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2005, Vol. 34 No. 1-12
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| Dec. 2005, Vol.34 No.12
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Web Release Date:
October 27, 2005
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| 1574
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Approaches to Size-selective Formation of Fullerenes by Cyclization of Highly Reactive Polyyne Chains
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Rui Umeda, Motohiro Sonoda, Tomonari Wakabayashi, and Yoshito Tobe
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As an approach to size-selective formation of fullerenes, we developed a method based on the cyclization of reactive cyclic polyynes which were generated by [2 + 2] cycloreversion of [4.3.2]propellatriene units. This method was proven to work successfully for the first time for the formation of fullerene ions C60+ and C60− in the gas phase. This protocol is useful for generation of a small three-dimensional carbon cluster ion C36− and a large fullerene C78−, as well.
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| Nov. 2005, Vol.34 No.11
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Web Release Date:
September 28, 2005
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| 1462
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Ruthenium-catalyzed Reconstructive Synthesis of Functional Organic Molecules via Cleavage of Carbon–Carbon Bonds
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Teruyuki Kondo and Take-aki Mitsudo
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In spite of the inertness of the carbon–carbon bonds in organic molecules, there have been growing interests in catalytic cleavage of carbon–carbon bonds which realizes rapid and reconstructive synthesis of new functional organic molecules. In this review, some of the strategies for achieving ruthenium-catalyzed carbon–carbon bond cleaving reactions were disclosed. Each of these reactions involves direct oxidative addition of carbon–carbon bonds, β-carbon elimination and/or formation of ruthenacycles, π-allylruthenium complexes, and ruthenium carbene or ketene complexes, respectively, as key steps of the selective carbon–carbon bond cleavage.
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| Oct. 2005, Vol.34 No.10
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Web Release Date:
August 28, 2005
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| 1304
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Azide Compounds: Nitrogen Sources for Atom-efficient and Ecologically Benign Nitrogen-atom-transfer Reactions
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Tsutomu Katsuki
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Azide compounds that are readily available and easily manageable, are desirable nitrogen sources for nitrogen-atom-transfer reactions such as aziridination and sulfimidation, in terms of atom-efficiency and ecological benignity. Recent development of catalysts has allowed some of these reactions to be carried out in a highly stereocontrolled manner under mild reaction conditions. This article describes recent progress in such nitrogen-atom-transfer reactions.
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| Sept. 2005, Vol.34 No.9
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Web Release Date:
July 30, 2005
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| 1206
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Central Dogma for a Molecular Design Based on DNA: DNB (Databasing/Designable Nanobio) → ENB (Engineering Nanobio) → FNB (Functional Nanobio)
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Shu-ichi Nakano and Naoki Sugimoto
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Nanobiomaterials have become of broader interest over the past few years. In this review, we demonstrate functional biomolecules that we have constructed based on the biophysical data on nucleotides. We propose three concepts for the development of new nanobiomaterials; DNB (Databasing or Designable Nanobio) is the process of storing the biomolecular properties, ENB (Engineering Nanobio) is the process of conversion of the biomolecular properties to a molecular design, and FNB (Functional Nanobio) is the process of constructing functional molecules based on DNA technologies. Our approach of DNB → ENB → FNB can be the central dogma for a molecular design.
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| Aug. 2005, Vol.34 No.8
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Web Release Date:
June 26, 2005
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| 1068
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Transition Metal-catalyzed Reactions Using Alkynes as Precursors of Carbene and Vinylidene Complexes
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Koji Miki, Sakae Uemura, and Kouichi Ohe
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The transition metal-induced in situ generation of carbene complexes from alkynes having a carbonyl or imino group as a nucleophilic functionality has been investigated. These reactive carbenoid species are generated with high atom efficiency through a 6-endo-dig cyclization mode based on the electrocyclization of vinylidene complexes or a 5-exo-dig cyclization mode in π-alkyne complexes and have been found to serve as versatile intermediates in catalytic carbene transfer reactions.
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| Jul. 2005, Vol.34 No.7
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Web Release Date:
May 28, 2005
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| 886
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A New Route to an Endohedral Fullerene by Way of σ-Framework Transformations
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Koichi Komatsu and Yasujiro Murata
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The molecular surgical approach has been shown to be applicable to preparation of an endohedral fullerene. Thus, an orifice large enough to insert an atom or molecule has been constructed on the surface of fullerene C60. The orifice has been enlarged to a 13-membered ring by insertion of a sulfur atom on the rim, and 100% encapsulation of molecular hydrogen has been attained. Then, the size reduction of the orifice, without the loss of incorporated hydrogen, and complete closure of the orifice have been achieved to afford a new endohedral fullerene, H2@C60. |
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| Jun. 2005, Vol.34 No.6
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Web Release Date:
May 25, 2005
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| 742
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Transition Metal-complexed Catenanes and Rotaxanes as Light-driven Molecular Machines Prototypes
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Jean-Paul Collin and Jean-Pierre Sauvage
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In the course of the last decade, many dynamic molecular systems, for which the movements are controlled from the outside, have been elaborated. These compounds are generally referred to as “molecular machines.” Our group has made and studied catenanes and rotaxanes since the early 80s. An important class of molecular machines is based on these interlocking or threaded ring compounds. Although a “molecular muscle” is briefly discussed in the present review article, we mostly focus on light-driven machines, consisting of ruthenium(II)-complexed rotaxanes or catenanes. The synthetic approach is based on the template effect of an octahedral ruthenium(II) centres. Two 1,10-phenanthroline ligands are incorporated in an axis or in a ring, affording the precursor to the rotaxane or the catenane, respectively. Ru(diimine)32+ complexes display the universally used 3MLCT (metal-to-ligand charge transfer) excited state and, another interesting excited state, the 3LF (ligand field) state, which is strongly dissociative. In the past, the 3LF state has mostly been considered as detrimental and thus, its reactivity has not been frequently utilised. By taking advantage of this latter state, it has been possible to propose a new family of molecular machines, which are set in motion by populating the dissociative 3LF state, thus leading to ligand exchange in the coordination sphere of the ruthenium(II) centre.
