Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 94 , Issue 4
Showing 1-31 articles out of 31 articles from the selected issue
CSJ Account
  • Gaoqian Yuan, Faliang Li, Kezhuo Li, Jie Liu, Junyi Li, Shaowei Zhang, ...
    2021 Volume 94 Issue 4 Pages 1142-1155
    Published: April 15, 2021
    Released: May 13, 2021
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    More and more wastewater containing hexavalent chromium (Cr(VI)), which causes increasingly threatening environmental events including death of plants or organisms, soil inactivation and canceration of human organs, has been caused by rapid industrial growth. Various methods, such as photocatalytic reduction, physical adsorption, electrochemical and photoelectrochemical approaches have been proposed to detoxify/remove Cr(VI) contained in wastewater. Quite significantly, photocatalytic Cr(VI) reduction grabs increasing attention with many advantages, including environmental friendliness, no sludge, low secondary pollution risk, high utilization of solar energy and low dosage of chemical reagents. For the purpose of improving the Cr(VI) removal efficiency during the photocatalytic reduction process, various kinds of catalysts were developed. In this mini-review, the photocatalytic reduction of Cr(VI) by ion doping photocatalysts, faceted photocatalysts, and heterostructure photocatalysts are briefly introduced. Furthermore, some suggestions for modifying photocatalysts to enhance their photocatalytic performance on Cr(VI) reduction are put forward.

    Different methods about the removal of toxic Cr(VI) were introduced and the effects of photocatalysts structure on their photocatalytic Cr(VI) reduction performance were emphasized. Fullsize Image
     
 
  • Toshihito Nakai
    2021 Volume 94 Issue 4 Pages 1156-1165
    Published: April 15, 2021
    Released: May 13, 2021
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    A perturbation approach comprehending infinite-order corrections is proposed so that NMR signals may be simulated without approximations. The present theoretical treatments based on Average Hamiltonian Theory put all the perturbative corrections into several tentative variables and eventually replace them by values resulting from experiments, as the renormalization theory does. The Hamiltonian for strongly-coupled two-spin-1/2 systems and the time evolutions of their coherences are analytically expressed using the proposed theory. The double-quantum excitation functions in 29Si solid-state MAS INADEQUATE measurements are observed for a zeolite sample and reproduced using the formula derived from the present theory. Thereby, it is proved to be possible to determine the internal spin interaction parameters including the J couplings between chemically-equivalent nuclei hidden in solution-state NMR spectroscopy, in addition to the parameters reflecting the high-order solid-state effects.

  • Haibiao Zhu, Liu Hong, Hirofumi Tanaka, Xiaoming Ma, Cheng Yang
    2021 Volume 94 Issue 4 Pages 1166-1171
    Published: April 15, 2021
    Released: May 13, 2021
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    Selective sorting of semiconducting single-walled carbon nanotubes (SWNTs) of single chirality is critical for constructing electronic nanodevices with high performance. Nevertheless, trade-off between yield and chirality purity often exists in conventional SWNTs sorting processes. To solve this problem, we present an extremely facile method for enriching SWNTs with both high yield and high chiral selectivity. Simply by using a solvent mixed with toluene and chlorobenzene at certain volume ratio, the sorting yield of (6,5)SWNTs was largely enhanced via polymer extraction, while the chirality purity of sorted SWNTs could be kept high as well. We further proved that the sorting efficiency would not be lowered even after multiple extractions, while the chirality selectivity of the obtained SWNTs was dependent on exact ratio between the two solvents. Solvent polarity-controlled polymer (or solvent molecule)-SWNTs interaction was believed responsible for our results, which was later successfully testified by molecular dynamics simulations. Our proposed strategy will simplify the selecting process of single chiral SWNTs and benefit the optimization of SWNTs-integrated devices in near future.

