Chemistry Letters
Online ISSN : 1348-0715
Print ISSN : 0366-7022
ISSN-L : 0366-7022
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Showing 1-50 articles out of 54 articles from the selected issue
Letter
Vol. 50 Commemorative Highlight Review
  • Chengxi Li, Pengfei Duan
    2021 Volume 50 Issue 4 Pages 546-552
    Published: April 05, 2021
    Released: April 16, 2021
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    Upconverted circularly polarized luminescence (UC-CPL) is coined by combining two individual concepts of photon upconversion (UC) and circularly polarized luminescence (CPL). It has exhibited great performance and potential applications in various fields, arousing enormous attention from scientists. The emergence, amplification and modulation of UC-CPL can be adjusted through regulation of the UC process and assembled state of emitters. Benefitting from the abundant upconverted photoluminescence mechanisms, we can flexibly build UC-CPL systems with distinct properties. In addition, based on different photophysical processes, the circular polarization of some UC-CPL can be promoted. Furthermore, the practical application of UC-CPL has been confirmed in enantioselective photopolymerization. Thus, in this review, we will briefly highlight the recent development and advances of UC-CPL. We envisage providing a guide for the development of those remarkable chiroptical materials.

    Upconverted circularly polarized luminescence (UC-CPL), with great application prospects, is coined by combining two individual concepts of photon upconversion (UC) and circularly polarized luminescence (CPL). Benefitting from the abundant UC mechanisms, we can flexibly build UC-CPL systems. Moreover, CPL can be improved in some UC photophysical processes. Here, we briefly highlight review the recent development and advances of UC-CPL. Fullsize Image
     
  • Minyan Wang, Zhaungzhi Shi
    2021 Volume 50 Issue 4 Pages 553-559
    Published: April 05, 2021
    Released: April 16, 2021
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    Catalytic enantioselective defluorinative functionalization of easily accessible allylic fluorines is well recognized as one of the most attractive strategies for creating allylic stereogenic centers with high enantioselectivity. This highlight review precisely aims to summarize the recent developments of this area mainly from the following six aspects: enantioselective defluoroarylation, enantioselective defluoroalkylation, enantioselective defluoroborylation, enantioselective defluorosilylation, enantioselective defluorohydrolation, and desymmetrization of difluoromethylene groups. Primarily, these reactions occur through two pathways, including β-fluorine elimination and C–F oxidative addition. Despite this, the mechanisms and limitations of these strategies have been a focus, and it is hoped that this review will provide a comprehensive overview to evaluate the prospects of this rapidly emerging field.

    Catalytic asymmetric defluorinative functionalization of easily accessible allylic fluorines has been well recognized as one of the most attractive strategies for creating allylic stereogenic centers. This highlight review precisely aims to summarize the recent developments of this area. We hope this review can provide a comprehensive overview to evaluate the prospects of this rapidly emerging field. Fullsize Image
     
Letter
Vol. 50 Commemorative Highlight Review
Letter
Vol. 50 Commemorative Highlight Review
  • Taku Hasobe
    2021 Volume 50 Issue 4 Pages 615-622
    Published: April 05, 2021
    Released: April 16, 2021
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    Organic-inorganic hybrid molecular architectures utilizing self-assembled monolayers (SAMs) of organic chromophores (e.g., acene derivatives) are systematically discussed to examine the photophysical properties together with covalently-linked dimeric and oligomeric forms. Multi-exciton generation (i.e., singlet fission) and light energy conversion processes that occur in a reaction site composed of chemically modified organic chromophores on the surface of inorganic nanomaterials such as gold nanocluster, gold nanorod and quantum dot are described.

    Organic-inorganic hybrid molecular architectures utilizing self-assembled monolayers (SAMs) of organic chromophores (e.g., acene derivatives) are systematically discussed to examine the photophysical properties together with covalently linked dimeric and oligomeric forms. Multi-exciton generation (i.e., singlet fission) and light energy conversion processes that occur in a reaction site composed of chemically modified organic chromophores on the surface of inorganic nanomaterials such as gold nanocluster, gold nanorod and quantum dots are described. Fullsize Image
     
Letter
  • Yoshihide Sawada, Koji Morikawa, Mikiya Fujii
    2021 Volume 50 Issue 4 Pages 623-626
    Published: April 05, 2021
    Released: April 16, 2021
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    In recent years, inverse material design using machine learning techniques has attracted attention for material development. Almost all studies have used crystal structures of materials, although material engineers rarely store the crystal information and they only save chemical compositions and target properties for high-throughput materials discovery. Thus, we propose a method to generate chemical compositions for desired target properties by using conditional generative adversarial networks (CondGAN) and a post-processing method to balance the oxidation numbers. Numerical experimental results demonstrate that our CondGAN generates chemical compositions holding the desired properties.

