Angewandte Chemie International Edition

Cover image for Vol. 45 Issue 7

February 6, 2006

Volume 45, Issue 7

Pages 1003–1165

    1. Cover Picture: Transcription and Amplification of Molecular Chirality to Oppositely Biased Supramolecular π Helices (Angew. Chem. Int. Ed. 7/2006) (page 1003)

      Ayyappanpillai Ajayaghosh, Reji Varghese, Subi Jacob George and Chakkooth Vijayakumar

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200690023

      Inversion of helicity and the formation of unusual fused supercoiled left and right helices of gel-forming linear π-conjugated molecules by a “sergeants and soldiers” approach, in which the achiral molecules (soldiers) mistake orders from the chiral molecules (sergeants), is described by A. Ajayaghosh et al. on page 1141 ff. The cover picture shows Janus, the double-faced Greek God, holding a left-handed DNA helix and a right-handed conch which epitomize the marvels of natural creations.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 7/2006 (pages 1006–1015)

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200690024

    3. George S. Hammond (1921–2005) (page 1018)

      Nicholas J. Turro and Harry Gray

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200600079

    4. A New Approach to the Inhibition of Metallo-β-lactamases (pages 1022–1026)

      James Spencer and Timothy R. Walsh

      Article first published online: 11 JAN 2006 | DOI: 10.1002/anie.200502984

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      Plan of attack: β-Lactam antibiotics remain at the forefront of the battle with pathogenic bacteria, particularly of Gram-negative strains that cause hospital-acquired infections. Metallo-β-lactamases, enzymes that confer resistance to almost all β-lactams, are spreading in these organisms. A new class of irreversible metallo-β-lactamase inhibitor (OPS; see picture) offers hope for the development of countermeasures to this growing clinical problem.

    5. Visual Essences, Readable Signs, Means of Construction: On the Relevance of Images in Science (pages 1028–1031)

      Michael Hampe

      Article first published online: 28 DEC 2005 | DOI: 10.1002/anie.200502407

      Seeing is believing, but images in science are often based on mathematical and philosophical presuppositions. Computation and imaging, which once seemed to be in conflict, have become interconvertible. It seems that pictures will become more and more important in science. This should not lead to new illusions about supposedly direct insights into the essence of things.

    6. Synthesis of Naturally Occurring Polyynes (pages 1034–1057)

      Annabelle L. K. Shi Shun and Rik R. Tykwinski

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200502071

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      Diverse structures and biological activities are shown by polyyne natural products (such as the compounds shown, isolated fron Anacyclus pyrethrum). Although some polyynes can be assembled with relative ease, most present a considerable synthetic challenge because of either a highly conjugated and unstable framework or stereochemical considerations. Recent strategies for the synthesis of these fascinating molecules are discussed.

    7. The Characterization of Weak Protein–Protein Interactions: Evidence from DEER for the Trimerization of a von Willebrand Factor A Domain in Solution (pages 1058–1061)

      Janet E. Banham, Christiane R. Timmel, Rachel J. M. Abbott, Susan M. Lea and Gunnar Jeschke

      Article first published online: 10 JAN 2006 | DOI: 10.1002/anie.200503720

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      Distance determination: A double electron electron resonance (DEER) measurement of a distance of 6.1 nm (green lines) between singly nitroxide-labeled human von Willebrand Factor A domains demonstrates oligomerization of this domain in dilute solution (see structure); probably in an arrangement similar to that observed in the crystal structure. The DEER technique should be generally applicable for characterizing noncovalent interactions between macromolecules in solution.

    8. The First Liquefaction of High-Rank Bituminous Coals by Preceding Hydrogenation with Homogeneous Borane or Iodine Catalysts (pages 1061–1066)

      Matthias W. Haenel, Janchig Narangerel, Udo-Burckhard Richter and Anna Rufińska

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200502614

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      In view of escalating oil prices, new processes are needed for the conversion of coal to liquid fuels. The first “real” coal hydrogenation in the sense of hydrogen addition to unsaturated C[BOND]C bonds enables the liquefaction of high-rank bituminous coals, which up to now could be processed only by combustion or gasification.

    9. Boron in the Coordination Spheres of Three Transition-Metal Atoms: Syntheses and Structures of Metalloborylenes Stabilized by a Transition-Metal Base (pages 1066–1069)

      Holger Braunschweig, Krzysztof Radacki, Daniela Rais and Fabian Seeler

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503807

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      Naked boron: Reaction of the bromoborylene complex [(η5-C5Me5)(OC)Fe(μ-CO)(μ-BBr)Pt(PCy3)Br] with [M(PCy3)2] (M=Pd, Pt) leads to complexes featuring the unprecedented coordination of one boron atom to three transition-metal centers (see picture). According to structural and DFT studies, the new compounds are best described as metalloborylene complexes stabilized by transition-metal bases.