  • Naohiro Kameta, Wuxiao Ding, Mitsutoshi Masuda
    2021 Volume 94 Issue 4 Pages 1172-1178
    Published: April 15, 2021
    Released: May 13, 2021
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    Three novel glycolipids were synthesized by amide bond formation among a d-gluconolactone, 12-aminododecanoic acids, and a glycine. Self-assembly of the glycolipids in water produced nanotubes, in which the glycolipids were tilted, packed in parallel, and formed monolayer membranes. The inner diameters of the nanotubes were smaller in glycolipids with a shorter distance between the glycine unit and the glucose headgroup. X-ray diffraction, infrared, and circular-dichroism spectroscopy revealed that the nanotubes with smaller inner diameter had weaker intermolecular hydrogen bonds between glycolipids and larger supramolecular chirality amplified by twist packing of the tilted glycolipids within the monolayer membranes. J-type aggregates of achiral dye molecules encapsulated into nanotubes with smaller inner diameter exhibited induced circular dichroism. These findings should be useful for the fine tuning of the inner diameter of supramolecular nanotubes.

  • Takayuki Ohyoshi, Hikaru Tano, Hideo Kigoshi
    2021 Volume 94 Issue 4 Pages 1179-1184
    Published: April 15, 2021
    Released: May 13, 2021
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    Aplysiasecosterol A, a 9,11-secosteroid, has a unique tricyclic γ-diketone skeleton including a hemiacetal. The concise and efficient synthesis of the tricyclic core was developed by using pseudo-desymmetrizing acetalization and acyl radical cyclization. Toward the total synthesis, an efficient method for the introduction of the D ring fragment was developed by using an organocuprate.

  • Kazutoshi Haraguchi, Yuji Kimura
    2021 Volume 94 Issue 4 Pages 1185-1191
    Published: April 15, 2021
    Released: May 13, 2021
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    Liquid water exhibits many anomalous physical properties because of its unique structure and hydrogen bonding networks, which were mostly uncovered at the beginning of the 20th century. Because of its interesting properties and microstructures under various conditions and in aqueous solutions, understanding the behavior of water is important, but remains scientifically challenging. Regarding the viscosity of aqueous solutions, despite the discovery 147 years ago that very small amounts of certain salts decrease the viscosity of water slightly, there has been no significant progress to date. Herein, we report new aqueous solutions, with low additive fractions and much lower viscosities than pure water, which exhibit unique viscosity–composition curves. The findings should spark renewed interest in scientific research on water, which may greatly impact numerous industries.

  • Soichi Sato, Akihisa Ooizumi, Masato Sakabe, Koh Funahashi, Wataru Fuj ...
    2021 Volume 94 Issue 4 Pages 1192-1200
    Published: April 15, 2021
    Released: May 13, 2021
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    Consecutive treatment of 2-(2-lithiophenyl)pyridine with chalcogen tetrachlorides (ChCl4; Ch = Se and Te) and KPF6 afforded the hexafluorophosphate salts of tris[2-(2-pyridyl)phenyl]selenonium [(ppy)3Se]+ ([1]+) and tris[2-(2-pyridyl)phenyl]telluronium [(ppy)3Te]+ ([2]+), respectively. The chalcogenonium salts [1][PF6] and [2][PF6] exhibit extremely high thermal stability and high melting points. Their solid-state structures revealed distorted octahedral bonding geometries with a C3-symmetrical facial configuration. Quantum chemical calculations on [1]+ and [2]+ strongly suggest that their HOMO−3s involve lone pairs of electrons (LPs) on the central chalcogen atoms, and that the three Ch–N (Ch = Se and Te) bonds are formed by LP(N)→σ*(Ch–C) donor-acceptor interactions. Based on theoretical calculations and 77Se and 125Te NMR spectral data, the C–Ch–N moieties of [1]+ and [2]+ were characterized as asymmetrical three-center four-electron σ-type bonds [σ(3c–4e)]. Both organochalcogenonium salts represent novel monomeric hexacoordinated species that bear 14 formal valence electrons (14–Se–6 and 14–Te–6, respectively). A quantum theory of atoms-in-molecules dual functional analysis predicted that the C–Ch interaction of the σ(3c–4e) C–Ch–N moiety (Ch = Se and Te) is weakly covalent, while the Se–N and Te–N interactions were predicted to have the typical characteristics of hydrogen bonds and molecular complexes, respectively. The differences between [2][PF6] and the recently reported [2][Br] were also carefully examined.

