Guests

Distribution by Scientific Domains
Distribution within Chemistry

Terms modified by Guests

  • guest chemistry
  • guest complex
  • guest editor
  • guest editorial
  • guest editors
  • guest editors introduction
  • guest encapsulation
  • guest inclusion
  • guest interaction
  • guest molecule
  • guest reviewer
  • guest species
  • guest stoichiometry
  • guest system
  • guest worker

  • Selected Abstracts


    Be El Caudillo's Guest: The Franco Regime's Quest for Rehabilitation and Dollars after World War II via the Promotion of U.S. Tourism to Spain

    DIPLOMATIC HISTORY, Issue 3 2006
    Neal Moses Rosendorf
    First page of article [source]


    How Zaynab Became the First Arabic Novel

    HISTORY COMPASS (ELECTRONIC), Issue 1 2009
    Elliott Colla
    This paper is part of a History Compass conference cluster tracing the formation of national culture in Egypt. Guest edited by Walter Armbrust, this cluster of articles was originally part of a conference in Oxford on January 12,13, 2007, organized by Walter Armbrust, Ronald Nettler, and Lucie Ryzova, and funded by the Middle East Centre (St. Antony's), The Faculty of Oriental Studies, The Khalid bin ,Abdullah Al-Sa'ud Professorship (Professor Clive Holes), and The Centre for Political Ideologies. The cluster is made up of the following articles: Guest Editor: Walter Armbrust ,The Formation of National Culture in Egypt in the Interwar Period: Cultural Trajectories', Walter Armbrust, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00571.x,Repackaging the Egyptian Monarchy: Faruq in the Public Spotlight, 1936,1939', Matthew Ellis, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00572.x,How Zaynab Became the First Arabic Novel', Elliott Colla, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00573.x,Women in the Singing Business, Women in Songs', Frédéric Lagrange, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00574.x,Long Live Patriarchy: Love in the Time of ,Abd al-Wahhab', Walter Armbrust, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00575.x,Football as National Allegory: Al-Ahram and the Olympics in 1920s Egypt', Shaun Lopez, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00576.x,The Professional Worldview of the Effendi Historian', Yoav Di-Capua, History Compass 6 (2008), DOI: 10.1111/j.1478-0542.2008.00577.x Despite a long-standing critical consensus that Muhammad Husayn Haykal's 1914 novel Zaynab was the first ,mature' Arabic novel, there is much evidence to the contrary. First, in terms of genre, Zaynab was not the first book calling itself by the term that later critics would call ,novel'; second, in terms of the bibliographic record, it was not a unique book on the cultural market in 1914; third, in terms of literary style, it was not at the time a particularly unique formal or thematic experiment in prose fiction; and finally, in terms of reception, it was not recognized as significant even by the small market segment and cultural field in which it initially appeared. This article revisits this critical debate and suggests that the canonization of Zaynab as the first Arabic novel cannot be explained by the work itself, but rather by subsequent developments , most especially, in the film adaptations of the novel and in the nationalization of university curricula during the Nasserist period. [source]


    Globalization, Health, and the Environment: An Integrated Perspective

    AMERICAN ANTHROPOLOGIST, Issue 2 2007
    RUTHBETH FINERMAN
    Globalization, Health, and the Environment: An Integrated Perspective. Greg Guest, ed. Lanham, MD: Rowman and Littlefield, 2006. 274 pp. [source]


    BISHOPS, WIVES AND CHILDREN: SPIRITUAL CAPITAL ACROSS THE GENERATIONS by Douglas J. Davies and Mathew Guest

    NEW BLACKFRIARS, Issue 1019 2008
    KIERAN FLANAGAN
    No abstract is available for this article. [source]


    An Unwelcome Guest: Aspergillus Colonization in Lung Transplantation and Its Association with Bronchiolitis Obliterans Syndrome

    AMERICAN JOURNAL OF TRANSPLANTATION, Issue 8 2009
    S. Garantziotis
    Aspergillus colonization may increase the risk for bronchiolitis obliterans syndrome after lung transplantation. See article by Weigt et al. on page 1903,1911. [source]


    Pest or Guest: The Zoology of Overabundance

    AUSTRAL ECOLOGY, Issue 7 2008
    ELIZABETH A. DALEY
    No abstract is available for this article. [source]