    10. Fluorescent Inhibitors for IspF, an Enzyme in the Non-Mevalonate Pathway for Isoprenoid Biosynthesis and a Potential Target for Antimalarial Therapy (pages 1069–1074)

      Christine M. Crane, Johannes Kaiser, Nicola L. Ramsden, Susan Lauw, Felix Rohdich, Wolfgang Eisenreich, William N. Hunter, Adelbert Bacher and François Diederich

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503003

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      Designed inhibitors (like 1) of IspF, a key enzyme in the non-mevalonate pathway for terpene biosynthesis and a potential antimalarial target, were synthesized and evaluated. Since fluorescent probes were introduced in these ligands, their affinity towards IspF from E. coli could be determined by fluorescence titrations. The binding modes of two ligands in ternary complexes with IspF and a ZnII ion were clarified by X-ray analysis.

    11. The [Ga2(C5Me5)]+ Ion: Bipyramidal Double-Cone Structure and Weakly Coordinated, Monovalent Ga+ (pages 1074–1076)

      Beatrice Buchin, Christian Gemel, Thomas Cadenbach, Rochus Schmid and Roland A. Fischer

      Article first published online: 15 DEC 2005 | DOI: 10.1002/anie.200503028

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      Partial protolysis of GaCp* with [H(OEt2)2]+[BArF] afforded the GaI compound [Ga2Cp*]+[BArF] (see structure). Experimental and computational studies confirm the mainly ionic structure of the cation, in which the Ga+ ions are only weakly covalently stabilized by a bridging Cp* ligand. Initial experiments point to the interesting synthetic potential of this compound as a source for Ga+ in solution.

      Corrected by:

      Corrigendum: The [Ga2(C5Me5)]+ Ion: Bipyramidal Double-Cone Structure and Weakly Coordinated, Monovalent Ga+

      Vol. 45, Issue 11, 1674, Article first published online: 1 MAR 2006

    12. A Convergent Synthesis of N-Glycopeptides (pages 1077–1081)

      Clyde M. Kaneshiro and Katja Michael

      Article first published online: 10 JAN 2006 | DOI: 10.1002/anie.200502687

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      Two birds are killed with one stone when N-glycopeptides are synthesized by condensation of photoreactive peptides with glycosylamines. Firstly, the aspartic acid side chain is protected as an amide with a nitroindoline moiety, which is then converted into a powerful acylating agent by UV light. Secondly, photoacylation is carried out under base-free conditions, which minimizes an undesired side reaction, the formation of aspartimide.

    13. Mechanics versus Thermodynamics: Swelling in Multiple-Temperature-Sensitive Core–Shell Microgels (pages 1081–1085)

      Ingo Berndt, Crisan Popescu, Franz-Josef Wortmann and Walter Richtering

      Article first published online: 10 JAN 2006 | DOI: 10.1002/anie.200502893

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      The thermal transition of a thermoresponsive microgel of poly-N-isopropylacrylamide (PNIPAM; transition temperature=34 °C) is shifted to higher temperatures when it is embedded in a shell of temperature-sensitive poly-N-isopropylmethacrylamide (PNIPMAM; transition temperature=44 °C). The magnitude of the shift depends on the shell/core mass ratio. A thick shell induces a third transition arising from strong mechanical forces exerted on the core.

    14. Distanna-closo-dodecaborate (pages 1085–1087)

      Dominik Joosten, Ingo Pantenburg and Lars Wesemann

      Article first published online: 28 DEC 2005 | DOI: 10.1002/anie.200503197

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      Hybrid clusters: Reductive cleavage of a novel dimeric closo-heteroborate (see picture; Sn blue, B green, H white), which was characterized by NMR spectroscopy and X-ray crystallography, provides a route to 1,2-distanna-closo-dodecaborate.

    15. Spectroscopic Characterization of Reaction Intermediates in a Model for Copper Nitrite Reductase (pages 1089–1092)

      Masato Kujime and Hiroshi Fujii

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503555

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      A nitrous acid complex was identified by spectroscopic and kinetic analyses under stopped-flow conditions as an intermediate in the reaction of copper(I) nitrite complex 1 with trifluoroacetic acid (see scheme). A reaction mechanism was proposed in which two protons are transferred in a stepwise manner to the nitrite anion. Intramolecular electron transfer from copper to the nitrite ligand occurs in the second protonation step.

