteroidal-meteoric complexes were identified by means of the criterion of similarity of quasistationary parameters μ, ν and Tisserand's invariant Ti. Each of these complexes consists of several meteor swarms and one or several asteroids. The existence of such complexes confirms the possibility of formation of meteor swarms by means of disintegration of asteroids and their fragments.

  9. Complex Constructivism: A Theoretical Model of Complexity and Cognition

    ERIC Educational Resources Information Center

    Doolittle, Peter E.

    2014-01-01

    Education has long been driven by its metaphors for teaching and learning. These metaphors have influenced both educational research and educational practice. Complexity and constructivism are two theories that provide functional and robust metaphors. Complexity provides a metaphor for the structure of myriad phenomena, while constructivism…

  10. The Ndc80 complex bridges two Dam1 complex rings

    PubMed Central

    Kim, Jae ook; Zelter, Alex; Umbreit, Neil T; Bollozos, Athena; Riffle, Michael; Johnson, Richard; MacCoss, Michael J; Asbury, Charles L; Davis, Trisha N

    2017-01-01

    Strong kinetochore-microtubule attachments are essential for faithful segregation of sister chromatids during mitosis. The Dam1 and Ndc80 complexes are the main microtubule binding components of the Saccharomyces cerevisiae kinetochore. Cooperation between these two complexes enhances kinetochore-microtubule coupling and is regulated by Aurora B kinase. We show that the Ndc80 complex can simultaneously bind and bridge across two Dam1 complex rings through a tripartite interaction, each component of which is regulated by Aurora B kinase. Mutations in any one of the Ndc80p interaction regions abrogates the Ndc80 complex’s ability to bind two Dam1 rings in vitro, and results in kinetochore biorientation and microtubule attachment defects in vivo. We also show that an extra-long Ndc80 complex, engineered to space the two Dam1 rings further apart, does not support growth. Taken together, our work suggests that each kinetochore in vivo contains two Dam1 rings and that proper spacing between the rings is vital. DOI: http://dx.doi.org/10.7554/eLife.21069.001 PMID:28191870

  11. The Tom Core Complex

    PubMed Central

    Ahting, Uwe; Thun, Clemens; Hegerl, Reiner; Typke, Dieter; Nargang, Frank E.; Neupert, Walter; Nussberger, Stephan

    1999-01-01

    Translocation of nuclear-encoded preproteins across the outer membrane of mitochondria is mediated by the multicomponent transmembrane TOM complex. We have isolated the TOM core complex of Neurospora crassa by removing the receptors Tom70 and Tom20 from the isolated TOM holo complex by treatment with the detergent dodecyl maltoside. It consists of Tom40, Tom22, and the small Tom components, Tom6 and Tom7. This core complex was also purified directly from mitochondria after solubilization with dodecyl maltoside. The TOM core complex has the characteristics of the general insertion pore; it contains high-conductance channels and binds preprotein in a targeting sequence-dependent manner. It forms a double ring structure that, in contrast to the holo complex, lacks the third density seen in the latter particles. Three-dimensional reconstruction by electron tomography exhibits two open pores traversing the complex with a diameter of ∼2.1 nm and a height of ∼7 nm. Tom40 is the key structural element of the TOM core complex. PMID:10579717

  12. Amorphic complexity

    NASA Astrophysics Data System (ADS)

    Fuhrmann, G.; Gröger, M.; Jäger, T.

    2016-02-01

    We introduce amorphic complexity as a new topological invariant that measures the complexity of dynamical systems in the regime of zero entropy. Its main purpose is to detect the very onset of disorder in the asymptotic behaviour. For instance, it gives positive value to Denjoy examples on the circle and Sturmian subshifts, while being zero for all isometries and Morse-Smale systems. After discussing basic properties and examples, we show that amorphic complexity and the underlying asymptotic separation numbers can be used to distinguish almost automorphic minimal systems from equicontinuous ones. For symbolic systems, amorphic complexity equals the box dimension of the associated Besicovitch space. In this context, we concentrate on regular Toeplitz flows and give a detailed description of the relation to the scaling behaviour of the densities of the p-skeletons. Finally, we take a look at strange non-chaotic attractors appearing in so-called pinched skew product systems. Continuous-time systems, more general group actions and the application to cut and project quasicrystals will be treated in subsequent work.

  13. Sustainability, Complexity and Learning: Insights from Complex Systems Approaches

    ERIC Educational Resources Information Center

    Espinosa, A.; Porter, T.

    2011-01-01

    Purpose: The purpose of this research is to explore core contributions from two different approaches to complexity management in organisations aiming to improve their sustainability,: the Viable Systems Model (VSM), and the Complex Adaptive Systems (CAS). It is proposed to perform this by summarising the main insights each approach offers to…

  14. Artistic forms and complexity.

    PubMed

    Boon, J-P; Casti, J; Taylor, R P

    2011-04-01

    We discuss the inter-relationship between various concepts of complexity by introducing a complexity 'triangle' featuring objective complexity, subjective complexity and social complexity. Their connections are explored using visual and musical compositions of art. As examples, we quantify the complexity embedded within the paintings of the Jackson Pollock and the musical works of Johann Sebastian Bach. We discuss the challenges inherent in comparisons of the spatial patterns created by Pollock and the sonic patterns created by Bach, including the differing roles that time plays in these investigations. Our results draw attention to some common intriguing characteristics suggesting 'universality' and conjecturing that the fractal nature of art might have an intrinsic value of more general significance.

  15. Putting Text Complexity in Context: Refocusing on Comprehension of Complex Text

    ERIC Educational Resources Information Center

    Valencia, Sheila W.; Wixson, Karen K.; Pearson, P. David

    2014-01-01

    The Common Core State Standards for English Language Arts have prompted enormous attention to issues of text complexity. The purpose of this article is to put text complexity in perspective by moving from a primary focus on the text itself to a focus on the comprehension of complex text. We argue that a focus on comprehension is at the heart of…

  16. Designing Complexity

    ERIC Educational Resources Information Center

    Glanville, Ranulph

    2007-01-01

    This article considers the nature of complexity and design, as well as relationships between the two, and suggests that design may have much potential as an approach to improving human performance in situations seen as complex. It is developed against two backgrounds. The first is a world view that derives from second order cybernetics and radical…

  17. Complex I-complex II ratio strongly differs in various organs of Arabidopsis thaliana.

    PubMed

    Peters, Katrin; Niessen, Markus; Peterhänsel, Christoph; Späth, Bettina; Hölzle, Angela; Binder, Stefan; Marchfelder, Anita; Braun, Hans-Peter

    2012-06-01

    In most studies, amounts of protein complexes of the oxidative phosphorylation (OXPHOS) system in different organs or tissues are quantified on the basis of isolated mitochondrial fractions. However, yield of mitochondrial isolations might differ with respect to tissue type due to varying efficiencies of cell disruption during organelle isolation procedures or due to tissue-specific properties of organelles. Here we report an immunological investigation on the ratio of the OXPHOS complexes in different tissues of Arabidopsis thaliana which is based on total protein fractions isolated from five Arabidopsis organs (leaves, stems, flowers, roots and seeds) and from callus. Antibodies were generated against one surface exposed subunit of each of the five OXPHOS complexes and used for systematic immunoblotting experiments. Amounts of all complexes are highest in flowers (likewise with respect to organ fresh weight or total protein content of the flower fraction). Relative amounts of protein complexes in all other fractions were determined with respect to their amounts in flowers. Our investigation reveals high relative amounts of complex I in green organs (leaves and stems) but much lower amounts in non-green organs (roots, callus tissue). In contrast, complex II only is represented by low relative amounts in green organs but by significantly higher amounts in non-green organs, especially in seeds. In fact, the complex I-complex II ratio differs by factor 37 between callus and leaf, indicating drastic differences in electron entry into the respiratory chain in these two fractions. Variation in amounts concerning complexes III, IV and V was less pronounced in different Arabidopsis tissues (quantification of complex V in leaves was not meaningful due to a cross-reaction of the antibody with the chloroplast form of this enzyme). Analyses were complemented by in gel activity measurements for the protein complexes of the OXPHOS system and comparative 2D blue native/SDS PAGE

  18. Complexity in Nature and Society: Complexity Management in the Age of Globalization

    NASA Astrophysics Data System (ADS)

    Mainzer, Klaus

    The theory of nonlinear complex systems has become a proven problem-solving approach in the natural sciences from cosmic and quantum systems to cellular organisms and the brain. Even in modern engineering science self-organizing systems are developed to manage complex networks and processes. It is now recognized that many of our ecological, social, economic, and political problems are also of a global, complex, and nonlinear nature. What are the laws of sociodynamics? Is there a socio-engineering of nonlinear problem solving? What can we learn from nonlinear dynamics for complexity management in social, economic, financial and political systems? Is self-organization an acceptable strategy to handle the challenges of complexity in firms, institutions and other organizations? It is a main thesis of the talk that nature and society are basically governed by nonlinear and complex information dynamics. How computational is sociodynamics? What can we hope for social, economic and political problem solving in the age of globalization?.

  19. [Tissue-specific nucleoprotein complexes].

    PubMed

    Riadnova, I Iu; Shataeva, L K; Khavinson, V Kh

    2000-01-01

    A method of isolation of native nucleorprotein complexes from cattle cerebral cortex, thymus, and liver was developed. Compositions of these complexes were studied by means of gel-chromatography and ion-exchange chromatography. These preparations were shown to consist of several fractions of proteins and their complexes differ by molecular mass and electro-chemical properties. Native nucleoprotein complexes revealed high tissue specific activity, which was not species-specific.

  20. Dynamical complexity of short and noisy time series. Compression-Complexity vs. Shannon entropy

    NASA Astrophysics Data System (ADS)

    Nagaraj, Nithin; Balasubramanian, Karthi

    2017-07-01

    Shannon entropy has been extensively used for characterizing complexity of time series arising from chaotic dynamical systems and stochastic processes such as Markov chains. However, for short and noisy time series, Shannon entropy performs poorly. Complexity measures which are based on lossless compression algorithms are a good substitute in such scenarios. We evaluate the performance of two such Compression-Complexity Measures namely Lempel-Ziv complexity (LZ) and Effort-To-Compress (ETC) on short time series from chaotic dynamical systems in the presence of noise. Both LZ and ETC outperform Shannon entropy (H) in accurately characterizing the dynamical complexity of such systems. For very short binary sequences (which arise in neuroscience applications), ETC has higher number of distinct complexity values than LZ and H, thus enabling a finer resolution. For two-state ergodic Markov chains, we empirically show that ETC converges to a steady state value faster than LZ. Compression-Complexity measures are promising for applications which involve short and noisy time series.

  1. Synthesis and Deprotonation of Aminophosphane Complexes: First K/N(H)R Phosphinidenoid Complexes and Access to a Complex with a P2 N-Ring Ligand.

    PubMed

    Majhi, Paresh Kumar; Kyri, Andreas Wolfgang; Schmer, Alexander; Schnakenburg, Gregor; Streubel, Rainer

    2016-10-17

    Synthesis of 1,1'-bifunctional aminophosphane complexes 3 a-e was achieved by the reaction of Li/Cl phosphinidenoid complex 2 with various primary amines (R=Me, iPr, tBu, Cy, Ph). Deprotonation of complex 3 a (R=Me) with potassium hexamethyldisilazide yielded a mixture of K/NHMe phosphinidenoid complex 4 a and potassium phosphanylamido complex 4 a'. Treatment of complex 3 c (R=tBu) and e (R=Ph) with KHMDS afforded the first examples of K/NHR phosphinidenoid complexes 4 c and e. The reaction of complex 3 c with 2 molar equivalents of KHMDS followed by PhPCl 2 afforded complexes 5 c,c', which possess a P 2 N-ring ligand. All complexes were characterized by NMR, IR, MS, and microanalysis, and additionally, complexes 3 b-e and 5 c' were scrutinized by single-crystal X-ray crystallography. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Highly Efficient Red and White Organic Light-Emitting Diodes with External Quantum Efficiency beyond 20% by Employing Pyridylimidazole-Based Metallophosphors.

    PubMed

    Miao, Yanqin; Tao, Peng; Wang, Kexiang; Li, Hongxin; Zhao, Bo; Gao, Long; Wang, Hua; Xu, Bingshe; Zhao, Qiang

    2017-11-01

    Two highly efficient red neutral iridium(III) complexes, Ir1 and Ir2, were rationally designed and synthesized by selecting two pyridylimidazole derivatives as the ancillary ligands. Both Ir1 and Ir2 show nearly the same photoluminescence emission with the maximum peak at 595 nm (shoulder band at about 638 nm) and achieve high solution quantum yields of up to 0.47 for Ir1 and 0.57 for Ir2. Employing Ir1 and Ir2 as emitters, the fabricated red organic light-emitting diodes (OLEDs) show outstanding performance with the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 20.98%, 33.04 cd/A, and 33.08 lm/W for the Ir1-based device and 22.15%, 36.89 cd/A, and 35.85 lm/W for the Ir2-based device, respectively. Furthermore, using Ir2 as red emitter, a trichromatic hybrid white OLED, showing good warm white emission with low correlated color temperature of <2200 K under the voltage of 4-6 V, was fabricated successfully. The white device also realizes excellent device efficiencies with the maximum EQE, CE, and PE reaching 22.74%, 44.77 cd/A, and 46.89 lm/W, respectively. Such high electroluminescence performance for red and white OLEDs indicates that Ir1 and Ir2 as efficient red phosphors have great potential for future OLED displays and lightings applications.

  3. Polystyrene Oxygen Optodes Doped with Ir(III) and Pd(II) meso-Tetrakis(pentafluorophenyl)porphyrin Using an LED-Based High-Sensitivity Phosphorimeter.

    PubMed

    Filho, Alexandre F De Moraes; Gewehr, Pedro M; Maia, Joaquim M; Jakubiak, Douglas R

    2018-06-15

    This paper presents a gaseous oxygen detection system based on time-resolved phosphorimetry (time-domain), which is used to investigate O2 optical transducers. The primary sensing elements were formed by incorporating iridium(III) and palladium(II) meso -tetrakis(pentafluorophenyl)porphyrin complexes (IrTFPP-CO-Cl and PdTFPP) in polystyrene (PS) solid matrices. Probe excitation was obtained using a violet light-emitting diode (LED) (low power), and the resulting phosphorescence was detected by a high-sensitivity compact photomultiplier tube. The detection system performance and the preparation of the transducers are presented along with their optical properties, phosphorescence lifetimes, calibration curves and photostability. The developed lifetime measuring system showed a good signal-to-noise ratio, and reliable results were obtained from the optodes, even when exposed to moderate levels of O2. The new IrTFPP-CO-Cl membranes exhibited room temperature phosphorescence and moderate sensitivity: <τ0>/<τ21%> ratio of ≈6. A typically high degree of dynamic phosphorescence quenching was observed for the traditional indicator PdTFPP: <τ0>/<τ21%> ratio of ≈36. Pulsed-source time-resolved phosphorimetry combined with a high-sensitivity photodetector can offer potential advantages such as: (i) major dynamic range, (ii) extended temporal resolution (Δτ/Δ[O2]) and (iii) high operational stability. IrTFPP-CO-Cl immobilized in polystyrene is a promising alternative for O2 detection, offering adequate photostability and potentially mid-range sensitivity over Pt(II) and Pd(II) metalloporphyrins.

  4. Selenophene transition metal complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    White, Carter James

    1994-07-27

    This research shows that selenophene transition metal complexes have a chemistry that is similar to their thiophene analogs. Selenophene coordination has been demonstrated and confirmed by molecular structure in both the η 5- and the η 1(Se)-coordination modes. The reaction chemistry of selenophene complexes closely resembles that of the analogous thiophene complexes. One major difference, however, is that selenophene is a better donor ligand than thiophene making the selenophene complexes more stable than the corresponding thiophene complexes. The 77Se NMR chemical shift values for selenophene complexes fall within distinct regions primarily depending on the coordination mode of the selenophene ligand.more » In the final paper, the C-H bond activation of η 1(S)-bound thiophenes, η 1(S)-benzothiophene and η 1(Se)-bound selenophenes has been demonstrated. The deprotonation and rearrangement of the η 1(E)-bound ligand to the carbon bound L-yl complex readily occurs in the presence of base. Reprotonation with a strong acid gives a carbene complex that is unreactive towards nucleophilic attack at the carbene carbon and is stable towards exposure to air. The molecular structure of [Cp(NO)(PPh 3)Re(2-benzothioenylcarbene)]O 3SCF 3 was determined and contains a Re-C bond with substantial double bond character. Methyl substitution for the thienylcarbene or selenylcarbene gives a carbene that rearranges thermally to give back the η 1(E)-bound complex. Based on these model reactions, a new mechanism for the H/D exchange of thiophene over the hydrodesulfurization catalyst has been proposed.« less

  5. Bacterial formate hydrogenlyase complex.

    PubMed

    McDowall, Jennifer S; Murphy, Bonnie J; Haumann, Michael; Palmer, Tracy; Armstrong, Fraser A; Sargent, Frank

    2014-09-23

    Under anaerobic conditions, Escherichia coli can carry out a mixed-acid fermentation that ultimately produces molecular hydrogen. The enzyme directly responsible for hydrogen production is the membrane-bound formate hydrogenlyase (FHL) complex, which links formate oxidation to proton reduction and has evolutionary links to Complex I, the NADH:quinone oxidoreductase. Although the genetics, maturation, and some biochemistry of FHL are understood, the protein complex has never been isolated in an intact form to allow biochemical analysis. In this work, genetic tools are reported that allow the facile isolation of FHL in a single chromatographic step. The core complex is shown to comprise HycE (a [NiFe] hydrogenase component termed Hyd-3), FdhF (the molybdenum-dependent formate dehydrogenase-H), and three iron-sulfur proteins: HycB, HycF, and HycG. A proportion of this core complex remains associated with HycC and HycD, which are polytopic integral membrane proteins believed to anchor the core complex to the cytoplasmic side of the membrane. As isolated, the FHL complex retains formate hydrogenlyase activity in vitro. Protein film electrochemistry experiments on Hyd-3 demonstrate that it has a unique ability among [NiFe] hydrogenases to catalyze production of H2 even at high partial pressures of H2. Understanding and harnessing the activity of the FHL complex is critical to advancing future biohydrogen research efforts.

  6. Curcumin complexation with cyclodextrins by the autoclave process: Method development and characterization of complex formation.

    PubMed

    Hagbani, Turki Al; Nazzal, Sami

    2017-03-30

    One approach to enhance curcumin (CUR) aqueous solubility is to use cyclodextrins (CDs) to form inclusion complexes where CUR is encapsulated as a guest molecule within the internal cavity of the water-soluble CD. Several methods have been reported for the complexation of CUR with CDs. Limited information, however, is available on the use of the autoclave process (AU) in complex formation. The aims of this work were therefore to (1) investigate and evaluate the AU cycle as a complex formation method to enhance CUR solubility; (2) compare the efficacy of the AU process with the freeze-drying (FD) and evaporation (EV) processes in complex formation; and (3) confirm CUR stability by characterizing CUR:CD complexes by NMR, Raman spectroscopy, DSC, and XRD. Significant differences were found in the saturation solubility of CUR from its complexes with CD when prepared by the three complexation methods. The AU yielded a complex with expected chemical and physical fingerprints for a CUR:CD inclusion complex that maintained the chemical integrity and stability of CUR and provided the highest solubility of CUR in water. Physical and chemical characterizations of the AU complexes confirmed the encapsulated of CUR inside the CD cavity and the transformation of the crystalline CUR:CD inclusion complex to an amorphous form. It was concluded that the autoclave process with its short processing time could be used as an alternate and efficient methods for drug:CD complexation. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Complexes and imagination.

    PubMed

    Kast, Verena

    2014-11-01

    Fantasies as imaginative activities are seen by Jung as expressions of psychic energy. In the various descriptions of active imagination the observation of the inner image and the dialogue with inner figures, if possible, are important. The model of symbol formation, as Jung describes it, can be experienced in doing active imagination. There is a correspondence between Jung's understanding of complexes and our imaginations: complexes develop a fantasy life. Complex episodes are narratives of difficult dysfunctional relationship episodes that have occurred repeatedly and are internalized with episodic memory. This means that the whole complex episode (the image for the child and the image for the aggressor, connected with emotions) is internalized and can get constellated in everyday relationship. Therefore inner dialogues do not necessarily qualify as active imaginations, often they are the expression of complex-episodes, very similar to fruitless soliloquies. If imaginations of this kind are repeated, new symbols and new possibilities of behaviour are not found. On the contrary, old patterns of behaviour and fantasies are perpetuated and become cemented. Imaginations of this kind need an intervention by the analyst. In clinical examples different kinds of imaginations are discussed. © 2014, The Society of Analytical Psychology.

  8. Structure of complexes between aluminum chloride and other chlorides, 2: Alkali-(chloroaluminates). Gaseous complexes

    NASA Technical Reports Server (NTRS)

    Hargittai, M.

    1980-01-01

    The structural chemistry of complexes between aluminum chloride and other metal chlorides is important both for practice and theory. Condensed-phase as well as vapor-phase complexes are of interest. Structural information on such complexes is reviewed. The first emphasis is given to the molten state because of its practical importance. Aluminum chloride forms volatile complexes with other metal chlorides and these vapor-phase complexes are dealt with in the second part. Finally, the variations in molecular shape and geometrical parameters are summarized.

  9. Complex Questions Promote Complex Thinking

    ERIC Educational Resources Information Center

    Degener, Sophie; Berne, Jennifer

    2017-01-01

    Intermediate-grade teachers often express concerns about meeting the Common Core State Standards for Reading, primarily because of the emphasis on deep understanding of complex texts. No matter how difficult the text, if teachers demand little of the reading, student meaning making is not challenged. This article offers a tool for teachers to…

  10. Physical Complexity and Cognitive Evolution

    NASA Astrophysics Data System (ADS)

    Jedlicka, Peter

    Our intuition tells us that there is a general trend in the evolution of nature, a trend towards greater complexity. However, there are several definitions of complexity and hence it is difficult to argue for or against the validity of this intuition. Christoph Adami has recently introduced a novel measure called physical complexity that assigns low complexity to both ordered and random systems and high complexity to those in between. Physical complexity measures the amount of information that an organism stores in its genome about the environment in which it evolves. The theory of physical complexity predicts that evolution increases the amount of `knowledge' an organism accumulates about its niche. It might be fruitful to generalize Adami's concept of complexity to the entire evolution (including the evolution of man). Physical complexity fits nicely into the philosophical framework of cognitive biology which considers biological evolution as a progressing process of accumulation of knowledge (as a gradual increase of epistemic complexity). According to this paradigm, evolution is a cognitive `ratchet' that pushes the organisms unidirectionally towards higher complexity. Dynamic environment continually creates problems to be solved. To survive in the environment means to solve the problem, and the solution is an embodied knowledge. Cognitive biology (as well as the theory of physical complexity) uses the concepts of information and entropy and views the evolution from both the information-theoretical and thermodynamical perspective. Concerning humans as conscious beings, it seems necessary to postulate an emergence of a new kind of knowledge - a self-aware and self-referential knowledge. Appearence of selfreflection in evolution indicates that the human brain reached a new qualitative level in the epistemic complexity.

  11. Multi-Dimensional Scaling based grouping of known complexes and intelligent protein complex detection.

    PubMed

    Rehman, Zia Ur; Idris, Adnan; Khan, Asifullah

    2018-06-01

    Protein-Protein Interactions (PPI) play a vital role in cellular processes and are formed because of thousands of interactions among proteins. Advancements in proteomics technologies have resulted in huge PPI datasets that need to be systematically analyzed. Protein complexes are the locally dense regions in PPI networks, which extend important role in metabolic pathways and gene regulation. In this work, a novel two-phase protein complex detection and grouping mechanism is proposed. In the first phase, topological and biological features are extracted for each complex, and prediction performance is investigated using Bagging based Ensemble classifier (PCD-BEns). Performance evaluation through cross validation shows improvement in comparison to CDIP, MCode, CFinder and PLSMC methods Second phase employs Multi-Dimensional Scaling (MDS) for the grouping of known complexes by exploring inter complex relations. It is experimentally observed that the combination of topological and biological features in the proposed approach has greatly enhanced prediction performance for protein complex detection, which may help to understand various biological processes, whereas application of MDS based exploration may assist in grouping potentially similar complexes. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Functionalized active-nucleus complex sensor

    DOEpatents

    Pines, Alexander; Wemmer, David E.; Spence, Megan; Rubin, Seth

    2003-11-25

    A functionalized active-nucleus complex sensor that selectively associates with one or more target species, and a method for assaying and screening for one or a plurality of target species utilizing one or a plurality of functionalized active-nucleus complexes with at least two of the functionalized active-nucleus complexes having an attraction affinity to different corresponding target species. The functionalized active-nucleus complex has an active-nucleus and a targeting carrier. The method involves functionalizing an active-nucleus, for each functionalized active-nucleus complex, by incorporating the active-nucleus into a macromolucular or molecular complex that is capable of binding one of the target species and then bringing the macromolecular or molecular complexes into contact with the target species and detecting the occurrence of or change in a nuclear magnetic resonance signal from each of the active-nuclei in each of the functionalized active-nucleus complexes.

  13. Subsumed complexity: abiogenesis as a by-product of complex energy transduction

    NASA Astrophysics Data System (ADS)

    Adam, Z. R.; Zubarev, D.; Aono, M.; Cleaves, H. James

    2017-11-01

    The origins of life bring into stark relief the inadequacy of our current synthesis of thermodynamic, chemical, physical and information theory to predict the conditions under which complex, living states of organic matter can arise. Origins research has traditionally proceeded under an array of implicit or explicit guiding principles in lieu of a universal formalism for abiogenesis. Within the framework of a new guiding principle for prebiotic chemistry called subsumed complexity, organic compounds are viewed as by-products of energy transduction phenomena at different scales (subatomic, atomic, molecular and polymeric) that retain energy in the form of bonds that inhibit energy from reaching the ground state. There is evidence for an emergent level of complexity that is overlooked in most conceptualizations of abiogenesis that arises from populations of compounds formed from atomic energy input. We posit that different forms of energy input can exhibit different degrees of dissipation complexity within an identical chemical medium. By extension, the maximum capacity for organic chemical complexification across molecular and macromolecular scales subsumes, rather than emerges from, the underlying complexity of energy transduction processes that drive their production and modification. This article is part of the themed issue 'Reconceptualizing the origins of life'.

  14. Complex chimerism

    PubMed Central

    Ma, Kimberly K.; Petroff, Margaret G.; Coscia, Lisa A.; Armenti, Vincent T.; Adams Waldorf, Kristina M.

    2013-01-01

    Thousands of women with organ transplantation have undergone successful pregnancies, however little is known about how the profound immunologic changes associated with pregnancy might influence tolerance or rejection of the allograft. Pregnant women with a solid organ transplant are complex chimeras with multiple foreign cell populations from the donor organ, fetus, and mother of the pregnant woman. We consider the impact of complex chimerism and pregnancy-associated immunologic changes on tolerance of the allograft both during pregnancy and the postpartum period. Mechanisms of allograft tolerance are likely dynamic during pregnancy and affected by the influx of fetal microchimeric cells, HLA relationships (between the fetus, pregnant woman and/or donor), peripheral T cell tolerance to fetal cells, and fetal minor histocompatibility antigens. Further research is necessary to understand the complex immunology during pregnancy and the postpartum period of women with a solid organ transplant. PMID:23974274

  15. Complexity Leadership: A Theoretical Perspective

    ERIC Educational Resources Information Center

    Baltaci, Ali; Balci, Ali

    2017-01-01

    Complex systems are social networks composed of interactive employees interconnected through collaborative, dynamic ties such as shared goals, perspectives and needs. Complex systems are largely based on "the complex system theory". The complex system theory focuses mainly on finding out and developing strategies and behaviours that…

  16. Complexity and robustness

    PubMed Central

    Carlson, J. M.; Doyle, John

    2002-01-01

    Highly optimized tolerance (HOT) was recently introduced as a conceptual framework to study fundamental aspects of complexity. HOT is motivated primarily by systems from biology and engineering and emphasizes, (i) highly structured, nongeneric, self-dissimilar internal configurations, and (ii) robust yet fragile external behavior. HOT claims these are the most important features of complexity and not accidents of evolution or artifices of engineering design but are inevitably intertwined and mutually reinforcing. In the spirit of this collection, our paper contrasts HOT with alternative perspectives on complexity, drawing on real-world examples and also model systems, particularly those from self-organized criticality. PMID:11875207

  17. Aspartate aminotransferase is potently inhibited by copper complexes: Exploring copper complex-binding proteome.

    PubMed

    Jia, Yuqi; Lu, Liping; Yuan, Caixia; Feng, Sisi; Zhu, Miaoli

    2017-05-01

    Recent researches indicated that a copper complex-binding proteome that potently interacted with copper complexes and then influenced cellular metabolism might exist in organism. In order to explore the copper complex-binding proteome, a copper chelating ion-immobilized affinity chromatography (Cu-IMAC) column and mass spectrometry were used to separate and identify putative Cu-binding proteins in primary rat hepatocytes. A total of 97 putative Cu-binding proteins were isolated and identified. Five higher abundance proteins, aspartate aminotransferase (AST), malate dehydrogenase (MDH), catalase (CAT), calreticulin (CRT) and albumin (Alb) were further purified using a SP-, and (or) Q-Sepharose Fast Flow column. The interaction between the purified proteins and selected 11 copper complexes and CuCl 2 was investigated. The enzymes inhibition tests demonstrated that AST was potently inhibited by copper complexes while MDH and CAT were weakly inhibited. Schiff-based copper complexes 6 and 7 potently inhibited AST with the IC 50 value of 3.6 and 7.2μM, respectively and exhibited better selectivity over MDH and CAT. Fluorescence titration results showed the two complexes tightly bound to AST with binding constant of 3.89×10 6 and 3.73×10 6 M -1 , respectively and a stoichiometry ratio of 1:1. Copper complex 6 was able to enter into HepG2 cells and further inhibit intracellular AST activity. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Organic Optoelectronic Devices Employing Small Molecules

    NASA Astrophysics Data System (ADS)

    Fleetham, Tyler Blain

    Organic optoelectronic devices have remained a research topic of great interest over the past two decades, particularly in the development of efficient organic photovoltaics (OPV) and organic light emitting diodes (OLED). In order to improve the efficiency, stability, and materials variety for organic optoelectronic devices a number of emitting materials, absorbing materials, and charge transport materials were developed and employed in a device setting. Optical, electrical, and photophysical studies of the organic materials and their corresponding devices were thoroughly carried out. Two major approaches were taken to enhance the efficiency of small molecule based OPVs: developing material with higher open circuit voltages or improved device structures which increased short circuit current. To explore the factors affecting the open circuit voltage (VOC) in OPVs, molecular structures were modified to bring VOC closer to the effective bandgap, DeltaE DA, which allowed the achievement of 1V VOC for a heterojunction of a select Ir complex with estimated exciton energy of only 1.55eV. Furthermore, the development of anode interfacial layer for exciton blocking and molecular templating provide a general approach for enhancing the short circuit current. Ultimately, a 5.8% PCE was achieved in a single heterojunction of C60 and a ZnPc material prepared in a simple, one step, solvent free, synthesis. OLEDs employing newly developed deep blue emitters based on cyclometalated complexes were demonstrated. Ultimately, a peak EQE of 24.8% and nearly perfect blue emission of (0.148,0.079) was achieved from PtON7dtb, which approaches the maximum attainable performance from a blue OLED. Furthermore, utilizing the excimer formation properties of square-planar Pt complexes, highly efficient and stable white devices employing a single emissive material were demonstrated. A peak EQE of over 20% for pure white color (0.33,0.33) and 80 CRI was achieved with the tridentate Pt complex, Pt

  19. Embracing uncertainty, managing complexity: applying complexity thinking principles to transformation efforts in healthcare systems.

    PubMed

    Khan, Sobia; Vandermorris, Ashley; Shepherd, John; Begun, James W; Lanham, Holly Jordan; Uhl-Bien, Mary; Berta, Whitney

    2018-03-21

    Complexity thinking is increasingly being embraced in healthcare, which is often described as a complex adaptive system (CAS). Applying CAS to healthcare as an explanatory model for understanding the nature of the system, and to stimulate changes and transformations within the system, is valuable. A seminar series on systems and complexity thinking hosted at the University of Toronto in 2016 offered a number of insights on applications of CAS perspectives to healthcare that we explore here. We synthesized topics from this series into a set of six insights on how complexity thinking fosters a deeper understanding of accepted ideas in healthcare, applications of CAS to actors within the system, and paradoxes in applications of complexity thinking that may require further debate: 1) a complexity lens helps us better understand the nebulous term "context"; 2) concepts of CAS may be applied differently when actors are cognizant of the system in which they operate; 3) actor responses to uncertainty within a CAS is a mechanism for emergent and intentional adaptation; 4) acknowledging complexity supports patient-centred intersectional approaches to patient care; 5) complexity perspectives can support ways that leaders manage change (and transformation) in healthcare; and 6) complexity demands different ways of implementing ideas and assessing the system. To enhance our exploration of key insights, we augmented the knowledge gleaned from the series with key articles on complexity in the literature. Ultimately, complexity thinking acknowledges the "messiness" that we seek to control in healthcare and encourages us to embrace it. This means seeing challenges as opportunities for adaptation, stimulating innovative solutions to ensure positive adaptation, leveraging the social system to enable ideas to emerge and spread across the system, and even more important, acknowledging that these adaptive actions are part of system behaviour just as much as periods of stability are. By

  20. Perimetric Complexity of Binary Digital Images: Notes on Calculation and Relation to Visual Complexity

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.

    2011-01-01

    Perimetric complexity is a measure of the complexity of binary pictures. It is defined as the sum of inside and outside perimeters of the foreground, squared, divided by the foreground area, divided by 4p . Difficulties arise when this definition is applied to digital images composed of binary pixels. In this paper we identify these problems and propose solutions. Perimetric complexity is often used as a measure of visual complexity, in which case it should take into account the limited resolution of the visual system. We propose a measure of visual perimetric complexity that meets this requirement.

  1. Complexity and the Arrow of Time

    NASA Astrophysics Data System (ADS)

    Lineweaver, Charles H.; Davies, Paul C. W.; Ruse, Michael

    2013-08-01

    1. What is complexity? Is it increasing? Charles H. Lineweaver, Paul C. W. Davies and Michael Ruse; 2. Directionality principles from cancer to cosmology Paul C. W. Davies; 3. A simple treatment of complexity: cosmological entropic boundary conditions on increasing complexity Charles H. Lineweaver; 4. Using complexity science to search for unity in the natural sciences Eric J. Chaisson; 5. On the spontaneous generation of complexity in the universe Seth Lloyd; 6. Emergent spatiotemporal complexity in field theory Marcelo Gleiser; 7. Life: the final frontier for complexity? Simon Conway Morris; 8. Evolution beyond Newton, Darwin, and entailing law: the origin of complexity in the evolving biosphere Stuart A. Kauffman; 9. Emergent order in processes: the interplay of complexity, robustness, correlation, and hierarchy in the biosphere D. Eric Smith; 10. The inferential evolution of biological complexity: forgetting nature by learning to nurture David C. Krakauer; 11. Information width: a way for the second law to increase complexity David Wolpert; 12. Wrestling with biological complexity: from Darwin to Dawkins Michael Ruse; 13. The role of generative entrenchment and robustness in the evolution of complexity William C. Wimsatt; 14. On the plurality of complexity-producing mechanisms Philip Clayton; Index.

  2. Method for preparing radiopharmaceutical complexes

    DOEpatents

    Jones, Alun G.; Davison, Alan; Abrams, Michael J.

    1989-05-02

    A method for preparing radiopharmaceutical complexes that are substantially free of the reaction materials used to produce the radiopharmaceutical complex is disclosed. The method involves admixing in a suitable first solvent in a container a target seeking ligand or salt or metal adduct thereof, a radionuclide label, and a reducing agent for said radionuclide, thereby forming said radiopharmaceutical complex; coating the interior walls of the container with said pharmaceutical complex; discarding the solvent containing by-products and unreacted starting reaction materials; and removing the radiopharmaceutical complex from said walls by dissolving it in a second solvent, thereby obtaining said radiopharmaceutical complex substantially free of by-products and unreacted starting materials.