    Guest,Framework Interaction in Type I Inorganic Clathrates with Promising Thermoelectric Properties: On the Ionic versus Neutral Nature of the Alkaline-Earth Metal Guest A in A8Ga16Ge30 (A: Sr, Ba)

    CHEMINFORM, Issue 50 2003
    Carlo Gatti
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Spin Crossover versus Low-Spin Behaviour Exhibited in 2D and 3D Supramolecular Isomers of [FeII(2,4-bpt)2],Guest,

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2010
    Xin Bao
    To spin or not to spin: Four supramolecular isomers based on a [Fe(2,4-bpt)2],guest were synthesised by judicious choice of solvents under solvothermal conditions (see figure). They can be categorised into a 2D spin crossover (SCO) branch and a 3D low-spin (LS) branch (all of them exhibit NbO topology, but one is non-interpenetrated and the other two are twofold interpenetrated). The differences in the supramolecular interactions play important roles in their magnetic behaviour. [source]


    Guest,Guest,Host Multicomponent Molecular Crystals: Entrapment of Guest,Guest in Honeycomb Networks Formed by Self-Assembly of 1,3,5-Tri(4-hydroxyaryl)benzenes

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010
    Jarugu, Narasimha Moorthy Prof.
    Abstract Sterically-engineered rigid trigonal molecular modules based on 1,3,5-tri(4-hydroxyphenyl)benzenes H1 and H2 undergo O-H,,,O hydrogen-bonded self-assembly into eight-fold catenated hexagonal (6,3) and two-fold interpenetrated undulated square (4,4) networks, respectively. In the presence of [18]crown-6 as a guest, the triphenol H1 is found to self-assemble into a honeycomb network with hexagonal voids created between three triphenol building blocks. The guest [18]crown-6 molecules are found to be nicely nested in hexagonal enclosures. The empty spaces within the crowns can be further filled with neutral (MeOH/water, MeOH/MeNO2) or ionic guest species such as KI/KAcAc to furnish novel multicomponent assemblies, that is, guest,guest,host, that typify Russian dolls. In contrast, triphenol H2 is found to yield analogous multicomponent molecular crystals in which the guest crown,K+ acts as a spacers in the hydrogen-bonded self-assembly that leads to distorted chicken wire networks. [source]


    Analysis of the Voltammetric Response of Electroactive Guests in the Presence of Non-Electroactive Hosts at Moderate Concentrations

    ELECTROANALYSIS, Issue 18 2004
    Sandra Mendoza
    Abstract In this work, we present a method to analyze the voltammetric response of reversible redox systems involving molecules that, bearing m non-interactive electroactive sites, can undergo fast complexation equilibria with host molecules present at concentrations of the same order of magnitude as those of the electroactive guest. The approach focuses on systems for which the relative values of the binding constants for the oxidized and reduced forms of the guest result in the displacement of the voltammetric response of the electroactive molecule as the concentration of the host is increased in the electrolytic solution. This behavior is commonly known as "one wave shift behavior". Based on a series of assumptions, the method allows calculation of all the thermodynamic parameters that describe the electrochemical and complexation equilibria of a given host-guest system. The main strength of the suggested method, however, relies on the fact that it only requires cyclic voltammetry data and that it can be used for systems in which large concentrations of the host can not be employed either due to important changes of the ionic strength or to solubility problems. Although the accuracy of the obtained information is limited by the quality of the data provided by the technique, and by the assumptions employed, it certainly represents an excellent starting point for subsequent refinement either using digital simulations or an independent experimental technique. [source]


    Hydrophobic Chemistry in Aqueous Solution: Stabilization and Stereoselective Encapsulation of Phosphonium Guests in a Supramolecular Host