    16. Catalytic Enantioselective Hydrogenolysis of [Cr(CO)3(5,8-Dibromonaphthalene)] (pages 1092–1095)

      E. Peter Kündig, Piyali Datta Chaudhuri, David House and Gérald Bernardinelli

      Article first published online: 11 JAN 2006 | DOI: 10.1002/anie.200502688

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      Split and run: A study of the asymmetric hydrogenolysis of an aryl-carbon–bromine bond in a naphthalene chromiumtricarbonyl complex shows the use of a new bulky phosphoramidite ligand to yield the product in highly enantiomerically enriched form (see scheme).

      Corrected by:

      Corrigendum: Catalytic Enantioselective Hydrogenolysis of [Cr(CO)3(5,8-Dibromonaphthalene)]

      Vol. 45, Issue 24, 3898, Article first published online: 1 JUN 2006

    17. How Can Uranium Ions (U+, U2+) Activate the O[BOND]H Bond of Water in the Gas Phase? (pages 1095–1099)

      Maria del Carmen Michelini, Nino Russo and Emilia Sicilia

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200501931

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      Intermediates in theory and experiment: Different approaches of the density functional theory were used to obtain a close description of the reaction mechanisms of the title reactions. They supplied the minima 13 for U+ and 46 for U2+. The theoretical results are compared with experimental data.

    18. A Mimicry of Primary Amines by Bis-Secondary Diamines as Components in the Ugi Four-Component Reaction (pages 1099–1102)

      Giovanni Battista Giovenzana, Gian Cesare Tron, Stefano Di Paola, Ivan Guglielmo Menegotto and Tracey Pirali

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503095

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      Splitting the amine! The Ugi four-component reaction (Ugi 4CR) relies on the presence of a component with a primary amino group. This protocol has been modified by “splitting” the primary amine into two secondary amines. The resulting variant of the Ugi 4CR proceeds with good to excellent yield and widens the versatility of the original multicomponent reaction by enabling variation of the molecular backbone.

    19. Conducting Polymer Actuator Mechanism Based on the Conformational Flexibility of Calix[4]arene (pages 1103–1105)

      Jordi Casanovas, David Zanuy and Carlos Alemán

      Article first published online: 30 DEC 2005 | DOI: 10.1002/anie.200503304

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      Contracted out: Quantum mechanical calculations and classical molecular dynamics simulations have been used to investigate the actuation mechanism of a substituted poly(calix[4]arene quaterthiophene). The results show that electrostatic repulsions between the charged atoms of the calix[4]arene scaffolds in the oxidized-deprotonated species induce a drastic contraction of the electrochemically activated polymer molecules.

    20. Gold-Catalyzed Intramolecular Reaction of Indoles with Alkynes: Facile Formation of Eight-Membered Rings and an Unexpected Allenylation (pages 1105–1109)

      Catalina Ferrer and Antonio M. Echavarren

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503484

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      Going for gold: Cationic gold(I) complexes favor formation of six- and seven-membered rings by 6-endo-dig, 6-exo-dig, and 7-exo-dig cyclizations of alkynyl indoles, whereas indoloazocines are favored with AuCl3 as catalyst (see scheme). Allenes are also formed by a fragmentation process.

    21. A Highly Unsaturated Platinum–Rhenium Cluster Complex Activates Hydrogen Reversibly (pages 1109–1112)

      Richard D. Adams, Burjor Captain and Mark D. Smith

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503736

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      Give and take: The compounds [PtRe2(CO)9(PtBu3)(μ-H)2] and [Pt2Re2(CO)7(PtBu3)2(μ-H)2] (1) are obtained from the reaction of [Pt(PtBu3)2] with [Re3(CO)12(μ-H)3]. Compound 1 adds hydrogen at 25 °C to yield the tetrahydrido complex [Pt2Re2(CO)7(PtBu3)2(μ-H)4] (2; see structure, red H, blue Pt, green Re, silver C, gold O, yellow P). When heated and also when irradiated, compound 2 eliminates one equivalent of H2 to regenerate 1 in high yield.