  • Shin Ogasawara, Tatsuya Takahashi, Yuichi Kitagawa, Hitoshi Tamiaki
    2021 Volume 94 Issue 4 Pages 1201-1203
    Published: April 15, 2021
    Released: May 13, 2021
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    p-Aminopyridines were oxidatively substituted at the C31-position of methyl pyropheophorbide-a, a chlorophyll-a derivative. The electron-donating p-dimethylamino groups induced silver metallation during the substitution and inhibited the electron-transfer quenching of fluorescence emission in the metal-free C31-cationic pyridinio adducts prepared by the acidic demetallation of the initially isolated Ag-chlorins.

  • Masashi Kanakubo, Yuki Yamamoto, Yuji Kubo
    2021 Volume 94 Issue 4 Pages 1204-1209
    Published: April 15, 2021
    Released: May 13, 2021
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    A thiophene-derived boronate ester-cross-linked polyvinyl alcohol, 1-PVA, has been prepared, which was found to exhibit room-temperature phosphorescence (RTP) at 475 nm upon UV irradiation (λem = 254 nm). The quantum yield (Φp) was determined to be 6.3% with a phosphorescence lifetime of 256 ms, the cyanish afterglow being visually detected after switching the UV lamp off. The emission properties were rationalized by El-Sayed’s rule, where introduction of a sulfur atom brings about n → π* transition in the T2 state to promote an ISC channel. Given that the phosphorescence spectrum at 77 K was consistent with that in the PVA film, the rigid environment of PVA-based matrix may stabilize the triplet state. In addition, the delayed emissive color was tuned by doping various amounts of sulforhodamine B (SRhoB) in the film; a triplet-to-singlet Förster-type resonance energy transfer process occurred from cross-linked thiophene boronate to SRhoB acceptor which modified the emission to a white-light afterglow. Given water-sensitivity of the resultant film, high-contrast water writing on the film was achieved, which would be profitable for a low-cost security film.

  • Koki Kodama, Mako Oiwa, Tohru Saitoh
    2021 Volume 94 Issue 4 Pages 1210-1214
    Published: April 15, 2021
    Released: May 13, 2021
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    A simple and rapid method for the purification of a basic dye, Rhodamine B (RB) was developed. It was conducted by adding crude RB to an aqueous solution containing 0.2% (v/v) ethanol followed by air bubble flotation in a cylindrical glass vessel having a sintered glass filter at the bottom. By feeding air bubbles, RB was enriched into foam on the water surfaces within 3 min, while source materials (phthalic acid and N,N-diethyl-3-aminophenol), intermediate compound {2-(4-diethylamino-2-hydroxybenzoyl)}, and other organic impurities remained in the bulk aqueous solution. The foam containing enriched RB was taken up with suction and placed into another flotation vessel for repeated separation. An HPLC-grade RB was successfully obtained by 3-fold air bubble flotation.

Award Account
The Chemical Society of Japan Award for Creative Work for 2016
  • Donglin Jiang
    2021 Volume 94 Issue 4 Pages 1215-1231
    Published: April 15, 2021
    Released: May 13, 2021
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    Covalent organic frameworks comprise a class of polymer which covalently links organic units into well-defined architectures to create ordered structures and offers an irreplaceable platform for designing organic/polymeric materials. In this award account, we trace our paths and show our initiatives to explore this class of molecular frameworks, by establishing design principle and synthetic strategies and developing functions and properties. By elucidating interplays of ordered structures with photons, excitons, electrons, holes, ions and molecules, we scrutinize unique structural features and functions which are specific to the ordered structures. We predict the key fundamental issues to be addressed in future and show the directions from perspectives of chemistry, physics, and materials science.