Vol. 50 Commemorative Highlight Review
  • Zhengtao Xu
    2021 Volume 50 Issue 4 Pages 627-631
    Published: April 05, 2021
    Released: April 16, 2021
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    Functions and performance metrics are much sought after by materials researchers and editors; not to be sidelined, however, are fundamental design works directed at general methodological breakthrough and wide-scope applicability. For a close union of form and function is often crucial in catalysing paradigm shift. We use two forms of contrast to illustrate: the hard/soft design in carboxyl-thiol molecules, and the starburst/backfolded alkyne motifs. The former affords thiol-decked Zr4+-carboxyl frameworks, the latter, domino cyclization for crosslinked nanographene components. The versatile reactivity of the thiol and alkyne functions (e.g., for metal uptake), deployed in symmetrical dendritic forms, serves to bridge the worlds of coordination and covalent solids.

    Not just pretty structures: symmetrical sulfur functions enhance framework stability, facilitate metal uptake, and impart versatile properties for applications in solar cells, electrocatalysis, and photocatalytic hydrogen production. We also outline a strategy toward ordered 3D graphene materials by way of domino alkyne cyclization on a pre-assembled crystalline coordination framework. Fullsize Image
     
Letter
Vol. 50 Commemorative Highlight Review
  • Suguru Ito
    2021 Volume 50 Issue 4 Pages 649-660
    Published: April 05, 2021
    Released: April 16, 2021
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    Mechanochromic luminescence (MCL) refers to a reversible color change of the solid-state emission induced by mechanical stimulus such as grinding, shearing, and compressing. A growing number of MCL materials has recently been reported owing to the wealth of their potential applications in advanced optoelectronic technologies. This review highlights recent progress on the development of organic crystalline compounds that exhibit various MCL behaviors, which include self-recovery of the original color, bathochromically and hypsochromically shifted emission from the same luminophore, two-step emission-color switching, and multi-stimuli-responsive emission. In addition, the creation of polymorphic and pseudopolymorphic crystals and the construction of two-component systems as promising strategies to control and improve MCL properties of organic crystals are discussed.

    Mechanochromic luminescence (MCL) refers to a reversible color change of the solid-state emission induced by mechanical stimulus. This review highlights recent progress on the development of organic crystalline compounds that exhibit various MCL behaviors. The creation of polymorphic and pseudopolymorphic crystals and the construction of two-component systems as promising strategies to control and improve MCL properties of organic crystals are also discussed. Fullsize Image
     
Letter
Vol. 50 Commemorative Highlight Review
  • Xiaofeng Huang, Yue-Biao Zhang
    2021 Volume 50 Issue 4 Pages 676-686
    Published: April 05, 2021
    Released: April 16, 2021
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    An energy crisis is presently encountered with a promising opportunity for the rise of hydrogen technology, while feasible production of hydrogen calls for sophisticated structural design of water-splitting photocatalysts in terms of light harvesting and photogenerated exciton separation. Tuning to these can be anticipated from reticular synthesis of a newly emerging porous crystalline materials, covalent organic frameworks (COFs). In this review, we highlight synthetic strategies to modulate the photocatalytic water splitting performance. Future investigations regarding mechanistic aspects of the photocatalytic process of COFs are also outlined.

    Feasible production of hydrogen calls for sophisticated structural design of water-splitting photocatalysts in terms of light harvesting and photogenerated exciton separation. In this review, we highlight strategies to optimize exciton migration and separation in covalent organic framework photocatalysts for water splitting. Fullsize Image
     
  • Katsutoshi Sato, Katsutoshi Nagaoka
    2021 Volume 50 Issue 4 Pages 687-696
    Published: April 05, 2021
    Released: April 16, 2021
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    Strong basic oxide–supported Ru catalysts are easily prepared and handled, and they have been used as effective catalysts for ammonia synthesis under mild reaction conditions since the 1970s. Recent research has revealed that precise control of the boundary states between the basic oxide (i.e., rare-earth oxide, alkali earth oxide), oxygen defect sites, and Ru nanoparticles can be used to enhance ammonia synthesis under mild reaction conditions and inhibit hydrogen poisoning, which is a typical drawback of strong basic oxide–supported Ru catalysts.