  3. The bacterial flagellar switch complex is getting more complex

    PubMed Central

    Cohen-Ben-Lulu, Galit N; Francis, Noreen R; Shimoni, Eyal; Noy, Dror; Davidov, Yaacov; Prasad, Krishna; Sagi, Yael; Cecchini, Gary; Johnstone, Rose M; Eisenbach, Michael

    2008-01-01

    The mechanism of function of the bacterial flagellar switch, which determines the direction of flagellar rotation and is essential for chemotaxis, has remained an enigma for many years. Here we show that the switch complex associates with the membrane-bound respiratory protein fumarate reductase (FRD). We provide evidence that FRD binds to preparations of isolated switch complexes, forms a 1:1 complex with the switch protein FliG, and that this interaction is required for both flagellar assembly and switching the direction of flagellar rotation. We further show that fumarate, known to be a clockwise/switch factor, affects the direction of flagellar rotation through FRD. These results not only uncover a new component important for switching and flagellar assembly, but they also reveal that FRD, an enzyme known to be primarily expressed and functional under anaerobic conditions in Escherichia coli, nonetheless, has important, unexpected functions under aerobic conditions. PMID:18337747

  4. Spectral simplicity of apparent complexity. II. Exact complexities and complexity spectra

    NASA Astrophysics Data System (ADS)

    Riechers, Paul M.; Crutchfield, James P.

    2018-03-01

    The meromorphic functional calculus developed in Part I overcomes the nondiagonalizability of linear operators that arises often in the temporal evolution of complex systems and is generic to the metadynamics of predicting their behavior. Using the resulting spectral decomposition, we derive closed-form expressions for correlation functions, finite-length Shannon entropy-rate approximates, asymptotic entropy rate, excess entropy, transient information, transient and asymptotic state uncertainties, and synchronization information of stochastic processes generated by finite-state hidden Markov models. This introduces analytical tractability to investigating information processing in discrete-event stochastic processes, symbolic dynamics, and chaotic dynamical systems. Comparisons reveal mathematical similarities between complexity measures originally thought to capture distinct informational and computational properties. We also introduce a new kind of spectral analysis via coronal spectrograms and the frequency-dependent spectra of past-future mutual information. We analyze a number of examples to illustrate the methods, emphasizing processes with multivariate dependencies beyond pairwise correlation. This includes spectral decomposition calculations for one representative example in full detail.

  5. Subsumed complexity: abiogenesis as a by-product of complex energy transduction.

    PubMed

    Adam, Z R; Zubarev, D; Aono, M; Cleaves, H James

    2017-12-28

    The origins of life bring into stark relief the inadequacy of our current synthesis of thermodynamic, chemical, physical and information theory to predict the conditions under which complex, living states of organic matter can arise. Origins research has traditionally proceeded under an array of implicit or explicit guiding principles in lieu of a universal formalism for abiogenesis. Within the framework of a new guiding principle for prebiotic chemistry called subsumed complexity , organic compounds are viewed as by-products of energy transduction phenomena at different scales (subatomic, atomic, molecular and polymeric) that retain energy in the form of bonds that inhibit energy from reaching the ground state. There is evidence for an emergent level of complexity that is overlooked in most conceptualizations of abiogenesis that arises from populations of compounds formed from atomic energy input. We posit that different forms of energy input can exhibit different degrees of dissipation complexity within an identical chemical medium. By extension, the maximum capacity for organic chemical complexification across molecular and macromolecular scales subsumes, rather than emerges from, the underlying complexity of energy transduction processes that drive their production and modification.This article is part of the themed issue 'Reconceptualizing the origins of life'. © 2017 The Author(s).

  6. Further Insight into the Lability of MeCN Ligands of Cytotoxic Cycloruthenated Compounds: Evidence for the Antisymbiotic Effect Trans to the Carbon Atom at the Ru Center.

    PubMed

    Barbosa, Ana Soraya Lima; Werlé, Christophe; Colunga, Claudia Olivia Oliva; Rodríguez, Cecilia Franco; Toscano, Ruben Alfredo; Le Lagadec, Ronan; Pfeffer, Michel

    2015-08-03

    The two MeCN ligands in [Ru(2-C6H4-2'-Py-κC,N)(Phen, trans-C)(MeCN)2]PF6 (1), both trans to a sp(2) hybridized N atom, cannot be substituted by any other ligand. In contrast, the isomerized derivative [Ru(2-C6H4-2'-Py-κC,N)(Phen, cis-C)(MeCN)2]PF6 (2), in which one MeCN ligand is now trans to the C atom of the phenyl ring orthometalated to Ru, leads to fast and quantitative substitution reactions with several monodentate ligands. With PPh3, 2 affords [Ru(2-C6H4-2'-Py-κC,N)(Phen, cis-C)(PPh3)(MeCN)]PF6 (3), in which PPh3 is trans to the C σ bound to Ru. Compound 3 is not kinetically stable, because, under thermodynamic control, it leads to 4, in which the PPh3 is trans to a N atom of the Phen ligand. Dimethylsulfoxide (DMSO) can also substitute a MeCN ligand in 2, leading to 5, in which DMSO is coordinated to Ru via its S atom trans to the N atom of the Phen ligand, the isomer under thermodynamic control being the only compound observed. We also found evidence for the fast to very fast substitution of MeCN in 2 by water or a chloride anion by studying the electronic spectra of 2 in the presence of water or NBu4Cl, respectively. An isomerization related to that observed between 3 and 4 is also found for the known monophosphine derivative [Ru(2-C6H4-2'-Py-κC,N)(PPh3, trans-C)(MeCN)3]PF6 (10), in which the PPh3 is located trans to the C of the cyclometalated 2-phenylpyridine, since, upon treatment by refluxing MeCN, it leads to its isomer 11, [Ru(2-C6H4-2'-Py-κC,N)(PPh3, cis-C)(MeCN)3]PF6. Further substitutions are also observed on 11, whereby N^N chelates (N^N = 2,2'-bipyridine and phenanthroline) substitute two MeCN ligands, affording [Ru(2-C6H4-2'-Py-κC,N)(PPh3, cis-C)(N^N)(MeCN)]PF6 (12a and 12b). Altogether, the behavior of the obtained complexes by ligand substitution reactions can be rationalized by an antisymbiotic effect on the Ru center, trans to the C atom of the cyclometalated unit, leading to compounds having the least nucleophilic ligand trans to C

  7. Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Du, Guodong

    In this work, the first examples of group 4 metalloporphyrin 1,2-diolato complexes were synthesized through a number of strategies. In general, treatment of imido metalloporphyrin complexes, (TTP)M=NR, (M = Ti, Zr, Hf), with vicinal diols led to the formation of a series of diolato complexes. Alternatively, the chelating pinacolate complexes could be prepared by metathesis of (TTP)MCl 2 (M = Ti, Hf) with disodium pinacolate. These complexes were found to undergo C-C cleavage reactions to produce organic carbonyl compounds. For titanium porphyrins, treatment of a titanium(II) alkyne adduct, (TTP)Ti(η 2-PhC≡CPh), with aromatic aldehydes or aryl ketones resulted in reductive couplingmore » of the carbonyl groups to produce the corresponding diolato complexes. Aliphatic aldehydes or ketones were not reactive towards (TTP)Ti(η 2-PhC≡CPh). However, these carbonyl compounds could be incorporated into a diolato complex on reaction with a reactive precursor, (TTP)Ti[O(Ph) 2C(Ph) 2O] to provide unsymmetrical diolato complexes via cross coupling reactions. In addition, an enediolato complex (TTP)Ti(OCPhCPhO) was obtained from the reaction of (TTP)Ti(η 2-PhC≡CPh) with benzoin. Titanium porphyrin diolato complexes were found to be intermediates in the (TTP)Ti=O-catalyzed cleavage reactions of vicinal diols, in which atmospheric oxygen was the oxidant. Furthermore, (TTP)Ti=O was capable of catalyzing the oxidation of benzyl alcohol and α-hydroxy ketones to benzaldehyde and α-diketones, respectively. Other high valent metalloporphyrin complexes also can catalyze the oxidative diol cleavage and the benzyl alcohol oxidation reactions with dioxygen. A comparison of Ti(IV) and Sn(IV) porphyrin chemistry was undertaken. While chelated diolato complexes were invariably obtained for titanium porphyrins on treatment with 1,2-diols, the reaction of vicinal diols with tin porphyrins gave a number of products, including mono-, bis-alkoxo, and chelating diolato complexes

  8. Mathematics and complex systems.

    PubMed

    Foote, Richard

    2007-10-19

    Contemporary researchers strive to understand complex physical phenomena that involve many constituents, may be influenced by numerous forces, and may exhibit unexpected or emergent behavior. Often such "complex systems" are macroscopic manifestations of other systems that exhibit their own complex behavior and obey more elemental laws. This article proposes that areas of mathematics, even ones based on simple axiomatic foundations, have discernible layers, entirely unexpected "macroscopic" outcomes, and both mathematical and physical ramifications profoundly beyond their historical beginnings. In a larger sense, the study of mathematics itself, which is increasingly surpassing the capacity of researchers to verify "by hand," may be the ultimate complex system.

  9. Visual complexity: a review.

    PubMed

    Donderi, Don C

    2006-01-01

    The idea of visual complexity, the history of its measurement, and its implications for behavior are reviewed, starting with structuralism and Gestalt psychology at the beginning of the 20th century and ending with visual complexity theory, perceptual learning theory, and neural circuit theory at the beginning of the 21st. Evidence is drawn from research on single forms, form and texture arrays and visual displays. Form complexity and form probability are shown to be linked through their reciprocal relationship in complexity theory, which is in turn shown to be consistent with recent developments in perceptual learning and neural circuit theory. Directions for further research are suggested.

  10. Hydridomethyl iridium complex

    DOEpatents

    Bergman, Robert G.; Buchanan, J. Michael; Stryker, Jeffrey M.; Wax, Michael J.

    1989-01-01

    A process for functionalizing methane comprising: (a) reacting methane with a hydridoalkyl metal complex of the formula: CpIr[P(R.sub.1).sub.3 ]H(R.sub.2) wherein Cp represents a cyclopentadienyl or alkylcyclopentadienyl radical having from 1 to 5 carbon atoms; Ir represents an iridium atom; P represents a phosphorus atom; R.sub.1 represents an alkyl group; R.sub.2 represents an alkyl group having at least two carbon atoms; and H represents a hydrogen atom, in the presence of a liquid alkane R.sub.3 H having at least three carbon atoms to form a hydridomethyl complex of the formula: CpIr[P(R.sub.1).sub.3 ]HMe where Me represents a methyl radical. (b) reacting said hydridomethyl complex with an organic halogenating agent such as a tetrahalomethane or a haloform of the formulas: CX'X"X'"X"" or CHX'X"X'"; wherein X', X", X"', and X"" represent halogens selected from bromine, iodine and chlorine, to halomethyl complex of step (a) having the formula: CpIr[P(R.sub.1).sub.3 ]MeX: (c) reacting said halomethyl complex with a mercuric halide of the formula HgX.sub.2 to form a methyl mercuric halide of the formula HgMeX; and (d) reacting said methyl mercuric halide with a molecular halogen of the formula X.sub.2 to form methyl halide.

  11. Predicting Physical Interactions between Protein Complexes*

    PubMed Central

    Clancy, Trevor; Rødland, Einar Andreas; Nygard, Ståle; Hovig, Eivind

    2013-01-01

    Protein complexes enact most biochemical functions in the cell. Dynamic interactions between protein complexes are frequent in many cellular processes. As they are often of a transient nature, they may be difficult to detect using current genome-wide screens. Here, we describe a method to computationally predict physical interactions between protein complexes, applied to both humans and yeast. We integrated manually curated protein complexes and physical protein interaction networks, and we designed a statistical method to identify pairs of protein complexes where the number of protein interactions between a complex pair is due to an actual physical interaction between the complexes. An evaluation against manually curated physical complex-complex interactions in yeast revealed that 50% of these interactions could be predicted in this manner. A community network analysis of the highest scoring pairs revealed a biologically sensible organization of physical complex-complex interactions in the cell. Such analyses of proteomes may serve as a guide to the discovery of novel functional cellular relationships. PMID:23438732

  12. Operational Shock Complexity Theory

    DTIC Science & Technology

    2005-05-26

    Theory : Recommendations For The National Strategy To Defeat Terrorism.” Student Issue Paper, Center for Strategic Leadership , US Army War College, July...Lens of Complexity Theory : Recommendations For The National Strategy To Defeat Terrorism.” (Student Issue Paper, Center for Strategic Leadership , US... Leadership Complexity theory affects the training of leaders. With the enemy system able to develop its complexity either through interaction with US

  13. Adaptive control for a class of nonlinear complex dynamical systems with uncertain complex parameters and perturbations.

    PubMed

    Liu, Jian; Liu, Kexin; Liu, Shutang

    2017-01-01

    In this paper, adaptive control is extended from real space to complex space, resulting in a new control scheme for a class of n-dimensional time-dependent strict-feedback complex-variable chaotic (hyperchaotic) systems (CVCSs) in the presence of uncertain complex parameters and perturbations, which has not been previously reported in the literature. In detail, we have developed a unified framework for designing the adaptive complex scalar controller to ensure this type of CVCSs asymptotically stable and for selecting complex update laws to estimate unknown complex parameters. In particular, combining Lyapunov functions dependent on complex-valued vectors and back-stepping technique, sufficient criteria on stabilization of CVCSs are derived in the sense of Wirtinger calculus in complex space. Finally, numerical simulation is presented to validate our theoretical results.

  14. Adaptive control for a class of nonlinear complex dynamical systems with uncertain complex parameters and perturbations

    PubMed Central

    Liu, Jian; Liu, Kexin; Liu, Shutang

    2017-01-01

    In this paper, adaptive control is extended from real space to complex space, resulting in a new control scheme for a class of n-dimensional time-dependent strict-feedback complex-variable chaotic (hyperchaotic) systems (CVCSs) in the presence of uncertain complex parameters and perturbations, which has not been previously reported in the literature. In detail, we have developed a unified framework for designing the adaptive complex scalar controller to ensure this type of CVCSs asymptotically stable and for selecting complex update laws to estimate unknown complex parameters. In particular, combining Lyapunov functions dependent on complex-valued vectors and back-stepping technique, sufficient criteria on stabilization of CVCSs are derived in the sense of Wirtinger calculus in complex space. Finally, numerical simulation is presented to validate our theoretical results. PMID:28467431

  15. Quantifying Complexity in Quantum Phase Transitions via Mutual Information Complex Networks

    NASA Astrophysics Data System (ADS)

    Valdez, Marc Andrew; Jaschke, Daniel; Vargas, David L.; Carr, Lincoln D.

    2017-12-01

    We quantify the emergent complexity of quantum states near quantum critical points on regular 1D lattices, via complex network measures based on quantum mutual information as the adjacency matrix, in direct analogy to quantifying the complexity of electroencephalogram or functional magnetic resonance imaging measurements of the brain. Using matrix product state methods, we show that network density, clustering, disparity, and Pearson's correlation obtain the critical point for both quantum Ising and Bose-Hubbard models to a high degree of accuracy in finite-size scaling for three classes of quantum phase transitions, Z2, mean field superfluid to Mott insulator, and a Berzinskii-Kosterlitz-Thouless crossover.

  16. Describing the complexity of systems: multivariable "set complexity" and the information basis of systems biology.

    PubMed

    Galas, David J; Sakhanenko, Nikita A; Skupin, Alexander; Ignac, Tomasz

    2014-02-01

    Context dependence is central to the description of complexity. Keying on the pairwise definition of "set complexity," we use an information theory approach to formulate general measures of systems complexity. We examine the properties of multivariable dependency starting with the concept of interaction information. We then present a new measure for unbiased detection of multivariable dependency, "differential interaction information." This quantity for two variables reduces to the pairwise "set complexity" previously proposed as a context-dependent measure of information in biological systems. We generalize it here to an arbitrary number of variables. Critical limiting properties of the "differential interaction information" are key to the generalization. This measure extends previous ideas about biological information and provides a more sophisticated basis for the study of complexity. The properties of "differential interaction information" also suggest new approaches to data analysis. Given a data set of system measurements, differential interaction information can provide a measure of collective dependence, which can be represented in hypergraphs describing complex system interaction patterns. We investigate this kind of analysis using simulated data sets. The conjoining of a generalized set complexity measure, multivariable dependency analysis, and hypergraphs is our central result. While our focus is on complex biological systems, our results are applicable to any complex system.

  17. Salen complexes with dianionic counterions

    DOEpatents

    Job, Gabriel E.; Farmer, Jay J.; Cherian, Anna E.

    2016-08-02

    The present invention describes metal salen complexes having dianionic counterions. Such complexes can be readily precipitated and provide an economical method for the purification and isolation of the complexes, and are useful to prepare novel polymer compositions.

  18. Restricted Complexity Framework for Nonlinear Adaptive Control in Complex Systems

    NASA Astrophysics Data System (ADS)

    Williams, Rube B.

    2004-02-01

    Control law adaptation that includes implicit or explicit adaptive state estimation, can be a fundamental underpinning for the success of intelligent control in complex systems, particularly during subsystem failures, where vital system states and parameters can be impractical or impossible to measure directly. A practical algorithm is proposed for adaptive state filtering and control in nonlinear dynamic systems when the state equations are unknown or are too complex to model analytically. The state equations and inverse plant model are approximated by using neural networks. A framework for a neural network based nonlinear dynamic inversion control law is proposed, as an extrapolation of prior developed restricted complexity methodology used to formulate the adaptive state filter. Examples of adaptive filter performance are presented for an SSME simulation with high pressure turbine failure to support extrapolations to adaptive control problems.

  19. Offdiagonal complexity: A computationally quick complexity measure for graphs and networks

    NASA Astrophysics Data System (ADS)

    Claussen, Jens Christian

    2007-02-01

    A vast variety of biological, social, and economical networks shows topologies drastically differing from random graphs; yet the quantitative characterization remains unsatisfactory from a conceptual point of view. Motivated from the discussion of small scale-free networks, a biased link distribution entropy is defined, which takes an extremum for a power-law distribution. This approach is extended to the node-node link cross-distribution, whose nondiagonal elements characterize the graph structure beyond link distribution, cluster coefficient and average path length. From here a simple (and computationally cheap) complexity measure can be defined. This offdiagonal complexity (OdC) is proposed as a novel measure to characterize the complexity of an undirected graph, or network. While both for regular lattices and fully connected networks OdC is zero, it takes a moderately low value for a random graph and shows high values for apparently complex structures as scale-free networks and hierarchical trees. The OdC approach is applied to the Helicobacter pylori protein interaction network and randomly rewired surrogates.

  20. SCAR/WAVE: A complex issue.

    PubMed

    Davidson, Andrew J; Insall, Robert H

    2013-11-01

    The SCAR/WAVE complex drives the actin polymerisation that underlies protrusion of the front of the cell and thus drives migration. However, it is not understood how the activity of SCAR/WAVE is regulated to generate the infinite range of cellular shape changes observed during cell motility. What are the relative roles of the subunits of the SCAR/WAVE complex? What signaling molecules do they interact with? And how does the complex integrate all this information in order to control the temporal and spatial polymerisation of actin during protrusion formation? Unfortunately, the interdependence of SCAR complex members has made genetic dissection hard. In our recent paper,(1) we describe stabilization of the Dictyostelium SCAR complex by a small fragment of Abi. Here we summarize the main findings and discuss how this approach can help reveal the inner workings of this impenetrable complex.

  1. Complexation-assisted reduction: complexes of glutaroimide-dioxime with tetravalent actinides (Np( iv ) and Th( iv ))

    DOE PAGES

    Zhang, Zhicheng; Parker, Bernard F.; Lohrey, Trevor D.; ...

    2018-01-01

    Glutaroimide-dioxime forms strong complexes with Np( iv ) and Th( iv ) in aqueous solution and in crystals. The formation of Np( iv ) complexes from initial Np( v ) is interpreted by a complexation-assisted reduction mechanism.

  2. Complexation-assisted reduction: complexes of glutaroimide-dioxime with tetravalent actinides (Np( iv ) and Th( iv ))

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Zhicheng; Parker, Bernard F.; Lohrey, Trevor D.

    Glutaroimide-dioxime forms strong complexes with Np( iv ) and Th( iv ) in aqueous solution and in crystals. The formation of Np( iv ) complexes from initial Np( v ) is interpreted by a complexation-assisted reduction mechanism.

  3. Complex adaptive systems: concept analysis.

    PubMed

    Holden, Lela M

    2005-12-01

    The aim of this paper is to explicate the concept of complex adaptive systems through an analysis that provides a description, antecedents, consequences, and a model case from the nursing and health care literature. Life is more than atoms and molecules--it is patterns of organization. Complexity science is the latest generation of systems thinking that investigates patterns and has emerged from the exploration of the subatomic world and quantum physics. A key component of complexity science is the concept of complex adaptive systems, and active research is found in many disciplines--from biology to economics to health care. However, the research and literature related to these appealing topics have generated confusion. A thorough explication of complex adaptive systems is needed. A modified application of the methods recommended by Walker and Avant for concept analysis was used. A complex adaptive system is a collection of individual agents with freedom to act in ways that are not always totally predictable and whose actions are interconnected. Examples include a colony of termites, the financial market, and a surgical team. It is often referred to as chaos theory, but the two are not the same. Chaos theory is actually a subset of complexity science. Complexity science offers a powerful new approach--beyond merely looking at clinical processes and the skills of healthcare professionals. The use of complex adaptive systems as a framework is increasing for a wide range of scientific applications, including nursing and healthcare management research. When nursing and other healthcare managers focus on increasing connections, diversity, and interactions they increase information flow and promote creative adaptation referred to as self-organization. Complexity science builds on the rich tradition in nursing that views patients and nursing care from a systems perspective.

  4. Humic acid protein complexation

    NASA Astrophysics Data System (ADS)

    Tan, W. F.; Koopal, L. K.; Weng, L. P.; van Riemsdijk, W. H.; Norde, W.

    2008-04-01

    Interactions of purified Aldrich humic acid (PAHA) with lysozyme (LSZ) are investigated. In solution LSZ is moderately positively and PAHA negatively charged at the investigated pH values. The proton binding of PAHA and of LSZ is determined by potentiometric proton titrations at various KCl concentrations. It is also measured for two mixtures of PAHA-LSZ and compared with theoretically calculated proton binding assuming no mutual interaction. The charge adaptation due to PAHA-LSZ interaction is relatively small and only significant at low and high pH. Next to the proton binding, the mass ratio PAHA/LSZ at the iso-electric point (IEP) of the complex at given solution conditions is measured together with the pH using the Mütek particle charge detector. From the pH changes the charge adaptation due to the interaction can be found. Also these measurements show that the net charge adaptation is weak for PAHA-LSZ complexes at their IEP. PAHA/LSZ mass ratios in the complexes at the IEP are measured at pH 5 and 7. At pH 5 and 50 mmol/L KCl the charge of the complex is compensated for 30-40% by K +; at pH 7, where LSZ has a rather low positive charge, this is 45-55%. At pH 5 and 5 mmol/L KCl the PAHA/LSZ mass ratio at the IEP of the complex depends on the order of addition. When LSZ is added to PAHA about 25% K + is included in the complex, but no K + is incorporated when PAHA is added to LSZ. The flocculation behavior of the complexes is also different. After LSZ addition to PAHA slow precipitation occurs (6-24 h) in the IEP, but after addition of PAHA to LSZ no precipitation can be seen after 12 h. Clearly, PAHA/LSZ complexation and the colloidal stability of PAHA-LSZ aggregates depend on the order of addition. Some implications of the observed behavior are discussed.

  5. Doxorubicin Lipid Complex Injection

    MedlinePlus

    ... has not improved or that has worsened after treatment with other medications. Doxorubicin lipid complex is also ... has not improved or that has worsened after treatment with other medications. Doxorubicin lipid complex is also ...

  6. Clearance and organ localization of particles and soluble complexes in mice with circulating complexes.

    PubMed Central

    Carter, S D; Brennan, F M; Grace, S A; Elson, C J

    1984-01-01

    The clearance and organ localization of a number of substances cleared by either Fc-dependent or -independent mechanisms was studied in normal mice and in mice with endogenously produced persistent circulating complexes. Clearance of covalent dimers of mouse IgG, chicken IgG and ovalbumin were no different between the two groups of mice. By contrast, hepatic and splenic uptake of dimeric mouse IgG (but not of chicken IgG or ovalbumin dimer) was impaired in the mice with persisting complexes. Surprisingly the rate of clearance of sheep red blood cells (SRBC) was increased in mice with persisting complexes as was hepatic uptake of polyvinyl pyrrolidone. It is suggested that the mononuclear phagocytes of mice with persistent circulating complexes are non-specifically stimulated while their ability to take up soluble complexes by Fc-dependent attachment is selectively impaired. PMID:6746002

  7. Internal complexity and environmental sensitivity in hospitals.

    PubMed

    Ashmos, D P; Duchon, D; Hauge, F E; McDaniel, R R

    1996-01-01

    Theory suggests that organizations should respond to external complexity with internal complexity. We examine whether "environmentally sensitive" hospitals are more internally complex than "environmentally insensitive" hospitals. Results show that environmentally sensitive and insensitive hospitals differed on three of the measures of internal complexity: goal complexity, strategic complexity, and relational complexity.

  8. Engineering complex tissues.

    PubMed

    Atala, Anthony; Kasper, F Kurtis; Mikos, Antonios G

    2012-11-14

    Tissue engineering has emerged at the intersection of numerous disciplines to meet a global clinical need for technologies to promote the regeneration of functional living tissues and organs. The complexity of many tissues and organs, coupled with confounding factors that may be associated with the injury or disease underlying the need for repair, is a challenge to traditional engineering approaches. Biomaterials, cells, and other factors are needed to design these constructs, but not all tissues are created equal. Flat tissues (skin); tubular structures (urethra); hollow, nontubular, viscus organs (vagina); and complex solid organs (liver) all present unique challenges in tissue engineering. This review highlights advances in tissue engineering technologies to enable regeneration of complex tissues and organs and to discuss how such innovative, engineered tissues can affect the clinic.

  9. Identification of a small TAF complex and its role in the assembly of TAF-containing complexes.

    PubMed

    Demény, Màté A; Soutoglou, Evi; Nagy, Zita; Scheer, Elisabeth; Jànoshàzi, Agnes; Richardot, Magalie; Argentini, Manuela; Kessler, Pascal; Tora, Laszlo

    2007-03-21

    TFIID plays a role in nucleating RNA polymerase II preinitiation complex assembly on protein-coding genes. TFIID is a multisubunit complex comprised of the TATA box binding protein (TBP) and 14 TBP-associated factors (TAFs). Another class of multiprotein transcriptional regulatory complexes having histone acetyl transferase (HAT) activity, and containing TAFs, includes TFTC, STAGA and the PCAF/GCN5 complex. Looking for as yet undiscovered subunits by a proteomic approach, we had identified TAF8 and SPT7L in human TFTC preparations. Subsequently, however, we demonstrated that TAF8 was not a stable component of TFTC, but that it is present in a small TAF complex (SMAT), containing TAF8, TAF10 and SPT7L, that co-purified with TFTC. Thus, TAF8 is a subunit of both TFIID and SMAT. The latter has to be involved in a pathway of complex formation distinct from the other known TAF complexes, since these three histone fold (HF)-containing proteins (TAF8, TAF10 and SPT7L) can never be found together either in TFIID or in STAGA/TFTC HAT complexes. Here we show that TAF8 is absolutely necessary for the integration of TAF10 in a higher order TFIID core complex containing seven TAFs. TAF8 forms a heterodimer with TAF10 through its HF and proline rich domains, and also interacts with SPT7L through its C-terminal region, and the three proteins form a complex in vitro and in vivo. Thus, the TAF8-TAF10 and TAF10-SPT7L HF pairs, and also the SMAT complex, seem to be important regulators of the composition of different TFIID and/or STAGA/TFTC complexes in the nucleus and consequently may play a role in gene regulation.

  10. Complexity science and leadership in healthcare.

    PubMed

    Burns, J P

    2001-10-01

    The emerging field of complexity science offers an alternative leadership strategy for the chaotic, complex healthcare environment. A survey revealed that healthcare leaders intuitively support principles of complexity science. Leadership that uses complexity principles offers opportunities in the chaotic healthcare environment to focus less on prediction and control and more on fostering relationships and creating conditions in which complex adaptive systems can evolve to produce creative outcomes.

  11. Activated Prothrombin Complex Concentrate Versus 4-Factor Prothrombin Complex Concentrate for Vitamin K-Antagonist Reversal.

    PubMed

    Rowe, A Shaun; Dietrich, Scott K; Phillips, John W; Foster, Kaci E; Canter, Joshua R

    2018-06-01

    To compare the international normalized ratio normalization efficacy of activated prothrombin complex concentrates and 4-factor prothrombin complex concentrates and to evaluate the thrombotic complications in patients treated with these products for warfarin-associated hemorrhage. Retrospective, Multicenter Cohort. Large, Community, Teaching Hospital. Patients greater than 18 years old and received either activated prothrombin complex concentrate or 4-factor prothrombin complex concentrate for the treatment of warfarin-associated hemorrhage. We excluded those patients who received either agent for an indication other than warfarin-associated hemorrhage, pregnant, had a baseline international normalized ratio of less than 2, received a massive transfusion as defined by hospital protocol, received plasma for treatment of warfarin-associated hemorrhage, or were treated for an acute warfarin ingestion. Patients in the activated prothrombin complex concentrate group (enrolled from one hospital) with an international normalized ratio of less than 5 received 500 IU and those with an international normalized ratio greater than 5 received 1,000 IU. Patients in the 4-factor prothrombin complex concentrate (enrolled from a separate hospital) group received the Food and Drug Administration approved dosing algorithm. A total of 158 patients were included in the final analysis (activated prothrombin complex concentrate = 118; 4-factor prothrombin complex concentrate = 40). Those in the 4-factor prothrombin complex concentrate group had a higher pretreatment international normalized ratio (2.7 ± 1.8 vs 3.5 ± 2.9; p = 0.0164). However, the posttreatment international normalized ratio was similar between the groups. In addition, even when controlling for differences in the pretreatment international normalized ratio, there was no difference in the ability to achieve a posttreatment international normalized ratio of less than 1.4 (odds ratio, 0.753 [95% CI, 0.637-0.890]; p

  12. Complex Functions with GeoGebra

    ERIC Educational Resources Information Center

    Breda, Ana Maria D'azevedo; Dos Santos, José Manuel Dos Santos

    2016-01-01

    Complex functions, generally feature some interesting peculiarities, seen as extensions of real functions. The visualization of complex functions properties usually requires the simultaneous visualization of two-dimensional spaces. The multiple Windows of GeoGebra, combined with its ability of algebraic computation with complex numbers, allow the…

  13. Daunorubicin Lipid Complex Injection

    MedlinePlus

    Daunorubicin lipid complex is used to treat advanced Kaposi's sarcoma (a type of cancer that causes abnormal tissue to ... body) related to acquired immunodeficiency syndrome (AIDS). Daunorubicin lipid complex is in a class of medications called ...

  14. Irinotecan Lipid Complex Injection

    MedlinePlus

    Irinotecan lipid complex is used in combination with other medications to treat pancreatic cancer that has spread to other ... worsened after treatment with other chemotherapy medications. Irinotecan lipid complex is in a class of antineoplastic medications ...

  15. The Complexity Trap

    DTIC Science & Technology

    2012-01-01

    proactively and effectively to today’s international environment, prioritization is the key first step —and precisely the opposite reaction to the complacency...formidable than just endless grains of sand.”32 This is not to deny the possibility of nonlinear phenomena, butterfly effects, self-organizing systems...The first step is replac- ing the current reactive worship of complexity with proactive prioritization. To escape the complexity trap, let us dare

  16. Problematisations of Complexity: On the Notion and Production of Diverse Complexities in Healthcare Interventions and Evaluations

    PubMed Central

    Broer, Tineke; Bal, Roland; Pickersgill, Martyn

    2017-01-01

    Abstract Within the literature on the evaluation of health (policy) interventions, complexity is a much-debated issue. In particular, many claim that so-called ‘complex interventions’ pose different challenges to evaluation studies than apparently ‘simple interventions’ do. Distinct ways of doing evaluation entail particular ontologies and epistemologies of complexity. They differ in terms of whether they define complexity as a quantitative trait of interventions, whether they see evaluation as part of or outside the intervention, and whether complexity can be regarded as an emergent property of the intervention and its evaluation. In practice, evaluators and commissioners of large health care improvement programmes rely on different, sometimes contradictory, repertoires about what it means to conduct a ‘good’ evaluation. This is an ongoing matter negotiated between and among commissioners, researchers, and—sometimes—programme managers. In particular, notions of evaluability, usefulness and distance/independence are problematised in different ways and with diverse consequences, which, in turn, produce other notions and layers of complexity such as temporal, institutional and affective complexities. When (social science) researchers claim that one method or another is better able to grasp complexity, they elide the issue that any methodological choice emphasises some complexities and lets others fade into the background. Analysing the practicalities and emotions involved in evaluation studies opens up the notion of complexity to analytical scrutiny, and suggests a basis for co-theorising between biomedical, public health and social scientists (including Science and Technology Studies scholars). PMID:28515573

  17. Fluoroquinolone-Gyrase-DNA Complexes

    PubMed Central

    Mustaev, Arkady; Malik, Muhammad; Zhao, Xilin; Kurepina, Natalia; Luan, Gan; Oppegard, Lisa M.; Hiasa, Hiroshi; Marks, Kevin R.; Kerns, Robert J.; Berger, James M.; Drlica, Karl

    2014-01-01

    DNA gyrase and topoisomerase IV control bacterial DNA topology by breaking DNA, passing duplex DNA through the break, and then resealing the break. This process is subject to reversible corruption by fluoroquinolones, antibacterials that form drug-enzyme-DNA complexes in which the DNA is broken. The complexes, called cleaved complexes because of the presence of DNA breaks, have been crystallized and found to have the fluoroquinolone C-7 ring system facing the GyrB/ParE subunits. As expected from x-ray crystallography, a thiol-reactive, C-7-modified chloroacetyl derivative of ciprofloxacin (Cip-AcCl) formed cross-linked cleaved complexes with mutant GyrB-Cys466 gyrase as evidenced by resistance to reversal by both EDTA and thermal treatments. Surprisingly, cross-linking was also readily seen with complexes formed by mutant GyrA-G81C gyrase, thereby revealing a novel drug-gyrase interaction not observed in crystal structures. The cross-link between fluoroquinolone and GyrA-G81C gyrase correlated with exceptional bacteriostatic activity for Cip-AcCl with a quinolone-resistant GyrA-G81C variant of Escherichia coli and its Mycobacterium smegmatis equivalent (GyrA-G89C). Cip-AcCl-mediated, irreversible inhibition of DNA replication provided further evidence for a GyrA-drug cross-link. Collectively these data establish the existence of interactions between the fluoroquinolone C-7 ring and both GyrA and GyrB. Because the GyrA-Gly81 and GyrB-Glu466 residues are far apart (17 Å) in the crystal structure of cleaved complexes, two modes of quinolone binding must exist. The presence of two binding modes raises the possibility that multiple quinolone-enzyme-DNA complexes can form, a discovery that opens new avenues for exploring and exploiting relationships between drug structure and activity with type II DNA topoisomerases. PMID:24497635

  18. Solar chemistry of metal complexes

    NASA Astrophysics Data System (ADS)

    Gray, H. B.; Maverick, A. W.

    1981-12-01

    Electronic excited states of certain transition metal complexes undergo oxidation-reduction reactions that store chemical energy. Such reactions have been extensively explored for mononuclear complexes. Two classes of polynuclear species exhibit similar properties, and these complexes are now being studied as possible homogeneous sensitizer-catalysts for hydrogen production from aqueous solutions.

  19. Studying the HIT-Complexity Interchange.

    PubMed

    Kuziemsky, Craig E; Borycki, Elizabeth M; Kushniruk, Andre W

    2016-01-01

    The design and implementation of health information technology (HIT) is challenging, particularly when it is being introduced into complex settings. While complex adaptive system (CASs) can be a valuable means of understanding relationships between users, HIT and tasks, much of the existing work using CASs is descriptive in nature. This paper addresses that issue by integrating a model for analyzing task complexity with approaches for HIT evaluation and systems analysis. The resulting framework classifies HIT-user tasks and issues as simple, complicated or complex, and provides insight on how to study them.