    This award account trailed our way toward and showed our initiatives of covalent organic frameworks, the exploration of design principle and synthetic strategies, and the development of functions and properties. By elucidating various interplays, we scrutinized the unique features of materials and the origins of different functions. Fullsize Image
     
Account/Review for Nanoarchitectonics
  • Gurwinder Singh, Jang Mee Lee, Gopalakrishnan Kothandam, Thavamani Pal ...
    2021 Volume 94 Issue 4 Pages 1232-1257
    Published: April 15, 2021
    Released: May 13, 2021
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    Around 29% of the world population does not have ready access to safe drinking water. Water contamination is a compelling issue, which needs to be addressed on a priority basis using novel technologies. Heavy metals are the dominant inorganic contaminants found in the water, whereas, organic contaminants are composed of several classes and pose a more widespread problem. The occurrence of radionuclides, such as uranium and caesium in groundwater is also raising a serious issue but it is often understudied. Nanoporous carbons are a good choice for removing water contaminants owing to their excellent physico-chemical properties. Their surface properties, which are highly critical for adsorption, vary significantly with the nature of the precursors used for synthesis. Their textural and surface characteristics can be tuned by adjusting the chemical composition of these precursors or the synthesis conditions, including activation or modification. Such materials can also be supported in a porous matrix, designed into desired morphologies and hybridized with other composite materials for enhancing the application efficiency. The review describes how the low-cost nanoporous carbons are outstanding adsorbent for the water remediation and provide an outlook to tap the unlimited opportunities by researching their new properties.

    The review encompasses a summary of the latest developments in the field of synthesis of nanoporous carbon-based materials from various precursors including biomass, coal and others. The crucial parameters required for good adsorption properties are highlighted. From an application point of view, the use of these materials for the removal of inorganic, organic and radioactive contaminants are discussed. Fullsize Image
     
 
  • Takuya Suga, Masaharu Nakamura, Ryusei Takada, Yutaka Ukaji
    2021 Volume 94 Issue 4 Pages 1258-1260
    Published: April 15, 2021
    Released: May 13, 2021
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    A new method for the generation of benzyl radicals from acetals via low-valent titanium-mediated homolytic C–O bond cleavage is presented. The low cost and availability of the developed titanium reagent enable efficient access to α-alkoxy carbon radical species via the developed reaction.

  • Sen-ichi Aizawa, Yoichi Takeuchi
    2021 Volume 94 Issue 4 Pages 1261-1263
    Published: April 15, 2021
    Released: May 13, 2021
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    Intimate kinetic investigation of Pd(II)-catalyzed ortho C-H iodination of benzamide substrate via cyclopalladation was performed for the first time by using molecular I2 as a sole oxidant and acetate as a base. The reaction rate of the cyclopalladation step is independent of benzamide concentration but increased with an increase in acetate concentration and then gradually decreased due to blocking on coordination sites of Pd(II) by acetate. On the other hand, the reaction rate of the subsequent iodination step was first-order with respect to I2 concentration. Though the total activation energies of the cyclopalladation and iodination processes are comparable, it is reasonable that the cyclopalladation appears to be the rate-determining step of Pd(II)-catalyzed ortho C-H iodination, in which substrates, I2, and acetate are used in large excess. From the present results, it can be proposed that a minimum amount of acetate required for deprotonation of amide and ortho proton for cyclopalladation and rather excess I2 should be used to provide acceleration and high performance of Pd(II)-catalyzed ortho C-H iodination.