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2004
    Julia L. Brumaghim
    Abstract Encapsulation of guest molecules inside supramolecular host assemblies provides a way to stabilize reactive species in aqueous solution. The stabilization of reactive phosphonium/ketone adducts of the general formula [R1MeC(OH)PR3]+ by encapsulation as guest molecules within a [Ga4L6]12, tetrahedral metal,ligand assembly is reported; although these cations decompose in aqueous solution, encapsulation inside the hydrophobic cavity of the assembly lengthens their lifetimes considerably, in some cases up to weeks. By varying the phosphane (PMe3, PEt3, PPhMe2, and PPh2Me) and ketone (acetone, methyl ethyl ketone, 1,1,1-trifluoroacetone, and fluoroacetone) which form these adducts, as well as the pD of the solutions, it was determined that the pH of the solution as well as the size and shape of the guest cations play an important role in the stability of these host,guest complexes. Encapsulation of chiral guests in the chiral [Ga4L6]12, assembly results in the formation of diastereomers, as characterized by 1H, 19F, and 31P NMR spectroscopy. Although the [Ga4L6]12, assembly is formed from non-chiral ligands, the assembly itself has ,,,, or ,,,, chirality around the metal centers. Due to the chirality of this assembly, diastereomeric selectivity is observed upon initial guest encapsulation (typical diastereomeric excesses are 30,50%). This initial diastereomeric selectivity decreases over time to reach an equilibrium but does not become 1:1, indicating both kinetic and thermodynamic processes promote selective guest encapsulation. These experiments demonstrate further the applications of nanoscale reaction vessels, self-assembled by design from non-chiral ligands, in providing a chiral and hydrophobic environment for guest molecules in aqueous solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


    Structural Studies on Hydrogen-Bonding Receptors for Barbiturate Guests That Use Metal Ions as Allosteric Inhibitors

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2004
    Mohammad H. Al-Sayah
    Abstract Receptor 1 was designed to bind barbiturate substrates through a six-point hydrogen-bonding motif only in the absence of metal allosteric cofactors. It was predicted that the binding of metal ions by bipyridine ligands in 1 would result in a geometric change in the receptor to inhibit substrate recognition. However, receptor 1 showed minimal affinity for the barbiturate guests even in the absence of the metal. Binding studies on model compounds 2, 3, 5, and 6 revealed that the inactivity of 1 is due to an intramolecular hydrogen bond between the N,H donor groups and the nitrogen atoms on the first heterocycle of the bipyridine ligands. This intramolecular hydrogen-bonding was eliminated by altering the position of the tether between the bipyridine ligands and the active site to produce receptor 7. Consequently, the high affinity exhibited by 7 for the barbiturate substrate (Ka = 2.8±0.7 × 103M,1 in 9:1 CD2Cl2/CD3CN) was significantly reduced by the addition of ZnII ions as a negative allosteric co-factor. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


    Glutathione-Induced Intracellular Release of Guests from Mesoporous Silica Nanocontainers with Cyclodextrin Gatekeepers

    ADVANCED MATERIALS, Issue 38 2010
    Hyehyeon Kim
    Cyclodextrins tethered onto a mesoporous silica nanoparticle via disulfide stalking are effective gatekeepers not only to entrap guest molecules in the pore but also to release the guest in response to glutathione (GSH). The PEGylated nanocontainers also exhibit efficient GSH-mediated release of doxorubicin in cancer cells. Our approach offers unique applications for multifunctional delivery systems. [source]


    Europe, Continent of Migrants

    AMERICAN ANTHROPOLOGIST, Issue 3 2001
    Jeffrey Cole
    Gender and Migration in Southern Europe: Women on the Move. Floya Anthias and Gabriella Lazaridis. eds. New York: Berg, 2000. 263 pp. Eldorado or Fortress? Migration in Southern Europe. Russell King. Gabriella Lazaridis. and Charalambos G. Tsadanidis. eds. New York: St. Martin's Press, 2000. 368 pp. Guests and Aliens. Saskia Sassen. New York: The New Press, 1999. 202 pp. [source]


    Inclusion of Anionic Guests inside a Molecular Cage with Palladium(II) Centers as Electrostatic Anchors,

    ANGEWANDTE CHEMIE, Issue 38 2009
    Guido
    Vier bananenförmige Liganden und zwei PdII -Ionen bauen quantitativ eine ballförmige Struktur mit vier großen Öffnungen auf (siehe Bild). Die beiden PdII -Ionen bilden mit Pyridindonoren der Liganden stabile quadratisch-planare Komplexe, sie können aber zusätzlich mit Anionen wechselwirken. Weil sie in einem bestimmten Abstand positioniert sind, der durch die starren Liganden vorgegeben ist, wirken die PdII -Ionen als elektrostatische Anker für dianionische Gäste entsprechender Größe. [source]


    Self-Assembly via Ionic Interactions of Calix[6]arene-Based Receptors Displaying Remarkable Host,Guest Properties Toward Neutral Guests.