  20. Definitions of Complexity are Notoriously Difficult

    NASA Astrophysics Data System (ADS)

    Schuster, Peter

    Definitions of complexity are notoriously difficult if not impossible at all. A good working hypothesis might be: Everything is complex that is not simple. This is precisely the way in which we define nonlinear behavior. Things appear complex for different reasons: i) Complexity may result from lack of insight, ii) complexity may result from lack of methods, and (iii) complexity may be inherent to the system. The best known example for i) is celestial mechanics: The highly complex Pythagorean epicycles become obsolete by the introduction of Newton's law of universal gravitation. To give an example for ii), pattern formation and deterministic chaos became not really understandable before extensive computer simulations became possible. Cellular metabolism may serve as an example for iii) and is caused by the enormous complexity of biochemical reaction networks with up to one hundred individual reaction fluxes. Nevertheless, only few fluxes are dominant in the sense that using Pareto optimal values for them provides near optimal values for all the others...

  1. The evolution of complex life.

    PubMed

    Billingham, J

    1989-01-01

    In considering the probabilities that intelligent life might exist elsewhere in the Universe, it is important to ask questions about the factors governing the emergence of complex living organisms in the context of evolutionary biology, planetary environments and events in space. Two important problems arise. First, what can be learned about the general laws governing the evolution of complex life anywhere in space by studying its history on the Earth? Second, how is the evolution of complex life affected by events in space? To address these problems, a series of Science Workshops on the Evolution of Complex Life was held at the Ames Research Center. Included in this paper are highlights of those workshops, with particular emphasis on the first question, namely the evolution of complex extraterrestrial life.

  2. Epidemic modeling in complex realities.

    PubMed

    Colizza, Vittoria; Barthélemy, Marc; Barrat, Alain; Vespignani, Alessandro

    2007-04-01

    In our global world, the increasing complexity of social relations and transport infrastructures are key factors in the spread of epidemics. In recent years, the increasing availability of computer power has enabled both to obtain reliable data allowing one to quantify the complexity of the networks on which epidemics may propagate and to envision computational tools able to tackle the analysis of such propagation phenomena. These advances have put in evidence the limits of homogeneous assumptions and simple spatial diffusion approaches, and stimulated the inclusion of complex features and heterogeneities relevant in the description of epidemic diffusion. In this paper, we review recent progresses that integrate complex systems and networks analysis with epidemic modelling and focus on the impact of the various complex features of real systems on the dynamics of epidemic spreading.

  3. On the Way to Appropriate Model Complexity

    NASA Astrophysics Data System (ADS)

    Höge, M.

    2016-12-01

    When statistical models are used to represent natural phenomena they are often too simple or too complex - this is known. But what exactly is model complexity? Among many other definitions, the complexity of a model can be conceptualized as a measure of statistical dependence between observations and parameters (Van der Linde, 2014). However, several issues remain when working with model complexity: A unique definition for model complexity is missing. Assuming a definition is accepted, how can model complexity be quantified? How can we use a quantified complexity to the better of modeling? Generally defined, "complexity is a measure of the information needed to specify the relationships between the elements of organized systems" (Bawden & Robinson, 2015). The complexity of a system changes as the knowledge about the system changes. For models this means that complexity is not a static concept: With more data or higher spatio-temporal resolution of parameters, the complexity of a model changes. There are essentially three categories into which all commonly used complexity measures can be classified: (1) An explicit representation of model complexity as "Degrees of freedom" of a model, e.g. effective number of parameters. (2) Model complexity as code length, a.k.a. "Kolmogorov complexity": The longer the shortest model code, the higher its complexity (e.g. in bits). (3) Complexity defined via information entropy of parametric or predictive uncertainty. Preliminary results show that Bayes theorem allows for incorporating all parts of the non-static concept of model complexity like data quality and quantity or parametric uncertainty. Therefore, we test how different approaches for measuring model complexity perform in comparison to a fully Bayesian model selection procedure. Ultimately, we want to find a measure that helps to assess the most appropriate model.

  4. Complexation and molecular modeling studies of europium(III)-gallic acid-amino acid complexes.

    PubMed

    Taha, Mohamed; Khan, Imran; Coutinho, João A P

    2016-04-01

    With many metal-based drugs extensively used today in the treatment of cancer, attention has focused on the development of new coordination compounds with antitumor activity with europium(III) complexes recently introduced as novel anticancer drugs. The aim of this work is to design new Eu(III) complexes with gallic acid, an antioxida'nt phenolic compound. Gallic acid was chosen because it shows anticancer activity without harming health cells. As antioxidant, it helps to protect human cells against oxidative damage that implicated in DNA damage, cancer, and accelerated cell aging. In this work, the formation of binary and ternary complexes of Eu(III) with gallic acid, primary ligand, and amino acids alanine, leucine, isoleucine, and tryptophan was studied by glass electrode potentiometry in aqueous solution containing 0.1M NaNO3 at (298.2 ± 0.1) K. Their overall stability constants were evaluated and the concentration distributions of the complex species in solution were calculated. The protonation constants of gallic acid and amino acids were also determined at our experimental conditions and compared with those predicted by using conductor-like screening model for realistic solvation (COSMO-RS) model. The geometries of Eu(III)-gallic acid complexes were characterized by the density functional theory (DFT). The spectroscopic UV-visible and photoluminescence measurements are carried out to confirm the formation of Eu(III)-gallic acid complexes in aqueous solutions. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Complexity in language learning and treatment.

    PubMed

    Thompson, Cynthia K

    2007-02-01

    To introduce a Clinical Forum focused on the Complexity Account of Treatment Efficacy (C. K. Thompson, L. P. Shapiro, S. Kiran, & J. Sobecks, 2003), a counterintuitive but effective approach for treating language disorders. This approach espouses training complex structures to promote generalized improvement of simpler, linguistically related structures. Three articles are included, addressing complexity in treatment of phonology, lexical-semantics, and syntax. Complexity hierarchies based on models of normal language representation and processing are discussed in each language domain. In addition, each article presents single-subject controlled experimental studies examining the complexity effect. By counterbalancing treatment of complex and simple structures across participants, acquisition and generalization patterns are examined as they emerge. In all language domains, cascading generalization occurs from more to less complex structures; however, the opposite pattern is rarely seen. The results are robust, with replication within and across participants. The construct of complexity appears to be a general principle that is relevant to treating a range of language disorders in both children and adults. While challenging the long-standing clinical notion that treatment should begin with simple structures, mounting evidence points toward the facilitative effects of using more complex structures as a starting point for treatment.

  6. Neurosurgical implications of Carney complex.

    PubMed

    Watson, J C; Stratakis, C A; Bryant-Greenwood, P K; Koch, C A; Kirschner, L S; Nguyen, T; Carney, J A; Oldfield, E H

    2000-03-01

    The authors present their neurosurgical experience with Carney complex. Carney complex, characterized by spotty skin pigmentation, cardiac myxomas, primary pigmented nodular adrenocortical disease, pituitary tumors, and nerve sheath tumors (NSTs), is a recently described, rare, autosomal-dominant familial syndrome that is relatively unknown to neurosurgeons. Neurosurgery is required to treat pituitary adenomas and a rare NST, the psammomatous melanotic schwannoma (PMS), in patients with Carney complex. Cushing's syndrome, a common component of the complex, is caused by primary pigmented nodular adrenocortical disease and is not secondary to an adrenocorticotropic hormone-secreting pituitary adenoma. The authors reviewed 14 cases of Carney complex, five from the literature and nine from their own experience. Of the 14 pituitary adenomas recognized in association with Carney complex, 12 developed growth hormone (GH) hypersecretion (producing gigantism in two patients and acromegaly in 10), and results of immunohistochemical studies in one of the other two were positive for GH. The association of PMSs with Carney complex was established in 1990. Of the reported tumors, 28% were associated with spinal nerve sheaths. The spinal tumors occurred in adults (mean age 32 years, range 18-49 years) who presented with pain and radiculopathy. These NSTs may be malignant (10%) and, as with the cardiac myxomas, are associated with significant rates of morbidity and mortality. Because of the surgical comorbidity associated with cardiac myxoma and/or Cushing's syndrome, recognition of Carney complex has important implications for perisurgical patient management and family screening. Study of the genetics of Carney complex and of the biological abnormalities associated with the tumors may provide insight into the general pathobiological abnormalities associated with the tumors may provide insight into the general pathobiological features of pituitary adenomas and NSTs.

  7. Architecture of the pontin/reptin complex, essential in the assembly of several macromolecular complexes

    PubMed Central

    Torreira, Eva; Jha, Sudhakar; López-Blanco, José R.; Arias-Palomo, Ernesto; Chacón, Pablo; Cañas, Cristina; Ayora, Sylvia; Dutta, Anindya; Llorca, Oscar

    2008-01-01

    Summary Pontin and reptin belong to the AAA+ family and they are essential for the structural integrity and catalytic activity of several chromatin remodeling complexes. They are also indispensable for the assembly of several ribonucleoprotein complexes, including telomerase. Here, we propose a structural model of the yeast pontin/reptin complex based on a cryo-electron microscopy reconstruction at 13 Å. Pontin/reptin hetero-dodecamers were purified from in vivo assembled complexes forming a double ring. Two rings interact through flexible domains projecting from each hexamer, constituting an atypical asymmetric form of oligomerization. These flexible domains and the AAA+ cores reveal significant conformational changes when compared to the crystal structure of human pontin that generate enlarged channels. This structure of endogenously assembled pontin/reptin complexes is different to previously described structures, suggesting that pontin and reptin could acquire distinct structural states to regulate their broad functions as molecular motors and scaffolds for nucleic acids and proteins. PMID:18940606

  8. Methods for protein complex prediction and their contributions towards understanding the organisation, function and dynamics of complexes.

    PubMed

    Srihari, Sriganesh; Yong, Chern Han; Patil, Ashwini; Wong, Limsoon

    2015-09-14

    Complexes of physically interacting proteins constitute fundamental functional units responsible for driving biological processes within cells. A faithful reconstruction of the entire set of complexes is therefore essential to understand the functional organisation of cells. In this review, we discuss the key contributions of computational methods developed till date (approximately between 2003 and 2015) for identifying complexes from the network of interacting proteins (PPI network). We evaluate in depth the performance of these methods on PPI datasets from yeast, and highlight their limitations and challenges, in particular at detecting sparse and small or sub-complexes and discerning overlapping complexes. We describe methods for integrating diverse information including expression profiles and 3D structures of proteins with PPI networks to understand the dynamics of complex formation, for instance, of time-based assembly of complex subunits and formation of fuzzy complexes from intrinsically disordered proteins. Finally, we discuss methods for identifying dysfunctional complexes in human diseases, an application that is proving invaluable to understand disease mechanisms and to discover novel therapeutic targets. We hope this review aptly commemorates a decade of research on computational prediction of complexes and constitutes a valuable reference for further advancements in this exciting area. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  9. COMPLEXITY IN ECOLOGICAL SYSTEMS

    EPA Science Inventory

    The enormous complexity of ecosystems is generally obvious under even the most cursory examination. In the modern world, this complexity is further augmented by the linkage of ecosystems to economic and social systems through the human use of the environment for technological pu...

  10. Complex Regional Pain Syndrome

    MedlinePlus

    ... Other major and minor traumas — such as surgery, heart attacks, infections and even sprained ankles — can also lead to complex regional pain syndrome. It's not well-understood why these injuries can trigger complex regional pain syndrome. Not everyone who has ...

  11. Effects of Task Complexity on the Fluency and Lexical Complexity in EFL Students' Argumentative Writing

    ERIC Educational Resources Information Center

    Ong, Justina; Zhang, Lawrence Jun

    2010-01-01

    Based on Robinson's (2001a,b, 2003) Cognition Hypothesis and Skehan's (1998) Limited Attentional Capacity Model, this study explored the effects of task complexity on the fluency and lexical complexity of 108 EFL students' argumentative writing. Task complexity was manipulated using three factors: (1) availability of planning time; (2) provision…

  12. A novel method for identifying disease associated protein complexes based on functional similarity protein complex networks.

    PubMed

    Le, Duc-Hau

    2015-01-01

    Protein complexes formed by non-covalent interaction among proteins play important roles in cellular functions. Computational and purification methods have been used to identify many protein complexes and their cellular functions. However, their roles in terms of causing disease have not been well discovered yet. There exist only a few studies for the identification of disease-associated protein complexes. However, they mostly utilize complicated heterogeneous networks which are constructed based on an out-of-date database of phenotype similarity network collected from literature. In addition, they only apply for diseases for which tissue-specific data exist. In this study, we propose a method to identify novel disease-protein complex associations. First, we introduce a framework to construct functional similarity protein complex networks where two protein complexes are functionally connected by either shared protein elements, shared annotating GO terms or based on protein interactions between elements in each protein complex. Second, we propose a simple but effective neighborhood-based algorithm, which yields a local similarity measure, to rank disease candidate protein complexes. Comparing the predictive performance of our proposed algorithm with that of two state-of-the-art network propagation algorithms including one we used in our previous study, we found that it performed statistically significantly better than that of these two algorithms for all the constructed functional similarity protein complex networks. In addition, it ran about 32 times faster than these two algorithms. Moreover, our proposed method always achieved high performance in terms of AUC values irrespective of the ways to construct the functional similarity protein complex networks and the used algorithms. The performance of our method was also higher than that reported in some existing methods which were based on complicated heterogeneous networks. Finally, we also tested our method with

  13. Information geometric methods for complexity

    NASA Astrophysics Data System (ADS)

    Felice, Domenico; Cafaro, Carlo; Mancini, Stefano

    2018-03-01

    Research on the use of information geometry (IG) in modern physics has witnessed significant advances recently. In this review article, we report on the utilization of IG methods to define measures of complexity in both classical and, whenever available, quantum physical settings. A paradigmatic example of a dramatic change in complexity is given by phase transitions (PTs). Hence, we review both global and local aspects of PTs described in terms of the scalar curvature of the parameter manifold and the components of the metric tensor, respectively. We also report on the behavior of geodesic paths on the parameter manifold used to gain insight into the dynamics of PTs. Going further, we survey measures of complexity arising in the geometric framework. In particular, we quantify complexity of networks in terms of the Riemannian volume of the parameter space of a statistical manifold associated with a given network. We are also concerned with complexity measures that account for the interactions of a given number of parts of a system that cannot be described in terms of a smaller number of parts of the system. Finally, we investigate complexity measures of entropic motion on curved statistical manifolds that arise from a probabilistic description of physical systems in the presence of limited information. The Kullback-Leibler divergence, the distance to an exponential family and volumes of curved parameter manifolds, are examples of essential IG notions exploited in our discussion of complexity. We conclude by discussing strengths, limits, and possible future applications of IG methods to the physics of complexity.

  14. On Reinventing Education in the Age of Complexity: A Vygotsky-­Inspired Generative Complexity Approach

    ERIC Educational Resources Information Center

    Jörg, Ton

    2017-01-01

    Reinventing education is the ultimate aim of this contribution. The approach taken is a radical new complexity-inspired bottom-up approach which shows complexity as the fount of creativity and innovation. Organizing complexity accordingly may be the foundation for a new complexified vision of education. It all starts with new thinking in…

  15. Influence of Hydrophobicity on Polyelectrolyte Complexation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao

    Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low-viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials, their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture, it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) withmore » methyl, ethyl, and propyl substituents—thereby increasing the hydrophobicity with increasing side chain length—and complexing them with a common anionic polyelectrolyte, poly(styrenesulfonate). The mechanical behavior of these complexes is compared to the more hydrophilic system of poly(styrenesulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling–modulus master curves that are quantified in this work. Furthermore, the rheological behaviors of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

  16. Influence of Hydrophobicity on Polyelectrolyte Complexation

    DOE PAGES

    Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao; ...

    2017-11-16

    Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low-viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials, their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture, it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) withmore » methyl, ethyl, and propyl substituents—thereby increasing the hydrophobicity with increasing side chain length—and complexing them with a common anionic polyelectrolyte, poly(styrenesulfonate). The mechanical behavior of these complexes is compared to the more hydrophilic system of poly(styrenesulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling–modulus master curves that are quantified in this work. Furthermore, the rheological behaviors of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

  17. Complexity leadership: a healthcare imperative.

    PubMed

    Weberg, Dan

    2012-01-01

    The healthcare system is plagued with increasing cost and poor quality outcomes. A major contributing factor for these issues is that outdated leadership practices, such as leader-centricity, linear thinking, and poor readiness for innovation, are being used in healthcare organizations. Complexity leadership theory provides a new framework with which healthcare leaders may practice leadership. Complexity leadership theory conceptualizes leadership as a continual process that stems from collaboration, complex systems thinking, and innovation mindsets. Compared to transactional and transformational leadership concepts, complexity leadership practices hold promise to improve cost and quality in health care. © 2012 Wiley Periodicals, Inc.

  18. Turbulent complex (dusty) plasma

    NASA Astrophysics Data System (ADS)

    Zhdanov, Sergey; Schwabe, Mierk

    2017-04-01

    As a paradigm of complex system dynamics, solid particles immersed into a weakly ionized plasma, so called complex (dusty) plasmas, were (and continue to be) a subject of many detailed studies. Special types of dynamical activity have been registered, in particular, spontaneous pairing, entanglement and cooperative action of a great number of particles resulting in formation of vortices, self-propelling, tunneling, and turbulent movements. In the size domain of 1-10 mkm normally used in experiments with complex plasmas, the characteristic dynamic time-scale is of the order of 0.01-0.1 s, and these particles can be visualized individually in real time, providing an atomistic (kinetic) level of investigations. The low-R turbulent flow induced either by the instability in a complex plasma cloud or formed behind a projectile passing through the cloud is a typical scenario. Our simulations showed formation of a fully developed system of vortices and demonstrated that the velocity structure functions scale very close to the theoretical predictions. As an important element of self-organization, cooperative and turbulent particle motions are present in many physical, astrophysical, and biological systems. Therefore, experiments with turbulent wakes and turbulent complex plasma oscillations are a promising mean to observe and study in detail the anomalous transport on the level of individual particles.

  19. Improved color stability of white organic light-emitting diodes without interlayer between red, orange and blue emission layers

    NASA Astrophysics Data System (ADS)

    Xue, Kaiwen; Chen, Ping; Duan, Yu; Sheng, Ren; Han, Guangguang; Zhao, Yi

    2016-03-01

    We demonstrated color stability improved white phosphorescent organic light-emitting diodes (WOLEDs) based on red, orange and blue emission layers. Iridium(III) Bis(3,5-diflouro)-2-(2-pyridyl)phenyl-(2-carboxypyridyl) was doped into red emission layer (R-EML) and orange emission layer (O-EML) to lower the electrons injection barrier and facilitate the ambipolar charge carriers balance. Consequently, the recombination region was extended to the R-EML and O-EML, leading to the excellently stable spectra and the reduction of triplet-triplet annihilation. Then the resulting device with a negligible Commission International de L'Eclairage coordinates shift of (0.003, 0.007) within a wide luminance range as well as a high color rendering index of 90 was gained, which was comparable to the profit caused by the conventional method of introducing the interlayer. And the emission mechanism of the WOLEDs was also discussed.

  20. Complexation of buffer constituents with neutral complexation agents: part I. Impact on common buffer properties.

    PubMed

    Riesová, Martina; Svobodová, Jana; Tošner, Zdeněk; Beneš, Martin; Tesařová, Eva; Gaš, Bohuslav

    2013-09-17

    The complexation of buffer constituents with the complexation agent present in the solution can very significantly influence the buffer properties, such as pH, ionic strength, or conductivity. These parameters are often crucial for selection of the separation conditions in capillary electrophoresis or high-pressure liquid chromatography (HPLC) and can significantly affect results of separation, particularly for capillary electrophoresis as shown in Part II of this paper series (Beneš, M.; Riesová, M.; Svobodová, J.; Tesařová, E.; Dubský, P.; Gaš, B. Anal. Chem. 2013, DOI: 10.1021/ac401381d). In this paper, the impact of complexation of buffer constituents with a neutral complexation agent is demonstrated theoretically as well as experimentally for the model buffer system composed of benzoic acid/LiOH or common buffers (e.g., CHES/LiOH, TAPS/LiOH, Tricine/LiOH, MOPS/LiOH, MES/LiOH, and acetic acid/LiOH). Cyclodextrins as common chiral selectors were used as model complexation agents. We were not only able to demonstrate substantial changes of pH but also to predict the general complexation characteristics of selected compounds. Because of the zwitterion character of the common buffer constituents, their charged forms complex stronger with cyclodextrins than the neutral ones do. This was fully proven by NMR measurements. Additionally complexation constants of both forms of selected compounds were determined by NMR and affinity capillary electrophoresis with a very good agreement of obtained values. These data were advantageously used for the theoretical descriptions of variations in pH, depending on the composition and concentration of the buffer. Theoretical predictions were shown to be a useful tool for deriving some general rules and laws for complexing systems.

  1. Being pragmatic about healthcare complexity: our experiences applying complexity theory and pragmatism to health services research.

    PubMed

    Long, Katrina M; McDermott, Fiona; Meadows, Graham N

    2018-06-20

    The healthcare system has proved a challenging environment for innovation, especially in the area of health services management and research. This is often attributed to the complexity of the healthcare sector, characterized by intersecting biological, social and political systems spread across geographically disparate areas. To help make sense of this complexity, researchers are turning towards new methods and frameworks, including simulation modeling and complexity theory. Herein, we describe our experiences implementing and evaluating a health services innovation in the form of simulation modeling. We explore the strengths and limitations of complexity theory in evaluating health service interventions, using our experiences as examples. We then argue for the potential of pragmatism as an epistemic foundation for the methodological pluralism currently found in complexity research. We discuss the similarities between complexity theory and pragmatism, and close by revisiting our experiences putting pragmatic complexity theory into practice. We found the commonalities between pragmatism and complexity theory to be striking. These included a sensitivity to research context, a focus on applied research, and the valuing of different forms of knowledge. We found that, in practice, a pragmatic complexity theory approach provided more flexibility to respond to the rapidly changing context of health services implementation and evaluation. However, this approach requires a redefinition of implementation success, away from pre-determined outcomes and process fidelity, to one that embraces the continual learning, evolution, and emergence that characterized our project.

  2. Human Ska complex and Ndc80 complex interact to form a load-bearing assembly that strengthens kinetochore–microtubule attachments

    PubMed Central

    Zelter, Alex; Riffle, Michael; MacCoss, Michael J.; Asbury, Charles L.; Davis, Trisha N.

    2018-01-01

    Accurate segregation of chromosomes relies on the force-bearing capabilities of the kinetochore to robustly attach chromosomes to dynamic microtubule tips. The human Ska complex and Ndc80 complex are outer-kinetochore components that bind microtubules and are required to fully stabilize kinetochore–microtubule attachments in vivo. While purified Ska complex tracks with disassembling microtubule tips, it remains unclear whether the Ska complex–microtubule interaction is sufficiently strong to make a significant contribution to kinetochore–microtubule coupling. Alternatively, Ska complex might affect kinetochore coupling indirectly, through recruitment of phosphoregulatory factors. Using optical tweezers, we show that the Ska complex itself bears load on microtubule tips, strengthens Ndc80 complex-based tip attachments, and increases the switching dynamics of the attached microtubule tips. Cross-linking mass spectrometry suggests the Ska complex directly binds Ndc80 complex through interactions between the Ska3 unstructured C-terminal region and the coiled-coil regions of each Ndc80 complex subunit. Deletion of the Ska complex microtubule-binding domain or the Ska3 C terminus prevents Ska complex from strengthening Ndc80 complex-based attachments. Together, our results indicate that the Ska complex can directly strengthen the kinetochore–microtubule interface and regulate microtubule tip dynamics by forming an additional connection between the Ndc80 complex and the microtubule. PMID:29487209

  3. Performance Improvement Assuming Complexity

    ERIC Educational Resources Information Center

    Rowland, Gordon

    2007-01-01

    Individual performers, work teams, and organizations may be considered complex adaptive systems, while most current human performance technologies appear to assume simple determinism. This article explores the apparent mismatch and speculates on future efforts to enhance performance if complexity rather than simplicity is assumed. Included are…

  4. U1A Complex

    ScienceCinema

    None

    2018-01-16

    Some of the most sophisticated experiments in the stockpile stewardship program are conducted in an environmentally safe manner, nearly 1000 feet below the ground at the site. The U1a complex a sprawling underground laboratory and tunnel complex is home to a number of unique capabilities.

  5. Computational Study of Pincer Iridium Catalytic Systems: C-H, N-H, and C-C Bond Activation and C-C Coupling Reactions

    NASA Astrophysics Data System (ADS)

    Zhou, Tian

    Computational chemistry has achieved vast progress in the last decades in the field, which was considered to be only experimental before. DFT (density functional theory) calculations have been proven to be able to be applied to large systems, while maintaining high accuracy. One of the most important achievements of DFT calculations is in exploring the mechanism of bond activation reactions catalyzed by organometallic complexes. In this dissertation, we discuss DFT studies of several catalytic systems explored in the lab of Professor Alan S. Goldman. Headlines in the work are: (1) (R4PCP)Ir alkane dehydrogenation catalysts are highly selective and different from ( R4POCOP)Ir catalysts, predicting different rate-/selectivity-determining steps; (2) The study of the mechanism for double C-H addition/cyclometalation of phenanthrene or biphenyl by (tBu4PCP)Ir(I) and ( iPr4PCP)Ir illustrates that neutral Ir(III) C-H addition products can undergo a very facile second C-H addition, particularly in the case of sterically less-crowded Ir(I) complexes; (3) (iPr4PCP)Ir pure solid phase catalyst is highly effective in producing high yields of alpha-olefin products, since the activation enthalpy for dehydrogenation is higher than that for isomerization via an allyl pathway; higher temperatures favor the dehydrogenation/isomerization ratio; (4) (PCP)Ir(H)2(N2H4) complex follows a hydrogen transfer mechanism to undergo both dehydrogenation to form N 2 and H2, as well as hydrogen transfer followed by N-N bond cleavage to form NH3, N2, and H2; (5) The key for the catalytic effect of solvent molecule in CO insertion reaction for RMn(CO)5 is hydrogen bond assisted interaction. The basicity of the solvent determines the strength of the hydrogen bond interaction during the catalytic path and determines the catalytic power of the solvent; and (6) Dehydrogenative coupling of unactivated C-H bonds (intermolecular vinyl-vinyl, intramolecular vinyl-benzyl) is catalyzed by precursors of the

  6. Unifying Complexity and Information

    NASA Astrophysics Data System (ADS)

    Ke, Da-Guan

    2013-04-01

    Complex systems, arising in many contexts in the computer, life, social, and physical sciences, have not shared a generally-accepted complexity measure playing a fundamental role as the Shannon entropy H in statistical mechanics. Superficially-conflicting criteria of complexity measurement, i.e. complexity-randomness (C-R) relations, have given rise to a special measure intrinsically adaptable to more than one criterion. However, deep causes of the conflict and the adaptability are not much clear. Here I trace the root of each representative or adaptable measure to its particular universal data-generating or -regenerating model (UDGM or UDRM). A representative measure for deterministic dynamical systems is found as a counterpart of the H for random process, clearly redefining the boundary of different criteria. And a specific UDRM achieving the intrinsic adaptability enables a general information measure that ultimately solves all major disputes. This work encourages a single framework coving deterministic systems, statistical mechanics and real-world living organisms.

  7. Influence of Hydrophobicity on Polyelectrolyte Complexation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao

    Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP)more » with methyl, ethyl and propyl substituents– thereby increasing the hydrophobicity with increasing side chain length– and complexing them with a common anionic polyelectrolyte, poly(styrene sulfonate). The mechanical 1 ACS Paragon Plus Environment behavior of these complexes is compared to the more hydrophilic system of poly(styrene sulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling-modulus master curves that are quantified in this work. The rheological behavior of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

  8. Workspace Program for Complex-Number Arithmetic

    NASA Technical Reports Server (NTRS)

    Patrick, M. C.; Howell, Leonard W., Jr.

    1986-01-01

    COMPLEX is workspace program designed to empower APL with complexnumber capabilities. Complex-variable methods provide analytical tools invaluable for applications in mathematics, science, and engineering. COMPLEX written in APL.

  9. Is a "Complex" Task Really Complex? Validating the Assumption of Cognitive Task Complexity

    ERIC Educational Resources Information Center

    Sasayama, Shoko

    2016-01-01

    In research on task-based learning and teaching, it has traditionally been assumed that differing degrees of cognitive task complexity can be inferred through task design and/or observations of differing qualities in linguistic production elicited by second language (L2) communication tasks. Without validating this assumption, however, it is…

  10. Leadership and transitions: maintaining the science in complexity and complex systems.

    PubMed

    Sturmberg, Joachim P; Martin, Carmel M

    2012-02-01

    It is the 'moral compass', however subtle, that underpins leadership. Leadership, meaning showing the way, demands as much conviction as gentile diplomacy in the discourse with supporters and detractors. In particular, leadership defends the goal by safeguarding its principles from its detractors. The authors writing in the Forum on Complexity in Medicine and Healthcare since its inception are leaders in an intellectual transition to complex systems thinking in medicine and health. © 2012 Blackwell Publishing Ltd.

  11. Structure Formation in Complex Plasma - Quantum Effects in Cryogenic Complex Plasmas

    DTIC Science & Technology

    2014-09-26

    pipe at the flange attached to the inner Dewar bottle. The temperature of the gas in the glass tube is controlled by the cryogenic liquid , liquid ...dust particles. The supersonic flow was possible to make in a complex plasma since dust acoustic wave is characterized by a sound speed of a few cm...through the illumination of laser light on dust particles. The supersonic flow was possible to make in a complex plasma since dust acoustic wave is

  12. Assessing Complexity in Learning Outcomes--A Comparison between the SOLO Taxonomy and the Model of Hierarchical Complexity

    ERIC Educational Resources Information Center

    Stålne, Kristian; Kjellström, Sofia; Utriainen, Jukka

    2016-01-01

    An important aspect of higher education is to educate students who can manage complex relationships and solve complex problems. Teachers need to be able to evaluate course content with regard to complexity, as well as evaluate students' ability to assimilate complex content and express it in the form of a learning outcome. One model for evaluating…

  13. Complexation of carboxylate on smectite surfaces.

    PubMed

    Liu, Xiandong; Lu, Xiancai; Zhang, Yingchun; Zhang, Chi; Wang, Rucheng

    2017-07-19

    We report a first principles molecular dynamics (FPMD) study of carboxylate complexation on clay surfaces. By taking acetate as a model carboxylate, we investigate its inner-sphere complexes adsorbed on clay edges (including (010) and (110) surfaces) and in interlayer space. Simulations show that acetate forms stable monodentate complexes on edge surfaces and a bidentate complex with Ca 2+ in the interlayer region. The free energy calculations indicate that the complexation on edge surfaces is slightly more stable than in interlayer space. By integrating pK a s and desorption free energies of Al coordinated water calculated previously (X. Liu, X. Lu, E. J. Meijer, R. Wang and H. Zhou, Geochim. Cosmochim. Acta, 2012, 81, 56-68; X. Liu, J. Cheng, M. Sprik, X. Lu and R. Wang, Geochim. Cosmochim. Acta, 2014, 140, 410-417), the pH dependence of acetate complexation has been revealed. It shows that acetate forms inner-sphere complexes on (110) in a very limited mildly acidic pH range while it can complex on (010) in the whole common pH range. The results presented in this study form a physical basis for understanding the geochemical processes involving clay-organics interactions.

  14. Complexity and valued landscapes

    Treesearch

    Michael M. McCarthy

    1979-01-01

    The variable "complexity," or "diversity," has received a great deal of attention in recent research efforts concerned with visual resource management, including the identification of complexity as one of the primary evaluation measures. This paper describes research efforts that support the hypothesis that the landscapes we value are those with...

  15. An index of floodplain surface complexity

    USGS Publications Warehouse

    Scown, Murray W.; Thoms, Martin C.; DeJager, Nathan R.

    2016-01-01

    Floodplain surface topography is an important component of floodplain ecosystems. It is the primary physical template upon which ecosystem processes are acted out, and complexity in this template can contribute to the high biodiversity and productivity of floodplain ecosystems. There has been a limited appreciation of floodplain surface complexity because of the traditional focus on temporal variability in floodplains as well as limitations to quantifying spatial complexity. An index of floodplain surface complexity (FSC) is developed in this paper and applied to eight floodplains from different geographic settings. The index is based on two key indicators of complexity, variability in surface geometry (VSG) and the spatial organisation of surface conditions (SPO), and was determined at three sampling scales. FSC, VSG, and SPO varied between the eight floodplains and these differences depended upon sampling scale. Relationships between these measures of spatial complexity and seven geomorphological and hydrological drivers were investigated. There was a significant decline in all complexity measures with increasing floodplain width, which was explained by either a power, logarithmic, or exponential function. There was an initial rapid decline in surface complexity as floodplain width increased from 1.5 to 5 km, followed by little change in floodplains wider than 10 km. VSG also increased significantly with increasing sediment yield. No significant relationships were determined between any of the four hydrological variables and floodplain surface complexity.

  16. Three perspectives on complexity: entropy, compression, subsymmetry

    NASA Astrophysics Data System (ADS)

    Nagaraj, Nithin; Balasubramanian, Karthi

    2017-12-01

    There is no single universally accepted definition of `Complexity'. There are several perspectives on complexity and what constitutes complex behaviour or complex systems, as opposed to regular, predictable behaviour and simple systems. In this paper, we explore the following perspectives on complexity: effort-to-describe (Shannon entropy H, Lempel-Ziv complexity LZ), effort-to-compress (ETC complexity) and degree-of-order (Subsymmetry or SubSym). While Shannon entropy and LZ are very popular and widely used, ETC is relatively a new complexity measure. In this paper, we also propose a novel normalized complexity measure SubSym based on the existing idea of counting the number of subsymmetries or palindromes within a sequence. We compare the performance of these complexity measures on the following tasks: (A) characterizing complexity of short binary sequences of lengths 4 to 16, (B) distinguishing periodic and chaotic time series from 1D logistic map and 2D Hénon map, (C) analyzing the complexity of stochastic time series generated from 2-state Markov chains, and (D) distinguishing between tonic and irregular spiking patterns generated from the `Adaptive exponential integrate-and-fire' neuron model. Our study reveals that each perspective has its own advantages and uniqueness while also having an overlap with each other.

  17. Softball Complex

    ERIC Educational Resources Information Center

    Ellis, Jim

    1977-01-01

    The Parks and Recreation Department of Montgomery, Alabama, has developed a five-field softball complex as part of a growing community park with facilities for camping, golf, aquatics, tennis, and picnicking. (MJB)

  18. Isolation of circulating immune complexes using Raji cells. Separation of antigens from immune complexes and production of antiserum.

    PubMed Central

    Theofilopoulos, A N; Eisenberg, R A; Dixon, F J

    1978-01-01

    Raji cells were used for the isolation of complement-fixing antigen-antibody complexes from serum. Immune complexes bound to these cells were radiolabeled at the cell surface with lactoperoxidase. The complexes were then eluted from the cells with isotonic citrate buffer pH 3.2 or recovered by immunoprecipitation of cell lysates. The antigen and antibody moieties of the complexes were isolated by dissociating sucrose density gradient centrifugation or by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A variety of preformed immune complexes were successfully isolated from serum with this approach. In addition, these techniques were used to isolate and identify the antigens in immune complexes in the serum of rabbits with chronic serum sickness and rats with Moloney virus-induced sarcomas. Methods were also developed for the production of antisera against the antigenic moiety of immune complexes isolated from serum. Repeated challenge of rabbits with whole Raji cells with bound complexes or eluates from such cells resulted in antibody production against the antigens of the immune complexes, although reactivity against cellular and serum components was also elicited. Monospecific antisera against the antigens in immune complexes were produced by immunizing rabbits with the alum-precipitated antigen isolated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These techniques may be useful in isolating antigens in immune complex-associated diseases of unknown etiology. Images PMID:659616

  19. [Health: an adaptive complex system].

    PubMed

    Toro-Palacio, Luis Fernando; Ochoa-Jaramillo, Francisco Luis

    2012-02-01

    This article points out the enormous gap that exists between complex thinking of an intellectual nature currently present in our environment, and complex experimental thinking that has facilitated the scientific and technological advances that have radically changed the world. The article suggests that life, human beings, global society, and all that constitutes health be considered as adaptive complex systems. This idea, in turn, prioritizes the adoption of a different approach that seeks to expand understanding. When this rationale is recognized, the principal characteristics and emerging properties of health as an adaptive complex system are sustained, following a care and services delivery model. Finally, some pertinent questions from this perspective are put forward in terms of research, and a series of appraisals are expressed that will hopefully serve to help us understand all that we have become as individuals and as a species. The article proposes that the delivery of health care services be regarded as an adaptive complex system.