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| May 2005, Vol.34 No.5
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Web Release Date:
March 26, 2005
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| 624
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Advances in Iron Catalyzed Cross Coupling Reactions
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Alois Fürstner and Rubén Martin
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Recent developments in the use of cheap, benign, and non-toxic iron salts as pre-catalysts for various types of cross coupling reactions are outlined. Selected applications to the total synthesis of bioactive natural products and pharmaceutically relevant compounds illustrate the scope of this methodology. |
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| Apr. 2005, Vol.34 No.4
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Web Release Date:
February 26, 2005
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| 454
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Iminium Alkaloids from Marine Invertebrates: Structure, Biological Activity, and Biogenesis
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Masaki Kita and Daisuke Uemura
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The discovery of new natural products frequently triggers a breakthrough in basic sciences. This review features marine iminium alkaloids, which control biologically and physiologically intriguing phenomena. Pinnatoxins, potent shellfish poisons purified from the Okinawan bivalve Pinna muricata, activate Ca2+ channels. Norzoanthamine hydrochloride, isolated from the colonial zoanthid Zoanthus sp., suppresses decreases in bone weight and strength in ovariectomized mice. Symbioimine, an amphoteric iminium metabolite from the dinoflagellate Symbiodinium sp., inhibits osteoclast differentiation. The latter two compounds are good candidates for antiosteoporotic drugs.
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| Mar. 2005, Vol.34 No.3
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Web Release Date:
January 29, 2005
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| 276
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Hydrothermal Synthesis and Characterization of Zeolites
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Toru Wakihara and Tatsuya Okubo
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Zeolites have been widely utilized in industry and in household products, for example as adsorbents, ion-exchangers, and catalysts, and have attracted considerable attention as host materials for various nanotechnology applications. Recent developments in analytical methods have enabled detailed studies on the crystallization mechanism of zeolites. The purpose of this review is to give a survey of recent progress in hydrothermal synthesis and characterization of zeolites. |
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| Feb. 2005, Vol.34 No.2
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Web Release Date:
January 15, 2005
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| 132
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Nanocrystals of Coordination Polymers
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Takashi Uemura and Susumu Kitagawa
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Development of synthetic method with controllable size and shape in nanometer regime as well as understanding of the size and surface effects of coordination polymer (CP) nanocrystals is urgently requisite on behalf of future application of them to new organic–inorganic hybrid nanomaterials.
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| Feb. 2005, Vol.34 No.2
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Web Release Date:
December 25, 2004
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| 126
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Elastic Cycles as Flexible Hosts: How Tubes Built by Cyclic Chalcogenaalkynes Individually Host Their Guests
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Rolf Gleiter and Daniel B. Werz
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Tubular structures arise in the solid state through close chalcogen–chalcogen contacts. Different approaches to include guest molecules into the hollow core are discussed. In some cases an enormous flexibility dependent on the size of the included guest molecule is observed.
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| Jan. 2005, Vol.34 No.1
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Web Release Date:
December 23, 2004
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Mesoscopic Solar Cells for Electricity and Hydrogen Production from Sunlight
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Michael Grätzel
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The quality of human life depends to a large degree on the availability of energy sources. The present annual worldwide energy consumption has already attained a level of over 400 exajoules and is expected to further augment steeply from the increase in world population and the rising demand of energy in the developing countries. This implies enhanced depletion of fossil fuel reserves leading to further aggravation of the environmental pollution. Quality of life on earth is threatened unless renewable energy resources can be developed in the near future. Chemistry is expected to make important contributions to identify environmentally friendly solutions of the energy problem. One attractive strategy discussed in this article is the development of systems that mimic natural photosynthesis in the conversion solar energy. The task to be accomplished by these systems is to harvest sunlight and convert it to electricity or drive an uphill chemical reaction. Learning from the concepts used by green plants, we have developed a molecular photovoltaic device whose overall efficiency for solar energy conversion to electricity has already attained 11%. The system is based on the sensitization of nanocrystalline oxide films by charge-transfer sensitizers. The underlying fundamental processes of light trapping by the sensitizer, heterogeneous electron transfer from the electronically excited chromophore into the conduction band of the semiconductor oxide and the percolative migration of the injected electrons through the mesoporous film to the collector electrode, will be described below in detail. The low cost and ease of production of the new cell should benefit large scale applications. These systems will undoubtedly promote the acceptance of renewable energy technologies, not least by setting new standards of convenience and economy. The nanocrystalline semiconductor junctions developed first for dye sensitized solar cells have meanwhile found a realm of other applications ranging from electrochromic and electroluminescent displays to high power lithium insertion batteries. They are also used in tandem cells for the cleavage of water into hydrogen and oxygen by sunlight.
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| Jan. 2005, Vol.34 No.1
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Web Release Date:
November 27, 2004
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| 2
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A Key Role of Orbital Interaction in the Main Group Element-containing π-Electron Systems
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Shigehiro Yamaguchi and Kohei Tamao
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Various types of main group element-containing π-electron systems have been synthesized using silole, dibenzoborole, or bis-silicon-bridged stilbene as the key building units. In these π-electron systems, the orbital interaction between the main group element moiety and the π-conjugated framework, such as pπ–π* and σ*–π* conjugation, plays a crucial role in determining their characteristic electronic structures and makes them promising materials for applications in organic electronics and optoelectronics.
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