    CHEMINFORM, Issue 49 2007
    Stephane Le Gac
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    Synthesis and Binding Study of New Aminopyridinyl Cavitand Receptors for the Recognition of Cationic Guests.

    CHEMINFORM, Issue 20 2003
    Byung-Sik Moon
    No abstract is available for this article. [source]


    Self-Assembled Supramolecular Nanocarrier Hosting Two Kinds of Guests in the Site-Isolation State

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 43 2009
    Xing-Long Lou
    Abstract Hyperbranched polyethylenimine (HPEI) was simply mixed with a solution of amphiphilic calix[4]arene (AC4), which possesses four phenol groups and four aliphatic chains, in chloroform. This resulted in the novel supramolecular complex HPEI,AC4 through the noncovalent interaction of the amino groups of HPEI with the phenol groups of AC4. The formed HPEI,AC4 supramolecular complexes were characterized by 1H,NMR spectroscopy and dynamic light scattering. The cationic water-soluble dye methyl blue (MB) and the anionic water-soluble dye methyl orange (MO) were used as the model guests to test the performance of HPEI,AC4 as a supramolecular nanocarrier. It was found that HPEI,AC4 could accommodate the anionic water-soluble MO guests into the HPEI core. The MO encapsulation capacity of HPEI,AC4 was pH sensitive, which reached maximum loading under weakly acidic conditions. The loaded MO molecules could be totally released when the pH value was reduced to be around 4.5 or raised to be around 9.5, and this process was reversible. HPEI,AC4 could not only accommodate the anionic MO with the HPEI core but could also simultaneously load the cationic MB molecules using the formed AC4 shell, thereby realizing the site isolation of the two kinds of functional units. The amount of MO and MB encapsulated by HPEI,AC4 could be controlled by varying the ratio of hydroxyl groups of AC4 to amino groups of HPEI. [source]


    Selective Guest Encapsulation by a Cobalt-Assembled Cage Molecule

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2005
    Roger G. Harrison Prof.
    Abstract Metal-assembled resorcinarene-based cages enclose space and entrap organic molecules from water. Addition of cobalt(II) ions to a neutral, aqueous solution of a resorcinarene that has iminodiacetic acids attached to its upper rim results in the formation of cages. These cages not only entrap organic molecules, but they do so in a selective manner. Guests with optimum size, shape, and polarity are preferentially entrapped. For example, selection of p -xylene is twenty thousand times more favorable than that of m -xylene. The enthalpy of resorcinarene deprotonation and cage formation was calculated by performing calorimetry studies and ranged from ,305 to ,348 kJ,mol,1. The change in enthalpy of guest encapsulation varied by as much as 43 kJ,mol,1. The differences in change in free energy of guest encapsulation varied by ,16 kJ,mol,1. The changes in enthalpy and free energy of guest encapsulation were used to calculate the changes in entropy, which ranged from ,97 to +37 J,mol,1,K,1. An enthalpy,entropy compensation of guest encapsulation was observed. [source]


    Contributions of Lipid Bilayer Hosts to Structure and Activity of Multifunctional Supramolecular Guests

    CHEMISTRY & BIODIVERSITY, Issue 6 2005
    Abhigyan Som
    The question of whether or not the surrounding lipid bilayer host contributes to structure and activity of included functional guests is a general topic of current scientific concern. We report that synthetic multifunctional pores are of use to address this elusive question, because the detection of their catalytic activity is membrane independent. According to their salt-rate profiles, unstable multifunctional supramolecules with permanent internal charges show highest membrane sensitivity, and the dependence of membrane sensitivity on the acidity of internal cations exceeds that on supramolecule stability. These results can, with all appropriate caution, be interpreted as indications for the existence of long-range EMP,ICR interactions (EMP: external membrane pressure, ICR: internal charge repulsion) between membrane hosts and functional guests that can, for instance, prevent the ,explosion' and promote the ,implosion' of over- and undercharged transmembrane barrel-stave supramolecules, respectively. [source]