  20. Complex systems in metabolic engineering.

    PubMed

    Winkler, James D; Erickson, Keesha; Choudhury, Alaksh; Halweg-Edwards, Andrea L; Gill, Ryan T

    2015-12-01

    Metabolic engineers manipulate intricate biological networks to build efficient biological machines. The inherent complexity of this task, derived from the extensive and often unknown interconnectivity between and within these networks, often prevents researchers from achieving desired performance. Other fields have developed methods to tackle the issue of complexity for their unique subset of engineering problems, but to date, there has not been extensive and comprehensive examination of how metabolic engineers use existing tools to ameliorate this effect on their own research projects. In this review, we examine how complexity affects engineering at the protein, pathway, and genome levels within an organism, and the tools for handling these issues to achieve high-performing strain designs. Quantitative complexity metrics and their applications to metabolic engineering versus traditional engineering fields are also discussed. We conclude by predicting how metabolic engineering practices may advance in light of an explicit consideration of design complexity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. A system of three-dimensional complex variables

    NASA Technical Reports Server (NTRS)

    Martin, E. Dale

    1986-01-01

    Some results of a new theory of multidimensional complex variables are reported, including analytic functions of a three-dimensional (3-D) complex variable. Three-dimensional complex numbers are defined, including vector properties and rules of multiplication. The necessary conditions for a function of a 3-D variable to be analytic are given and shown to be analogous to the 2-D Cauchy-Riemann equations. A simple example also demonstrates the analogy between the newly defined 3-D complex velocity and 3-D complex potential and the corresponding ordinary complex velocity and complex potential in two dimensions.

  2. Dissecting Complex Diseases in Complex Populations

    PubMed Central

    Choudhry, Shweta; Seibold, Max A.; Borrell, Luisa N.; Tang, Hua; Serebrisky, Denise; Chapela, Rocio; Rodriguez-Santana, José R.; Avila, Pedro C.; Ziv, Elad; Rodriguez-Cintron, William; Risch, Neil J.; Burchard, Esteban González

    2007-01-01

    Asthma is a common but complex respiratory ailment; current data indicate that interaction of genetic and environmental factors lead to its clinical expression. In the United States, asthma prevalence, morbidity, and mortality vary widely among different Latino ethnic groups. The prevalence of asthma is highest in Puerto Ricans, intermediate in Dominicans and Cubans, and lowest in Mexicans and Central Americans. Independently, known socioeconomic, environmental, and genetic differences do not fully account for this observation. One potential explanation is that there may be unique and ethnic-specific gene–environment interactions that can differentially modify risk for asthma in Latino ethnic groups. These gene–environment interactions can be tested using genetic ancestry as a surrogate for genetic risk factors. Latinos are admixed and share varying proportions of African, Native American, and European ancestry. Most Latinos are unaware of their precise ancestry and report their ancestry based on the national origin of their family and their physical appearance. The unavailability of precise ancestry and the genetic complexity among Latinos may complicate asthma research studies in this population. On the other hand, precisely because of this rich mixture of ancestry, Latinos present a unique opportunity to disentangle the clinical, social, environmental, and genetic underpinnings of population differences in asthma prevalence, severity, and bronchodilator drug responsiveness. PMID:17607004

  3. Life without complex I: proteome analyses of an Arabidopsis mutant lacking the mitochondrial NADH dehydrogenase complex

    PubMed Central

    Fromm, Steffanie; Senkler, Jennifer; Eubel, Holger; Peterhänsel, Christoph; Braun, Hans-Peter

    2016-01-01

    The mitochondrial NADH dehydrogenase complex (complex I) is of particular importance for the respiratory chain in mitochondria. It is the major electron entry site for the mitochondrial electron transport chain (mETC) and therefore of great significance for mitochondrial ATP generation. We recently described an Arabidopsis thaliana double-mutant lacking the genes encoding the carbonic anhydrases CA1 and CA2, which both form part of a plant-specific ‘carbonic anhydrase domain’ of mitochondrial complex I. The mutant lacks complex I completely. Here we report extended analyses for systematically characterizing the proteome of the ca1ca2 mutant. Using various proteomic tools, we show that lack of complex I causes reorganization of the cellular respiration system. Reduced electron entry into the respiratory chain at the first segment of the mETC leads to induction of complexes II and IV as well as alternative oxidase. Increased electron entry at later segments of the mETC requires an increase in oxidation of organic substrates. This is reflected by higher abundance of proteins involved in glycolysis, the tricarboxylic acid cycle and branched-chain amino acid catabolism. Proteins involved in the light reaction of photosynthesis, the Calvin cycle, tetrapyrrole biosynthesis, and photorespiration are clearly reduced, contributing to the significant delay in growth and development of the double-mutant. Finally, enzymes involved in defense against reactive oxygen species and stress symptoms are much induced. These together with previously reported insights into the function of plant complex I, which were obtained by analysing other complex I mutants, are integrated in order to comprehensively describe ‘life without complex I’. PMID:27122571

  4. Predicting perceived visual complexity of abstract patterns using computational measures: The influence of mirror symmetry on complexity perception

    PubMed Central

    Leder, Helmut

    2017-01-01

    Visual complexity is relevant for many areas ranging from improving usability of technical displays or websites up to understanding aesthetic experiences. Therefore, many attempts have been made to relate objective properties of images to perceived complexity in artworks and other images. It has been argued that visual complexity is a multidimensional construct mainly consisting of two dimensions: A quantitative dimension that increases complexity through number of elements, and a structural dimension representing order negatively related to complexity. The objective of this work is to study human perception of visual complexity utilizing two large independent sets of abstract patterns. A wide range of computational measures of complexity was calculated, further combined using linear models as well as machine learning (random forests), and compared with data from human evaluations. Our results confirm the adequacy of existing two-factor models of perceived visual complexity consisting of a quantitative and a structural factor (in our case mirror symmetry) for both of our stimulus sets. In addition, a non-linear transformation of mirror symmetry giving more influence to small deviations from symmetry greatly increased explained variance. Thus, we again demonstrate the multidimensional nature of human complexity perception and present comprehensive quantitative models of the visual complexity of abstract patterns, which might be useful for future experiments and applications. PMID:29099832

  5. Visual Complexity: A Review

    ERIC Educational Resources Information Center

    Donderi, Don C.

    2006-01-01

    The idea of visual complexity, the history of its measurement, and its implications for behavior are reviewed, starting with structuralism and Gestalt psychology at the beginning of the 20th century and ending with visual complexity theory, perceptual learning theory, and neural circuit theory at the beginning of the 21st. Evidence is drawn from…

  6. Complex equiangular tight frames

    NASA Astrophysics Data System (ADS)

    Tropp, Joel A.

    2005-08-01

    A complex equiangular tight frame (ETF) is a tight frame consisting of N unit vectors in Cd whose absolute inner products are identical. One may view complex ETFs as a natural geometric generalization of an orthonormal basis. Numerical evidence suggests that these objects do not arise for most pairs (d, N). The goal of this paper is to develop conditions on (d, N) under which complex ETFs can exist. In particular, this work concentrates on the class of harmonic ETFs, in which the components of the frame vectors are roots of unity. In this case, it is possible to leverage field theory to obtain stringent restrictions on the possible values for (d, N).

  7. BFV-Complex and Higher Homotopy Structures

    NASA Astrophysics Data System (ADS)

    Schätz, Florian

    2009-03-01

    We present a connection between the BFV-complex (abbreviation for Batalin-Fradkin-Vilkovisky complex) and the strong homotopy Lie algebroid associated to a coisotropic submanifold of a Poisson manifold. We prove that the latter structure can be derived from the BFV-complex by means of homotopy transfer along contractions. Consequently the BFV-complex and the strong homotopy Lie algebroid structure are L ∞ quasi-isomorphic and control the same formal deformation problem. However there is a gap between the non-formal information encoded in the BFV-complex and in the strong homotopy Lie algebroid respectively. We prove that there is a one-to-one correspondence between coisotropic submanifolds given by graphs of sections and equivalence classes of normalized Maurer-Cartan elemens of the BFV-complex. This does not hold if one uses the strong homotopy Lie algebroid instead.

  8. Chemical bonding in silicon-carbene complexes.

    PubMed

    Liu, Z

    2009-06-04

    The bonding situations in the newly synthesized silicon-carbene complexes with formulas L:SiCl4, L:(Cl)Si-Si(Cl):L, and L:Si=Si:L (where L: is an N-heterocyclic carbene), are reported using density functional theory at the BP86/TZ2P level. The bonding analysis clearly shows that the bonding situation in the silicon-carbene complexes cannot be described in terms of donor-acceptor interactions depicted in the Dewar-Chatt-Duncanson model. The energy decomposition analysis (EDA) shows that the electrostatic attraction plays an important or even dominant role for the Si-C(carbene) binding interactions in the silicon-carbene complexes. That the molecular orbitals of the silicon-carbene complexes are lower in energy than the parent orbitals of carbenes indicates that these complexes are better described as stabilized carbene complexes.

  9. An Additive Definition of Molecular Complexity.

    PubMed

    Böttcher, Thomas

    2016-03-28

    A framework for molecular complexity is established that is based on information theory and consistent with chemical knowledge. The resulting complexity index Cm is derived from abstracting the information content of a molecule by the degrees of freedom in the microenvironments on a per-atom basis, allowing the molecular complexity to be calculated in a simple and additive way. This index allows the complexity of any molecule to be universally assessed and is sensitive to stereochemistry, heteroatoms, and symmetry. The performance of this complexity index is evaluated and compared against the current state of the art. Its additive character gives consistent values also for very large molecules and supports direct comparisons of chemical reactions. Finally, this approach may provide a useful tool for medicinal chemistry in drug design and lead selection, as demonstrated by correlating molecular complexities of antibiotics with compound-specific parameters.

  10. Bell Inequalities for Complex Networks

    DTIC Science & Technology

    2015-10-26

    AFRL-AFOSR-VA-TR-2015-0355 YIP Bell Inequalities for Complex Networks Greg Ver Steeg UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES Final Report 10/26...performance report PI: Greg Ver Steeg Young Investigator Award Grant Title: Bell Inequalities for Complex Networks Grant #: FA9550-12-1-0417 Reporting...October 20, 2015 Final Report for “Bell Inequalities for Complex Networks” Greg Ver Steeg Abstract This effort studied new methods to understand the effect

  11. Relating Complexity and Error Rates of Ontology Concepts. More Complex NCIt Concepts Have More Errors.

    PubMed

    Min, Hua; Zheng, Ling; Perl, Yehoshua; Halper, Michael; De Coronado, Sherri; Ochs, Christopher

    2017-05-18

    Ontologies are knowledge structures that lend support to many health-information systems. A study is carried out to assess the quality of ontological concepts based on a measure of their complexity. The results show a relation between complexity of concepts and error rates of concepts. A measure of lateral complexity defined as the number of exhibited role types is used to distinguish between more complex and simpler concepts. Using a framework called an area taxonomy, a kind of abstraction network that summarizes the structural organization of an ontology, concepts are divided into two groups along these lines. Various concepts from each group are then subjected to a two-phase QA analysis to uncover and verify errors and inconsistencies in their modeling. A hierarchy of the National Cancer Institute thesaurus (NCIt) is used as our test-bed. A hypothesis pertaining to the expected error rates of the complex and simple concepts is tested. Our study was done on the NCIt's Biological Process hierarchy. Various errors, including missing roles, incorrect role targets, and incorrectly assigned roles, were discovered and verified in the two phases of our QA analysis. The overall findings confirmed our hypothesis by showing a statistically significant difference between the amounts of errors exhibited by more laterally complex concepts vis-à-vis simpler concepts. QA is an essential part of any ontology's maintenance regimen. In this paper, we reported on the results of a QA study targeting two groups of ontology concepts distinguished by their level of complexity, defined in terms of the number of exhibited role types. The study was carried out on a major component of an important ontology, the NCIt. The findings suggest that more complex concepts tend to have a higher error rate than simpler concepts. These findings can be utilized to guide ongoing efforts in ontology QA.

  12. Complexity, Systems, and Software

    DTIC Science & Technology

    2014-08-14

    2014 Carnegie Mellon University Complexity, Systems, and Software Software Engineering Institute Carnegie Mellon University Pittsburgh, PA...this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services , Directorate for Information...OMB control number. 1. REPORT DATE 29 OCT 2014 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Complexity, Systems, and Software

  13. Maximizing information exchange between complex networks

    NASA Astrophysics Data System (ADS)

    West, Bruce J.; Geneston, Elvis L.; Grigolini, Paolo

    2008-10-01

    Science is not merely the smooth progressive interaction of hypothesis, experiment and theory, although it sometimes has that form. More realistically the scientific study of any given complex phenomenon generates a number of explanations, from a variety of perspectives, that eventually requires synthesis to achieve a deep level of insight and understanding. One such synthesis has created the field of out-of-equilibrium statistical physics as applied to the understanding of complex dynamic networks. Over the past forty years the concept of complexity has undergone a metamorphosis. Complexity was originally seen as a consequence of memory in individual particle trajectories, in full agreement with a Hamiltonian picture of microscopic dynamics and, in principle, macroscopic dynamics could be derived from the microscopic Hamiltonian picture. The main difficulty in deriving macroscopic dynamics from microscopic dynamics is the need to take into account the actions of a very large number of components. The existence of events such as abrupt jumps, considered by the conventional continuous time random walk approach to describing complexity was never perceived as conflicting with the Hamiltonian view. Herein we review many of the reasons why this traditional Hamiltonian view of complexity is unsatisfactory. We show that as a result of technological advances, which make the observation of single elementary events possible, the definition of complexity has shifted from the conventional memory concept towards the action of non-Poisson renewal events. We show that the observation of crucial processes, such as the intermittent fluorescence of blinking quantum dots as well as the brain’s response to music, as monitored by a set of electrodes attached to the scalp, has forced investigators to go beyond the traditional concept of complexity and to establish closer contact with the nascent field of complex networks. Complex networks form one of the most challenging areas of

  14. A developmental approach to complex PTSD: childhood and adult cumulative trauma as predictors of symptom complexity.

    PubMed

    Cloitre, Marylene; Stolbach, Bradley C; Herman, Judith L; van der Kolk, Bessel; Pynoos, Robert; Wang, Jing; Petkova, Eva

    2009-10-01

    Exposure to multiple traumas, particularly in childhood, has been proposed to result in a complex of symptoms that includes posttraumatic stress disorder (PTSD) as well as a constrained, but variable group of symptoms that highlight self-regulatory disturbances. The relationship between accumulated exposure to different types of traumatic events and total number of different types of symptoms (symptom complexity) was assessed in an adult clinical sample (N = 582) and a child clinical sample (N = 152). Childhood cumulative trauma but not adulthood trauma predicted increasing symptom complexity in adults. Cumulative trauma predicted increasing symptom complexity in the child sample. Results suggest that Complex PTSD symptoms occur in both adult and child samples in a principled, rule-governed way and that childhood experiences significantly influenced adult symptoms. Copyright © 2009 International Society for Traumatic Stress Studies.

  15. Cumulative complexity: a functional, patient-centered model of patient complexity can improve research and practice.

    PubMed

    Shippee, Nathan D; Shah, Nilay D; May, Carl R; Mair, Frances S; Montori, Victor M

    2012-10-01

    To design a functional, patient-centered model of patient complexity with practical applicability to analytic design and clinical practice. Existing literature on patient complexity has mainly identified its components descriptively and in isolation, lacking clarity as to their combined functions in disrupting care or to how complexity changes over time. The authors developed a cumulative complexity model, which integrates existing literature and emphasizes how clinical and social factors accumulate and interact to complicate patient care. A narrative literature review is used to explicate the model. The model emphasizes a core, patient-level mechanism whereby complicating factors impact care and outcomes: the balance between patient workload of demands and patient capacity to address demands. Workload encompasses the demands on the patient's time and energy, including demands of treatment, self-care, and life in general. Capacity concerns ability to handle work (e.g., functional morbidity, financial/social resources, literacy). Workload-capacity imbalances comprise the mechanism driving patient complexity. Treatment and illness burdens serve as feedback loops, linking negative outcomes to further imbalances, such that complexity may accumulate over time. With its components largely supported by existing literature, the model has implications for analytic design, clinical epidemiology, and clinical practice. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Reduction of Subjective and Objective System Complexity

    NASA Technical Reports Server (NTRS)

    Watson, Michael D.

    2015-01-01

    Occam's razor is often used in science to define the minimum criteria to establish a physical or philosophical idea or relationship. Albert Einstein is attributed the saying "everything should be made as simple as possible, but not simpler". These heuristic ideas are based on a belief that there is a minimum state or set of states for a given system or phenomena. In looking at system complexity, these heuristics point us to an idea that complexity can be reduced to a minimum. How then, do we approach a reduction in complexity? Complexity has been described as a subjective concept and an objective measure of a system. Subjective complexity is based on human cognitive comprehension of the functions and inter relationships of a system. Subjective complexity is defined by the ability to fully comprehend the system. Simplifying complexity, in a subjective sense, is thus gaining a deeper understanding of the system. As Apple's Jonathon Ive has stated," It's not just minimalism or the absence of clutter. It involves digging through the depth of complexity. To be truly simple, you have to go really deep". Simplicity is not the absence of complexity but a deeper understanding of complexity. Subjective complexity, based on this human comprehension, cannot then be discerned from the sociological concept of ignorance. The inability to comprehend a system can be either a lack of knowledge, an inability to understand the intricacies of a system, or both. Reduction in this sense is based purely on a cognitive ability to understand the system and no system then may be truly complex. From this view, education and experience seem to be the keys to reduction or eliminating complexity. Objective complexity, is the measure of the systems functions and interrelationships which exist independent of human comprehension. Jonathon Ive's statement does not say that complexity is removed, only that the complexity is understood. From this standpoint, reduction of complexity can be approached

  17. Rhodium complexes as therapeutic agents.

    PubMed

    Ma, Dik-Lung; Wang, Modi; Mao, Zhifeng; Yang, Chao; Ng, Chan-Tat; Leung, Chung-Hang

    2016-02-21

    The landscape of inorganic medicinal chemistry has been dominated by the investigation of platinum, and to a lesser extent ruthenium, complexes over the past few decades. Recently, complexes based on other metal centers such as rhodium have attracted attention due to their tunable chemical and biological properties as well as distinct mechanisms of action. This perspective highlights recent examples of rhodium complexes that show diverse biological activities against various targets, including enzymes and protein-protein interactions.

  18. Increasing complexity with quantum physics.

    PubMed

    Anders, Janet; Wiesner, Karoline

    2011-09-01

    We argue that complex systems science and the rules of quantum physics are intricately related. We discuss a range of quantum phenomena, such as cryptography, computation and quantum phases, and the rules responsible for their complexity. We identify correlations as a central concept connecting quantum information and complex systems science. We present two examples for the power of correlations: using quantum resources to simulate the correlations of a stochastic process and to implement a classically impossible computational task.

  19. Children with medical complexity in Canada

    PubMed Central

    Dewan, Tammie; Cohen, Eyal

    2013-01-01

    The burden of chronic disease is placing pressure on the Canadian health care system. A small but important chronic disease population is children with medical complexity, defined as individuals with: high family-identified needs; complex chronic disease necessitating specialized care; functional disability; and high health care utilization. These patients present a challenge to community providers who are expected to provide holistic care and manage complex issues, often with a paucity of services and supports. Alternative models of care may address the complex needs of this population. In addition, strategies can be implemented in community practices that may assist with the care of children with medical complexity such as collaborative care, engagement of key workers, focus on goal-directed care and use of care plans. The paediatric community should engage in health care reform discussions focused on chronic disease to ensure that the complex needs of these children are met. PMID:24497777

  20. Cytochrome bc1 complexes of microorganisms.

    PubMed Central

    Trumpower, B L

    1990-01-01

    The cytochrome bc1 complex is the most widely occurring electron transfer complex capable of energy transduction. Cytochrome bc1 complexes are found in the plasma membranes of phylogenetically diverse photosynthetic and respiring bacteria, and in the inner mitochondrial membrane of all eucaryotic cells. In all of these species the bc1 complex transfers electrons from a low-potential quinol to a higher-potential c-type cytochrome and links this electron transfer to proton translocation. Most bacteria also possess alternative pathways of quinol oxidation capable of circumventing the bc1 complex, but these pathways generally lack the energy-transducing, protontranslocating activity of the bc1 complex. All cytochrome bc1 complexes contain three electron transfer proteins which contain four redox prosthetic groups. These are cytochrome b, which contains two b heme groups that differ in their optical and thermodynamic properties; cytochrome c1, which contains a covalently bound c-type heme; and a 2Fe-2S iron-sulfur protein. The mechanism which links proton translocation to electron transfer through these proteins is the proton motive Q cycle, and this mechanism appears to be universal to all bc1 complexes. Experimentation is currently focused on understanding selected structure-function relationships prerequisite for these redox proteins to participate in the Q-cycle mechanism. The cytochrome bc1 complexes of mitochondria differ from those of bacteria, in that the former contain six to eight supernumerary polypeptides, in addition to the three redox proteins common to bacteria and mitochondria. These extra polypeptides are encoded in the nucleus and do not contain redox prosthetic groups. The functions of the supernumerary polypeptides of the mitochondrial bc1 complexes are generally not known and are being actively explored by genetically manipulating these proteins in Saccharomyces cerevisiae. Images PMID:2163487

  1. On synchronisation of a class of complex chaotic systems with complex unknown parameters via integral sliding mode control

    NASA Astrophysics Data System (ADS)

    Tirandaz, Hamed; Karami-Mollaee, Ali

    2018-06-01

    Chaotic systems demonstrate complex behaviour in their state variables and their parameters, which generate some challenges and consequences. This paper presents a new synchronisation scheme based on integral sliding mode control (ISMC) method on a class of complex chaotic systems with complex unknown parameters. Synchronisation between corresponding states of a class of complex chaotic systems and also convergence of the errors of the system parameters to zero point are studied. The designed feedback control vector and complex unknown parameter vector are analytically achieved based on the Lyapunov stability theory. Moreover, the effectiveness of the proposed methodology is verified by synchronisation of the Chen complex system and the Lorenz complex systems as the leader and the follower chaotic systems, respectively. In conclusion, some numerical simulations related to the synchronisation methodology is given to illustrate the effectiveness of the theoretical discussions.

  2. Mapping on complex neutrosophic soft expert sets

    NASA Astrophysics Data System (ADS)

    Al-Quran, Ashraf; Hassan, Nasruddin

    2018-04-01

    We introduce the mapping on complex neutrosophic soft expert sets. Further, we investigated the basic operations and other related properties of complex neutrosophic soft expert image and complex neutrosophic soft expert inverse image of complex neutrosophic soft expert sets.

  3. Manufacturing complexity analysis

    NASA Technical Reports Server (NTRS)

    Delionback, L. M.

    1977-01-01

    The analysis of the complexity of a typical system is presented. Starting with the subsystems of an example system, the step-by-step procedure for analysis of the complexity of an overall system is given. The learning curves for the various subsystems are determined as well as the concurrent numbers of relevant design parameters. Then trend curves are plotted for the learning curve slopes versus the various design-oriented parameters, e.g. number of parts versus slope of learning curve, or number of fasteners versus slope of learning curve, etc. Representative cuts are taken from each trend curve, and a figure-of-merit analysis is made for each of the subsystems. Based on these values, a characteristic curve is plotted which is indicative of the complexity of the particular subsystem. Each such characteristic curve is based on a universe of trend curve data taken from data points observed for the subsystem in question. Thus, a characteristic curve is developed for each of the subsystems in the overall system.

  4. Multidimensional, mapping-based complex wavelet transforms.

    PubMed

    Fernandes, Felix C A; van Spaendonck, Rutger L C; Burrus, C Sidney

    2005-01-01

    Although the discrete wavelet transform (DWT) is a powerful tool for signal and image processing, it has three serious disadvantages: shift sensitivity, poor directionality, and lack of phase information. To overcome these disadvantages, we introduce multidimensional, mapping-based, complex wavelet transforms that consist of a mapping onto a complex function space followed by a DWT of the complex mapping. Unlike other popular transforms that also mitigate DWT shortcomings, the decoupled implementation of our transforms has two important advantages. First, the controllable redundancy of the mapping stage offers a balance between degree of shift sensitivity and transform redundancy. This allows us to create a directional, nonredundant, complex wavelet transform with potential benefits for image coding systems. To the best of our knowledge, no other complex wavelet transform is simultaneously directional and nonredundant. The second advantage of our approach is the flexibility to use any DWT in the transform implementation. As an example, we exploit this flexibility to create the complex double-density DWT: a shift-insensitive, directional, complex wavelet transform with a low redundancy of (3M - 1)/(2M - 1) in M dimensions. No other transform achieves all these properties at a lower redundancy, to the best of our knowledge. By exploiting the advantages of our multidimensional, mapping-based complex wavelet transforms in seismic signal-processing applications, we have demonstrated state-of-the-art results.

  5. Heteroleptic Cycloplatinated N-Heterocyclic Carbene Complexes: A New Approach to Highly Efficient Blue-Light Emitters.

    PubMed

    Fuertes, Sara; Chueca, Andrés J; Arnal, Lorenzo; Martín, Antonio; Giovanella, Umberto; Botta, Chiara; Sicilia, Violeta

    2017-05-01

    New heteroleptic compounds of platinum(II)-containing cyclometalated N-heterocyclic carbenes, [PtCl(R-C^C*)(PPh 3 )] [R-CH^C*-κC* = 3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene (R-C = Naph; 1A), 1-[4-(ethoxycarbonyl)phenyl]-3-methyl-1H-imidazol-2-ylidene (R = CO 2 Et; 1B), and [Pt(R-C^C*)(py)(PPh 3 )]PF 6 (py = pyridine; R-C = Naph, 2A; R = CO 2 Et, 2B], have been prepared and fully characterized. All of them were obtained as the trans-(C*,PPh 3 ) isomer in high yields. The selectivity of their synthesis has been explained in terms of the degree of transphobia (T) of pairs of ligands in trans positions. X-ray diffraction studies on both 2A and 2B revealed that only in 2A, containing a C^C* with a more extended π system, do the molecules assemble themselves into head-to-tail pairs through intermolecular π···π contacts. The photophysical properties of 2A and 2B and those of the related compounds [Pt(NC-C^C*)(PPh 3 )L]PF 6 [NC-CH^C*-κC* = 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene; L = pyridine (py; 2C), 2,6-dimethylphenylisocyanide (CNXyl; 3C), and 2-mercapto-1-methylimidazole (MMI; 4C)] have been examined to analyze the influence of the R substituent on R-C^C* (R-C = Naph; R = CO 2 Et, CN) and that of the ancillary ligands (L) on them. Experimental data and time-dependent density functional theory calculations showed the similarity of the electronic features associated with R-C^C* (R = CN, CO 2 Et) and their difference with respect to R-C^C* (R-C = Naph). All of the compounds are very efficient blue emitters in poly(methyl methacrylate) films under an argon atmosphere, with QY values ranging from 68% (2B) to 93% (2C). In the solid state, the color of the emission changes to yellowish-orange for compounds 2A (λ max = 600 nm) and 3C (λ max = 590 nm) because of the formation of aggregates through intermolecular π···π interactions. 2C and 3C were chosen to fabricate fully solution-processed electroluminescent devices with blue-light (2C

  6. The multitalented Mediator complex.

    PubMed

    Carlsten, Jonas O P; Zhu, Xuefeng; Gustafsson, Claes M

    2013-11-01

    The Mediator complex is needed for regulated transcription of RNA polymerase II (Pol II)-dependent genes. Initially, Mediator was only seen as a protein bridge that conveyed regulatory information from enhancers to the promoter. Later studies have added many other functions to the Mediator repertoire. Indeed, recent findings show that Mediator influences nearly all stages of transcription and coordinates these events with concomitant changes in chromatin organization. We review the multitude of activities associated with Mediator and discuss how this complex coordinates transcription with other cellular events. We also discuss the inherent difficulties associated with in vivo characterization of a coactivator complex that can indirectly affect diverse cellular processes via changes in gene transcription. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. The complexity of divisibility.

    PubMed

    Bausch, Johannes; Cubitt, Toby

    2016-09-01

    We address two sets of long-standing open questions in linear algebra and probability theory, from a computational complexity perspective: stochastic matrix divisibility, and divisibility and decomposability of probability distributions. We prove that finite divisibility of stochastic matrices is an NP-complete problem, and extend this result to nonnegative matrices, and completely-positive trace-preserving maps, i.e. the quantum analogue of stochastic matrices. We further prove a complexity hierarchy for the divisibility and decomposability of probability distributions, showing that finite distribution divisibility is in P, but decomposability is NP-hard. For the former, we give an explicit polynomial-time algorithm. All results on distributions extend to weak-membership formulations, proving that the complexity of these problems is robust to perturbations.

  8. The sleeping brain as a complex system.

    PubMed

    Olbrich, Eckehard; Achermann, Peter; Wennekers, Thomas

    2011-10-13

    'Complexity science' is a rapidly developing research direction with applications in a multitude of fields that study complex systems consisting of a number of nonlinear elements with interesting dynamics and mutual interactions. This Theme Issue 'The complexity of sleep' aims at fostering the application of complexity science to sleep research, because the brain in its different sleep stages adopts different global states that express distinct activity patterns in large and complex networks of neural circuits. This introduction discusses the contributions collected in the present Theme Issue. We highlight the potential and challenges of a complex systems approach to develop an understanding of the brain in general and the sleeping brain in particular. Basically, we focus on two topics: the complex networks approach to understand the changes in the functional connectivity of the brain during sleep, and the complex dynamics of sleep, including sleep regulation. We hope that this Theme Issue will stimulate and intensify the interdisciplinary communication to advance our understanding of the complex dynamics of the brain that underlies sleep and consciousness.

  9. Measuring the Complexity of Seismicity Pattern Evolution

    NASA Astrophysics Data System (ADS)

    Goltz, C.

    2004-12-01

    ``Complexity'' has become an ubiquitous term in science. However, there is, much as with ``fractality'', no clear definition of what complexity actually means. Yet, it is important to distinguish between what is merely complicated and what is complex in the sense that simple rules can give rise to very rich behaviour. Seismicity is certainly a complicated phenomenon (difficult to understand) but simple models such as cellular automata indicate that earthquakes are truly complex. From the observational point of view, there exists the problem of quantification of complexity in real world seismicity patterns (in the absence of even a rigid definition of complexity). Such a measurement is desirable, however, not only for fundamental understanding but also for monitoring and possibly for prediction purposes. Maybe the most workable definitions of complexity exist in informatics, summarised under the topic of algorithmic complexity. Here, after introducing the concepts, I apply such measures of complexity to temporally evolving seismicity patterns from different geographic regions. Finally, I discuss the usefulness of the approach and discuss results in view of the occurrence of large earthquakes.

  10. The 2-Oxoacid Dehydrogenase Complexes in Mitochondria Can Produce Superoxide/Hydrogen Peroxide at Much Higher Rates Than Complex I*

    PubMed Central

    Quinlan, Casey L.; Goncalves, Renata L. S.; Hey-Mogensen, Martin; Yadava, Nagendra; Bunik, Victoria I.; Brand, Martin D.

    2014-01-01

    Several flavin-dependent enzymes of the mitochondrial matrix utilize NAD+ or NADH at about the same operating redox potential as the NADH/NAD+ pool and comprise the NADH/NAD+ isopotential enzyme group. Complex I (specifically the flavin, site IF) is often regarded as the major source of matrix superoxide/H2O2 production at this redox potential. However, the 2-oxoglutarate dehydrogenase (OGDH), branched-chain 2-oxoacid dehydrogenase (BCKDH), and pyruvate dehydrogenase (PDH) complexes are also capable of considerable superoxide/H2O2 production. To differentiate the superoxide/H2O2-producing capacities of these different mitochondrial sites in situ, we compared the observed rates of H2O2 production over a range of different NAD(P)H reduction levels in isolated skeletal muscle mitochondria under conditions that favored superoxide/H2O2 production from complex I, the OGDH complex, the BCKDH complex, or the PDH complex. The rates from all four complexes increased at higher NAD(P)H/NAD(P)+ ratios, although the 2-oxoacid dehydrogenase complexes produced superoxide/H2O2 at high rates only when oxidizing their specific 2-oxoacid substrates and not in the reverse reaction from NADH. At optimal conditions for each system, superoxide/H2O2 was produced by the OGDH complex at about twice the rate from the PDH complex, four times the rate from the BCKDH complex, and eight times the rate from site IF of complex I. Depending on the substrates present, the dominant sites of superoxide/H2O2 production at the level of NADH may be the OGDH and PDH complexes, but these activities may often be misattributed to complex I. PMID:24515115

  11. Rheology of polyelectrolyte complex materials

    NASA Astrophysics Data System (ADS)

    Tirrell, Matthew

    Fluid polyelectrolyte complexes, sometimes known as complex coacervates, have rheological properties that are very sensitive to structure and salt concentration. Dynamic moduli of such viscoelastic materials very many orders of magnitude between solutions of no added salt to of order tenth molar salt, typical, for example of physiological saline. Indeed, salt plays a role in the rheology of complex coacervates analogous to that which temperature plays on polymer melts, leading to an empirical observation of what may be termed time-salt or frequency salt superposition. Block copolymers containing complexing ionic blocks also exhibit strong salt sensitivity of their rheological properties. Data representing these phenomena will be presented and discussed. Support from NIST, Department of Commerce, via the Center for Hierarchical Materials Design at Northwestern University and the University of Chicago is gratefully acknowledged.

  12. Complex bile duct injuries: management

    PubMed Central

    Ardiles, V.; Pekolj, J.

    2008-01-01

    Background. Laparoscopic cholecystectomy is the present treatment of choice for patients with gallbladder stones, despite its being associated with a higher incidence of biliary injuries compared with the open procedure. Injuries occurring during the laparoscopic approach seem to be more complex. A complex biliary injury is a disease that is difficult to diagnose and treat. We considered complex injuries: 1) injuries that involve the confluence; 2) injuries in which repair attempts have failed; 3) any bile duct injury associated with a vascular injury; 4) or any biliary injury in association with portal hypertension or secondary biliary cirrhosis. The present review is an evaluation of our experience in the treatment of these complex biliary injuries and an analysis of the international literature on the management of patients. PMID:18695753

  13. Complex Event Recognition Architecture

    NASA Technical Reports Server (NTRS)

    Fitzgerald, William A.; Firby, R. James

    2009-01-01

    Complex Event Recognition Architecture (CERA) is the name of a computational architecture, and software that implements the architecture, for recognizing complex event patterns that may be spread across multiple streams of input data. One of the main components of CERA is an intuitive event pattern language that simplifies what would otherwise be the complex, difficult tasks of creating logical descriptions of combinations of temporal events and defining rules for combining information from different sources over time. In this language, recognition patterns are defined in simple, declarative statements that combine point events from given input streams with those from other streams, using conjunction, disjunction, and negation. Patterns can be built on one another recursively to describe very rich, temporally extended combinations of events. Thereafter, a run-time matching algorithm in CERA efficiently matches these patterns against input data and signals when patterns are recognized. CERA can be used to monitor complex systems and to signal operators or initiate corrective actions when anomalous conditions are recognized. CERA can be run as a stand-alone monitoring system, or it can be integrated into a larger system to automatically trigger responses to changing environments or problematic situations.

  14. Complexity measures of music

    NASA Astrophysics Data System (ADS)

    Pease, April; Mahmoodi, Korosh; West, Bruce J.

    2018-03-01

    We present a technique to search for the presence of crucial events in music, based on the analysis of the music volume. Earlier work on this issue was based on the assumption that crucial events correspond to the change of music notes, with the interesting result that the complexity index of the crucial events is mu ~ 2, which is the same inverse power-law index of the dynamics of the brain. The search technique analyzes music volume and confirms the results of the earlier work, thereby contributing to the explanation as to why the brain is sensitive to music, through the phenomenon of complexity matching. Complexity matching has recently been interpreted as the transfer of multifractality from one complex network to another. For this reason we also examine the mulifractality of music, with the observation that the multifractal spectrum of a computer performance is significantly narrower than the multifractal spectrum of a human performance of the same musical score. We conjecture that although crucial events are demonstrably important for information transmission, they alone are not suficient to define musicality, which is more adequately measured by the multifractality spectrum.