  • Akira Obuchi
    2021 Volume 94 Issue 4 Pages 1264-1272
    Published: April 15, 2021
    Released: May 13, 2021
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    By applying a geometrical heating program, i.e., heating an object by the same ratio in absolute temperature per unit time instead of by a constant degree as conventionally applied, a new method has been developed for the deconvolution of temperature-programmed reaction (TPR) data composed of reactants independent of one another and obeying first-order kinetics with the same pre-exponential factor and different activation energies (E). With this heating pattern, the TPR curve obtained is proved as a convoluted function of an E distribution function and a TPR curve of a single E, and consequently the TPR curve obtained can be deconvoluted back to the E distribution function via Fourier and inverse Fourier transformation (FT) procedures. Practicability of this method is demonstrated by experimental case studies.

  • Naoya Kinoshita, Kento Suzuki, Mohamad Safuwan bin Alias, Takashi Shir ...
    2021 Volume 94 Issue 4 Pages 1273-1284
    Published: April 15, 2021
    Released: May 13, 2021
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    Dimethyl substituted donors, 2-(4,5-dimethyl-1,3-dithiol-2-ylidene)-5-(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (DMDT-DA-TTP) and 2-(4,5-dimethyl-1,3-dithiol-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (DMDT-DH-TTP), were successfully synthesized, and (DMDT-DA-TTP)2X (X = PF6, AsF6, and SbF6) and (DMDT-DH-TTP)2X (X = PF6 and AsF6) were prepared. All the DMDT-DA-TTP and DMDT-DH-TTP salts adopt β-type molecular packing with a head-to-tail molecular stacking. Although the overlap modes of donor molecules in the DMDT-DA-TTP and DMDT-DH-TTP salts are similar, the degree of dimerization of donor molecules is quite different. That is, electronically strong dimerization of the DMDT-DA-TTP molecules was assessed in the salts, while the DMDT-DH-TTP molecules have electronically almost uniform stacking in the salts. A tight-binding band calculation suggested that all the DMDT-DA-TTP salts have effectively half-filled energy bands with narrow bandwidths of 0.39–0.40 eV, while the bandwidths of DMDT-DH-TTP salts (0.96 eV) are relatively wide due to the lack of an energy gap. The calculated Fermi surfaces of all the salts are quasi-one-dimensional. In correspondence with the different band structures, all the DMDT-DA-TTP salts exhibited semiconducting behavior derived from the Mott-insulating nature. In contrast, both the DMDT-DH-TTP salts showed metallic temperature dependence down to 5–7 K.

Article for Frontiers of Molecular Science
BCSJ Award Article
  • Kei Nishii, Guangli Zhou, Yusuke Saito, Atsushi Yamamoto, Masayoshi Ni ...
    2021 Volume 94 Issue 4 Pages 1285-1291
    Published: April 15, 2021
    Released: May 13, 2021
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    Regio- and stereoselectivity control in the polymerization of 1,3-conjugated dienes is of much interest and importance. We report herein for the first time the isospecific trans-1,4-selective living polymerization of (E)-1,3-pentadiene (EPD) by a C5H5-ligated yttrium catalyst (C5H5)Y(CH2C6H4-NMe2-o)2/[Ph3C][B(C6F5)4], which afforded crystalline isotactic-trans-1,4-polypentadiene showing good elastic properties without vulcanization (tensile strength up to 7.1 MPa with elongation at break of 2600%). The DFT calculations revealed that the stereoselectivity was mainly due to steric repulsion between the C5H5 ligand in the catalyst and the methyl group in EPD.