    Analysis of the Voltammetric Response of Electroactive Guests in the Presence of Non-Electroactive Hosts at Moderate Concentrations

    ELECTROANALYSIS, Issue 18 2004
    Sandra Mendoza
    Abstract In this work, we present a method to analyze the voltammetric response of reversible redox systems involving molecules that, bearing m non-interactive electroactive sites, can undergo fast complexation equilibria with host molecules present at concentrations of the same order of magnitude as those of the electroactive guest. The approach focuses on systems for which the relative values of the binding constants for the oxidized and reduced forms of the guest result in the displacement of the voltammetric response of the electroactive molecule as the concentration of the host is increased in the electrolytic solution. This behavior is commonly known as "one wave shift behavior". Based on a series of assumptions, the method allows calculation of all the thermodynamic parameters that describe the electrochemical and complexation equilibria of a given host-guest system. The main strength of the suggested method, however, relies on the fact that it only requires cyclic voltammetry data and that it can be used for systems in which large concentrations of the host can not be employed either due to important changes of the ionic strength or to solubility problems. Although the accuracy of the obtained information is limited by the quality of the data provided by the technique, and by the assumptions employed, it certainly represents an excellent starting point for subsequent refinement either using digital simulations or an independent experimental technique. [source]


    Self-Assembled Lanthanide Salicylaldimines with a Unique Coordination Mode

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2010
    gorzata T. Kaczmarek
    Abstract New lanthanide salicylaldimine complexes of the formula [Ln(H2L)3(NO3)3](H2L), where Ln = La3+ (1), Nd3+ (2), Eu3+ (3), Gd3+ (4), Ho3+ (5), Er3+ (6), Tb3+ (7) or Yb3+ (8), and H2L = N,N,-bis(salicylidene)-4-methyl-1,3-phenylenediamine, were formed in a self-assembly process involving the lanthanide template-induced one-step [2+1] Schiff base condensation reaction between salicylaldehyde and 4-methyl-1,3-phenylenediamine. The unusual coordination pattern of salen-type ligands in these complexes, in which the three potentially tetradentate N2O2 salicylaldimines function as undeprotonated, monodentate, exclusively O-donor ligands without involving the nitrogen atoms in the coordination environment, was proved by single-crystal X-ray diffraction analysis and correlated with spectroscopic characterization. In this species with the nine-coordinate distorted tricapped trigonal prism geometry, the nitrates act as bidentate chelators occupying six coordination sites and leaving the remaining sites available for salicylaldimine ligands formed in situ in the template process. The additional salicylaldimine molecule acts as a guest for the salicylaldimine complex host and stabilizes the overall self-assembled supramolecular network. [source]


    Solid-State Anion,Guest Encapsulation by Metallosupramolecular Capsules Made from Two Tetranuclear Copper(II) Complexes

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2007
    Emilio Pardo
    Abstract A new cationic tetranuclear copper(II) complex self-assembles from one 1,3-phenylenebis(oxamato) (mpba) bridging ligand and four CuII ions partially blocked with N,N,N,,N, -tetramethylethylenediamine (tmen) terminal ligands. In the solid state, two of these tetracopper(II) oxamato complexes of bowl-like shape and helical conformation then serve as a building block for the generation of either hetero- (MP) or homochiral (MM/PP) dimeric capsules depending on the nature of the encapsulated anion guest, perchlorate or hexafluorophosphate. The overall magnetic behaviour of these metallosupramolecular capsules does not depend on the nature of the encapsulated anion guest, but it is consistent with the dimer-of-dimer structure of the tetracopper(II) cation host, where the interdimer magnetic coupling through the meta -phenylenediamidate bridge is negligibly smallrelative to the reasonably strong intradimer one across the oxamato bridge.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]


    Dicopper(II) Complexes with the Enantiomers of a Bidentate Chiral Reduced Schiff Base: Inclusion of Chlorinated Solvents and Chiral Recognition of1,2-Dichloroethane Rotamers in the Crystal Lattice