    22. Efficient Homogeneous Catalytic Hydrogenation of Esters to Alcohols (pages 1113–1115)

      Jing Zhang, Gregory Leitus, Yehoshoa Ben-David and David Milstein

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503771

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      With open arms: A ruthenium PNN complex (see scheme) catalyzes the hydrogenation of esters in high yields under neutral conditions. The analogous PNP complex is less active. A mechanism is proposed based on the hemilabile nature of the PNN ligand which allows a vacant site to be created by decoordination of the [BOND]CH2NEt2 arm.

    23. Sonochemical Formation of Single-Crystalline Gold Nanobelts (pages 1116–1119)

      Jianling Zhang, Jimin Du, Buxing Han, Zhimin Liu, Tao Jiang and Zhaofu Zhang

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503762

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      Benign belts: Single-crystalline gold nanobelts (see SEM image) can be synthesized by ultrasound irradiation of an aqueous solution of HAuCl4 containing α-D-glucose as a biological directing agent. The gold nanobelts are typically 30–50 nm wide and several micrometers long. The method is simple, rapid, and avoids hazardous substances.

    24. Self-Organization of Spherical, Core–Shell Palladium Aggregates by Laser-Induced and Thermal Decomposition of [Pd(PPh3)4] (pages 1120–1123)

      Enyi Ye, Hua Tan, Shuping Li and Wai Yip Fan

      Article first published online: 30 DEC 2005 | DOI: 10.1002/anie.200503408

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      Metal in the middle: Uniform, spherical, core–shell aggregates (100±20 nm; see picture) are obtained by photodecomposition of [Pd(PPh3)4] to form the metal core, followed by aggregation of smaller Pd nanocrystals and free phosphanes, produced by thermal decomposition of the remaining precursor, around this core. Prolonged irradiation or thermal decomposition alone yields only the core structure or the shell structure, respectively. This enables the nanoparticle structure to be tuned.

    25. The Local Structure of Ionic Liquids: Cation–Cation NOE Interactions and Internuclear Distances in Neat [BMIM][BF4] and [BDMIM][BF4] (pages 1123–1126)

      Andrea Mele, Greta Romanò, Matteo Giannone, Enzio Ragg, Giovanni Fronza, Guido Raos and Valentina Marcon

      Article first published online: 13 JAN 2006 | DOI: 10.1002/anie.200503745

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      The polar domains within model ionic liquids are assessed by intermolecular NOE interaction studies. The cation–cation distances in pure ionic liquids 1-butyl-3-methylimidazolium (see picture) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate are obtained and used to provide models of the local structure of the liquids.

    26. A Biomimetic Chromanol Cyclization Leading to α-Tocopherol (pages 1126–1130)

      Christian Grütter, Emma Alonso, Antoinette Chougnet and Wolf-D. Woggon

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200503123

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      Vitamin E synthesis: Covalently linked dipeptides serve as readily removable and recyclable chiral auxiliaries in the diastereoselective cyclization of phytylhydroquinones. Depending on the chirality of the handle, (2R)- or (2S)-α-tocopherol (vitamin E) can be produced with a diastereomeric excess of up to 80 % (see scheme).

    27. A Biomimetic Model for the Active Site of Iron-Only Hydrogenases Covalently Bonded to a Porphyrin Photosensitizer (pages 1130–1133)

      Li-Cheng Song, Ming-Yi Tang, Fu-Hai Su and Qing-Mei Hu

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503602

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      Efficient communication: The first porphyrin-photosensitizer-containing biomimetic model for the active site of Fe-only hydrogenases has been synthesized and structurally characterized (see picture). Its fluorescence spectrum reveals that an efficient electronic communication occurs between the porphyrin unit and the covalently linked diiron–azadithiolate moiety.

    28. Tuning the Structure and Orientation of Hexagonally Ordered Mesoporous Channels in Anodic Alumina Membrane Hosts: A 2D Small-Angle X-ray Scattering Study (pages 1134–1138)

      Barbara Platschek, Nikolay Petkov and Thomas Bein

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503301

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      Circular or columnar orientations of mesoporous silica can be selectively prepared by tuning the silica-to-surfactant ratio and the humidity during the synthesis of the mesoporous material within the regular larger channels of anodic alumina membranes. The transmission electron microscopy image shows the circular orientation of these highly ordered hexagonal mesostructures.