    The controlled isospecific trans-1,4-selective living polymerization of (E)-1,3-pentadiene has been achieved for the first time by the use of a half-sandwich yttrium catalyst. The resulting polymers showed good elastic properties with high tensile strength and high elongation at break (up to 7.1 MPa with 2600%) without vulcanization. Fullsize Image
     
 
  • Sho Kitano, Mei Lee Ooi, Tomokazu Yamamoto, Syo Matsumura, Miho Yamauc ...
    2021 Volume 94 Issue 4 Pages 1292-1299
    Published: April 15, 2021
    Released: May 13, 2021
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    Electrooxidation of NH3 has gained extensive attention for energy and environmental applications such as fuel cells and water purification. Pt-based precious metal alloy catalysts have been intensively studied as anode catalysts for the NH3 electrooxidation whereas applicability of earth-abundant transition metals to catalysts has not been sufficiently examined. In this study, we synthesized carbon-supported simple metal-nanoparticle, binary- and ternary-nanoalloy (NA) catalysts composed of Fe-group elements, i.e., Fe, Co and Ni, and systematically investigated catalytic performance of these catalysts for NH3 electrooxidation in alkaline media. We found that the affinity of constituent metals to nitrogen species controls overpotential and durability for the NH3 electrooxidation on Fe-group simple monometal and NA catalysts for the first time. Furthermore, each Fe-group element shows distinctive catalytic features for the NH3 electrooxidation, i.e., Ni ensures chemical stability, Fe effectively lowers overpotential and Co increases current density. The ternary FeCoNi/C shows excellent activities due to combination of all the catalytic features and synergetic effects exerted by the alloying.

Account/Review for Masterpiece Materials with Functional Excellence
Award Account
The Chemical Society of Japan Award for Creative Work for 2017
  • Hideyuki Mitomo, Kuniharu Ijiro
    2021 Volume 94 Issue 4 Pages 1300-1310
    Published: April 15, 2021
    Released: May 13, 2021
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    This review introduces recent advances in the fabrication of metal nanostructures via self-assembly with a particular focus on our studies. As nanostructures, in particular metal nanostructures, show unique properties which are not observed in bulk materials, the development of nanofabrication techniques has attracted much attention in the research fields of nanoscience and nanotechnologies. From the viewpoint of biomimetics, it is imagined that sophisticated structures with spatio-temporal controllability on a nanoscale are crucial. Thus, much effort has been paid to the fabrication of 3- and 4-dimensional metal nanostructures. Although there are various approaches, the most promising is the self-assembly of gold nanoparticles (AuNPs) and their combination with soft matters. To obtain further controlled nanostructures for better properties, their systems have become more and more complex. For future expansion of these technologies, simplified systems are preferable for refining them based on clear mechanisms. From this point of view, we have worked on the self-assembly of AuNPs modified with oligo(ethylene glycol) (OEG)-derivatives as a small, simple molecule with a definite chemical structure and fabricated 3D hollow capsule structures and reversibly changeable structures responding to certain stimuli in solution and on/in soft matters. These results are expected to support the creation of novel nanodevices.

    Fabrication of sophisticated metal nanostructures has attracted much attention. In this review, we introduce recent advances in the fabrication of metal nanostructures via self-assembly with a particular focus on our studies, in which AuNPs are modified with oligo(ethylene glycol) (OEG)-terminated alkane thiol derivatives as simple small molecules with definite structures. Fullsize Image
     
Account/Review for Frontiers of Molecular Science
  • Inés García-Benito, Javier Urieta-Mora, Agustín Molina-Ontoria, Nazari ...
    2021 Volume 94 Issue 4 Pages 1311-1323
    Published: April 15, 2021
    Released: May 13, 2021
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    This review summarizes our recent achievements in the development of new chalcogen-containing materials employed as hole-transporting materials (HTMs) in efficient perovskite solar cells (PSCs). Following a simple and inexpensive synthetic methodology we prepared new heterocycle-based HTMs with comparable photovoltaic (PV) behaviour to the widely used spiro-OMeTAD. In particular, new star-shaped HTMs have been obtained through an easy synthetic route by crosslinking electron-donor groups with a central scaffold. As sulfur-containing cores, benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene (BTT) and the corresponding isomers (bbb-BTT and bbc-BTT), thieno[3,2-b]thiophene (TbT), cyclooctatetrathiophene (CoTh), anthra[1,2-b:4,3-b′:5,6-b′′:8,7-b′′′]tetrathiophene (ATT), dibenzothieno[1,2-b:4,3-b′:6,7-b′′:9,8-b′′′]quinquethiophene (DBQT), dibenzothieno[3,2-b]thiophen[1,2-b:4,3-b′:6,7-b′′:9,8-b′′′]sexithiophene (DBST) and thioxanthone have been employed. To extend the comparison, HTMs with heteroatoms such as oxygen or selenium in the central unit, namely xanthone (BX), benzotrifuran (BTF) or benzotriselenophene (BTSe), were also designed, synthesized and employed in PSCs.