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2006
    Vamsee Krishna Muppidi
    Abstract Bisphenoxo-bridged dicopper(II) complexes [Cu2Ln2Cl2] {1 (n = 1) and 2 (n = 2)} with the N,O-donor reduced Schiff bases N -(2-hydroxybenzyl)-(R)-,-methylbenzylamine (HL1) and N -(2-hydroxybenzyl)-(S)-,-methylbenzylamine (HL2) have been synthesised and characterised. In both 1 and 2, the bidentate chiral ligands coordinate the metal centres through the secondary amine N atom and the bridging phenolate O atom. The chloride ion occupies the fourth coordination site and completes a slightly distorted square-planar NO2Cl environment around each copper(II) centre. Magnetic susceptibility measurements in the solid state suggest a strong antiferromagnetic interaction between the metal centres in both complexes. Both 1 and 2 readily form 1:1 host-guest compounds with chlorinated solvents such as CH2Cl2, CHCl3 and Cl(CH2)2Cl. All the host-guest compounds crystallise in noncentrosymmetric space groups. 1·CH2Cl2 and 2·CH2Cl2 crystallise in the P21 space group while 1·CHCl3, 2·CHCl3, 1·Cl(CH2)2Cl and 2·Cl(CH2)2Cl crystallise in the P212121 space group. In these inclusion crystals, the C,H···Cl interactions between the guest and the host molecules are primarily responsible for enclatheration of the chloroalkane molecules. In the case of CH2Cl2, one of its Cl atoms acts as the acceptor. On the other hand, for CHCl3 and Cl(CH2)2Cl, the metal coordinated Cl atom of the host complex acts as the acceptor. The structures of 1·(P)-Cl(CH2)2Cl and 2·(M)-Cl(CH2)2Cl provide rare examples for chiral recognition of the right handed (P) and the left handed (M) gauche forms of Cl(CH2)2Cl in molecular assemblies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


    Novel Metallosupramolecular Networks Constructed from CuII, NiII, and CdII with Mixed Ligands: Crystal Structures, Fluorescence, and Magnetism

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2006
    Miao Du
    Abstract Reactions of mixed ligands succinic acid (H2suc) and bent dipyridines, such as 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and its 4- N -donor analog (4-bpo), with inorganic CuII, NiII, and CdII salts yield three new metal-organic coordination frameworks {[Cu(suc)(3-bpo)(H2O)2]·(H2O)1.75}n (1), {[Ni(suc)(4-bpo)(H2O)2]·(H2O)5}n (3), and {[Cd2(suc)2(3-bpo)2(H2O)2]·(H2O)6.75}n (4), in which the metal centers are linked by bridging ligands 3-bpo/4-bpo and suc2, along two directions to form 2D infinite networks. The corrugated 2D nets of 1 and 4, obtained under hydrothermal conditions, align in an interdigitated manner with the presence of significant aromatic-stacking interactions to result in similar 3D architectures. The 2D sheets in 3 are extended by interlayer hydrogen bonds to afford a 3D structure. However, when succinic acid is replaced by fumaric acid (H2fum) in the reaction with 3-bpo and CuII salt, a metallacyclophane [Cu(Hfum)2(3-bpo)(H2O)]2·(3-bpo)2·(H2O)6 (2) is generated. The binuclear coordinated motifs are hydrogen-bonded to the lattice water chains to furnish a unique 3D channel-like framework, in which the guest 3-bpo molecules are accommodated. The thermal stabilities of these new materials were investigated by thermogravimetric analysis (TGA) of mass loss. The magnetic coupling in complexes 1,3 is antiferromagnetic and very small, which is as expected considering the long organic bridges between the paramagnetic centers. The solid-state luminescence properties of 4 reveal an intense fluorescence emission at 378 nm. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


    Complexation and Dynamic Switching Properties of Fluorophore-Appended Resorcin[4]arene Cavitands