  15. Multisubunit tethering complexes in higher plants.

    PubMed

    Ravikumar, Raksha; Steiner, Alexander; Assaad, Farhah F

    2017-12-01

    Tethering complexes mediate the initial, specific contact between donor and acceptor membranes. This review focuses on the modularity and function of multisubunit tethering complexes (MTCs) in higher plants. One emphasis is on molecular interactions of plant MTCs. Here, a number of insights have been gained concerning interactions between different tethering complexes, and between tethers and microtubule-associated proteins. The roles of tethering complexes in abiotic stress responses appear indirect, but in the context of biotic stress responses it has been suggested that some tethers are direct targets of pathogen effectors or virulence factors. In light of the central roles tethering complexes play in plant development, an emerging concept is that tethers may be co-opted for plant adaptive responses. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Metal Complexation in Xylem Fluid 1

    PubMed Central

    White, Michael C.; Chaney, Rufus L.; Decker, A. Morris

    1981-01-01

    The capacity of ligands in xylem fluid to form metal complexes was tested with a series of in vitro experiments using paper electrophoresis and radiographs. The xylem fluid was collected hourly for 8 hours from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. Metal complexation was assayed by anodic or reduced cathodic movement of radionuclides (63Ni, 65Zn, 109Cd, 54Mn) that were presumed to have formed negatively charged complexes. Electrophoretic migration of Ni, Zn, Cd, and Mn added to xylem exudate and spotted on KCl- or KNO3-wetted paper showed that stable Ni, Zn, and Cd metal complexes were formed by exudate ligands. No anodic Mn complexes were observed in this test system. Solution pH, plant species, exudate collection time, and Zn phytotoxicity all affected the amount of metal complex formed in exudate. As the pH increased, there was increased anodic metal movement. Soybean exudate generally bound more of each metal than did tomato exudate. Metal binding usually decreased with increasing exudate collection time, and less metal was bound by the high-Zn exudate. Ni, Zn, Cd, and Mn in exudate added to exudate-wetted paper demonstrated the effect of ligand concentration on stable metal complex formation. Complexes for each metal were demonstratable with this method. Cathodic metal movement increased with time of exudate collection, and it was greater in the high-Zn exudate than in the normal-Zn exudate. A model study illustrated the effect of ligand concentration on metal complex stability in the electrophoretic field. Higher ligand (citric acid) concentrations increased the stability for all metals tested. Images PMID:16661666

  17. Cytokine/Antibody complexes: an emerging class of immunostimulants.

    PubMed

    Mostböck, Sven

    2009-01-01

    In recent years, complexes formed from a cytokine and antibodies against that respective cytokine (cytokine/Ab complex) have been shown to induce remarkable powerful changes in the immune system. Strong interest exists especially for complexes formed with Interleukin (IL)-2 and anti-IL-2-antibody (IL-2/Ab complex). IL-2/Ab complex activates maturation and proliferation in CD8(+) T cells and natural killer (NK) cells to a much higher degree than conventional IL-2 therapy. In addition, IL-2/Ab complex does not stimulate regulatory T cells as much as IL-2 alone. This suggests the possibility to replace the conventional IL-2 therapy with a therapy using low-dose IL-2/Ab complex. Further synthetic cytokine/Ab complexes are studied currently, including IL-3/Ab complex for its effects on the mast cell population, and IL-4/Ab complex and IL-7/Ab complex for inducing B and T cell expansion and maturation. Cytokine complexes can also be made from a cytokine and its soluble receptor. Pre-association of IL-15 with soluble IL-15 receptor alpha produces a complex with strong agonistic functions that lead to an expansion of CD8(+) T cells and NK cells. However, cytokine/Ab complexes also occur naturally in humans. A multitude of auto-antibodies to cytokines are found in human sera, and many of these auto-antibodies build cytokine/Ab complexes. This review presents naturally occurring auto-antibodies to cytokines and cytokine/Ab complexes in health and disease. It further summarizes recent research on synthetic cytokine/Ab complexes with a focus on the basic mechanisms behind the function of cytokine/Ab complexes.

  18. Analytic complexity of functions of two variables

    NASA Astrophysics Data System (ADS)

    Beloshapka, V. K.

    2007-09-01

    The definition of analytic complexity of an analytic function of two variables is given. It is proved that the class of functions of a chosen complexity is a differentialalgebraic set. A differential polynomial defining the functions of first class is constructed. An algorithm for obtaining relations defining an arbitrary class is described. Examples of functions are given whose order of complexity is equal to zero, one, two, and infinity. It is shown that the formal order of complexity of the Cardano and Ferrari formulas is significantly higher than their analytic complexity. The complexity classes turn out to be invariant with respect to a certain infinite-dimensional transformation pseudogroup. In this connection, we describe the orbits of the action of this pseudogroup in the jets of orders one, two, and three. The notion of complexity order is extended to plane (or “planar”) 3-webs. It is discovered that webs of complexity order one are the hexagonal webs. Some problems are posed.

  19. Starch-lipid complexes: Interesting material and applications from amylose-fatty acid salt inclusion complexes

    USDA-ARS?s Scientific Manuscript database

    Aqueous slurries of high amylose starch can be steam jet cooked and blended with aqueous solutions of fatty acid salts to generate materials that contain inclusion complexes between amylose and the fatty acid salt. These complexes are simply prepared on large scale using commercially available steam...

  20. On the interconnection of stable protein complexes: inter-complex hubs and their conservation in Saccharomyces cerevisiae and Homo sapiens networks.

    PubMed

    Guerra, Concettina

    2015-01-01

    Protein complexes are key molecular entities that perform a variety of essential cellular functions. The connectivity of proteins within a complex has been widely investigated with both experimental and computational techniques. We developed a computational approach to identify and characterise proteins that play a role in interconnecting complexes. We computed a measure of inter-complex centrality, the crossroad index, based on disjoint paths connecting proteins in distinct complexes and identified inter-complex hubs as proteins with a high value of the crossroad index. We applied the approach to a set of stable complexes in Saccharomyces cerevisiae and in Homo sapiens. Just as done for hubs, we evaluated the topological and biological properties of inter-complex hubs addressing the following questions. Do inter-complex hubs tend to be evolutionary conserved? What is the relation between crossroad index and essentiality? We found a good correlation between inter-complex hubs and both evolutionary conservation and essentiality.

  1. A Computer Story: Complexity from Simplicity

    ERIC Educational Resources Information Center

    DeLeo, Gary; Weidenhammer, Amanda; Wecht, Kristen

    2012-01-01

    In this technological age, digital devices are conspicuous examples of extraordinary complexity. When a user clicks on computer icons or presses calculator buttons, these devices channel electricity through a complex system of decision-making circuits. Yet, in spite of this remarkable complexity, the hearts of these devices are components that…

  2. Game Building with Complex-Valued Functions

    ERIC Educational Resources Information Center

    Dittman, Marki; Soto-Johnson, Hortensia; Dickinson, Scott; Harr, Tim

    2017-01-01

    In this paper, we describe how we integrated complex analysis into the second semester of a geometry course designed for preservice secondary mathematics teachers. As part of this inquiry-based course, the preservice teachers incorporated their geometric understanding of the arithmetic of complex numbers and complex-valued functions to create a…

  3. Effects of trial complexity on decision making.

    PubMed

    Horowitz, I A; ForsterLee, L; Brolly, I

    1996-12-01

    The ability of a civil jury to render fair and rational decisions in complex trials has been questioned. However, the nature, dimensions, and effects of trial complexity on decision making have rarely been addressed. In this research, jury-eligible adults saw a videotape of a complex civil trial that varied in information load and complexity of the language of the witnesses. Information load and complexity differentially affected liability and compensatory decisions. An increase in the number of plaintiffs decreased blameworthiness assigned to the defendant despite contrary evidence and amount of probative evidence processed. Complex language did not affect memory but did affect jurors' ability to appropriately compensate differentially worthy plaintiffs. Jurors assigned compensatory awards commensurate with the plaintiffs' injuries only under low-load and less complex language conditions.

  4. Failure of ESI Spectra to Represent Metal-Complex Solution Composition: A Study of Lanthanide-Carboxylate Complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McDonald, Luther W.; Campbell, James A.; Clark, Sue B.

    2014-01-21

    Electrospray ionization - mass spectrometry (ESI-MS) was used for the characterization of uranyl complexed to tributyl phosphate (TBP) and dibutyl phosphate (DBP). The stoichiometry of uranyl with TBP and DBP was determined, and the gas phase speciation was found to be dependent on the cone voltage applied to induce fragmentation on the gas phase complexes. To quantitatively compare the gas phase distribution of species to solution, apparent stability constants were calculated. With a cone voltage of 80V, the apparent stability constants for the complexes UO2(NO3)2•2TBP, UO2(NO3)2(H2O)•2TBP, and UO2(DBP)+ were determined. With a lower cone voltage applied, larger complexes were observedmore » and stability constants for the complexes UO2(NO3)2•3TBP and UO2(DBP)42- were determined.« less

  5. Metal complexes as DNA intercalators.

    PubMed

    Liu, Hong-Ke; Sadler, Peter J

    2011-05-17

    DNA has a strong affinity for many heterocyclic aromatic dyes, such as acridine and its derivatives. Lerman in 1961 first proposed intercalation as the source of this affinity, and this mode of DNA binding has since attracted considerable research scrutiny. Organic intercalators can inhibit nucleic acid synthesis in vivo, and they are now common anticancer drugs in clinical therapy. The covalent attachment of organic intercalators to transition metal coordination complexes, yielding metallointercalators, can lead to novel DNA interactions that influence biological activity. Metal complexes with σ-bonded aromatic side arms can act as dual-function complexes: they bind to DNA both by metal coordination and through intercalation of the attached aromatic ligand. These aromatic side arms introduce new modes of DNA binding, involving mutual interactions of functional groups held in close proximity. The biological activity of both cis- and trans-diamine Pt(II) complexes is dramatically enhanced by the addition of σ-bonded intercalators. We have explored a new class of organometallic "piano-stool" Ru(II) and Os(II) arene anticancer complexes of the type [(η(6)-arene)Ru/Os(XY)Cl](+). Here XY is, for example, ethylenediamine (en), and the arene ligand can take many forms, including tetrahydroanthracene, biphenyl, or p-cymene. Arene-nucleobase stacking interactions can have a significant influence on both the kinetics and thermodynamics of DNA binding. In particular, the cytotoxic activity, conformational distortions, recognition by DNA-binding proteins, and repair mechanisms are dependent on the arene. A major difficulty in developing anticancer drugs is cross-resistance, a phenomenon whereby a cell that is resistant to one drug is also resistant to another drug in the same class. These new complexes are non-cross-resistant with cisplatin towards cancer cells: they constitute a new class of anticancer agents, with a mechanism of action that differs from the anticancer

  6. Characterization of Non-Innocent Metal Complexes Using Solid-State NMR Spectroscopy: o-Dioxolene Vanadium Complexes

    PubMed Central

    Chatterjee, Pabitra B.; Goncharov-Zapata, Olga; Quinn, Laurence L.; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W.; Polenova, Tatyana; Crans, Debbie C.

    2012-01-01

    51V solid-state NMR (SSNMR) studies of a series of non-innocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that 51V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic 51V NMR chemical shifts cover a wide range from −200 ppm to 400 ppm in solution and from −219 to 530 ppm in the solid state. A linear correlation of 51V NMR isotropic solution and solid-state chemical shifts of complexes containing non-innocent ligands is observed. These experimental results provide the information needed for the application of 51V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems, and in particular those containing non-innocent ligands and that have chemical shifts outside the populated range of −300 ppm to −700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from 51V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (DFT) calculations of NMR parameters for [VO(hshed)(Cat)] yield 51V CSA tensor in reasonable agreement with the experimental results, but surprisingly, the calculated quadrupolar coupling constant is significantly greater than the experimental value. The studies demonstrate that substitution of the

  7. Complexation of polyoxometalates with cyclodextrins.

    PubMed

    Wu, Yilei; Shi, Rufei; Wu, Yi-Lin; Holcroft, James M; Liu, Zhichang; Frasconi, Marco; Wasielewski, Michael R; Li, Hui; Stoddart, J Fraser

    2015-04-01

    Although complexation of hydrophilic guests inside the cavities of hydrophobic hosts is considered to be unlikely, we demonstrate herein the complexation between γ- and β-cyclodextrins (γ- and β-CDs) with an archetypal polyoxometalate (POM)--namely, the [PMo12O40](3-) trianion--which has led to the formation of two organic-inorganic hybrid 2:1 complexes, namely [La(H2O)9]{[PMo12O40]⊂[γ-CD]2} (CD-POM-1) and [La(H2O)9] {[PMo12O40]⊂[β-CD]2} (CD-POM-2), in the solid state. The extent to which these complexes assemble in solution has been investigated by (i) (1)H, (13)C, and (31)P NMR spectroscopies and (ii) small- and wide-angle X-ray scattering, as well as (iii) mass spectrometry. Single-crystal X-ray diffraction reveals that both complexes have a sandwich-like structure, wherein one [PMo12O40](3-) trianion is encapsulated by the primary faces of two CD tori through intermolecular [C-H···O═Mo] interactions. X-ray crystal superstructures of CD-POM-1 and CD-POM-2 show also that both of these 2:1 complexes are lined up longitudinally in a one-dimensional columnar fashion by means of [O-H···O] interactions. A beneficial nanoconfinement-induced stabilizing effect is supported by the observation of slow color changes for these supermolecules in aqueous solution phase. Electrochemical studies show that the redox properties of [PMo12O40](3-) trianions encapsulated by CDs in the complexes are largely preserved in solution. The supramolecular complementarity between the CDs and the [PMo12O40](3-) trianion provides yet another opportunity for the functionalization of POMs under mild conditions by using host-guest chemistry.

  8. Trypanosoma brucei RNA Editing Complex

    PubMed Central

    O'Hearn, Sean F.; Huang, Catherine E.; Hemann, Mike; Zhelonkina, Alevtina; Sollner-Webb, Barbara

    2003-01-01

    Maturation of Trypanosoma brucei mitochondrial mRNA involves massive posttranscriptional insertion and deletion of uridine residues. This RNA editing utilizes an enzymatic complex with seven major proteins, band I through band VII. We here use RNA interference (RNAi) to examine the band II and band V proteins. Band II is found essential for viability; it is needed to maintain the normal structure of the editing complex and to retain the band V ligase protein. Previously, band III was found essential for certain activities, including maintenance of the editing complex and retention of the band IV ligase protein. Thus, band II and band V form a protein pair with features analogous to the band III/band IV ligase pair. Since band V is specific for U insertion and since band IV is needed for U deletion, their parallel organization suggests that the editing complex has a pseudosymmetry. However, unlike the essential band IV ligase, RNAi to band V has only a morphological but no growth rate effect, suggesting that it is stimulatory but nonessential. Indeed, in vitro analysis of band V RNAi cell extract demonstrates that band IV can seal U insertion when band V is lacking. Thus, band IV ligase is the first activity of the basic editing complex shown able to serve in both forms of editing. Our studies also indicate that the U insertional portion may be less central in the editing complex than the corresponding U deletional portion. PMID:14560033

  9. Amphotericin B Lipid Complex Injection

    MedlinePlus

    Amphotericin B lipid complex injection is used to treat serious, possibly life-threatening fungal infections in people who did not respond ... to tolerate conventional amphotericin B therapy. Amphotericin B lipid complex injection is in a class of medications ...

  10. Complex systems: physics beyond physics

    NASA Astrophysics Data System (ADS)

    Holovatch, Yurij; Kenna, Ralph; Thurner, Stefan

    2017-03-01

    Complex systems are characterised by specific time-dependent interactions among their many constituents. As a consequence they often manifest rich, non-trivial and unexpected behaviour. Examples arise both in the physical and non-physical worlds. The study of complex systems forms a new interdisciplinary research area that cuts across physics, biology, ecology, economics, sociology, and the humanities. In this paper we review the essence of complex systems from a physicists' point of view, and try to clarify what makes them conceptually different from systems that are traditionally studied in physics. Our goal is to demonstrate how the dynamics of such systems may be conceptualised in quantitative and predictive terms by extending notions from statistical physics and how they can often be captured in a framework of co-evolving multiplex network structures. We mention three areas of complex-systems science that are currently studied extensively, the science of cities, dynamics of societies, and the representation of texts as evolutionary objects. We discuss why these areas form complex systems in the above sense. We argue that there exists plenty of new ground for physicists to explore and that methodical and conceptual progress is needed most.

  11. Complex fuzzy soft expert sets

    NASA Astrophysics Data System (ADS)

    Selvachandran, Ganeshsree; Hafeed, Nisren A.; Salleh, Abdul Razak

    2017-04-01

    Complex fuzzy sets and its accompanying theory although at its infancy, has proven to be superior to classical type-1 fuzzy sets, due its ability in representing time-periodic problem parameters and capturing the seasonality of the fuzziness that exists in the elements of a set. These are important characteristics that are pervasive in most real world problems. However, there are two major problems that are inherent in complex fuzzy sets: it lacks a sufficient parameterization tool and it does not have a mechanism to validate the values assigned to the membership functions of the elements in a set. To overcome these problems, we propose the notion of complex fuzzy soft expert sets which is a hybrid model of complex fuzzy sets and soft expert sets. This model incorporates the advantages of complex fuzzy sets and soft sets, besides having the added advantage of allowing the users to know the opinion of all the experts in a single model without the need for any additional cumbersome operations. As such, this model effectively improves the accuracy of representation of problem parameters that are periodic in nature, besides having a higher level of computational efficiency compared to similar models in literature.

  12. Approaching human language with complex networks.

    PubMed

    Cong, Jin; Liu, Haitao

    2014-12-01

    The interest in modeling and analyzing human language with complex networks is on the rise in recent years and a considerable body of research in this area has already been accumulated. We survey three major lines of linguistic research from the complex network approach: 1) characterization of human language as a multi-level system with complex network analysis; 2) linguistic typological research with the application of linguistic networks and their quantitative measures; and 3) relationships between the system-level complexity of human language (determined by the topology of linguistic networks) and microscopic linguistic (e.g., syntactic) features (as the traditional concern of linguistics). We show that the models and quantitative tools of complex networks, when exploited properly, can constitute an operational methodology for linguistic inquiry, which contributes to the understanding of human language and the development of linguistics. We conclude our review with suggestions for future linguistic research from the complex network approach: 1) relationships between the system-level complexity of human language and microscopic linguistic features; 2) expansion of research scope from the global properties to other levels of granularity of linguistic networks; and 3) combination of linguistic network analysis with other quantitative studies of language (such as quantitative linguistics). Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Approaching human language with complex networks

    NASA Astrophysics Data System (ADS)

    Cong, Jin; Liu, Haitao

    2014-12-01

    The interest in modeling and analyzing human language with complex networks is on the rise in recent years and a considerable body of research in this area has already been accumulated. We survey three major lines of linguistic research from the complex network approach: 1) characterization of human language as a multi-level system with complex network analysis; 2) linguistic typological research with the application of linguistic networks and their quantitative measures; and 3) relationships between the system-level complexity of human language (determined by the topology of linguistic networks) and microscopic linguistic (e.g., syntactic) features (as the traditional concern of linguistics). We show that the models and quantitative tools of complex networks, when exploited properly, can constitute an operational methodology for linguistic inquiry, which contributes to the understanding of human language and the development of linguistics. We conclude our review with suggestions for future linguistic research from the complex network approach: 1) relationships between the system-level complexity of human language and microscopic linguistic features; 2) expansion of research scope from the global properties to other levels of granularity of linguistic networks; and 3) combination of linguistic network analysis with other quantitative studies of language (such as quantitative linguistics).

  14. Teacher Modeling Using Complex Informational Texts

    ERIC Educational Resources Information Center

    Fisher, Douglas; Frey, Nancy

    2015-01-01

    Modeling in complex texts requires that teachers analyze the text for factors of qualitative complexity and then design lessons that introduce students to that complexity. In addition, teachers can model the disciplinary nature of content area texts as well as word solving and comprehension strategies. Included is a planning guide for think aloud.

  15. 21 CFR 178.3290 - Chromic chloride complexes.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Chromic chloride complexes. 178.3290 Section 178... SANITIZERS Certain Adjuvants and Production Aids § 178.3290 Chromic chloride complexes. Myristo chromic chloride complex and stearato chromic chloride complex may be safely used as release agents in the closure...

  16. Complex Topographic Feature Ontology Patterns

    USGS Publications Warehouse

    Varanka, Dalia E.; Jerris, Thomas J.

    2015-01-01

    Semantic ontologies are examined as effective data models for the representation of complex topographic feature types. Complex feature types are viewed as integrated relations between basic features for a basic purpose. In the context of topographic science, such component assemblages are supported by resource systems and found on the local landscape. Ontologies are organized within six thematic modules of a domain ontology called Topography that includes within its sphere basic feature types, resource systems, and landscape types. Context is constructed not only as a spatial and temporal setting, but a setting also based on environmental processes. Types of spatial relations that exist between components include location, generative processes, and description. An example is offered in a complex feature type ‘mine.’ The identification and extraction of complex feature types are an area for future research.

  17. Oxidative mutagenesis of doxorubicin-Fe(III) complex.

    PubMed

    Kostoryz, E L; Yourtee, D M

    2001-02-20

    Doxorubicin has a high affinity for inorganic iron, Fe(III), and has potential to form doxorubicin-Fe(III) complexes in biological systems. Indirect involvement of iron has been substantiated in the oxidative mutagenicity of doxorubicin. In this study, however, direct involvement of Fe(III) was evaluated in mutagenicity studies with the doxorubicin-Fe(III) complex. The Salmonella mutagenicity assay with strain TA102 was used with a pre-incubation step. The highest mutagenicity of doxorubicin-Fe(III) complex was observed at the dose of 2.5nmol/plate of the complex. The S9-mix decreased this highest mutagenicity but increased the number of revertants at a higher dose of 10nmol/plate of the complex. On the other hand, the mutagenicity of the doxorubicin-Fe(III) complex at the doses of 0.25, 0.5, 1 and 2nmol/plate was enhanced about twice by the addition of glutathione plus H(2)O(2). This enhanced mutagenicity as well as of the complex itself, the complex plus glutathione, and the complex plus H(2)O(2) were reduced by the addition of ADR-529, an Fe(III) chelator, and potassium iodide, a hydroxyl radical scavenger. These results indicate that doxorubicin-Fe(III) complex exert the mutagenicity through oxidative DNA damage and that Fe(III) is a required element in the mutagenesis of doxorubicin.

  18. Management of complex dynamical systems

    NASA Astrophysics Data System (ADS)

    MacKay, R. S.

    2018-02-01

    Complex dynamical systems are systems with many interdependent components which evolve in time. One might wish to control their trajectories, but a more practical alternative is to control just their statistical behaviour. In many contexts this would be both sufficient and a more realistic goal, e.g. climate and socio-economic systems. I refer to it as ‘management’ of complex dynamical systems. In this paper, some mathematics for management of complex dynamical systems is developed in the weakly dependent regime, and questions are posed for the strongly dependent regime.

  19. The Complexity Analysis Tool

    DTIC Science & Technology

    1988-10-01

    overview of the complexity analysis tool ( CAT ), an automated tool which will analyze mission critical computer resources (MCCR) software. CAT is based...84 MAR UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE 19. ABSTRACT: (cont) CAT automates the metric for BASIC (HP-71), ATLAS (EQUATE), Ada (subset...UNIX 5.2). CAT analyzes source code and computes complexity on a module basis. CAT also generates graphic representations of the logic flow paths and

  20. Complexity in electronic negotiation support systems.

    PubMed

    Griessmair, Michele; Strunk, Guido; Vetschera, Rudolf; Koeszegi, Sabine T

    2011-10-01

    It is generally acknowledged that the medium influences the way we communicate and negotiation research directs considerable attention to the impact of different electronic communication modes on the negotiation process and outcomes. Complexity theories offer models and methods that allow the investigation of how pattern and temporal sequences unfold over time in negotiation interactions. By focusing on the dynamic and interactive quality of negotiations as well as the information, choice, and uncertainty contained in the negotiation process, the complexity perspective addresses several issues of central interest in classical negotiation research. In the present study we compare the complexity of the negotiation communication process among synchronous and asynchronous negotiations (IM vs. e-mail) as well as an electronic negotiation support system including a decision support system (DSS). For this purpose, transcripts of 145 negotiations have been coded and analyzed with the Shannon entropy and the grammar complexity. Our results show that negotiating asynchronically via e-mail as well as including a DSS significantly reduces the complexity of the negotiation process. Furthermore, a reduction of the complexity increases the probability of reaching an agreement.

  1. The building blocks of economic complexity

    PubMed Central

    Hidalgo, César A.; Hausmann, Ricardo

    2009-01-01

    For Adam Smith, wealth was related to the division of labor. As people and firms specialize in different activities, economic efficiency increases, suggesting that development is associated with an increase in the number of individual activities and with the complexity that emerges from the interactions between them. Here we develop a view of economic growth and development that gives a central role to the complexity of a country's economy by interpreting trade data as a bipartite network in which countries are connected to the products they export, and show that it is possible to quantify the complexity of a country's economy by characterizing the structure of this network. Furthermore, we show that the measures of complexity we derive are correlated with a country's level of income, and that deviations from this relationship are predictive of future growth. This suggests that countries tend to converge to the level of income dictated by the complexity of their productive structures, indicating that development efforts should focus on generating the conditions that would allow complexity to emerge to generate sustained growth and prosperity. PMID:19549871

  2. Generative complexity of Gray-Scott model

    NASA Astrophysics Data System (ADS)

    Adamatzky, Andrew

    2018-03-01

    In the Gray-Scott reaction-diffusion system one reactant is constantly fed in the system, another reactant is reproduced by consuming the supplied reactant and also converted to an inert product. The rate of feeding one reactant in the system and the rate of removing another reactant from the system determine configurations of concentration profiles: stripes, spots, waves. We calculate the generative complexity-a morphological complexity of concentration profiles grown from a point-wise perturbation of the medium-of the Gray-Scott system for a range of the feeding and removal rates. The morphological complexity is evaluated using Shannon entropy, Simpson diversity, approximation of Lempel-Ziv complexity, and expressivity (Shannon entropy divided by space-filling). We analyse behaviour of the systems with highest values of the generative morphological complexity and show that the Gray-Scott systems expressing highest levels of the complexity are composed of the wave-fragments (similar to wave-fragments in sub-excitable media) and travelling localisations (similar to quasi-dissipative solitons and gliders in Conway's Game of Life).

  3. Complexity of the AdS soliton

    NASA Astrophysics Data System (ADS)

    Reynolds, Alan P.; Ross, Simon F.

    2018-05-01

    We consider the holographic complexity conjectures in the context of the AdS soliton, which is the holographic dual of the ground state of a field theory on a torus with antiperiodic boundary conditions for fermions on one cycle. The complexity is a non-trivial function of the size of the circle with antiperiodic boundary conditions, which sets an IR scale in the dual geometry. We find qualitative differences between the calculations of complexity from spatial volume and action (CV and CA). In the CV calculation, the complexity for antiperiodic boundary conditions is smaller than for periodic, and decreases monotonically with increasing IR scale. In the CA calculation, the complexity for antiperiodic boundary conditions is larger than for periodic, and initially increases with increasing IR scale, eventually decreasing to zero as the IR scale becomes of order the UV cutoff. We compare these results to a simple calculation for free fermions on a lattice, where we find the complexity for antiperiodic boundary conditions is larger than for periodic.

  4. [VGKC-complex antibodies].

    PubMed

    Watanabe, Osamu

    2013-04-01

    Various antibodies are associated with voltage-gated potassium channels (VGKCs). Representative antibodies to VGKCs were first identified by radioimmunoassays using radioisotope-labeled alpha-dendrotoxin-VGKCs solubilized from rabbit brain. These antibodies were detected only in a proportion of patients with acquired neuromyotonia (Isaacs' syndrome). VGKC antibodies were also detected in patients with Morvan's syndrome and in those with a form of autoimmune limbic encephalitis. Recent studies indicated that the "VGKC" antibodies are mainly directed toward associated proteins (for example LGI-1 and CASPR-2) that complex with the VGKCs themselves. The "VGKC" antibodies are now commonly known as VGKC-complex antibodies. In general, LGI-1 antibodies are most commonly detected in patients with limbic encephalitis with syndrome of inappropriate secretion of antidiuretic hormone. CASPR-2 antibodies are present in the majority of patients with Morvan's syndrome. These patients develop combinations of CNS symptoms, autonomic dysfunction, and peripheral nerve hyperexcitability. Furthermore, VGKC-complex antibodies are tightly associated with chronic idiopathic pain. Hyperexcitability of nociceptive pathways has also been implicated. These antibodies may be detected in sera of some patients with neurodegenerative diseases (for example, amyotrophic lateral sclerosis and Creutzfeldt-Jakob disease).

  5. Effect of Stepwise Doping on Lifetime and Efficiency of Blue and White Phosphorescent Organic Light Emitting Diodes.

    PubMed

    Lee, Song Eun; Lee, Ho Won; Lee, Seok Jae; Koo, Ja-ryong; Lee, Dong Hyung; Yang, Hyung Jin; Kim, Hye Jeong; Yoon, Seung Soo; Kim, Young Kwan

    2015-02-01

    We investigated a light emission mechanism of blue phosphorescent organic light emitting diodes (PHOLEDs), using a stepwise doping profile of 2, 8, and 14 wt.% within the emitting layer (EML). We fabricated several blue PHOLEDs with phosphorescent blue emitter iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate doped in N,N'-dicarbazolyl-3,5-benzene as a p-type host material. A blue PHOLED with the highest doping concentration as part of the EML close to an electron transporting layer showed a maximum luminous efficiency of 20.74 cd/A, and a maximum external quantum efficiency of 10.52%. This can be explained by effective electron injection through a highly doped EML side. Additionally, a white OLED based on the doping profile was fabricated with two thin red EMLs within a blue EML maintaining a thickness of 30 nm for the entire EML. Keywords: Blue Phosphorescent Organic Light Emitting Diodes, Stepwise Doping Structure, Charge Trapping Effect.

  6. Molecular architecture of the human GINS complex

    PubMed Central

    Boskovic, Jasminka; Coloma, Javier; Aparicio, Tomás; Zhou, Min; Robinson, Carol V; Méndez, Juan; Montoya, Guillermo

    2007-01-01

    Chromosomal DNA replication is strictly regulated through a sequence of steps that involve many macromolecular protein complexes. One of these is the GINS complex, which is required for initiation and elongation phases in eukaryotic DNA replication. The GINS complex consists of four paralogous subunits. At the G1/S transition, GINS is recruited to the origins of replication where it assembles with cell-division cycle protein (Cdc)45 and the minichromosome maintenance mutant (MCM)2–7 to form the Cdc45/Mcm2–7/GINS (CMG) complex, the presumed replicative helicase. We isolated the human GINS complex and have shown that it can bind to DNA. By using single-particle electron microscopy and three-dimensional reconstruction, we obtained a medium-resolution volume of the human GINS complex, which shows a horseshoe shape. Analysis of the protein interactions using mass spectrometry and monoclonal antibody mapping shows the subunit organization within the GINS complex. The structure and DNA-binding data suggest how GINS could interact with DNA and also its possible role in the CMG helicase complex. PMID:17557111

  7. New Communitarianism Movements and Complex Utopia

    NASA Astrophysics Data System (ADS)

    Akdeniz, K. Gediz

    Simulation is a rapidly growing field in social sciences. Simulation theories in social sciences are considered to critique social dynamics and societies which are mostly simulated by media, cinema, TV, internet, etc. Recently we (Akdeniz KG, Disorder in complex human system. In: Fritzsch H, Phua KK (eds) Singapore: proceedings of the conference in Honour of Murray Gell-Mann's 80th birthday quantum mechanics, elementary particles, quantum cosmology and complexity. World Scientific Publishing, Hackensack, pp 630-637, 2009) purposed a simulation theory as a critique theory to investigate disordered human behaviors. In this theory, "Disorder-Sensitive Human Behaviors (DSHB) Simulation Theory", chaotic awareness is also considered as a reality principle in simulation world to complete Baudrillard Simulation Theory (Baudrillard J, Simulacra and simulation. University of Michigan Press, Michigan, 1995). We call the emergence of this reality as zuhur which is different than simulacra. More recently we proposed the complex utopia (Akdeniz KG, From Simulacra to Zuhur in Complex Utopia. 11th International Conference of the Utopian Studies Society, Lublin, 2010; Akdeniz KG, The new identities of the physicist: cyborg-physicist and post-physicist. In: Proceedings of the conference of world international conference of technology and education, Beirut, 2010) to critique the complex societies and communities in simulation world. The challenging agents in the complex utopia are both simulacra and zuhur. In this paper we would like to review "What is the complex utopia?" And we shall critique some global events in framework of complex utopia with particular examples in socio-economic and political contexts.

  8. Modeling the assembly order of multimeric heteroprotein complexes

    PubMed Central

    Esquivel-Rodriguez, Juan; Terashi, Genki; Christoffer, Charles; Shin, Woong-Hee

    2018-01-01

    Protein-protein interactions are the cornerstone of numerous biological processes. Although an increasing number of protein complex structures have been determined using experimental methods, relatively fewer studies have been performed to determine the assembly order of complexes. In addition to the insights into the molecular mechanisms of biological function provided by the structure of a complex, knowing the assembly order is important for understanding the process of complex formation. Assembly order is also practically useful for constructing subcomplexes as a step toward solving the entire complex experimentally, designing artificial protein complexes, and developing drugs that interrupt a critical step in the complex assembly. There are several experimental methods for determining the assembly order of complexes; however, these techniques are resource-intensive. Here, we present a computational method that predicts the assembly order of protein complexes by building the complex structure. The method, named Path-LzerD, uses a multimeric protein docking algorithm that assembles a protein complex structure from individual subunit structures and predicts assembly order by observing the simulated assembly process of the complex. Benchmarked on a dataset of complexes with experimental evidence of assembly order, Path-LZerD was successful in predicting the assembly pathway for the majority of the cases. Moreover, when compared with a simple approach that infers the assembly path from the buried surface area of subunits in the native complex, Path-LZerD has the strong advantage that it can be used for cases where the complex structure is not known. The path prediction accuracy decreased when starting from unbound monomers, particularly for larger complexes of five or more subunits, for which only a part of the assembly path was correctly identified. As the first method of its kind, Path-LZerD opens a new area of computational protein structure modeling and will be

  9. Modeling the assembly order of multimeric heteroprotein complexes.

    PubMed

    Peterson, Lenna X; Togawa, Yoichiro; Esquivel-Rodriguez, Juan; Terashi, Genki; Christoffer, Charles; Roy, Amitava; Shin, Woong-Hee; Kihara, Daisuke

    2018-01-01

    Protein-protein interactions are the cornerstone of numerous biological processes. Although an increasing number of protein complex structures have been determined using experimental methods, relatively fewer studies have been performed to determine the assembly order of complexes. In addition to the insights into the molecular mechanisms of biological function provided by the structure of a complex, knowing the assembly order is important for understanding the process of complex formation. Assembly order is also practically useful for constructing subcomplexes as a step toward solving the entire complex experimentally, designing artificial protein complexes, and developing drugs that interrupt a critical step in the complex assembly. There are several experimental methods for determining the assembly order of complexes; however, these techniques are resource-intensive. Here, we present a computational method that predicts the assembly order of protein complexes by building the complex structure. The method, named Path-LzerD, uses a multimeric protein docking algorithm that assembles a protein complex structure from individual subunit structures and predicts assembly order by observing the simulated assembly process of the complex. Benchmarked on a dataset of complexes with experimental evidence of assembly order, Path-LZerD was successful in predicting the assembly pathway for the majority of the cases. Moreover, when compared with a simple approach that infers the assembly path from the buried surface area of subunits in the native complex, Path-LZerD has the strong advantage that it can be used for cases where the complex structure is not known. The path prediction accuracy decreased when starting from unbound monomers, particularly for larger complexes of five or more subunits, for which only a part of the assembly path was correctly identified. As the first method of its kind, Path-LZerD opens a new area of computational protein structure modeling and will be

  10. Complexity-Entropy Causality Plane as a Complexity Measure for Two-Dimensional Patterns

    PubMed Central

    Ribeiro, Haroldo V.; Zunino, Luciano; Lenzi, Ervin K.; Santoro, Perseu A.; Mendes, Renio S.