    Currently, there is no doubt that organic compounds are an important part of the PSCs architecture. Nevertheless, the future commercialization of PSCs is driven by the development of HTMs away from the comprehension of structure-property relationships. Therefore, our main goal is to contribute to a better understanding of the chemistry behind competitive HTMs and provide a clear picture of the effect of chalcogen-containing HTMs in device performances.

    Currently, there is no doubt that organic compounds are an important part of the PSCs architecture. This review summarizes our recent achievements in the development of new chalcogen-containing materials employed as HTMs in efficient PSCs. Therefore, our main goal is to contribute to a better understanding of the chemistry behind competitive HTMs and provide a clear picture of the effect of chalcogen-containing HTMs in device performances. Fullsize Image
     
  • Zhen Lei, Xiao-Li Pei, Hitoshi Ube, Mitsuhiko Shionoya
    2021 Volume 94 Issue 4 Pages 1324-1330
    Published: April 15, 2021
    Released: May 13, 2021
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    Ubiquitous intramolecular aurophilic interactions in gold clusters have usually been assigned as the main determinants of their molecular geometry and various properties. By utilizing N-heterocyclic carbene (NHC) ligands instead of phosphine ligands which have been exclusively used, we have developed ligand-specific photophysical properties of C-centered hexagold(I) (C@Au6) clusters. This account describes the recent development of carbene-protected C@Au6 clusters. First of all, a strong intramolecular C–H•••Au interaction was found as a key structural feature of these clusters. These are also present in the newly emerged NHC-gold nanoclusters, but are negligible in the phosphine counterparts. Interestingly, the use of NHC ligands also produces clusters with a nearly identical metal kernel, but their luminescence changes significantly. In addition, a simple extension of the π-conjugated system of NHCs from imidazolylidene to benzimidazolylidene is expected to produce significant changes in both absorption coefficient and emission wavelength. These results show the promising potential of carbene ligands in character modulation of metal clusters, and may help in the rational design of carbene ligands for constructing functional metal clusters.

    N-Heterocyclic carbene ligands were successfully utilized to reconstitute C-centered hexagold(I) clusters. Strong intramolecular C(sp3)–H···Au interactions with the minimum gold-hydrogen distance of 2.566 Å were found as a key structural feature in the resulting clusters. Significantly enhanced absorption and shifted luminescence were also observed. Fullsize Image
     
 
  • Takashi Shirahata, Masahide Ikeda, Hiroshi Watadzu, Hideki Fujiwara, T ...
    2021 Volume 94 Issue 4 Pages 1331-1339
    Published: April 15, 2021
    Released: May 13, 2021
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    A π-electron donor incorporating pyran-4-ylidene moiety, 2-(pyran-4-ylidene)-1,3-dithiole (PDT, 1a), and its derivatives (1be) have been synthesized. Cyclic voltammetry revealed that the derivatives of 1 exhibited two pairs of redox waves. Comparison of the first redox potentials (E1) indicated that the donating ability of PDT (E1 = −0.16 V vs. Fc/Fc+, in benzonitrile) is stronger than that of TTF (E1 = −0.09 V), but is weaker than the sulfur analog TPDT (E1 = −0.19 V). X-ray structure analyses of radical cation salts based on the ethylendithio derivative (1d)2X (X = ClO4, ReO4, and GaCl4) revealed that the donors form two-dimensional conducting sheets, in which the donors adopt the so-called β-type packing with a uniform head-to-tail stacking. Calculation of the overlap integrals of the HOMOs suggest that (1d)2X has a small intrastack overlap compared to the TTF-type conductors because of a head-to-tail stacking of the unsymmetrical π-electron framework. A tight-binding band calculation suggested that all the salts have quasi-one-dimensional Fermi surfaces. They exhibited relatively high conductivity of σrt = 0.79–20 S cm−1 on a single crystal and showed weak but metal-like temperature dependence of resistivity.