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2010
    Laura D. Shirtcliff
    Abstract Fluorophore-appended resorcin[4]arene-based cavitands having pyrene (2) and anthracene (3) moieties attached to the rims were prepared by short synthetic routes. Both undergo reversible temperature- and acid- (CF3COOD) induced vase,,,kite switching as evidenced by 1H NMR spectroscopy. The 1H NMR spectra also suggest that suitably sized solvents, such as [D8]toluene, efficiently solvate the cavity, reducing the conformational flexibility. In [D12]mesitylene, both cavitands undergo remarkably stable host-guest inclusion complexation with cycloalkanes. The larger cavity of 3 preferentially hosts cyclohexane, whereas the smaller cavity of 2 forms the most stable complex with cyclopentane. The propensity for the cavitands to facilitate ,,, stacking between the chromophores was confirmed by both 1H NMR and fluorescence spectroscopy. The interchromophoric interaction is strongly solvent-dependent: ,,, stacking between the pyrene moieties of 2 is not as efficient in [D8]toluene, as it solvates the inner cavity and prevents the two chromophores from approaching each other. Fluorescence studies revealed an unexpectedly large conformational flexibility of the cavitand structures both in the vase and kite forms, which was further confirmed by molecular dynamics simulations. Excimer formation is most preferred in [D12]mesitylene when the cavities are empty, whereas efficient solvation or guest binding in the interior spaces reduces the propensity for excimer formation. The observed high conformational flexibility of the cavitands in solution explains previous differences from the behavior of related systems in the solid state. This study shows that the rigid, perfect vase and kite geometries found for bridged resorcin[4]arene cavitands in the solid state are largely a result of crystal packing effects and that the conformational flexibility of the structures in solution is rather high. [source]


    Synthesis of Dicarboxylate "C-Clamp" 1,2-Diethynylarene Compounds as Potential Transition-Metal Ion Hosts

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 1 2008
    Erwin Reisner
    Abstract We report an efficient convergent synthesis of a new type of C-clamp ligand with a 1,2-diethynylarene scaffold involving a chelate host capable of binding a guest molecule in its endo -dicarboxylate pocket. The chemistry involves a combination of palladium-catalyzed Sonogashira, Heck, and Suzuki cross-coupling reactions. The compounds 2,3-bis[2-(2,-carboxybiphenyl-4-yl)ethynyl]triptycene and 4,5-bis[2-(2,-carboxybiphenyl-4-yl)ethynyl]veratrole and their 2,-carboxy- m -terphenyl-4-yl analogues were designed as dinucleating ligands to assemble carboxylate-bridged transition-metal complexes with a windmill geometry. The X-ray crystal structure of one such C-clamp compound containing co-crystallized water molecules reveals strong hydrogen bonds of the aqua guest to the endo -oriented carboxylic acid entities of the C-clamp host. In addition, two syn -N-donor ligands were prepared as a synthetic scaffold to mimic the geometric arrangement of N-donor atoms in carboxylate-bridged dinuclear proteins. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]


    Controlling Light Emission in Luminescent Solar Concentrators Through Use of Dye Molecules Aligned in a Planar Manner by Liquid Crystals

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Paul P. C. Verbunt
    Abstract A luminescent solar concentrator (LSC) is a potential low-cost enhancement of the standard large-area silicon photovoltaic panels for the generation of electricity from sunlight. In this work, guest,host systems are investigated using anisotropic fluorescent dyes and liquid crystal mesogens to control the direction of emitted light in the LSC. It is determined that up to 30% more light is emitted from the edge of an LSC waveguide with planar dye alignment parallel to the alignment direction than from any edge of an LSC with no alignment (isotropic). The aligned samples continue to show dichroic performance after additions of both edge mirrors and rear scattering layer. [source]


    A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl-Substituted Fluorene Units for Highly Efficient Blue Electrophosphorescence

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Fang-Ming Hsu
    Abstract Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N -diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato- N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenyl-phosphoryl)fluorene segment linked through the sp3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (ET) of 2.75,eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest. In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7,wt% FIrpic exhibits a very low turn-on voltage (2.5,V) and high electroluminescence efficiencies (20.6% and 36.7,lm W,1). Even at the practical brightnesses of 100 and 1000,cd m,2, the efficiencies remain high (20.2%/33.8,lm W,1 and 18.8%/24.3,lm W,1, respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources. [source]


    Guest-Induced Chirality in the Ferrimagnetic Nanoporous Diamond Framework Mn3(HCOO)6,

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2007
    B. Zhang
    Abstract Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2-chloropropan-1-ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading. [source]