    29. A μ-η22-Disulfide Dicopper(II) Complex from Reaction of S8 with a Copper(I) Precursor: Reactivity of the Bound Disulfur Moiety (pages 1138–1141)

      Matthew E. Helton, Debabrata Maiti, Lev N. Zakharov, Arnold L. Rheingold, John A. Porco Jr. and Kenneth D. Karlin

      Article first published online: 30 DEC 2005 | DOI: 10.1002/anie.200503216

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      Side on: Elemental sulfur (S8) reacts with a tridentate chelate (MePY2)math image copper(I) compound, generating a side on μ-η22-disulfido bridged complex [{CuII(MePY2)math image}2(S22−)]2+ (see structure: yellow S, green Cu, blue N, gray C); its reactivity towards PPh3, RNC, CO, O2, PhCH2Br, and a tetradentate chelating ligand are described.

    30. Transcription and Amplification of Molecular Chirality to Oppositely Biased Supramolecular π Helices (pages 1141–1144)

      Ayyappanpillai Ajayaghosh, Reji Varghese, Subi Jacob George and Chakkooth Vijayakumar

      Article first published online: 6 DEC 2005 | DOI: 10.1002/anie.200503142

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      Let's twist again: Transcription of molecular chirality from common stereogenic centers to amplified supramolecular chirality during the coassembly of gel-forming π-conjugated molecules by inverted helicity results in the formation of longitudinally fused M and P helices. This “sergeants and soldiers” approach to coassembly under stereomutation has been confirmed by CD and AFM techniques (see picture).

      Corrected by:

      Corrigendum: Transcription and Amplification of Molecular Chirality to Oppositely Biased Supramolecular π Helices

      Vol. 45, Issue 12, 1834, Article first published online: 6 MAR 2006

    31. The Molecular Origin of the “Continuous” Infrared Absorption in Aqueous Solutions of Acids: A Computational Approach (pages 1144–1147)

      Radu Iftimie and Mark E. Tuckerman

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200502259

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      The origin of the continuum region (equation image=1000–3000 cm−1) in the IR absorption spectra of solutions of strong acids is well understood, but in weak acids, it has remained a mystery until now. An ab initio molecular dynamics approach is used to explain the molecular origin of this continuum for aqueous solutions of the weak acid HF and identify the structure and chemical nature of the dominant species (see picture).

    32. Chirally Aminated 2-Naphthols—Organocatalytic Synthesis of Non-Biaryl Atropisomers by Asymmetric Friedel–Crafts Amination (pages 1147–1151)

      Sebastian Brandes, Marco Bella, Anne Kjærsgaard and Karl Anker Jørgensen

      Article first published online: 3 JAN 2006 | DOI: 10.1002/anie.200503042

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      Cinchona alkaloids are employed in an organocatalyzed asymmetric Friedel–Crafts amination reaction of 2-naphthols. These amination reactions proceed in high yields with up to 98 % ee and have led to a new class of non-biaryl atropisomer. The rotation barriers of the chiral aminated 2-naphthols have been investigated by experimental and computational methods.

    33. Diagnostics of Single Base-Mismatch DNA Hybridization on Gold Nanoparticles by Using the Hyper-Rayleigh Scattering Technique (pages 1151–1154)

      Paresh Chandra Ray

      Article first published online: 11 JAN 2006 | DOI: 10.1002/anie.200503114

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      Highly sensitive: The hyper-Rayleigh Scattering (HRS) technique has been used to achieve the ultrasensitive detection of single base-pair mismatches in oligonucleotide strands without any modification of DNA. A very distinct HRS intensity change is observed after hybridization even at the concentration of 10-nanomolar probe single-stranded DNA.

      Corrected by:

      Corrigendum: Diagnostics of Single Base-Mismatch DNA Hybridization on Gold Nanoparticles by Using the Hyper-Rayleigh Scattering Technique

      Vol. 45, Issue 14, 2162, Article first published online: 17 MAR 2006

    34. You have free access to this content
      Uniformly a-Oriented MFI Zeolite Films by Secondary Growth (pages 1154–1158)

      Jungkyu Choi, Shubhajit Ghosh, Zhiping Lai and Michael Tsapatsis

      Article first published online: 30 DEC 2005 | DOI: 10.1002/anie.200503011

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      Oriented assembly of zeolite crystals on a porous support followed by secondary growth leads to continuous, thin, uniformly oriented zeolite films (see picture for a cross-sectional SEM image) of MFI with the 5.1×5.5-Å zigzag channels perpendicular to the support. These a-oriented films along with their previously reported b-oriented counterparts are the first set of thin molecular-sieve membranes with uniform but drastically different orientations.

    35. You have free access to this content
      Preview: Angew. Chem. Int. Ed. 7/2006 (page 1165)

      Article first published online: 30 JAN 2006 | DOI: 10.1002/anie.200690025

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