    2012-01-01

    Complexity measures are essential to understand complex systems and there are numerous definitions to analyze one-dimensional data. However, extensions of these approaches to two or higher-dimensional data, such as images, are much less common. Here, we reduce this gap by applying the ideas of the permutation entropy combined with a relative entropic index. We build up a numerical procedure that can be easily implemented to evaluate the complexity of two or higher-dimensional patterns. We work out this method in different scenarios where numerical experiments and empirical data were taken into account. Specifically, we have applied the method to fractal landscapes generated numerically where we compare our measures with the Hurst exponent; liquid crystal textures where nematic-isotropic-nematic phase transitions were properly identified; 12 characteristic textures of liquid crystals where the different values show that the method can distinguish different phases; and Ising surfaces where our method identified the critical temperature and also proved to be stable. PMID:22916097

  11. A Statistical Physics Characterization of the Complex Systems Dynamics: Quantifying Complexity from Spatio-Temporal Interactions

    NASA Astrophysics Data System (ADS)

    Koorehdavoudi, Hana; Bogdan, Paul

    2016-06-01

    Biological systems are frequently categorized as complex systems due to their capabilities of generating spatio-temporal structures from apparent random decisions. In spite of research on analyzing biological systems, we lack a quantifiable framework for measuring their complexity. To fill this gap, in this paper, we develop a new paradigm to study a collective group of N agents moving and interacting in a three-dimensional space. Our paradigm helps to identify the spatio-temporal states of the motion of the group and their associated transition probabilities. This framework enables the estimation of the free energy landscape corresponding to the identified states. Based on the energy landscape, we quantify missing information, emergence, self-organization and complexity for a collective motion. We show that the collective motion of the group of agents evolves to reach the most probable state with relatively lowest energy level and lowest missing information compared to other possible states. Our analysis demonstrates that the natural group of animals exhibit a higher degree of emergence, self-organization and complexity over time. Consequently, this algorithm can be integrated into new frameworks to engineer collective motions to achieve certain degrees of emergence, self-organization and complexity.

  12. A Statistical Physics Characterization of the Complex Systems Dynamics: Quantifying Complexity from Spatio-Temporal Interactions

    PubMed Central

    Koorehdavoudi, Hana; Bogdan, Paul

    2016-01-01

    Biological systems are frequently categorized as complex systems due to their capabilities of generating spatio-temporal structures from apparent random decisions. In spite of research on analyzing biological systems, we lack a quantifiable framework for measuring their complexity. To fill this gap, in this paper, we develop a new paradigm to study a collective group of N agents moving and interacting in a three-dimensional space. Our paradigm helps to identify the spatio-temporal states of the motion of the group and their associated transition probabilities. This framework enables the estimation of the free energy landscape corresponding to the identified states. Based on the energy landscape, we quantify missing information, emergence, self-organization and complexity for a collective motion. We show that the collective motion of the group of agents evolves to reach the most probable state with relatively lowest energy level and lowest missing information compared to other possible states. Our analysis demonstrates that the natural group of animals exhibit a higher degree of emergence, self-organization and complexity over time. Consequently, this algorithm can be integrated into new frameworks to engineer collective motions to achieve certain degrees of emergence, self-organization and complexity. PMID:27297496

  13. Cranberry Proanthocyanidins - Protein complexes for macrophage activation.

    PubMed

    Carballo, Sergio M; Haas, Linda; Krueger, Christian G; Reed, Jess D

    2017-09-20

    In this work we characterize the interaction of cranberry (Vaccinium macrocarpon) proanthocyanidins (PAC) with bovine serum albumin (BSA) and hen egg-white lysozyme (HEL) and determine the effects of these complexes on macrophage activation and antigen presentation. We isolated PAC from cranberry and complexed the isolated PAC with BSA and HEL. The properties of the PAC-protein complexes were studied by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS), gel electrophoresis and zeta-potential. The effects of PAC-BSA complexes on macrophage activation were studied in RAW 264.7 macrophage like cells after treatment with lipopolysaccharide (LPS). Fluorescence microscopy was used to study the endocytosis of PAC-BSA complexes. The effects of the PAC complexes on macrophage antigen presentation were studied in an in vitro model of HEL antigen presentation by mouse peritoneal mononuclear cells to a T-cell hybridoma. The mass spectra of the PAC complexes with BSA and HEL differed from the spectra of the proteins alone by the presence of broad shoulders on the singly and doubly charged protein peaks. Complexation with PAC altered the electrophoretic mobility shift assay in native agarose gel and the electrophoretic mobility (ζ-potential) values. These results indicate that the PAC-protein complexes are stable and alter the protein structure without precipitating the protein. Fluorescence microscopy showed that the RAW 264.7 macrophages endocytosed BSA and PAC-BSA complexes in discrete vesicles that surrounded the nucleus. Macrophages treated with increasing amounts of PAC-BSA complexes had significantly reduced COX-2 and iNOS expression in response to treatment with lipopolysaccharide (LPS) in comparison to the controls. The PAC-HEL complexes modulated antigen uptake, processing and presentation in murine peritoneal macrophages. After 4 h of pre-incubation, only trace amounts of IL-2 were detected in the co-cultures treated with HEL

  14. Implementation of Complexity Analyzing Based on Additional Effect

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Li, Na; Liang, Yanhong; Liu, Fang

    According to the Complexity Theory, there is complexity in the system when the functional requirement is not be satisfied. There are several study performances for Complexity Theory based on Axiomatic Design. However, they focus on reducing the complexity in their study and no one focus on method of analyzing the complexity in the system. Therefore, this paper put forth a method of analyzing the complexity which is sought to make up the deficiency of the researches. In order to discussing the method of analyzing the complexity based on additional effect, this paper put forth two concepts which are ideal effect and additional effect. The method of analyzing complexity based on additional effect combines Complexity Theory with Theory of Inventive Problem Solving (TRIZ). It is helpful for designers to analyze the complexity by using additional effect. A case study shows the application of the process.

  15. Synchronization in complex networks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Arenas, A.; Diaz-Guilera, A.; Moreno, Y.

    Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. We also overview the new emergent features coming out from the interplay between the structure and the function of the underlying pattern of connections. Extensive numerical work as well as analyticalmore » approaches to the problem are presented. Finally, we review several applications of synchronization in complex networks to different disciplines: biological systems and neuroscience, engineering and computer science, and economy and social sciences.« less

  16. Minimal perceptrons for memorizing complex patterns

    NASA Astrophysics Data System (ADS)

    Pastor, Marissa; Song, Juyong; Hoang, Danh-Tai; Jo, Junghyo

    2016-11-01

    Feedforward neural networks have been investigated to understand learning and memory, as well as applied to numerous practical problems in pattern classification. It is a rule of thumb that more complex tasks require larger networks. However, the design of optimal network architectures for specific tasks is still an unsolved fundamental problem. In this study, we consider three-layered neural networks for memorizing binary patterns. We developed a new complexity measure of binary patterns, and estimated the minimal network size for memorizing them as a function of their complexity. We formulated the minimal network size for regular, random, and complex patterns. In particular, the minimal size for complex patterns, which are neither ordered nor disordered, was predicted by measuring their Hamming distances from known ordered patterns. Our predictions agree with simulations based on the back-propagation algorithm.

  17. Synthesis, spectral characterization and catalytic activity of Co(II) complexes of drugs: crystal structure of Co(II)-trimethoprim complex.

    PubMed

    Madhupriya, Selvaraj; Elango, Kuppanagounder P

    2014-01-24

    New Co(II) complexes with drugs such as trimethoprim (TMP), cimetidine (CTD), niacinamide (NAM) and ofloxacin (OFL) as ligands were synthesized. The complexes were characterized by analytical analysis, various spectral techniques such as FT-IR, UV-Vis, magnetic measurements and molar conductivity. The magnetic susceptibility results coupled with the electronic spectra suggested a tetrahedral geometry for the complexes. The coordination mode of trimethoprim ligand and geometry of the complex were confirmed by single crystal X-ray studies. In this complex the metal ion possesses a tetrahedral geometry with two nitrogen atom from two TMP ligands and two chloride ions coordinated to it. The catalytic activity of the complexes in aryl-aryl coupling reaction was screened and the results indicated that among the four complexes [Co(OFL)Cl(H2O)] exhibited excellent catalytic activity. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. CORUM: the comprehensive resource of mammalian protein complexes

    PubMed Central

    Ruepp, Andreas; Brauner, Barbara; Dunger-Kaltenbach, Irmtraud; Frishman, Goar; Montrone, Corinna; Stransky, Michael; Waegele, Brigitte; Schmidt, Thorsten; Doudieu, Octave Noubibou; Stümpflen, Volker; Mewes, H. Werner

    2008-01-01

    Protein complexes are key molecular entities that integrate multiple gene products to perform cellular functions. The CORUM (http://mips.gsf.de/genre/proj/corum/index.html) database is a collection of experimentally verified mammalian protein complexes. Information is manually derived by critical reading of the scientific literature from expert annotators. Information about protein complexes includes protein complex names, subunits, literature references as well as the function of the complexes. For functional annotation, we use the FunCat catalogue that enables to organize the protein complex space into biologically meaningful subsets. The database contains more than 1750 protein complexes that are built from 2400 different genes, thus representing 12% of the protein-coding genes in human. A web-based system is available to query, view and download the data. CORUM provides a comprehensive dataset of protein complexes for discoveries in systems biology, analyses of protein networks and protein complex-associated diseases. Comparable to the MIPS reference dataset of protein complexes from yeast, CORUM intends to serve as a reference for mammalian protein complexes. PMID:17965090

  19. Aging and the complexity of cardiovascular dynamics

    NASA Technical Reports Server (NTRS)

    Kaplan, D. T.; Furman, M. I.; Pincus, S. M.; Ryan, S. M.; Lipsitz, L. A.; Goldberger, A. L.

    1991-01-01

    Biomedical signals often vary in a complex and irregular manner. Analysis of variability in such signals generally does not address directly their complexity, and so may miss potentially useful information. We analyze the complexity of heart rate and beat-to-beat blood pressure using two methods motivated by nonlinear dynamics (chaos theory). A comparison of a group of healthy elderly subjects with healthy young adults indicates that the complexity of cardiovascular dynamics is reduced with aging. This suggests that complexity of variability may be a useful physiological marker.

  20. Interdisciplinary conflict and organizational complexity.

    PubMed

    Guy, M E

    1986-01-01

    Most people think that conflict among the professional staff is inevitable and results from each profession's unique set of values. Each profession then defends itself by claiming its own turf. This article demonstrates that organizational complexity, not professional territorialism, influences the amount of intraorganizational conflict. In a comparison of two psychiatric hospitals, this study shows that there is not necessarily greater conflict across professions than within professions. However, there is a significantly greater amount of conflict among staff at a structurally more complex hospital than at a less-complex hospital, regardless of profession. Implications for management are discussed.

  1. Abnormal carbene-silicon halide complexes.

    PubMed

    Wang, Yuzhong; Xie, Yaoming; Wei, Pingrong; Schaefer, Henry F; Robinson, Gregory H

    2016-04-14

    Reaction of the anionic N-heterocyclic dicarbene (NHDC), [:C{[N(2,6-Pr(i)2C6H3)]2CHCLi}]n (1), with SiCl4 gives the trichlorosilyl-substituted (at the C4 carbon) N-heterocyclic carbene complex (7). Abnormal carbene-SiCl4 complex (8) may be conveniently synthesized by combining 7 with HCl·NEt3. In addition, 7 may react with CH2Cl2 in warm hexane, giving the abnormal carbene-complexed SiCl3(+) cation (9). The nature of the bonding in 9 was probed with complementary DFT computations.

  2. Managing Complexity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chassin, David P.; Posse, Christian; Malard, Joel M.

    2004-08-01

    Physical analogs have shown considerable promise for understanding the behavior of complex adaptive systems, including macroeconomics, biological systems, social networks, and electric power markets. Many of today’s most challenging technical and policy questions can be reduced to a distributed economic control problem. Indeed, economically-based control of large-scale systems is founded on the conjecture that the price-based regulation (e.g., auctions, markets) results in an optimal allocation of resources and emergent optimal system control. This paper explores the state of the art in the use physical analogs for understanding the behavior of some econophysical systems and to deriving stable and robust controlmore » strategies for them. In particular we review and discussion applications of some analytic methods based on the thermodynamic metaphor according to which the interplay between system entropy and conservation laws gives rise to intuitive and governing global properties of complex systems that cannot be otherwise understood.« less

  3. Charon Complexity

    NASA Image and Video Library

    2015-09-10

    This image of Pluto's largest moon Charon, taken by NASA's New Horizons spacecraft 10 hours before its closest approach to Pluto on July 14, 2015 from a distance of 290,000 miles (470,000 kilometers), is a recently downlinked, much higher quality version of a Charon image released on July 15. Charon, which is 750 miles (1,200 kilometers) in diameter, displays a surprisingly complex geological history, including tectonic fracturing; relatively smooth, fractured plains in the lower right; several enigmatic mountains surrounded by sunken terrain features on the right side; and heavily cratered regions in the center and upper left portion of the disk. There are also complex reflectivity patterns on Charon's surface, including bright and dark crater rays, and the conspicuous dark north polar region at the top of the image. The smallest visible features are 2.9 miles 4.6 kilometers) in size. http://photojournal.jpl.nasa.gov/catalog/PIA19932

  4. Characterization of aspartame-cyclodextrin complexation.

    PubMed

    Sohajda, Tamás; Béni, Szabolcs; Varga, Erzsébet; Iványi, Róbert; Rácz, Akos; Szente, Lajos; Noszál, Béla

    2009-12-05

    The inclusion complex formation of aspartame (guest) and various cyclodextrins (host) were examined using 1H NMR titration and capillary electrophoresis. Initially the protonation constants of aspartame were determined by NMR-pH titration with in situ pH measurement to yield log K1=7.83 and log K2=2.96. Based on these values the stability of the complexes formed by aspartame and 21 different cyclodextrins (CDs) were studied at pH 2.5, pH 5.2 and pH 9.0 values where aspartame exists predominantly in monocationic, zwitterionic and monoanionic form, respectively. The host cyclodextrin derivatives differed in various sidechains, degree of substitution, charge and purity so that the effect of these properties could be examined systematically. Concerning size, the seven-membered beta-cyclodextrin and its derivatives have been found to be the most suitable host molecules for complexation. Highest stability was observed for the acetylated derivative with a degree of substitution of 7. The purity of the CD enhanced the complexation while the degree of substitution did not provide obvious consequences. Finally, geometric aspects of the inclusion complex were assessed by 2D ROESY NMR and molecular modelling which proved that the guest's aromatic ring enters the wider end of the host cavity.

  5. A preference for some types of complexity comment on "perceived beauty of random texture patterns: A preference for complexity".

    PubMed

    Gauvrit, Nicolas; Soler-Toscano, Fernando; Guida, Alessandro

    2017-03-01

    In two experiments, Friedenberg and Liby (2016) studied how a diversity of complexity estimates such as density, number of blocks, GIF compression rate and edge length impact the perception of beauty of semi-random two-dimensional patterns. They concluded that aesthetics ratings are positively linked with GIF compression metrics and edge length, but not with the number of blocks. They also found an inverse U-shaped link between aesthetic judgments and density. These mixed results originate in the variety of metrics used to estimate what is loosely called "complexity" in psychology and indeed refers to conflicting notions. Here, we reanalyze their data adding two more conventional and normative mathematical measures of complexity: entropy and algorithmic complexity. We show that their results can be interpreted as an aesthetic preference for low redundancy, balanced patterns and "crooked" figures, but not for high algorithmic complexity. We conclude that participants tend to have a preference for some types of complexity, but not for all. These findings may help understand divergent results in the study of perceived beauty and complexity, and illustrate the need to specify the notion of complexity used in psychology. The field would certainly benefit from a precise taxonomy of complexity measures. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Artificial synthetic Mn(IV)Ca-oxido complexes mimic the oxygen-evolving complex in photosystem II.

    PubMed

    Chen, Changhui; Zhang, Chunxi; Dong, Hongxing; Zhao, Jingquan

    2015-03-14

    A novel family of heteronuclear Mn(IV)Ca-oxido complexes containing Mn(IV)Ca-oxido cuboidal moieties and reactive water molecules on Ca(2+) have been synthesized and characterized to mimic the oxygen-evolving complex (OEC) of photosystem II (PSII) in nature.

  7. Complexity perplexity: a systematic review to describe the measurement of medication regimen complexity.

    PubMed

    Paquin, Allison M; Zimmerman, Kristin M; Kostas, Tia R; Pelletier, Lindsey; Hwang, Angela; Simone, Mark; Skarf, Lara M; Rudolph, James L

    2013-11-01

    Complex medication regimens are error prone and challenging for patients, which may impact medication adherence and safety. No universal method to assess the complexity of medication regimens (CMRx) exists. The authors aim to review literature for CMRx measurements to establish consistencies and, secondarily, describe CMRx impact on healthcare outcomes. A search of EMBASE and PubMed for studies analyzing at least two medications and complexity components, among those self-managing medications, was conducted. Out of 1204 abstracts, 38 studies were included in the final sample. The majority (74%) of studies used one of five validated CMRx scales; their components and scoring were compared. Universal CMRx assessment is needed to identify and reduce complex regimens, and, thus, improve safety. The authors highlight commonalities among five scales to help build consensus. Common components (i.e., regimen factors) included dosing frequency, units per dose, and non-oral routes. Elements (e.g., twice daily) of these components (e.g., dosing frequency) and scoring varied. Patient-specific factors (e.g., dexterity, cognition) were not addressed, which is a shortcoming of current scales and a challenge for future scales. As CMRx has important outcomes, notably adherence and healthcare utilization, a standardized tool has potential for far-reaching clinical, research, and patient-safety impact.

  8. Exploiting Complexity Information for Brain Activation Detection

    PubMed Central

    Zhang, Yan; Liang, Jiali; Lin, Qiang; Hu, Zhenghui

    2016-01-01

    We present a complexity-based approach for the analysis of fMRI time series, in which sample entropy (SampEn) is introduced as a quantification of the voxel complexity. Under this hypothesis the voxel complexity could be modulated in pertinent cognitive tasks, and it changes through experimental paradigms. We calculate the complexity of sequential fMRI data for each voxel in two distinct experimental paradigms and use a nonparametric statistical strategy, the Wilcoxon signed rank test, to evaluate the difference in complexity between them. The results are compared with the well known general linear model based Statistical Parametric Mapping package (SPM12), where a decided difference has been observed. This is because SampEn method detects brain complexity changes in two experiments of different conditions and the data-driven method SampEn evaluates just the complexity of specific sequential fMRI data. Also, the larger and smaller SampEn values correspond to different meanings, and the neutral-blank design produces higher predictability than threat-neutral. Complexity information can be considered as a complementary method to the existing fMRI analysis strategies, and it may help improving the understanding of human brain functions from a different perspective. PMID:27045838

  9. A Simple Explanation of Complexation

    ERIC Educational Resources Information Center

    Elliott, J. Richard

    2010-01-01

    The topics of solution thermodynamics, activity coefficients, and complex formation are introduced through computational exercises and sample applications. The presentation is designed to be accessible to freshmen in a chemical engineering computations course. The MOSCED model is simplified to explain complex formation in terms of hydrogen…

  10. Investigation of a protein complex network

    NASA Astrophysics Data System (ADS)

    Mashaghi, A. R.; Ramezanpour, A.; Karimipour, V.

    2004-09-01

    The budding yeast Saccharomyces cerevisiae is the first eukaryote whose genome has been completely sequenced. It is also the first eukaryotic cell whose proteome (the set of all proteins) and interactome (the network of all mutual interactions between proteins) has been analyzed. In this paper we study the structure of the yeast protein complex network in which weighted edges between complexes represent the number of shared proteins. It is found that the network of protein complexes is a small world network with scale free behavior for many of its distributions. However we find that there are no strong correlations between the weights and degrees of neighboring complexes. To reveal non-random features of the network we also compare it with a null model in which the complexes randomly select their proteins. Finally we propose a simple evolutionary model based on duplication and divergence of proteins.

  11. Argument Complexity: Teaching Undergraduates to Make Better Arguments

    ERIC Educational Resources Information Center

    Kelly, Matthew A.; West, Robert L.

    2017-01-01

    The task of turning undergrads into academics requires teaching them to reason about the world in a more complex way. We present the Argument Complexity Scale, a tool for analysing the complexity of argumentation, based on the Integrative Complexity and Conceptual Complexity Scales from, respectively, political psychology and personality theory.…

  12. Engineering Complex Tissues

    PubMed Central

    MIKOS, ANTONIOS G.; HERRING, SUSAN W.; OCHAREON, PANNEE; ELISSEEFF, JENNIFER; LU, HELEN H.; KANDEL, RITA; SCHOEN, FREDERICK J.; TONER, MEHMET; MOONEY, DAVID; ATALA, ANTHONY; VAN DYKE, MARK E.; KAPLAN, DAVID; VUNJAK-NOVAKOVIC, GORDANA

    2010-01-01

    This article summarizes the views expressed at the third session of the workshop “Tissue Engineering—The Next Generation,” which was devoted to the engineering of complex tissue structures. Antonios Mikos described the engineering of complex oral and craniofacial tissues as a “guided interplay” between biomaterial scaffolds, growth factors, and local cell populations toward the restoration of the original architecture and function of complex tissues. Susan Herring, reviewing osteogenesis and vasculogenesis, explained that the vascular arrangement precedes and dictates the architecture of the new bone, and proposed that engineering of osseous tissues might benefit from preconstruction of an appropriate vasculature. Jennifer Elisseeff explored the formation of complex tissue structures based on the example of stratified cartilage engineered using stem cells and hydrogels. Helen Lu discussed engineering of tissue interfaces, a problem critical for biological fixation of tendons and ligaments, and the development of a new generation of fixation devices. Rita Kandel discussed the challenges related to the re-creation of the cartilage-bone interface, in the context of tissue engineered joint repair. Frederick Schoen emphasized, in the context of heart valve engineering, the need for including the requirements derived from “adult biology” of tissue remodeling and establishing reliable early predictors of success or failure of tissue engineered implants. Mehmet Toner presented a review of biopreservation techniques and stressed that a new breakthrough in this field may be necessary to meet all the needs of tissue engineering. David Mooney described systems providing temporal and spatial regulation of growth factor availability, which may find utility in virtually all tissue engineering and regeneration applications, including directed in vitro and in vivo vascularization of tissues. Anthony Atala offered a clinician’s perspective for functional tissue

  13. Hydrogen-impurity complexes in III V semiconductors

    NASA Astrophysics Data System (ADS)

    Ulrici, W.

    2004-12-01

    This review summarizes the presently available knowledge concerning hydrogen-impurity complexes in III-V compounds. The impurities form shallow acceptors on group III sites (Be, Zn, Cd) and on group V sites (C, Si, Ge) as well as shallow donors on group V sites (S, Se, Te) and on group III sites (Si, Sn). These complexes are mainly revealed by their hydrogen stretching modes. Therefore, nearly all information about their structure and dynamic properties is derived from vibrational spectroscopy. The complexes of shallow impurities with hydrogen have been most extensively investigated in GaAs, GaP and InP. This holds also for Mg-H in GaN. The complexes exhibit a different microscopic structure, which is discussed in detail. The isoelectronic impurity nitrogen, complexed with one hydrogen atom, is investigated in detail in GaAs and GaP. Those complexes can exist in different charge states. The experimental results such as vibrational frequencies, the microscopic structure and the activation energy for reorientation for many of these complexes are in very good agreement with results of ab initio calculations. Different types of oxygen-hydrogen complexes in GaAs and GaP are described, with one hydrogen atom or two hydrogen atoms bonded to oxygen. Three of these complexes in GaAs were found to be electrically active.

  14. Mathematicians, Attributional Complexity, and Gender

    NASA Astrophysics Data System (ADS)

    Stalder, Daniel R.

    Given indirect indications in sex role and soda! psychology research that mathematical-deductive reasoning may negatively relate to social acuity, Study 1 investigated whether mathematicians were less attributionally complex than nonmathematicians. Study 1 administered the Attributional Complexity Scale, a measure of social acuity, to female and male faculty members and graduate students in four Midwestern schools. Atlrihutional complexity (AC) is the ability and motivation to give complex explanations for behavior. Study 1 found a significant interaction between field and gender. Only among women did mathematicians score lower on AC. In addition, an established gender difference in AC (that women score higher than men) was present only among nonmathematicians. Studies 2 and 3 offered some preliminary support for the possibility that it is generally female students who score tow on AC who aspire to he mathematicians and for the underlying view that female students' perceived similarity to mathematicians can influence their vocational choices.

  15. Self-assembled virus-membrane complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Lihua; Liang, Hongjun; Angelini, Thomas

    Anionic polyelectrolytes and cationic lipid membranes can self-assemble into lamellar structures ranging from alternating layers of membranes and polyelectrolytes to 'missing layer' superlattice structures. We show that these structural differences can be understood in terms of the surface-charge-density mismatch between the polyelectrolyte and membrane components by examining complexes between cationic membranes and highly charged M13 viruses, a system that allowed us to vary the polyelectrolyte diameter independently of the charge density. Such virus-membrane complexes have pore sizes that are about ten times larger in area than DNA-membrane complexes, and can be used to package and organize large functional molecules; correlatedmore » arrays of Ru(bpy){sub 3}{sup 2+} macroionic dyes have been directly observed within the virus-membrane complexes using an electron-density reconstruction. These observations elucidate fundamental design rules for rational control of self-assembled polyelectrolyte-membrane structures, which have applications ranging from non-viral gene therapy to biomolecular templates for nanofabrication.« less

  16. Grammatical complexity for two-dimensional maps

    NASA Astrophysics Data System (ADS)

    Hagiwara, Ryouichi; Shudo, Akira

    2004-11-01

    We calculate the grammatical complexity of the symbol sequences generated from the Hénon map and the Lozi map using the recently developed methods to construct the pruning front. When the map is hyperbolic, the language of symbol sequences is regular in the sense of the Chomsky hierarchy and the corresponding grammatical complexity takes finite values. It is found that the complexity exhibits a self-similar structure as a function of the system parameter, and the similarity of the pruning fronts is discussed as an origin of such self-similarity. For non-hyperbolic cases, it is observed that the complexity monotonically increases as we increase the resolution of the pruning front.

  17. Structural complexity and molecular heterogeneity of a butterfly ejaculate reflect a complex history of selection

    PubMed Central

    Cherwin, Tamara S.; Plakke, Melissa S.; Hill, Jason; Small, Brandon S.; Goetz, Breanna J.; Wheat, Christopher W.; Morehouse, Nathan I.

    2017-01-01

    Male ejaculates are often structurally complex, and this complexity is likely to influence key reproductive interactions between males and females. However, despite its potential evolutionary significance, the molecular underpinnings of ejaculate structural complexity have received little empirical attention. To address this knowledge gap, we sought to understand the biochemical and functional properties of the structurally complex ejaculates of Pieris rapae butterflies. Males in this species produce large ejaculates called spermatophores composed of an outer envelope, an inner matrix, and a bolus of sperm. Females are thought to benefit from the nutrition contained in the soluble inner matrix through increases in longevity and fecundity. However, the indigestible outer envelope of the spermatophore delays female remating, allowing males to monopolize paternity for longer. Here, we show that these two nonsperm-containing spermatophore regions, the inner matrix and the outer envelope, differ in their protein composition and functional properties. We also reveal how these divergent protein mixtures are separately stored in the male reproductive tract and sequentially transferred to the female reproductive tract during spermatophore assembly. Intriguingly, we discovered large quantities of female-derived proteases in both spermatophore regions shortly after mating, which may contribute to spermatophore digestion and hence, female control over remating rate. Finally, we report evidence of past selection on these spermatophore proteins and female proteases, indicating a complex evolutionary history. Our findings illustrate how structural complexity of ejaculates may allow functionally and/or spatially associated suites of proteins to respond rapidly to divergent selective pressures, such as sexual conflict or reproductive cooperation. PMID:28630352

  18. Complex band structure and electronic transmission eigenchannels

    NASA Astrophysics Data System (ADS)

    Jensen, Anders; Strange, Mikkel; Smidstrup, Søren; Stokbro, Kurt; Solomon, Gemma C.; Reuter, Matthew G.

    2017-12-01

    It is natural to characterize materials in transport junctions by their conductance length dependence, β. Theoretical estimations of β are made employing two primary theories: complex band structure and density functional theory (DFT) Landauer transport. It has previously been shown that the β value derived from total Landauer transmission can be related to the β value from the smallest |ki| complex band; however, it is an open question whether there is a deeper relationship between the two. Here we probe the details of the relationship between transmission and complex band structure, in this case individual eigenchannel transmissions and different complex bands. We present calculations of decay constants for the two most conductive states as determined by complex band structure and standard DFT Landauer transport calculations for one semi-conductor and two molecular junctions. The molecular junctions show that both the length dependence of the total transmission and the individual transmission eigenvalues can be, almost always, found through the complex band structure. The complex band structure of the semi-conducting material, however, does not predict the length dependence of the total transmission but only of the individual channels, at some k-points, due to multiple channels contributing to transmission. We also observe instances of vertical bands, some of which are the smallest |ki| complex bands, that do not contribute to transport. By understanding the deeper relationship between complex bands and individual transmission eigenchannels, we can make a general statement about when the previously accepted wisdom linking transmission and complex band structure will fail, namely, when multiple channels contribute significantly to the transmission.

  19. Trimethylaluminum and borane complexes of primary amines.

    PubMed

    Németh, Balázs; Guégan, Jean-Paul; Veszprémi, Tamás; Guillemin, Jean-Claude

    2013-01-07

    Trimethylaluminum (TMA) complexes of methyl-, n-propyl-, cyclopropyl-, allyl-, and propargylamine were synthesized and their experimental properties and theoretical characteristics were compared with the respective amine-borane analogues. The amine ligand of an amine-TMA Lewis acid-base complex can be easily changed by another amine through a 2:1 amine-TMA intermediate in pentane at room temperature. The exchange of the same ligands in the case of amine-boranes requires remarkably more time in line with the calculated relative energy of the respective transition state. The (1)H and (13)C NMR experiments examining the addition of one or more equivalent of amine to the respective Lewis acid-base complex conclude in the fast exchange of the amine ligand in the NMR time scale only in the cases of amine-TMA complexes, which could also be caused by similar 2:1 complexes. However, in gas phase, only 1:1 amine-TMA complexes are present as evidenced by ultraviolet photoelectron spectroscopy (UPS). The observed UP spectra, which are the first recorded photoelectron spectra of primary amine-TMA compounds, indicate that the stabilization effect of the lone electron pair of nitrogen atom in amines during the borane complexation is stronger than that of the TMA complexation. In line with this observation, the destabilization of the σ(Al-C) orbitals is lower than that of σ(B-H) orbitals during the formation of amine-TMA and amine-borane complexes, respectively. As showed by theoretical calculations, the CH(4) elimination of the studied amine-TMA complexes is exothermic, indicating the possibility of using these compounds in metal organic chemical vapor deposition techniques (MOCVD). On the other hand, our experimental conditions avoid this methane elimination and constitutes the first procedure employing distillation to isolate primary amine-TMA complexes.

  20. Simple versus complex degenerative mitral valve disease.

    PubMed

    Javadikasgari, Hoda; Mihaljevic, Tomislav; Suri, Rakesh M; Svensson, Lars G; Navia, Jose L; Wang, Robert Z; Tappuni, Bassman; Lowry, Ashley M; McCurry, Kenneth R; Blackstone, Eugene H; Desai, Milind Y; Mick, Stephanie L; Gillinov, A Marc

    2018-07-01

    At a center where surgeons favor mitral valve (MV) repair for all subsets of leaflet prolapse, we compared results of patients undergoing repair for simple versus complex degenerative MV disease. From January 1985 to January 2016, 6153 patients underwent primary isolated MV repair for degenerative disease, 3101 patients underwent primary isolated MV repair for simple disease (posterior prolapse), and 3052 patients underwent primary isolated MV repair for complex disease (anterior or bileaflet prolapse), based on preoperative echocardiographic images. Logistic regression analysis was used to generate propensity scores for risk-adjusted comparisons (n = 2065 matched pairs). Durability was assessed by longitudinal recurrence of mitral regurgitation and reoperation. Compared with patients with simple disease, those undergoing repair of complex pathology were more likely to be younger and female (both P values < .0001) but with similar symptoms (P = .3). The most common repair technique was ring/band annuloplasty (3055/99% simple vs 3000/98% complex; P = .5), followed by leaflet resection (2802/90% simple vs 2249/74% complex; P < .0001). Among propensity-matched patients, recurrence of severe mitral regurgitation 10 years after repair was 6.2% for simple pathology versus 11% for complex pathology (P = .007), reoperation at 18 years was 6.3% for simple pathology versus 11% for complex pathology, and 20-year survival was 62% for simple pathology versus 61% for complex pathology (P = .6). Early surgical intervention has become more common in patients with degenerative MV disease, regardless of valve prolapse complexity or symptom status. Valve repair was associated with similarly low operative risk and time-related survival but less durability in complex disease. Lifelong annual echocardiographic surveillance after MV repair is recommended, particularly in patients with complex disease. Copyright © 2018 The American Association for Thoracic Surgery

  1. Multi-stage complex contagions.

    PubMed

    Melnik, Sergey; Ward, Jonathan A; Gleeson, James P; Porter, Mason A

    2013-03-01

    The spread of ideas across a social network can be studied using complex contagion models, in which agents are activated by contact with multiple activated neighbors. The investigation of complex contagions can provide crucial insights into social influence and behavior-adoption cascades on networks. In this paper, we introduce a model of a multi-stage complex contagion on networks. Agents at different stages-which could, for example, represent differing levels of support for a social movement or differing levels of commitment to a certain product or idea-exert different amounts of influence on their neighbors. We demonstrate that the presence of even one additional stage introduces novel dynamical behavior, including interplay between multiple cascades, which cannot occur in single-stage contagion models. We find that cascades-and hence collective action-can be driven not only by high-stage influencers but also by low-stage influencers.

  2. Multi-stage complex contagions

    NASA Astrophysics Data System (ADS)

    Melnik, Sergey; Ward, Jonathan A.; Gleeson, James P.; Porter, Mason A.

    2013-03-01

    The spread of ideas across a social network can be studied using complex contagion models, in which agents are activated by contact with multiple activated neighbors. The investigation of complex contagions can provide crucial insights into social influence and behavior-adoption cascades on networks. In this paper, we introduce a model of a multi-stage complex contagion on networks. Agents at different stages—which could, for example, represent differing levels of support for a social movement or differing levels of commitment to a certain product or idea—exert different amounts of influence on their neighbors. We demonstrate that the presence of even one additional stage introduces novel dynamical behavior, including interplay between multiple cascades, which cannot occur in single-stage contagion models. We find that cascades—and hence collective action—can be driven not only by high-stage influencers but also by low-stage influencers.

  3. An information dimension of weighted complex networks

    NASA Astrophysics Data System (ADS)

    Wen, Tao; Jiang, Wen

    2018-07-01

    The fractal and self-similarity are important properties in complex networks. Information dimension is a useful dimension for complex networks to reveal these properties. In this paper, an information dimension is proposed for weighted complex networks. Based on the box-covering algorithm for weighted complex networks (BCANw), the proposed method can deal with the weighted complex networks which appear frequently in the real-world, and it can get the influence of the number of nodes in each box on the information dimension. To show the wide scope of information dimension, some applications are illustrated, indicating that the proposed method is effective and feasible.

  4. Complex adaptive behavior and dexterous action

    PubMed Central

    Harrison, Steven J.; Stergiou, Nicholas

    2016-01-01

    Dexterous action, as conceptualized by Bernstein in his influential ecological analysis of human behavior, is revealed in the ability to flexibly generate behaviors that are adaptively tailored to the demands of the context in which they are embedded. Conceived as complex adaptive behavior, dexterity depends upon the qualities of robustness and degeneracy, and is supported by the functional complexity of the agent-environment system. Using Bernstein’s and Gibson’s ecological analyses of behavior situated in natural environments as conceptual touchstones, we consider the hypothesis that complex adaptive behavior capitalizes upon general principles of self-organization. Here, we outline a perspective in which the complex interactivity of nervous-system, body, and environment is revealed as an essential resource for adaptive behavior. From this perspective, we consider the implications for interpreting the functionality and dysfunctionality of human behavior. This paper demonstrates that, optimal variability, the topic of this special issue, is a logical consequence of interpreting the functionality of human behavior as complex adaptive behavior. PMID:26375932

  5. [Complexity of care: meanings and interpretation].