    Strong basic oxide-supported Ru catalysts are easily prepared and handled, and have been used as effective catalysts for ammonia synthesis since the 1970s. Recent research has revealed that precise control of the boundary states between the basic oxide, oxygen defect sites, and Ru nanoparticles can be used to enhance ammonia synthesis under mild reaction conditions and inhibit hydrogen poisoning. Fullsize Image
     
  • Nobuto Yoshinari, Takumi Konno
    2021 Volume 50 Issue 4 Pages 697-710
    Published: April 05, 2021
    Released: April 16, 2021
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    Coordination compounds have been increasingly studied as a new class of promising candidates for the matrix of ionic conducting materials because of their designability and high crystallinity. The ionic conduction of light alkali metal ions (Li+ and Na+) has been developed in polymeric coordination systems, which are commonly used under nonaqueous conditions. Recent studies have shown that discrete coordination compounds, as well as hydrated polymeric coordination compounds, can function as excellent ionic conductors even for heavier K+.

    Coordination compounds have become a promising candidate for the matrix of ion-conducting materials because of their designability and high crystallinity. The ionic conduction of light alkali metal ions (Li+ and Na+) has been a focus in polymeric coordination systems under nonaqueous conditions. However, a recent study has shown that a discrete coordination system or hydrated polymeric system can exhibit a high ionic conductivity even for heavier K+. Fullsize Image
     
Letter
CSJ Account
  • Bin Shao, Hongshuo Chen, Chuanjin Cui, Jing Li, Ruikun Gonge
    2021 Volume 50 Issue 4 Pages 714-723
    Published: April 05, 2021
    Released: April 16, 2021
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    Metal organic framework materials (MOFs) have a drawback that limits their wider application: poor electrical conductivity. In this paper, some research advances in improving the conductivity of MOFs in recent years are reviewed. They are divided into two categories: intrinsic improvement of conductivity and extrinsic improvement of conductivity. The application of MOFs with improved electrical conductivity in the construction of biosensors is shown. Finally, research trends of improving the conductivity of MOFs and their applications in biosensors are summarized, and promising directions such as the comprehensive application of multiple strategies and the space-oriented assembly of MOFs are proposed.

    This article focuses on the strategy to overcome the poor conductivity of MOFs in the construction of biosensors. So take the most common strategy of doping guest molecules as an example to show how to improve conductivity. Use guest molecules as internal bridges to connect the parts that are difficult to form charge transfer in MOFs. Fullsize Image
     
Letter
  • Shohei Tada, Kenta Iyoki
    2021 Volume 50 Issue 4 Pages 724-726
    Published: April 05, 2021
    Released: April 16, 2021
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    To open up the possibility of synthesizing useful substances from CO2, we have developed new catalysts that hydrogenate CO2 to methanol with high yield at 300 °C and higher. In this study, methanol synthesis via CO2 hydrogenation at 250–350 °C and 10 bar was investigated using Zr-based metal oxide catalysts, MZrOx (M = Al, Mn, Cu, Zn, Ga, and In). The different metals (M) determined the suitable reaction temperature wherein the maximum yield of methanol was obtained. CuZrOx was a suitable catalyst for low-temperature methanol synthesis because the yield decreased with increasing reaction temperature from 250 °C to 350 °C. In contrast, ZnZrOx, GaZrOx, and InZrOx were suitable for methanol synthesis at 300 °C and higher. In particular, ZnZrOx afforded the highest yield of methanol (60 mLSTP h−1 g−1 at 300 °C) among the prepared MZrOx catalysts.

Vol. 50 Commemorative Highlight Review
  • Kenji Hirai, Hiroshi Uji-i
    2021 Volume 50 Issue 4 Pages 727-732
    Published: April 05, 2021
    Released: April 16, 2021
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    Even without external photon pumping, cavity vacuum fields can be strongly coupled with molecular transitions (electronic excitation and molecular vibration), resulting in the formation of polaritonic states. The energy states of molecular systems are altered under strong coupling, revealing intriguing phenomena, such as improvements in energy/exciton transfer and modulation of chemical reactions. In this review, we highlight recent advances in cavity strong coupling, including exciton strong coupling and vibrational strong coupling, from a chemistry-based viewpoint.