    PubMed

    Cologna, Marina; Zanolli, Daniela; Saiani, Luisa

    2010-01-01

    Although the concept of complexity of care is widely used and discussed, its meaning is blurred and its characteristics are not well defined. To identify the words used to define the concept of complexity in the literature and its meaning. A literature search was performed on the following databases: Pubmed, Medline, Ebsco, Cinahl and Cochrane. No temporal limits were set; publications written in English and Italian were included. Several terms are used to define the concept of complexity, often interchangeably notwithstanding their different meaning. Three main concepts were identified: nursing intensity that includes the concepts of dependency, severity and complexity of patients care; nursing workload that comprises the concept of nursing intensity and all the activities not patient-related; and the patient acuity that includes the severity of illness and the caring intensity. A common definition is needed to be able to use the concept of complexity of care to allocate nursing resources.

  6. Improve Reading with Complex Texts

    ERIC Educational Resources Information Center

    Fisher, Douglas; Frey, Nancy

    2015-01-01

    The Common Core State Standards have cast a renewed light on reading instruction, presenting teachers with the new requirements to teach close reading of complex texts. Teachers and administrators should consider a number of essential features of close reading: They are short, complex texts; rich discussions based on worthy questions; revisiting…

  7. Understanding and Teaching Complex Texts

    ERIC Educational Resources Information Center

    Fisher, Douglas; Frey, Nancy

    2014-01-01

    Teachers in today's classrooms struggle every day to design instructional interventions that would build students' reading skills and strategies in order to ensure their comprehension of complex texts. Text complexity can be determined in both qualitative and quantitative ways. In this article, the authors describe various innovative…

  8. PROCOS: computational analysis of protein-protein complexes.

    PubMed

    Fink, Florian; Hochrein, Jochen; Wolowski, Vincent; Merkl, Rainer; Gronwald, Wolfram

    2011-09-01

    One of the main challenges in protein-protein docking is a meaningful evaluation of the many putative solutions. Here we present a program (PROCOS) that calculates a probability-like measure to be native for a given complex. In contrast to scores often used for analyzing complex structures, the calculated probabilities offer the advantage of providing a fixed range of expected values. This will allow, in principle, the comparison of models corresponding to different targets that were solved with the same algorithm. Judgments are based on distributions of properties derived from a large database of native and false complexes. For complex analysis PROCOS uses these property distributions of native and false complexes together with a support vector machine (SVM). PROCOS was compared to the established scoring schemes of ZRANK and DFIRE. Employing a set of experimentally solved native complexes, high probability values above 50% were obtained for 90% of these structures. Next, the performance of PROCOS was tested on the 40 binary targets of the Dockground decoy set, on 14 targets of the RosettaDock decoy set and on 9 targets that participated in the CAPRI scoring evaluation. Again the advantage of using a probability-based scoring system becomes apparent and a reasonable number of near native complexes was found within the top ranked complexes. In conclusion, a novel fully automated method is presented that allows the reliable evaluation of protein-protein complexes. Copyright © 2011 Wiley Periodicals, Inc.

  9. Status of Complex Langevin

    NASA Astrophysics Data System (ADS)

    Seiler, Erhard

    2018-03-01

    I review the status of the Complex Langevin method, which was invented to make simulations of models with complex action feasible. I discuss the mathematical justification of the procedure, as well as its limitations and open questions. Various pragmatic measures for dealing with the existing problems are described. Finally I report on the progress in the application of the method to QCD, with the goal of determining the phase diagram of QCD as a function of temperature and baryonic chemical potential.

  10. Subunit mass fingerprinting of mitochondrial complex I.

    PubMed

    Morgner, Nina; Zickermann, Volker; Kerscher, Stefan; Wittig, Ilka; Abdrakhmanova, Albina; Barth, Hans-Dieter; Brutschy, Bernhard; Brandt, Ulrich

    2008-10-01

    We have employed laser induced liquid bead ion desorption (LILBID) mass spectrometry to determine the total mass and to study the subunit composition of respiratory chain complex I from Yarrowia lipolytica. Using 5-10 pmol of purified complex I, we could assign all 40 known subunits of this membrane bound multiprotein complex to peaks in LILBID subunit fingerprint spectra by comparing predicted protein masses to observed ion masses. Notably, even the highly hydrophobic subunits encoded by the mitochondrial genome were easily detectable. Moreover, the LILBID approach allowed us to spot and correct several errors in the genome-derived protein sequences of complex I subunits. Typically, the masses of the individual subunits as determined by LILBID mass spectrometry were within 100 Da of the predicted values. For the first time, we demonstrate that LILBID spectrometry can be successfully applied to a complex I band eluted from a blue-native polyacrylamide gel, making small amounts of large multiprotein complexes accessible for subunit mass fingerprint analysis even if they are membrane bound. Thus, the LILBID subunit mass fingerprint method will be of great value for efficient proteomic analysis of complex I and its assembly intermediates, as well as of other water soluble and membrane bound multiprotein complexes.

  11. The Ontologies of Complexity and Learning about Complex Systems

    ERIC Educational Resources Information Center

    Jacobson, Michael J.; Kapur, Manu; So, Hyo-Jeong; Lee, June

    2011-01-01

    This paper discusses a study of students learning core conceptual perspectives from recent scientific research on complexity using a hypermedia learning environment in which different types of scaffolding were provided. Three comparison groups used a hypermedia system with agent-based models and scaffolds for problem-based learning activities that…

  12. Pedagogy of complex relationality exploring complexity theory, neuro-phenomenology, and attentiveness for education

    NASA Astrophysics Data System (ADS)

    Khattar, Randa

    What do the new sciences of complex relationality offer education? This work draws on complexity theory, neurological understandings of biology and phenomenology, and attentiveness to study what the new sciences might offer education and the possibilities of a pedagogical understanding of embodied knowing. Complexity theory provides understandings of local-global relationality, self-organization, far-from-equilibrium conditions, and emergent dynamics that are important for describing pedagogical relationality. In itself, however, complexity theory is lacking an attention to issues of embodiment that respond directly to an ethical understanding of relationality. Phenomenology provides important views on the human experience of perception, for example, Merleau-Ponty's, whose research opens up possibilities for embodiment and attentiveness. At the level of pedagogical practice, I will pose, following biologists Humberto Maturana and Francisco Varela's autopoietic self-making understanding of life, that attentiveness perspectives, which have been largely absent from western pedagogical theory and practice, are crucial to promoting embodied knowing for education. Maturana and Varela's autopoietic perspective offers an embodied understanding of living---and therefore education---which opens up necessary attentive spaces to listen to one another in non judgmental awareness in the present moment of experience. I offer insights into a relationally complex conception of education drawing on this biological and autopoietically-grounded framework. These insights are framed in the context of five clusters of relations: (1) emergence, far-from-equilibrium, and local-global relationality; (2) autopoietic autonomy, structural determination and sensory-motor coupling; (3) triggering perturbations, structural plasticity, and autopoietic organization; (4) knowing as adequate action, domains of interaction, and blind spots; and (5) attentiveness and responsive relationality. Four

  13. Complexity Thinking in PE: Game-Centred Approaches, Games as Complex Adaptive Systems, and Ecological Values

    ERIC Educational Resources Information Center

    Storey, Brian; Butler, Joy

    2013-01-01

    Background: This article draws on the literature relating to game-centred approaches (GCAs), such as Teaching Games for Understanding, and dynamical systems views of motor learning to demonstrate a convergence of ideas around games as complex adaptive learning systems. This convergence is organized under the title "complexity thinking"…

  14. Modification in band gap of zirconium complexes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sharma, Mayank, E-mail: mayank30134@gmail.com; Singh, J.; Chouhan, S.

    2016-05-06

    The optical properties of zirconium complexes with amino acid based Schiff bases are reported here. The zirconium complexes show interesting stereo chemical features, which are applicable in organometallic and organic synthesis as well as in catalysis. The band gaps of both Schiff bases and zirconium complexes were obtained by UV-Visible spectroscopy. It was found that the band gap of zirconium complexes has been modified after adding zirconium compound to the Schiff bases.

  15. Complex Variables throughout the Curriculum

    ERIC Educational Resources Information Center

    D'Angelo, John P.

    2017-01-01

    We offer many specific detailed examples, several of which are new, that instructors can use (in lecture or as student projects) to revitalize the role of complex variables throughout the curriculum. We conclude with three primary recommendations: revise the syllabus of Calculus II to allow early introductions of complex numbers and linear…

  16. The Complexity of Language Learning

    ERIC Educational Resources Information Center

    Nelson, Charles

    2011-01-01

    This paper takes a complexity theory approach to looking at language learning, an approach that investigates how language learners adapt to and interact with people and their environment. Based on interviews with four graduate students, it shows how complexity theory can help us understand both the situatedness of language learning and also…

  17. Teacher Knowledge: A Complex Tapestry

    ERIC Educational Resources Information Center

    Adoniou, Misty

    2015-01-01

    Teachers need to know a great deal, in many areas and in multiple ways. Teacher knowledge is a complex tapestry, and teachers must successfully weave the multiple threads. In this article, I present a conceptualisation of teacher knowledge that provides a framework for describing the complexity of teacher knowledge. The framework describes three…

  18. Heart rate complexity in sinoaortic-denervated mice.

    PubMed

    Silva, Luiz Eduardo V; Rodrigues, Fernanda Luciano; de Oliveira, Mauro; Salgado, Hélio Cesar; Fazan, Rubens

    2015-02-01

    What is the central question of this study? New measurements for cardiovascular complexity, such as detrended fluctuation analysis (DFA) and multiscale entropy (MSE), have been shown to predict cardiovascular outcomes. Given that cardiovascular diseases are accompanied by autonomic imbalance and decreased baroreflex sensitivity, the central question is: do baroreceptors contribute to cardiovascular complexity? What is the main finding and its importance? Sinoaortic denervation altered both DFA scaling exponents and MSE, indicating that both short- and long-term mechanisms of complexity are altered in sinoaortic denervated mice, resulting in a loss of physiological complexity. These results suggest that the baroreflex is a key element in the complex structures involved in heart rate variability regulation. Recently, heart rate (HR) oscillations have been recognized as complex behaviours derived from non-linear processes. Physiological complexity theory is based on the idea that healthy systems present high complexity, i.e. non-linear, fractal variability at multiple scales, with long-range correlations. The loss of complexity in heart rate variability (HRV) has been shown to predict adverse cardiovascular outcomes. Based on the idea that most cardiovascular diseases are accompanied by autonomic imbalance and a decrease in baroreflex sensitivity, we hypothesize that the baroreflex plays an important role in complex cardiovascular behaviour. Mice that had been subjected to sinoaortic denervation (SAD) were implanted with catheters in the femoral artery and jugular vein 5 days prior to the experiment. After recording the baseline arterial pressure (AP), pulse interval time series were generated from the intervals between consecutive values of diastolic pressure. The complexity of the HRV was determined using detrended fluctuation analysis and multiscale entropy. The detrended fluctuation analysis α1 scaling exponent (a short-term index) was remarkably decreased in the

  19. In vivo quantitative visualization of hypochlorous acid in the liver using a novel selective two-photon fluorescent probe

    NASA Astrophysics Data System (ADS)

    Wang, Haolu; Jayachandran, Aparna; Gravot, Germain; Liang, Xiaowen; Thorling, Camilla A.; Zhang, Run; Liu, Xin; Roberts, Michael S.

    2016-11-01

    Hypochlorous acid (HOCl) plays a vital role in physiological events and diseases. During hepatic ischemia-reperfusion (I/R) injury, HOCl is generated by neutrophils and diffuses into hepatocytes, causing oxidant stress-mediated injury. Although many probes have been developed to detect HOCl, most were difficult to be distinguished from endogenous fluorophores in intravital imaging and only can be employed under one-photon microscopy. A novel iridium(III) complex-based ferrocene dual-signaling chemosensor (Ir-Fc) was designed and synthesized. Ir-Fc exhibited a strong positive fluorescent response only in the presence of HOCl, whereas negligible fluorescent signals were observed upon the additions of other reactive oxygen/nitrogen species and metal ions. There was a good linear relationship between probe responsive fluorescent intensity and HOCl concentration. Ir-Fc was then intravenously injected into BALB/c mice at the final concentration of 50 μM and the mouse livers were imaged using multiphoton microscopy (MPM). In the I/R liver, reduced autofluorescence was detected by MPM, indicating the hepatocyte necrosis. Remarkable enhancement of red fluorescence was observed in hepatocytes with decreased autofluorescence, indicating the reaction of Ir-Fc with endogenous HOCl molecules. The cellular concentration of HOCl was first calculated based on the intensity of MPM images. No obvious toxic effects were observed in histological examination of major organs after Ir-Fc injection. In summary, Ir-Fc has low cytotoxicity, high specificity to HOCl, and rapid "off-on" fluorescence. It is suitable for dynamic quantitatively monitoring HOCl generation using MPM at the cellular level. This technique can be readily extended to examination of liver diseases and injury.

  20. Understanding large multiprotein complexes: applying a multiple allosteric networks model to explain the function of the Mediator transcription complex.

    PubMed

    Lewis, Brian A

    2010-01-15

    The regulation of transcription and of many other cellular processes involves large multi-subunit protein complexes. In the context of transcription, it is known that these complexes serve as regulatory platforms that connect activator DNA-binding proteins to a target promoter. However, there is still a lack of understanding regarding the function of these complexes. Why do multi-subunit complexes exist? What is the molecular basis of the function of their constituent subunits, and how are these subunits organized within a complex? What is the reason for physical connections between certain subunits and not others? In this article, I address these issues through a model of network allostery and its application to the eukaryotic RNA polymerase II Mediator transcription complex. The multiple allosteric networks model (MANM) suggests that protein complexes such as Mediator exist not only as physical but also as functional networks of interconnected proteins through which information is transferred from subunit to subunit by the propagation of an allosteric state known as conformational spread. Additionally, there are multiple distinct sub-networks within the Mediator complex that can be defined by their connections to different subunits; these sub-networks have discrete functions that are activated when specific subunits interact with other activator proteins.

  1. Complex adaptive chronic care.

    PubMed

    Martin, Carmel; Sturmberg, Joachim

    2009-06-01

    The Chronic Care Model (CCM) is widely taken up as the universal operational framework for redesigning health systems to address the increasing chronic disease burden of an ageing population. Chronic care encompasses health promotion, prevention, self management, disease control, treatment and palliation to address 'chronicity' of long journeys through disease, illness and care in the varying contexts of complex health systems. Yet at an operational level, CCM activities are predominantly based on an evidence-base of discreet chronic disease interventions in specific settings; and their demonstrable impact is limited to processes of select disease management such as diabetes in specific disease management programs. This paper proposes a framework that makes sense of the nature of chronicity and its multiple dimensions beyond disease and argues for a set of building blocks and leverage points that should constitute the starting points for 'redesign'? Complex Adaptive Chronic Care is proposed as an idea for an explanatory and implementation framework for addressing chronicity in existing and future chronic care models. Chronicity is overtly conceptualized to encompass the phenomena of an individual journey, with simple and complicated, complex and chaotic phases, through long term asymptomatic disease to bodily dysfunction and illness, located in family and communities. Chronicity encompasses trajectories of self-care and health care, as health, illness and disease co-exist and co-evolve in the setting of primary care, local care networks and at times institutions. A systems approach to individuals in their multi-layered networks making sense of and optimizing experiences of their chronic illness would build on core values and agency around a local vision of health, empowerment of individuals and adaptive leadership, and it responds in line with the local values inherent in the community's disease-based knowledge and the local service's history and dynamics. Complex

  2. Complexity is simple!

    NASA Astrophysics Data System (ADS)

    Cottrell, William; Montero, Miguel

    2018-02-01

    In this note we investigate the role of Lloyd's computational bound in holographic complexity. Our goal is to translate the assumptions behind Lloyd's proof into the bulk language. In particular, we discuss the distinction between orthogonalizing and `simple' gates and argue that these notions are useful for diagnosing holographic complexity. We show that large black holes constructed from series circuits necessarily employ simple gates, and thus do not satisfy Lloyd's assumptions. We also estimate the degree of parallel processing required in this case for elementary gates to orthogonalize. Finally, we show that for small black holes at fixed chemical potential, the orthogonalization condition is satisfied near the phase transition, supporting a possible argument for the Weak Gravity Conjecture first advocated in [1].

  3. Graphing Powers and Roots of Complex Numbers.

    ERIC Educational Resources Information Center

    Embse, Charles Vonder

    1993-01-01

    Using De Moivre's theorem and a parametric graphing utility, examines powers and roots of complex numbers and allows students to establish connections between the visual and numerical representations of complex numbers. Provides a program to numerically verify the roots of complex numbers. (MDH)

  4. Tuberous sclerosis complex surveillance and management: recommendations of the 2012 International Tuberous Sclerosis Complex Consensus Conference.

    PubMed

    Krueger, Darcy A; Northrup, Hope

    2013-10-01

    Tuberous sclerosis complex is a genetic disorder affecting every organ system, but disease manifestations vary significantly among affected individuals. The diverse and varied presentations and progression can be life-threatening with significant impact on cost and quality of life. Current surveillance and management practices are highly variable among region and country, reflective of the fact that last consensus recommendations occurred in 1998 and an updated, comprehensive standard is lacking that incorporates the latest scientific evidence and current best clinical practices. The 2012 International Tuberous Sclerosis Complex Consensus Group, comprising 79 specialists from 14 countries, was organized into 12 separate subcommittees, each led by a clinician with advanced expertise in tuberous sclerosis complex and the relevant medical subspecialty. Each subcommittee focused on a specific disease area with important clinical management implications and was charged with formulating key clinical questions to address within its focus area, reviewing relevant literature, evaluating the strength of data, and providing a recommendation accordingly. The updated consensus recommendations for clinical surveillance and management in tuberous sclerosis complex are summarized here. The recommendations are relevant to the entire lifespan of the patient, from infancy to adulthood, including both individuals where the diagnosis is newly made as well as individuals where the diagnosis already is established. The 2012 International Tuberous Sclerosis Complex Consensus Recommendations provide an evidence-based, standardized approach for optimal clinical care provided for individuals with tuberous sclerosis complex. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  5. [Physico-chemical features of dinitrosyl iron complexes with natural thiol-containing ligands underlying biological activities of these complexes].

    PubMed

    Vanin, A F; Borodulin, R R; Kubrina, L N; Mikoian, V D; Burbaev, D Sh

    2013-01-01

    Current notions and new experimental data of the authors on physico-chemical features of dinitrosyl iron complexes with natural thiol-containing ligands (glutathione or cysteine), underlying the ability of the complexes to act as NO molecule and nitrosonium ion donors, are considered. This ability determines various biological activities of dinitrosyl iron complexes--inducing long-lasting vasodilation and thereby long-lasting hypotension in human and animals, inhibiting pellet aggregation, increasing red blood cell elasticity, thereby stimulating microcirculation, and reducing necrotic zone in animals with myocardial infarction. Moreover, dinitrosyl iron complexes are capable of accelerating skin wound healing, improving the function of penile cavernous tissue, blocking apoptosis development in cell cultures. When decomposed dinitrosyl iron complexes can exert cytotoxic effect that can be used for curing infectious and carcinogenic pathologies.

  6. The Algebra of Complex Numbers.

    ERIC Educational Resources Information Center

    LePage, Wilbur R.

    This programed text is an introduction to the algebra of complex numbers for engineering students, particularly because of its relevance to important problems of applications in electrical engineering. It is designed for a person who is well experienced with the algebra of real numbers and calculus, but who has no experience with complex number…

  7. Communication Analysis of Information Complexes.

    ERIC Educational Resources Information Center

    Malik, M. F.

    Communication analysis is a tool for perceptual assessment of existing or projected information complexes, i.e., an established reality perceived by one or many humans. An information complex could be of a physical nature, such as a building, landscape, city street; or of a pure informational nature, such as a film, television program,…

  8. Crystallization of bFGF-DNA Aptamer Complexes Using a Sparse Matrix Designed for Protein-Nucleic Acid Complexes

    NASA Technical Reports Server (NTRS)

    Cannone, Jaime J.; Barnes, Cindy L.; Achari, Aniruddha; Kundrot, Craig E.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The Sparse Matrix approach for obtaining lead crystallization conditions has proven to be very fruitful for the crystallization of proteins and nucleic acids. Here we report a Sparse Matrix developed specifically for the crystallization of protein-DNA complexes. This method is rapid and economical, typically requiring 2.5 mg of complex to test 48 conditions. The method was originally developed to crystallize basic fibroblast growth factor (bFGF) complexed with DNA sequences identified through in vitro selection, or SELEX, methods. Two DNA aptamers that bind with approximately nanomolar affinity and inhibit the angiogenic properties of bFGF were selected for co-crystallization. The Sparse Matrix produced lead crystallization conditions for both bFGF-DNA complexes.

  9. Complexing of Green Tea Catechins with Food Constituents and Degradation of the Complexes by Lactobacillus plantarum

    PubMed Central

    HAYASHI, Taeko; UEDA, Shuhei; TSURUTA, Hiroki; KUWAHARA, Hiroshige; OSAWA, Ro

    2012-01-01

    Complexing of green tea catechins with food constituents and their hydrolysis by tannase-producing Lactobacillus plantarum strains, were investigated. Our observations indicated that 1) epigallocatechin gallate (EGCg) and other catechin galloyl esters bound with food ingredients (i.e., proteins) to form a complex that is likely to be unabsorbable through the intestinal wall, whereas most catechins not esterified with gallic acid (GA) remain in free form, not complexing with food ingredients; 2) tannase activity of L. plantarum is strain dependent, possibly grouped into those with high tannase activity hydrolyzing EGCg to epigallocatechin and GA and those with the low activity; and 3) L. plantarum strains with high tannase activity are capable of hydrolyzing not only intact EGCg but also EGCg and other catechin galloyl esters complexed with dietary proteins to free non-galloyl ester catechins and GA. The evidence suggests that L. plantarum with high tannase activity, if it colonizes the human intestine, would release free non-galloyl-ester catechins and GA that are readily absorbed through the human intestinal epithelia from the complexes, thereby ensuring maximum delivery of the bioactive polyphenols of green tea to the host. PMID:24936346

  10. Molecular complexes in close and far away

    PubMed Central

    Klemperer, William; Vaida, Veronica

    2006-01-01

    In this review, gas-phase chemistry of interstellar media and some planetary atmospheres is extended to include molecular complexes. Although the composition, density, and temperature of the environments discussed are very different, molecular complexes have recently been considered as potential contributors to chemistry. The complexes reviewed include strongly bound aggregates of molecules with ions, intermediate-strength hydrogen bonded complexes (primarily hydrates), and weakly bonded van der Waals molecules. In low-density, low-temperature environments characteristic of giant molecular clouds, molecular synthesis, known to involve gas-phase ion-molecule reactions and chemistry at the surface of dust and ice grains is extended here to involve molecular ionic clusters. At the high density and high temperatures found on planetary atmospheres, molecular complexes contribute to both atmospheric chemistry and climate. Using the observational, laboratory, and theoretical database, the role of molecular complexes in close and far away is discussed. PMID:16740667

  11. Dynamics of Fos-Jun-NFAT1 complexes

    PubMed Central

    Ramirez-Carrozzi, Vladimir R.; Kerppola, Tom K.

    2001-01-01

    Transcription initiation in eukaryotes is controlled by nucleoprotein complexes formed through cooperative interactions among multiple transcription regulatory proteins. These complexes may be assembled via stochastic collisions or defined pathways. We investigated the dynamics of Fos-Jun-NFAT1 complexes by using a multicolor fluorescence resonance energy transfer assay. Fos-Jun heterodimers can bind to AP-1 sites in two opposite orientations, only one of which is populated in mature Fos-Jun-NFAT1 complexes. We studied the reversal of Fos-Jun binding orientation in response to NFAT1 by measuring the efficiencies of energy transfer from donor fluorophores linked to opposite ends of an oligonucleotide to an acceptor fluorophore linked to one subunit of the heterodimer. The reorientation of Fos-Jun by NFAT1 was not inhibited by competitor oligonucleotides or heterodimers. The rate of Fos-Jun reorientation was faster than the rate of heterodimer dissociation at some binding sites. The facilitated reorientation of Fos-Jun heterodimers therefore can enhance the efficiency of Fos-Jun-NFAT1 complex formation. We also examined the influence of the preferred orientation of Fos-Jun binding on the stability and transcriptional activity of Fos-Jun-NFAT1 complexes. Complexes formed at sites where Fos-Jun favored the same binding orientation in the presence and absence of NFAT1 exhibited an 8-fold slower dissociation rate than complexes formed at sites where Fos-Jun favored the opposite binding orientation. Fos-Jun-NFAT1 complexes also exhibited greater transcription activation at promoter elements that favored the same orientation of Fos-Jun binding in the presence and absence of NFAT1. Thus, the orientation of heterodimer binding can influence both the dynamics and promoter selectivity of multiprotein transcription regulatory complexes. PMID:11320240

  12. Dynamics of Fos-Jun-NFAT1 complexes.

    PubMed

    Ramirez-Carrozzi, V R; Kerppola, T K

    2001-04-24

    Transcription initiation in eukaryotes is controlled by nucleoprotein complexes formed through cooperative interactions among multiple transcription regulatory proteins. These complexes may be assembled via stochastic collisions or defined pathways. We investigated the dynamics of Fos-Jun-NFAT1 complexes by using a multicolor fluorescence resonance energy transfer assay. Fos-Jun heterodimers can bind to AP-1 sites in two opposite orientations, only one of which is populated in mature Fos-Jun-NFAT1 complexes. We studied the reversal of Fos-Jun binding orientation in response to NFAT1 by measuring the efficiencies of energy transfer from donor fluorophores linked to opposite ends of an oligonucleotide to an acceptor fluorophore linked to one subunit of the heterodimer. The reorientation of Fos-Jun by NFAT1 was not inhibited by competitor oligonucleotides or heterodimers. The rate of Fos-Jun reorientation was faster than the rate of heterodimer dissociation at some binding sites. The facilitated reorientation of Fos-Jun heterodimers therefore can enhance the efficiency of Fos-Jun-NFAT1 complex formation. We also examined the influence of the preferred orientation of Fos-Jun binding on the stability and transcriptional activity of Fos-Jun-NFAT1 complexes. Complexes formed at sites where Fos-Jun favored the same binding orientation in the presence and absence of NFAT1 exhibited an 8-fold slower dissociation rate than complexes formed at sites where Fos-Jun favored the opposite binding orientation. Fos-Jun-NFAT1 complexes also exhibited greater transcription activation at promoter elements that favored the same orientation of Fos-Jun binding in the presence and absence of NFAT1. Thus, the orientation of heterodimer binding can influence both the dynamics and promoter selectivity of multiprotein transcription regulatory complexes.

  13. Hilbert complexes of nonlinear elasticity

    NASA Astrophysics Data System (ADS)

    Angoshtari, Arzhang; Yavari, Arash

    2016-12-01

    We introduce some Hilbert complexes involving second-order tensors on flat compact manifolds with boundary that describe the kinematics and the kinetics of motion in nonlinear elasticity. We then use the general framework of Hilbert complexes to write Hodge-type and Helmholtz-type orthogonal decompositions for second-order tensors. As some applications of these decompositions in nonlinear elasticity, we study the strain compatibility equations of linear and nonlinear elasticity in the presence of Dirichlet boundary conditions and the existence of stress functions on non-contractible bodies. As an application of these Hilbert complexes in computational mechanics, we briefly discuss the derivation of a new class of mixed finite element methods for nonlinear elasticity.

  14. Carney complex review: Genetic features.

    PubMed

    Bosco Schamun, María Belén; Correa, Ricardo; Graffigna, Patricia; de Miguel, Valeria; Fainstein Day, Patricia

    2018-01-01

    Carney complex is a multiple neoplasia syndrome having endocrine and non-endocrine manifestations. Diagnostic criteria include myxoma, lentigines, and primary pigmented nodular adrenocortical disease, amongst other signs/symptoms. In most cases it is an autosomal dominant disease, and diagnosis therefore requires study and follow-up of the family members. Inactivating mutations of the PRKAR1A gene were identified as the main cause of the disease, although since 2015 other disease-related genes, including PRKACA and PRKACB activating mutations, have also been related with Carney complex. This review will address the genetic aspects related to Carney complex. Copyright © 2017 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.

  15. The Complexity of Primary Care Psychology: Theoretical Foundations.

    PubMed

    Smit, E H; Derksen, J J L

    2015-07-01

    How does primary care psychology deal with organized complexity? Has it escaped Newtonian science? Has it, as Weaver (1991) suggests, found a way to 'manage problems with many interrelated factors that cannot be dealt by statistical techniques'? Computer simulations and mathematical models in psychology are ongoing positive developments in the study of complex systems. However, the theoretical development of complex systems in psychology lags behind these advances. In this article we use complexity science to develop a theory on experienced complexity in the daily practice of primary care psychologists. We briefly answer the ontological question of what we see (from the perspective of primary care psychology) as reality, the epistemological question of what we can know, the methodological question of how to act, and the ethical question of what is good care. Following our empirical study, we conclude that complexity science can describe the experienced complexity of the psychologist and offer room for personalized client-centered care. Complexity science is slowly filling the gap between the dominant reductionist theory and complex daily practice.

  16. Social networks as embedded complex adaptive systems.

    PubMed

    Benham-Hutchins, Marge; Clancy, Thomas R

    2010-09-01

    As systems evolve over time, their natural tendency is to become increasingly more complex. Studies in the field of complex systems have generated new perspectives on management in social organizations such as hospitals. Much of this research appears as a natural extension of the cross-disciplinary field of systems theory. This is the 15th in a series of articles applying complex systems science to the traditional management concepts of planning, organizing, directing, coordinating, and controlling. In this article, the authors discuss healthcare social networks as a hierarchy of embedded complex adaptive systems. The authors further examine the use of social network analysis tools as a means to understand complex communication patterns and reduce medical errors.

  17. Necroptosis-inducing rhenium(V) oxo complexes.

    PubMed

    Suntharalingam, Kogularamanan; Awuah, Samuel G; Bruno, Peter M; Johnstone, Timothy C; Wang, Fang; Lin, Wei; Zheng, Yao-Rong; Page, Julia E; Hemann, Michael T; Lippard, Stephen J

    2015-03-04

    Rhenium(V) oxo complexes of general formula [ReO(OMe)(N^N)Cl2], where N^N = 4,7-diphenyl-1,10-phenanthroline, 1, or 3,4,7,8-tetramethyl-1,10-phenanthroline, 2, effectively kill cancer cells by triggering necroptosis, a non-apoptotic form of cell death. Both complexes evoke necrosome (RIP1-RIP3)-dependent intracellular reactive oxygen species (ROS) production and propidium iodide uptake. The complexes also induce mitochondrial membrane potential depletion, a possible downstream effect of ROS production. Apparently, 1 and 2 are the first rhenium complexes to evoke cellular events consistent with programmed necrosis in cancer cells. Furthermore, 1 and 2 display low acute toxicity in C57BL/6 mice and reasonable stability in fresh human blood.

  18. Necroptosis-Inducing Rhenium(V) Oxo Complexes

    PubMed Central

    Suntharalingam, Kogularamanan; Awuah, Samuel G.; Bruno, Peter M.; Johnstone, Timothy C.; Wang, Fang; Lin, Wei; Zheng, Yao-Rong; Page, Julia E.; Hemann, Michael T.; Lippard, Stephen J.

    2015-01-01

    Rhenium(V) oxo complexes of general formula [ReO(OMe)(N^N)Cl2], where N^N = 4,7-diphenyl-1,10-phenanthroline, 1, or 3,4,7,8-tetramethyl-1,10-phenanthroline, 2, effectively kill cancer cells by triggering necroptsosis, a non-apoptotic form of cell death. Both complexes evoke necrosome (RIP1-RIP3)-dependent intracellular ROS production and propidium iodide uptake. The complexes also induce mitochondrial membrane potential depletion, a possible downstream effect of ROS production. Apparently, 1 and 2 are the first rhenium complexes to evoke cellular events consistent with programmed necrosis in cancer cells. Furthermore, 1 and 2 display low acute toxicity in C57BL/6 mice and reasonable stability in fresh human blood. PMID:25698398

  19. Web life: ComplexityBlog.com

    NASA Astrophysics Data System (ADS)

    2010-02-01

    The site's homepage calls it "a repository of ideas and perspectives regarding the science, engineering and philosophy of complexity", and it pretty much does what it says on the tin. Part blog, part links archive, part library of modelling tips and tricks, the site is chock full of information that comes under the general heading of "complexity".

  20. Isolation and characterization of PSI-LHCI super-complex and their sub-complexes from a red alga Cyanidioschyzon merolae.

    PubMed

    Tian, Lirong; Liu, Zheyi; Wang, Fangjun; Shen, Liangliang; Chen, Jinghua; Chang, Lijing; Zhao, Songhao; Han, Guangye; Wang, Wenda; Kuang, Tingyun; Qin, Xiaochun; Shen, Jian-Ren

    2017-09-01

    Photosystem I (PSI)-light-harvesting complex I (LHCI) super-complex and its sub-complexes PSI core and LHCI, were purified from a unicellular red alga Cyanidioschyzon merolae and characterized. PSI-LHCI of C. merolae existed as a monomer with a molecular mass of 580 kDa. Mass spectrometry analysis identified 11 subunits (PsaA, B, C, D, E, F, I, J, K, L, O) in the core complex and three LHCI subunits, CMQ142C, CMN234C, and CMN235C in LHCI, indicating that at least three Lhcr subunits associate with the red algal PSI core. PsaG was not found in the red algae PSI-LHCI, and we suggest that the position corresponding to Lhca1 in higher plant PSI-LHCI is empty in the red algal PSI-LHCI. The PSI-LHCI complex was separated into two bands on native PAGE, suggesting that two different complexes may be present with slightly different protein compositions probably with respective to the numbers of Lhcr subunits. Based on the results obtained, a structural model was proposed for the red algal PSI-LHCI. Furthermore, pigment analysis revealed that the C. merolae PSI-LHCI contained a large amount of zeaxanthin, which is mainly associated with the LHCI complex whereas little zeaxanthin was found in the PSI core. This indicates a unique feature of the carotenoid composition of the Lhcr proteins and may suggest an important role of Zea in the light-harvesting and photoprotection of the red algal PSI-LHCI complex.

  1. Evolution and complexity: the double-edged sword.

    PubMed

    Miconi, Thomas

    2008-01-01

    We attempt to provide a comprehensive answer to the question of whether, and when, an arrow of complexity emerges in Darwinian evolution. We note that this expression can be interpreted in different ways, including a passive, incidental growth, or a pervasive bias towards complexification. We argue at length that an arrow of complexity does indeed occur in evolution, which can be most reasonably interpreted as the result of a passive trend rather than a driven one. What, then, is the role of evolution in the creation of this trend, and under which conditions will it emerge? In the later sections of this article we point out that when certain proper conditions (which we attempt to formulate in a concise form) are met, Darwinian evolution predictably creates a sustained trend of increase in maximum complexity (that is, an arrow of complexity) that would not be possible without it; but if they are not, evolution will not only fail to produce an arrow of complexity, but may actually prevent any increase in complexity altogether. We conclude that, with regard to the growth of complexity, evolution is very much a double-edged sword.

  2. THE BIOLOGICAL ACTIVITY OF SOLUBLE ANTIGEN-ANTIBODY COMPLEXES

    PubMed Central

    Ishizaka, Kimishige; Ishizaka, Teruko; Campbell, Dan H.

    1959-01-01

    Soluble BSA-anti-BSA complexes, formed in antigen excess, give immediate skin reactions in normal guinea pigs. The mechanism of the reaction is not that of passive or reversed passive anaphylaxis. The complex itself is toxic. Skin activity of the complex depends on its composition. It has become obvious that the complex composed of two antigen molecules and one antibody molecule, (Ag2Ab), does not have the activity, whereas, Ag3Ab2 and more complicated complexes do. The role of complement as well as speculation on the structural changes of antibody-antigen complexes is presented. PMID:13620844

  3. Multifaceted Modelling of Complex Business Enterprises

    PubMed Central

    2015-01-01

    We formalise and present a new generic multifaceted complex system approach for modelling complex business enterprises. Our method has a strong focus on integrating the various data types available in an enterprise which represent the diverse perspectives of various stakeholders. We explain the challenges faced and define a novel approach to converting diverse data types into usable Bayesian probability forms. The data types that can be integrated include historic data, survey data, and management planning data, expert knowledge and incomplete data. The structural complexities of the complex system modelling process, based on various decision contexts, are also explained along with a solution. This new application of complex system models as a management tool for decision making is demonstrated using a railway transport case study. The case study demonstrates how the new approach can be utilised to develop a customised decision support model for a specific enterprise. Various decision scenarios are also provided to illustrate the versatility of the decision model at different phases of enterprise operations such as planning and control. PMID:26247591

  4. A Complexity Metric for Automated Separation

    NASA Technical Reports Server (NTRS)

    Aweiss, Arwa

    2009-01-01

    A metric is proposed to characterize airspace complexity with respect to an automated separation assurance function. The Maneuver Option metric is a function of the number of conflict-free trajectory change options the automated separation assurance function is able to identify for each aircraft in the airspace at a given time. By aggregating the metric for all aircraft in a region of airspace, a measure of the instantaneous complexity of the airspace is produced. A six-hour simulation of Fort Worth Center air traffic was conducted to assess the metric. Results showed aircraft were twice as likely to be constrained in the vertical dimension than the horizontal one. By application of this metric, situations found to be most complex were those where level overflights and descending arrivals passed through or merged into an arrival stream. The metric identified high complexity regions that correlate well with current air traffic control operations. The Maneuver Option metric did not correlate with traffic count alone, a result consistent with complexity metrics for human-controlled airspace.

  5. Multifaceted Modelling of Complex Business Enterprises.

    PubMed

    Chakraborty, Subrata; Mengersen, Kerrie; Fidge, Colin; Ma, Lin; Lassen, David

    2015-01-01

    We formalise and present a new generic multifaceted complex system approach for modelling complex business enterprises. Our method has a strong focus on integrating the various data types available in an enterprise which represent the diverse perspectives of various stakeholders. We explain the challenges faced and define a novel approach to converting diverse data types into usable Bayesian probability forms. The data types that can be integrated include historic data, survey data, and management planning data, expert knowledge and incomplete data. The structural complexities of the complex system modelling process, based on various decision contexts, are also explained along with a solution. This new application of complex system models as a management tool for decision making is demonstrated using a railway transport case study. The case study demonstrates how the new approach can be utilised to develop a customised decision support model for a specific enterprise. Various decision scenarios are also provided to illustrate the versatility of the decision model at different phases of enterprise operations such as planning and control.

  6. Measures of complexity in signal analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kurths, J.; Schwarz, U.; Witt, A.

    Observational data of natural systems, as measured in astrophysical, geophysical or physiological experiments are typically quite different from those obtained in laboratories. Due to the peculiarities with these data, well-known characteristics processes, such as periodicities or fractal dimension, often do not provide a suitable description. To study such data, we present here the use of measures of complexity, which are mainly basing on symbolic dynamics. We distinguish two types of such quantities: traditional measures (e.g. algorithmic complexity) which are measures of randomness and alternative measures (e.g. {epsilon}-complexity) which relate highest complexity to some critical points. It is important to notemore » that there is no optimum measure of complexity. Its choice should depend on the context. Mostly, a combination of some such quantities is appropriate. Applying this concept to three examples in astrophysics, cardiology and cognitive psychology, we show that it can be helpful also in cases where other tools of data analysis fail. {copyright} {ital 1996 American Institute of Physics.}« less

  7. Development of Novel DNA Cleavage Systems Based on Copper Complexes. Synthesis and Characterisation of Cu(II) Complexes of Hydroxyflavones

    PubMed Central

    el Amrani, F. Ben-Allal; Perelló, L.; Torres, L.

    2000-01-01

    Copper(II) complexes of several hydroxyflavones were prepared and characterised through their physico-chemical properties. The nuclease activity of three synthesised complexes is reported. These copper(II) complexes present more nuclease activity than the ligands and the copper(II) ion. PMID:18475969

  8. The Search Engine for Multi-Proteoform Complexes: An Online Tool for the Identification and Stoichiometry Determination of Protein Complexes.

    PubMed

    Skinner, Owen S; Schachner, Luis F; Kelleher, Neil L

    2016-12-08

    Recent advances in top-down mass spectrometry using native electrospray now enable the analysis of intact protein complexes with relatively small sample amounts in an untargeted mode. Here, we describe how to characterize both homo- and heteropolymeric complexes with high molecular specificity using input data produced by tandem mass spectrometry of whole protein assemblies. The tool described is a "search engine for multi-proteoform complexes," (SEMPC) and is available for free online. The output is a list of candidate multi-proteoform complexes and scoring metrics, which are used to define a distinct set of one or more unique protein subunits, their overall stoichiometry in the intact complex, and their pre- and post-translational modifications. Thus, we present an approach for the identification and characterization of intact protein complexes from native mass spectrometry data. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  9. The life of plant mitochondrial complex I.

    PubMed

    Braun, Hans-Peter; Binder, Stefan; Brennicke, Axel; Eubel, Holger; Fernie, Alisdair R; Finkemeier, Iris; Klodmann, Jennifer; König, Ann-Christine; Kühn, Kristina; Meyer, Etienne; Obata, Toshihiro; Schwarzländer, Markus; Takenaka, Mizuki; Zehrmann, Anja

    2014-11-01

    The mitochondrial NADH dehydrogenase complex (complex I) of the respiratory chain has several remarkable features in plants: (i) particularly many of its subunits are encoded by the mitochondrial genome, (ii) its mitochondrial transcripts undergo extensive maturation processes (e.g. RNA editing, trans-splicing), (iii) its assembly follows unique routes, (iv) it includes an additional functional domain which contains carbonic anhydrases and (v) it is, indirectly, involved in photosynthesis. Comprising about 50 distinct protein subunits, complex I of plants is very large. However, an even larger number of proteins are required to synthesize these subunits and assemble the enzyme complex. This review aims to follow the complete "life cycle" of plant complex I from various molecular perspectives. We provide arguments that complex I represents an ideal model system for studying the interplay of respiration and photosynthesis, the cooperation of mitochondria and the nucleus during organelle biogenesis and the evolution of the mitochondrial oxidative phosphorylation system. Copyright © 2014 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

  10. Holographic complexity in Vaidya spacetimes. Part I

    NASA Astrophysics Data System (ADS)

    Chapman, Shira; Marrochio, Hugo; Myers, Robert C.

    2018-06-01

    We examine holographic complexity in time-dependent Vaidya spacetimes with both the complexity=volume (CV) and complexity=action (CA) proposals. We focus on the evolution of the holographic complexity for a thin shell of null fluid, which collapses into empty AdS space and forms a (one-sided) black hole. In order to apply the CA approach, we introduce an action principle for the null fluid which sources the Vaidya geometries, and we carefully examine the contribution of the null shell to the action. Further, we find that adding a particular counterterm on the null boundaries of the Wheeler-DeWitt patch is essential if the gravitational action is to properly describe the complexity of the boundary state. For both the CV proposal and the CA proposal (with the extra boundary counterterm), the late time limit of the growth rate of the holographic complexity for the one-sided black hole is precisely the same as that found for an eternal black hole.

  11. LINCing complex functions at the nuclear envelope

    PubMed Central

    Rothballer, Andrea; Schwartz, Thomas U.; Kutay, Ulrike

    2013-01-01

    Linker of nucleoskeleton and cytoskeleton (LINC) complexes span the double membrane of the nuclear envelope (NE) and physically connect nuclear structures to cytoskeletal elements. LINC complexes are envisioned as force transducers in the NE, which facilitate processes like nuclear anchorage and migration, or chromosome movements. The complexes are built from members of two evolutionary conserved families of transmembrane (TM) proteins, the SUN (Sad1/UNC-84) domain proteins in the inner nuclear membrane (INM) and the KASH (Klarsicht/ANC-1/SYNE homology) domain proteins in the outer nuclear membrane (ONM). In the lumen of the NE, the SUN and KASH domains engage in an intimate assembly to jointly form a NE bridge. Detailed insights into the molecular architecture and atomic structure of LINC complexes have recently revealed the molecular basis of nucleo-cytoskeletal coupling. They bear important implications for LINC complex function and suggest new potential and as yet unexplored roles, which the complexes may play in the cell. PMID:23324460

  12. The Complex Route to Success: Complex Problem-Solving Skills in the Prediction of University Success

    ERIC Educational Resources Information Center

    Stadler, Matthias J.; Becker, Nicolas; Greiff, Samuel; Spinath, Frank M.

    2016-01-01

    Successful completion of a university degree is a complex matter. Based on considerations regarding the demands of acquiring a university degree, the aim of this paper was to investigate the utility of complex problem-solving (CPS) skills in the prediction of objective and subjective university success (SUS). The key finding of this study was that…

  13. Co-complexes Derived from Alkene Insertion to Alkyne-dicobaltpentacarbonyl complexes: Insight into the Regioselectivity of Pauson-Khand Reactions of Cyclopropenes

    PubMed Central

    Pallerla, Mahesh K.; Yap, Glenn P. A.; Fox, Joseph M.

    2009-01-01

    Described are the X-ray crystallographic and spectral properties of Co-complexes that were isolated from two Pauson-Khand reactions of chiral cyclopropenes. These are the first examples of isolated Co-complexes derived from the putative alkene-insertion intermediates of Pauson-Khand reactions. The binuclear Co-complexes are coordinated to μ-bonded, five-carbon “flyover” carbene ligands. It is proposed that the complexes result from cyclopropane fragmentation subsequent to alkene insertion. The observation of these metal complexes provides a rationale for the origin of regioselectivity in Pauson-Khand reactions of cyclopropenes. PMID:18637694

  14. Co-complexes derived from alkene insertion to alkyne-dicobaltpentacarbonyl complexes: insight into the regioselectivity of pauson-khand reactions of cyclopropenes.

    PubMed

    Pallerla, Mahesh K; Yap, Glenn P A; Fox, Joseph M

    2008-08-15

    Described are the X-ray crystallographic and spectral properties of Co-complexes that were isolated from two Pauson-Khand reactions of chiral cyclopropenes. These are the first examples of isolated Co-complexes derived from the putative alkene-insertion intermediates of Pauson-Khand reactions. The binuclear Co-complexes are coordinated to mu-bonded, five-carbon "flyover" carbene ligands. It is proposed that the complexes result from cyclopropane fragmentation subsequent to alkene insertion. The observation of these metal complexes provides a rationale for the origin of regioselectivity in Pauson-Khand reactions of cyclopropenes.

  15. Planning Complex Projects Automatically

    NASA Technical Reports Server (NTRS)

    Henke, Andrea L.; Stottler, Richard H.; Maher, Timothy P.

    1995-01-01

    Automated Manifest Planner (AMP) computer program applies combination of artificial-intelligence techniques to assist both expert and novice planners, reducing planning time by orders of magnitude. Gives planners flexibility to modify plans and constraints easily, without need for programming expertise. Developed specifically for planning space shuttle missions 5 to 10 years ahead, with modifications, applicable in general to planning other complex projects requiring scheduling of activities depending on other activities and/or timely allocation of resources. Adaptable to variety of complex scheduling problems in manufacturing, transportation, business, architecture, and construction.

  16. Chiral discrimination in cyclodextrin complexes of amino acid derivatives: beta-cyclodextrin/N-acetyl-L-phenylalanine and N-acetyl-D-phenylalanine complexes.

    PubMed

    Alexander, Jennifer M; Clark, Joanna L; Brett, Tom J; Stezowski, John J

    2002-04-16

    In a systematic study of molecular recognition of amino acid derivatives in solid-state beta-cyclodextrin (beta-CD) complexes, we have determined crystal structures for complexes of beta-cyclodextrin/N-acetyl-L-phenylalanine at 298 and 20 K and for N-acetyl-D-phenylalanine at 298 K. The crystal structures for the N-acetyl-L-phenylalanine complex present disordered inclusion complexes for which the distribution of guest molecules at room temperature is not resolvable; however, they can be located with considerable confidence at low temperature. In contrast, the complex with N-acetyl-D-phenylalanine is well ordered at room temperature. The latter complex presents an example of a complex in this series in which a water molecule is included deeply in the hydrophobic torus of the extended dimer host. In an effort to understand the mechanisms of molecular recognition giving rise to the dramatic differences in crystallographic order in these crystal structures, we have examined the intermolecular interactions in detail and have examined insertion of the enantiomer of the D-complex into the chiral beta-CD complex crystal lattice.

  17. An Assembly Funnel Makes Biomolecular Complex Assembly Efficient

    PubMed Central

    Zenk, John; Schulman, Rebecca

    2014-01-01

    Like protein folding and crystallization, the self-assembly of complexes is a fundamental form of biomolecular organization. While the number of methods for creating synthetic complexes is growing rapidly, most require empirical tuning of assembly conditions and/or produce low yields. We use coarse-grained simulations of the assembly kinetics of complexes to identify generic limitations on yields that arise because of the many simultaneous interactions allowed between the components and intermediates of a complex. Efficient assembly occurs when nucleation is fast and growth pathways are few, i.e. when there is an assembly “funnel”. For typical complexes, an assembly funnel occurs in a narrow window of conditions whose location is highly complex specific. However, by redesigning the components this window can be drastically broadened, so that complexes can form quickly across many conditions. The generality of this approach suggests assembly funnel design as a foundational strategy for robust biomolecular complex synthesis. PMID:25360818

  18. Biogenesis of the yeast cytochrome bc1 complex.

    PubMed

    Zara, Vincenzo; Conte, Laura; Trumpower, Bernard L

    2009-01-01

    The mitochondrial respiratory chain is composed of four different protein complexes that cooperate in electron transfer and proton pumping across the inner mitochondrial membrane. The cytochrome bc1 complex, or complex III, is a component of the mitochondrial respiratory chain. This review will focus on the biogenesis of the bc1 complex in the mitochondria of the yeast Saccharomyces cerevisiae. In wild type yeast mitochondrial membranes the major part of the cytochrome bc1 complex was found in association with one or two copies of the cytochrome c oxidase complex. The analysis of several yeast mutant strains in which single genes or pairs of genes encoding bc1 subunits had been deleted revealed the presence of a common set of bc1 sub-complexes. These sub-complexes are represented by the central core of the bc1 complex, consisting of cytochrome b bound to subunit 7 and subunit 8, by the two core proteins associated with each other, by the Rieske protein associated with subunit 9, and by those deriving from the unexpected interaction of each of the two core proteins with cytochrome c1. Furthermore, a higher molecular mass sub-complex is that composed of cytochrome b, cytochrome c1, core protein 1 and 2, subunit 6, subunit 7 and subunit 8. The identification and characterization of all these sub-complexes may help in defining the steps and the molecular events leading to bc1 assembly in yeast mitochondria.

  19. Structural evaluation of crystalline ternary γ-cyclodextrin complex.

    PubMed

    Higashi, Kenjirou; Ideura, Saori; Waraya, Haruka; Moribe, Kunikazu; Yamamoto, Keiji

    2011-01-01

    The structure of a crystalline γ-cyclodextrin (γ-CD) ternary complex containing salicylic acid (SA) and flurbiprofen (FBP) prepared by sealed heating was investigated. FBP/γ-CD inclusion complex was prepared by coprecipitation; its molar ratio was determined as 1/1. Powder X-ray diffraction measurements showed that the molecular packing of γ-CD changed from hexagonal to monoclinic columnar form by sealed heating of SA with dried FBP/γ-CD inclusion complex, indicating ternary complex formation. The stoichiometry of SA/FBP/γ-CD was estimated as 2/1/1. Solid-state transformation of γ-CD molecular packing upon water vapor adsorption and desorption was irreversible for this ternary complex, in contrast to the reversible transition for the FBP/γ-CD inclusion complex. The ternary complex contained one FBP molecule in the cavity of γ-CD and two SA molecules in the intermolecular space between neighboring γ-CD column stacks. Infrared and (13) C solid-state NMR spectroscopies revealed that the molecular states of SA and FBP changed upon ternary complex formation. In the complex, dimer FBP molecules were sandwiched between two γ-CD molecules whereas each monomer SA molecule was present in the intermolecular space of γ-CD. Ternary complex formation was also observed for other drug-guest systems using naproxen and ketoprofen. Thus, the complex can be used to formulate variety of drugs. Copyright © 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  20. Spectroscopic studies of Np(V) complexation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stout, B.E.

    The complexation of Np(V) with aliphatic (oxalic, malonic, succinic, glutaric, and maleic) and aromatic (phthalic, pyromellitic, hemimellitic, trimellitic, and mellitic) polycarboxylic acids was studied by spectrophotometry at 1 M ionic strength (NaClO{sub 4}) and 23 C. For the aliphatic systems, the stability of the neptunyl complexes was found to decrease as the carbon chain length of the ligand increased which was attributed to an entropy effect. In polycarboxylate systems, the stability constant decreased in the order hemimellitate > mellitate > pyromellitate > trimellitate, phthalate. With the exception of hemimellitate, this trend follows the order of decreasing basicity of the ligand.more » After correction of the stability constant for statistical effects, the stability of the mellitate, pyromellitate, trimellitate, and phthalate complexes were approximately the same. The unexpected strength the hemimellitate complexation was attributed to an increase in electron density at the binding site from the non-chelating carboxylate group through induction. The complexation of phthalate, trimellitate and hemimellitate and mellitate were studied as a function of pH. Trimellitate and mellitate were found to form ML as well as ML complexes while for phthalate and hemimellitate only ML species were observed. The stability constants of the cation-cation complexes Np(V)-U(VI) and Np(V)-Np(V), measured at 6 M ionic strength (HClO{sub 4}) and 25 C, were found to be 2.45 {+-} 0.05 and 1.41 {+-} 0.14, respectively. The change in enthalpy for the Np(V)-U(VI) system as determined by the measurement of the stability constant as function of temperature was -14.3 {+-} 1.6 kJ/mol.« less

  1. Complex systems as lenses on learning and teaching

    NASA Astrophysics Data System (ADS)

    Hurford, Andrew C.

    From metaphors to mathematized models, the complexity sciences are changing the ways disciplines view their worlds, and ideas borrowed from complexity are increasingly being used to structure conversations and guide research on teaching and learning. The purpose of this corpus of research is to further those conversations and to extend complex systems ideas, theories, and modeling to curricula and to research on learning and teaching. A review of the literatures of learning and of complexity science and a discussion of the intersections between those disciplines are provided. The work reported represents an evolving model of learning qua complex system and that evolution is the result of iterative cycles of design research. One of the signatures of complex systems is the presence of scale invariance and this line of research furnishes empirical evidence of scale invariant behaviors in the activity of learners engaged in participatory simulations. The offered discussion of possible causes for these behaviors and chaotic phase transitions in human learning favors real-time optimization of decision-making as the means for producing such behaviors. Beyond theoretical development and modeling, this work includes the development of teaching activities intended to introduce pre-service mathematics and science teachers to complex systems. While some of the learning goals for this activity focused on the introduction of complex systems as a content area, we also used complex systems to frame perspectives on learning. Results of scoring rubrics and interview responses from students illustrate attributes of the proposed model of complex systems learning and also how these pre-service teachers made sense of the ideas. Correlations between established theories of learning and a complex adaptive systems model of learning are established and made explicit, and a means for using complex systems ideas for designing instruction is offered. It is a fundamental assumption of this

  2. Identification of Complex Carbon Nanotube Structures

    NASA Technical Reports Server (NTRS)

    Han, Jie; Saini, Subhash (Technical Monitor)

    1998-01-01

    A variety of complex carbon nanotube (CNT) structures have been observed experimentally. These include sharp bends, branches, tori, and helices. They are believed to be formed by using topological defects such as pentagons and heptagons to connect different CNT. The effects of type, number, and arrangement (separation and orientation) of defects on atomic structures and energetics of complex CNT are investigated using topology, quantum mechanics and molecular mechanics calculations. Energetically stable models are derived for identification of observed complex CNT structures.

  3. Phosphine/Sulfoxide-Supported Carbon(0) Complex.

    PubMed

    Lozano González, Mariana; Bousquet, Laura; Hameury, Sophie; Alvarez Toledano, Cecilio; Saffon-Merceron, Nathalie; Branchadell, Vicenç; Maerten, Eddy; Baceiredo, Antoine

    2018-02-21

    A new carbon(0) complex 2 with two different L ligands, a phosphine and a sulfoxide, was synthesized and fully characterized. This new type of carbone exhibits excellent coordination ability, in contrast to the related phosphine/sulfide-supported carbon(0) complexes. Several organometallic complexes were isolated and, of special interest, the ν av (CO) value of Rh I -dicarbonyl complex indicates that 2 has a donor capability superior to classical NHCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Complexity and demographic explanations of cumulative culture.

    PubMed

    Querbes, Adrien; Vaesen, Krist; Houkes, Wybo

    2014-01-01

    Formal models have linked prehistoric and historical instances of technological change (e.g., the Upper Paleolithic transition, cultural loss in Holocene Tasmania, scientific progress since the late nineteenth century) to demographic change. According to these models, cumulation of technological complexity is inhibited by decreasing--while favoured by increasing--population levels. Here we show that these findings are contingent on how complexity is defined: demography plays a much more limited role in sustaining cumulative culture in case formal models deploy Herbert Simon's definition of complexity rather than the particular definitions of complexity hitherto assumed. Given that currently available empirical evidence doesn't afford discriminating proper from improper definitions of complexity, our robustness analyses put into question the force of recent demographic explanations of particular episodes of cultural change.

  5. Robustness and structure of complex networks

    NASA Astrophysics Data System (ADS)

    Shao, Shuai

    This dissertation covers the two major parts of my PhD research on statistical physics and complex networks: i) modeling a new type of attack -- localized attack, and investigating robustness of complex networks under this type of attack; ii) discovering the clustering structure in complex networks and its influence on the robustness of coupled networks. Complex networks appear in every aspect of our daily life and are widely studied in Physics, Mathematics, Biology, and Computer Science. One important property of complex networks is their robustness under attacks, which depends crucially on the nature of attacks and the structure of the networks themselves. Previous studies have focused on two types of attack: random attack and targeted attack, which, however, are insufficient to describe many real-world damages. Here we propose a new type of attack -- localized attack, and study the robustness of complex networks under this type of attack, both analytically and via simulation. On the other hand, we also study the clustering structure in the network, and its influence on the robustness of a complex network system. In the first part, we propose a theoretical framework to study the robustness of complex networks under localized attack based on percolation theory and generating function method. We investigate the percolation properties, including the critical threshold of the phase transition pc and the size of the giant component Pinfinity. We compare localized attack with random attack and find that while random regular (RR) networks are more robust against localized attack, Erdoḧs-Renyi (ER) networks are equally robust under both types of attacks. As for scale-free (SF) networks, their robustness depends crucially on the degree exponent lambda. The simulation results show perfect agreement with theoretical predictions. We also test our model on two real-world networks: a peer-to-peer computer network and an airline network, and find that the real-world networks

  6. Making mobility-related disability better: a complex response to a complex problem.

    PubMed

    Rockwood, Kenneth

    2012-10-15

    Mobility disability in older adults can arise from single system problems, such as discrete musculoskeletal injury. In frail older adults, however, mobility disability is part of a complex web of problems. The approach to their rehabilitation must take that complexity into account, as is reported by Fairhall et al. First, their overall health state must be assessed, which is achieved by a comprehensive geriatric assessment. The assessment can show how a particular patient came to be disabled, so that an individualized care plan can be worked out. Whether this approach works in general can be evaluated by looking at group differences in mean mobility test scores. Knowing whether it has worked in the individual patient requires an individualized measure. This is because not every patient starts from the same point, and not every patient achieves success by aiming for the same goal. For one patient, walking unassisted for three metres would be a triumph; for another it would be a tragedy. Unless we understand the complexity of the needs of frail older adults, we will neither be able to treat them effectively nor evaluate our efforts sensibly.Please see related article http://www.biomedcentral.com/1741-7015/10/120.

  7. Complexity Bounds for Quantum Computation

    DTIC Science & Technology

    2007-06-22

    Programs Trustees of Boston University Boston, MA 02215 - Complexity Bounds for Quantum Computation REPORT DOCUMENTATION PAGE 18. SECURITY CLASSIFICATION...Complexity Bounds for Quantum Comp[utation Report Title ABSTRACT This project focused on upper and lower bounds for quantum computability using constant...classical computation models, particularly emphasizing new examples of where quantum circuits are more powerful than their classical counterparts. A second

  8. The Effect of Pressure and Temperature on Separation of Free Gadolinium(III) From Gd-DTPA Complex by Nanofiltration-Complexation Method

    NASA Astrophysics Data System (ADS)

    Rahayu, Iman; Anggraeni, Anni; Ukun, MSS; Bahti, Husein H.

    2017-05-01

    Nowdays, the utilization of rare earth elements has been carried out widely in industry and medicine, one of them is gadolinium in Gd-DTPA complex is used as a contrast agent in a magnetic resonance imaging (MRI) diagnostic to increase the visual contrast between normal tissue and diseased. Although the stability of a given complex may be high enough, the complexation step couldnot have been completed, so there is possible to gadolinium(III) in the complex compound. Therefore, the function of that compounds should be dangerous because of the toxicity of gadolinium(III) in human body. So, it is necessarry to separate free gadolinium(III) from Gd-DTPA complex by nanofiltration-complexation. The method of this study is complexing of Gd2O3 with DTPA ligand by reflux and separation of Gd-DTPA complex from gadolinium(III) with a nanofiltration membrane on the variation of pressures(2, 3, 4, 5, 6 bars) and temperature (25, 30, 35, 40 °C) and determined the flux and rejection. The results of this study are the higher of pressures and temperatures, permeation flux are increasing and ion rejections are decreasing and gave the free gadolinium(III) rejection until 86.26%.

  9. Graph distance for complex networks

    NASA Astrophysics Data System (ADS)

    Shimada, Yutaka; Hirata, Yoshito; Ikeguchi, Tohru; Aihara, Kazuyuki

    2016-10-01

    Networks are widely used as a tool for describing diverse real complex systems and have been successfully applied to many fields. The distance between networks is one of the most fundamental concepts for properly classifying real networks, detecting temporal changes in network structures, and effectively predicting their temporal evolution. However, this distance has rarely been discussed in the theory of complex networks. Here, we propose a graph distance between networks based on a Laplacian matrix that reflects the structural and dynamical properties of networked dynamical systems. Our results indicate that the Laplacian-based graph distance effectively quantifies the structural difference between complex networks. We further show that our approach successfully elucidates the temporal properties underlying temporal networks observed in the context of face-to-face human interactions.

  10. 40 CFR 721.5325 - Nickel acrylate complex.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Nickel acrylate complex. 721.5325... Substances § 721.5325 Nickel acrylate complex. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance nickel acrylate complex (PMN P-85-1034) is subject to reporting under...

  11. 40 CFR 721.5325 - Nickel acrylate complex.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Nickel acrylate complex. 721.5325... Substances § 721.5325 Nickel acrylate complex. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance nickel acrylate complex (PMN P-85-1034) is subject to reporting under...

  12. 40 CFR 721.5325 - Nickel acrylate complex.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Nickel acrylate complex. 721.5325... Substances § 721.5325 Nickel acrylate complex. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance nickel acrylate complex (PMN P-85-1034) is subject to reporting under...

  13. 40 CFR 721.5325 - Nickel acrylate complex.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Nickel acrylate complex. 721.5325... Substances § 721.5325 Nickel acrylate complex. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance nickel acrylate complex (PMN P-85-1034) is subject to reporting under...

  14. The clinical educator and complexity: a review.

    PubMed

    Schoo, Adrian; Kumar, Koshila

    2018-02-08

    Complexity science perspectives have helped in examining fundamental assumptions about learning and teaching in the health professions. The implications of complexity thinking for how we understand the role and development of the clinical educator is less well articulated. This review article outlines: the key principles of complexity science; a conceptual model that situates the clinical educator in a complex system; and the implications for the individual, organisation and the system. Our conceptual model situates the clinical educator at the centre of a complex and dynamic system spanning four domains and multiple levels. The four domains are: personal (encompassing personal/professional needs and expectations); health services (health agencies and their consumers); educational (educational institutions and their health students); and societal (local community/region and government). The system also comprises: micro or individual, meso or organisational, and macro or socio-political levels. Our model highlights that clinical educators are situated within a complex system comprising different agents and connections. It emphasises that individuals, teams and organisations need to recognise and be responsive to the unpredictability, interconnectedness and evolving nature of this system. Importantly, our article also calls for an epistemological shift from faculty development to capacity building in health professions education, aimed at developing individual, team, organisational and system capabilities to work with(in) complexity. Clinical educators are situated within a complex system comprising different agents and connections. © 2018 John Wiley & Sons Ltd and The Association for the Study of Medical Education.

  15. Juxtaposed Polycomb complexes co-regulate vertebral identity.

    PubMed

    Kim, Se Young; Paylor, Suzanne W; Magnuson, Terry; Schumacher, Armin

    2006-12-01

    Best known as epigenetic repressors of developmental Hox gene transcription, Polycomb complexes alter chromatin structure by means of post-translational modification of histone tails. Depending on the cellular context, Polycomb complexes of diverse composition and function exhibit cooperative interaction or hierarchical interdependency at target loci. The present study interrogated the genetic, biochemical and molecular interaction of BMI1 and EED, pivotal constituents of heterologous Polycomb complexes, in the regulation of vertebral identity during mouse development. Despite a significant overlap in dosage-sensitive homeotic phenotypes and co-repression of a similar set of Hox genes, genetic analysis implicated eed and Bmi1 in parallel pathways, which converge at the level of Hox gene regulation. Whereas EED and BMI1 formed separate biochemical entities with EzH2 and Ring1B, respectively, in mid-gestation embryos, YY1 engaged in both Polycomb complexes. Strikingly, methylated lysine 27 of histone H3 (H3-K27), a mediator of Polycomb complex recruitment to target genes, stably associated with the EED complex during the maintenance phase of Hox gene repression. Juxtaposed EED and BMI1 complexes, along with YY1 and methylated H3-K27, were detected in upstream regulatory regions of Hoxc8 and Hoxa5. The combined data suggest a model wherein epigenetic and genetic elements cooperatively recruit and retain juxtaposed Polycomb complexes in mammalian Hox gene clusters toward co-regulation of vertebral identity.

  16. Acute stress influences the discrimination of complex scenes and complex faces in young healthy men.

    PubMed

    Paul, M; Lech, R K; Scheil, J; Dierolf, A M; Suchan, B; Wolf, O T

    2016-04-01

    The stress-induced release of glucocorticoids has been demonstrated to influence hippocampal functions via the modulation of specific receptors. At the behavioral level stress is known to influence hippocampus dependent long-term memory. In recent years, studies have consistently associated the hippocampus with the non-mnemonic perception of scenes, while adjacent regions in the medial temporal lobe were associated with the perception of objects, and faces. So far it is not known whether and how stress influences non-mnemonic perceptual processes. In a behavioral study, fifty male participants were subjected either to the stressful socially evaluated cold-pressor test or to a non-stressful control procedure, before they completed a visual discrimination task, comprising scenes and faces. The complexity of the face and scene stimuli was manipulated in easy and difficult conditions. A significant three way interaction between stress, stimulus type and complexity was found. Stressed participants tended to commit more errors in the complex scenes condition. For complex faces a descriptive tendency in the opposite direction (fewer errors under stress) was observed. As a result the difference between the number of errors for scenes and errors for faces was significantly larger in the stress group. These results indicate that, beyond the effects of stress on long-term memory, stress influences the discrimination of spatial information, especially when the perception is characterized by a high complexity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Making sense in a complex landscape: how the Cynefin Framework from Complex Adaptive Systems Theory can inform health promotion practice.

    PubMed

    Van Beurden, Eric K; Kia, Annie M; Zask, Avigdor; Dietrich, Uta; Rose, Lauren

    2013-03-01

    Health promotion addresses issues from the simple (with well-known cause/effect links) to the highly complex (webs and loops of cause/effect with unpredictable, emergent properties). Yet there is no conceptual framework within its theory base to help identify approaches appropriate to the level of complexity. The default approach favours reductionism--the assumption that reducing a system to its parts will inform whole system behaviour. Such an approach can yield useful knowledge, yet is inadequate where issues have multiple interacting causes, such as social determinants of health. To address complex issues, there is a need for a conceptual framework that helps choose action that is appropriate to context. This paper presents the Cynefin Framework, informed by complexity science--the study of Complex Adaptive Systems (CAS). It introduces key CAS concepts and reviews the emergence and implications of 'complex' approaches within health promotion. It explains the framework and its use with examples from contemporary practice, and sets it within the context of related bodies of health promotion theory. The Cynefin Framework, especially when used as a sense-making tool, can help practitioners understand the complexity of issues, identify appropriate strategies and avoid the pitfalls of applying reductionist approaches to complex situations. The urgency to address critical issues such as climate change and the social determinants of health calls for us to engage with complexity science. The Cynefin Framework helps practitioners make the shift, and enables those already engaged in complex approaches to communicate the value and meaning of their work in a system that privileges reductionist approaches.

  18. Regulation of outer kinetochore Ndc80 complex-based microtubule attachments by the central kinetochore Mis12/MIND complex

    PubMed Central

    Kudalkar, Emily M.; Scarborough, Emily A.; Umbreit, Neil T.; Zelter, Alex; Gestaut, Daniel R.; Riffle, Michael; Johnson, Richard S.; MacCoss, Michael J.; Asbury, Charles L.; Davis, Trisha N.

    2015-01-01

    Multiple protein subcomplexes of the kinetochore cooperate as a cohesive molecular unit that forms load-bearing microtubule attachments that drive mitotic chromosome movements. There is intriguing evidence suggesting that central kinetochore components influence kinetochore–microtubule attachment, but the mechanism remains unclear. Here, we find that the conserved Mis12/MIND (Mtw1, Nsl1, Nnf1, Dsn1) and Ndc80 (Ndc80, Nuf2, Spc24, Spc25) complexes are connected by an extensive network of contacts, each essential for viability in cells, and collectively able to withstand substantial tensile load. Using a single-molecule approach, we demonstrate that an individual MIND complex enhances the microtubule-binding affinity of a single Ndc80 complex by fourfold. MIND itself does not bind microtubules. Instead, MIND binds Ndc80 complex far from the microtubule-binding domain and confers increased microtubule interaction of the complex. In addition, MIND activation is redundant with the effects of a mutation in Ndc80 that might alter its ability to adopt a folded conformation. Together, our results suggest a previously unidentified mechanism for regulating microtubule binding of an outer kinetochore component by a central kinetochore complex. PMID:26430240

  19. Liquid-crystalline dendrimer Cu(II) complexes and Cu(0) nanoclusters based on the Cu(II) complexes: An electron paramagnetic resonance investigation

    NASA Astrophysics Data System (ADS)

    Domracheva, N. E.; Mirea, A.; Schwoerer, M.; Torre-Lorente, L.; Lattermann, G.

    2007-07-01

    New nanostructured materials, namely, the liquid-crystalline copper(II) complexes that contain poly(propylene imine) dendrimer ligands of the first (ligand 1) and second (ligand 2) generations and which have a columnar mesophase and different copper contents (x = Cu/L), are investigated by EPR spectroscopy. The influence of water molecules and nitrate counterions on the magnetic properties of complex 2 (x = 7.3) is studied. It is demonstrated that water molecules can extract some of the copper ions from dendrimer complexes and form hexaaqua copper complexes with free ions. The dimer spectra of fully hydrated complex 2 (x = 7.3) are observed at temperatures T < 10 K. For this complex, the structure is identified and the distance between the copper ions is determined. It is shown that the nitrate counterion plays the role of a bridge between the hexaaqua copper(II) complex and the dendrimer copper(II) complex. The temperature-induced valence tautomerism attended by electron transport is revealed for the first time in blue dendrimer complexes 1 (x = 1.9) with a dimer structure. The activation energy for electron transport is estimated to be 0.35 meV. The coordination of the copper ion site (NO4) and the structural arrangement of green complexes 1 (x = 1.9) in the columnar mesophase are determined. Complexes of this type form linear chains in which nitrate counterions serve as bridges between copper centers. It is revealed that green complexes 1 (x = 1.9) dissolved in isotropic inert solvents can be oriented in the magnetic field (B 0 = 8000 G). The degree of orientation of these complexes is rather high (S z = 0.76) and close to that of systems with a complete ordering (S z = 1) in the magnetic field. Copper(0) nanoclusters prepared by reduction of complex 2 (x = 7.3) in two reducing agents (NaBH4, N2H4 · H2O) are examined. A model is proposed for a possible location of Cu(0) nanoclusters in a dendrimer matrix.

  20. Fitness and Individuality in Complex Life Cycles.

    PubMed

    Herron, Matthew D

    2016-12-01

    Complex life cycles are common in the eukaryotic world, and they complicate the question of how to define individuality. Using a bottom-up, gene-centric approach, I consider the concept of fitness in the context of complex life cycles. I analyze the fitness effects of an allele (or a trait) on different biological units within a complex life history and how these effects drive evolutionary change within populations. Based on these effects, I attempt to construct a concept of fitness that accurately predicts evolutionary change in the context of complex life cycles.