    Cavity vacuum fields are strongly coupled with molecular transitions, resulting in the formation of polaritonic states. The energy states of molecular systems are altered under strong coupling, revealing intriguing phenomena, such as improvements in energy/exciton transfer and modulation of chemical reactions. In this review, we highlight recent advances in cavity strong coupling, including exciton strong coupling and vibrational strong coupling. Fullsize Image
     
  • Takeshi Kondo
    2021 Volume 50 Issue 4 Pages 733-741
    Published: April 05, 2021
    Released: April 16, 2021
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    Boron-doped diamond powder (BDDP) and boron-doped nanodiamond (BDND) were developed with the aim of expanding the area of application of conductive diamond electrodes. BDDP and BDND are conductive diamond powders obtained by depositing a boron-doped diamond (BDD) layer on the surface of diamond powder (DP) and nanodiamond (ND) substrates, respectively, by using the chemical vapor deposition method. As the particle size of BDDP depends on that of the DP substrate, it can be arbitrarily selected in the range of at least submicrometer to several micrometers. BDDP can be used for an electrode material of screen-printed diamond electrode, which is a disposable and sensitive electrode for electrochemical detection even from biological fluids. BDDP can also be applied to a durable cathode catalyst support of a polymer electrolyte fuel cell. BDND is a conductive diamond particle with a large specific surface area of 650 m2/g or more, and is expected to be used as an electrode material for aqueous electric double-layer capacitors with a large cell voltage leading to high energy and high-power densities. BDDP and BDND are highly versatile functional electrode materials that can be made into inks and pastes, and can be combined easily with other compounds. Therefore, they should be useful for greatly expanding the application fields of diamond electrodes.

    Boron-doped diamond powder (BDDP) and boron-doped nanodiamond (BDND) were developed with the aim of expanding the area of application of conductive diamond electrodes including screen-printed diamond electrodes for sensitive electroanalysis, durable PEFC cathode catalyst support, and high energy and high power density aqueous EDLC. Fullsize Image
     
  • Katsuya Inoue
    2021 Volume 50 Issue 4 Pages 742-751
    Published: April 05, 2021
    Released: April 16, 2021
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    The synthesis, structure, magnetic properties and magnetic structure of two molecular chiral magnets and one inorganic chiral magnet are presented. In magnetic crystals belonging to the Sohncke group, which includes the chiral group, the chiral non-collinear spin structure is achieved through Dzyaloshinsky-Moriya interactions in addition to the usual exchange spin interactions and dipole-dipole spin interactions. Experimentally, a chiral helical magnetic (CHM) structure is observed as the ground state in most of this category of uniaxial chiral magnets as a non-collinear spin structure. CHM structure transforms into a chiral spin soliton (CS) magnetic structure in a magnetic field. The (CS) magnetic structure forms a chiral spin soliton lattice (CSL) magnetic structure when the nearest neighbor magnetic interaction is ferromagnetic. Since the CHM and CSL magnetic structures are topologically protected, they are not affected by defects and are therefore extremely stable. A series of studies have revealed that the chiral magnetic structure is perfectly coupled to the non-symmetric crystal structure. It was also found that the CHM and CSL magnetic structures are macroscopic spin-phase coherent states.

    Non-collinear spin structures are realized in non-centrosymmetric magnets due to Dzyaloshinsky-Moriya interactions. A series of studies have revealed that the chiral magnetic structure is coupled to the non-symmetric crystal structure. It was also found that the CHM and CSL magnetic structures are macroscopic spin-phase coherent states. Fullsize Image
     
  • Satoshi Hinokuma, Kazuhiko Sato
    2021 Volume 50 Issue 4 Pages 752-759
    Published: April 05, 2021
    Released: April 16, 2021
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    Recent developments for ammonia (NH3) combustion catalysts are covered in this highlight review. NH3 has been proposed as a renewable and carbon-free energy source. However, use of NH3 fuel poses the problems of high ignition temperature and nitrogen oxide (N2O/NOx) production. In order to overcome these issues, a novel catalytic combustion system was probed, and high performance catalysts were developed. This review introduces their research with including related studies.

    Recent developments in NH3 combustion catalysts are covered in this highlight review. NH3 has been proposed as a renewable and carbon-free energy source. However, use of NH3 fuel poses the problems of high ignition temperature and nitrogen oxide (N2O/NOx) production. In order to overcome these issues, a novel catalytic combustion system was probed, and high performance catalysts were developed. This review introduces their research with including related studies. Fullsize Image
     
  • Daisuke Takeuchi
    2021 Volume 50 Issue 4 Pages 760-766
    Published: April 05, 2021
    Released: April 16, 2021
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    Pd-catalyzed reaction of olefins is sometimes accompanied by isomerization of the Pd center along the aliphatic chain (chain walking). The chain walking reaction enables synthesis of polyolefins with regulated structure, via C-C bond formation between vinyl or vinylene groups with the carbon atom at a remote position of the olefin monomers. The chain walking reaction also allows synthesis of poly(arylene alkenylene)s by three-component polycondensation of diiodoarenes, non-conjugated dienes and nucleophiles. Polycondensation of diols, diacids, and diamines with long alkylene chain, obtained by chain-walking alkoxycarbonylation, affords long-chain polyesters and polyamides.

    Chain walking reaction enables synthesis of polyolefins with regulated structure, via C-C bond formation between vinyl or vinylene group with the carbon atom at a remote position of the olefin monomers. The chain walking reaction also allows synthesis of poly(arylene alkenylene)s, and syntheses of diols, diacids, and diamines with long alkylene chain, usable for polycondensation. Fullsize Image
     
  • Nalinthip Chanthaset, Hiroharu Ajiro
    2021 Volume 50 Issue 4 Pages 767-777
    Published: April 05, 2021
    Released: April 16, 2021
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    Of the various synthetic biodegradable polymers, polylactide, poly(butylene succinate), and poly(hydroxyalkanoate) have been widely studied and developed. This review focuses on studies of the chain end modification of these polymers. The selected research was categorized into initiators, chain end modification, including chain extending, and the degradation reaction. We cover the recent literature on this topic, and discuss the developing trends and challenges of biodegradable polymers.

    Of the various synthetic biodegradable polymers, polylactide (PLA), poly(butylene succinate) (PBS), and poly(hydroxyalkanoate) (PHA) have been widely studied and developed. This review focuses on studies of the chain end modification of these polymers. The selected papers were categorized into initiators, chain end modification, including chain extending, and the degradation reaction, from the viewpoint of the modification approaches. Fullsize Image
     
  • Hisako Hashimoto, Koichi Nagata
    2021 Volume 50 Issue 4 Pages 778-787
    Published: April 05, 2021
    Released: April 16, 2021
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    Transition-metal complexes featuring triple bonds to heavier Group 14 elements (Si, Ge, Sn, and Pb), which have long been synthetic challenges in organometallic chemistry, have been synthesized in the last few decades. In this highlight, synthetic methods for numerous kinds of complexes and their structural properties are overviewed. Application leading to new multiple bonded systems with M≡Ge–Ge≡M, M≡Si–M, and M=Si=M linkages, and to relevant metallotetrylenes are also highlighted.

    Transition-metal complexes featuring triple bonds to heavier Group 14 elements (Si, Ge, Sn, and Pb), which have long been synthetic challenges in organometallic chemistry, have been synthesized in the last few decades. In this highlight, synthetic methods for all these complexes and their structural properties are overviewed. Application leading to new multiple bonded systems with M≡Ge-Ge≡M, M≡Si-M, and M=Si=M linkages, and to relevant metallotetrylenes are also highlighted. Fullsize Image
     
Letter
Vol. 50 Commemorative Highlight Review
  • Haruki Mizoguchi, Akira Sakakura
    2021 Volume 50 Issue 4 Pages 792-799
    Published: April 05, 2021
    Released: April 16, 2021
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    This highlight review describes the recent development of an electrophile-triggered 1,2-metallate rearrangement of organoboronic ester ate-complex, which proceeds through 1,2-difunctionalization of carbon–carbon σ- and π-bonds, using strain energy as a driving force. Coupling reactions of small ring carbocyclic boronic esters, such as cyclopropyl-, bicyclo[1.1.0]butyl-, and cyclopropenyl-boronic ester, are summarized along with the proposed reaction mechanisms and representative examples.

    This highlight review describes the recent development of an electrophile-triggered 1,2-metallate rearrangement of organoboronic ester ate-complex, which proceeds through 1,2-difunctionalization of carboncarbon σ- and π-bonds, using strain energy as a driving force. Coupling reactions of small ring carbocyclic boronic esters, such as cyclopropyl-, bicyclo[1.1.0]butyl-, and cyclopropenyl-boronic ester, are summarized along with the proposed reaction mechanisms and representative examples. Fullsize Image
     
Letter
  • Masashi Mamada, Kenichi Goushi, Ryota Nakamura, Hironori Kaji, Chihaya ...
    2021 Volume 50 Issue 4 Pages 800-803
    Published: April 05, 2021
    Released: April 16, 2021
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    A tetracene dimer, 5,5′-bitetracene (55BT), has successfully been synthesized for the first time and its structure was confirmed by X-ray single crystal analysis. The electrochemical and optical properties of 55BT were investigated and compared to those of tetracene. Although the photoluminescence quantum yield of 55BT was slightly higher than that of tetracene, the results of the transient absorption spectroscopy suggested triplet formation by singlet fission in solution.

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