  • Ryosuke Kobayashi, Ryoto Inaba, Hiroaki Imoto, Kensuke Naka
    2021 Volume 94 Issue 4 Pages 1340-1346
    Published: April 15, 2021
    Released: May 13, 2021
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    Tetranuclear cubic copper(I) iodide (CuI) complexes were synthesized by utilizing tertiary arsine ligands such as triphenylarsine, tri(p-tolyl)arsine, 9-phenyl-9-arsafluorene, and 1-phenylarsolane; except for triphenylarsine, these ligands were prepared by the practical methods that we previously developed. The obtained complexes exhibited intense emission in the crystalline states even at room temperature. Their emission colors were drastically changed by mechanical stimulus, temperature, and excitation wavelength. These complexes are the first examples of cubic Cu4I4 complexes with arsenic ligands exhibiting stimuli-responsive and excitation wavelength-dependent luminescence.

  • Jonathan P. Hill, Rekha Goswami Shrestha, Jingwen Song, Qingmin Ji, Ka ...
    2021 Volume 94 Issue 4 Pages 1347-1354
    Published: April 15, 2021
    Released: May 13, 2021
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    Release of silver from the supramolecular fullerene-silver(I) nitrate complex C60(AgNO3)5 was investigated. Silver(I) nitrate release from the complex on treatment with solvent was monitored using the small molecule organo-supergelator 1-phenyl-3-(quinolin-5-yl)urea, which interacts selectively with AgNO3 yielding a stable gel whose extent (i.e. volume fraction of solvent gelated) and persistence indicate that Ag+ cations are continuously released from the complex when immersed in 2-propanol over extended periods of time. The effect of AgNO3 release on the morphology of the C60(AgNO3)5 complex crystals was evaluated using scanning electron microscopy showing that AgNO3 is concurrently deposited as silver nanoparticles at the crystal-solution interface onto an insoluble C60 crystalline framework. Silver release was also monitored potentiometrically revealing emergence of Ag nanoparticles. Initial intense release of Ag+ (in the form of AgNO3) is followed by reductive fixing of silver in nanoparticulate form for longer term bactericidal activity. The latter was established by observing viability of bacterial colonies in aqueous medium where their growth was essentially arrested when C60(AgNO3)5 crystals were present in the medium in contrast to the case for pristine C60 where colony growth proceeded unhindered. Cell proliferation studies using HeLa cell line revealed that C60(AgNO3)5 crystals also exhibit antiproliferative properties in aqueous media.

Account/Review for Frontiers of Molecular Science
  • Yasushi Hirose, Tetsuya Hasegawa
    2021 Volume 94 Issue 4 Pages 1355-1363
    Published: April 15, 2021
    Released: May 13, 2021
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    Metal oxynitrides are expected to show unique chemical and physical properties suitable for various applications. However, compared with oxides, the chemical space of oxynitrides has not been well explored mainly due to their thermal instability and high reaction temperature required in conventional bulk synthesis methods. Highly nonequilibrium thin film growth is a promising route for obtaining those unexplored oxynitrides. In this account, we will overview recent studies on thin film synthesis of oxynitrides, especially focusing on exploration of metastable phases, such as mid- and late-transition metal compounds, metastable polymorphs, geometrical isomers with respect to anion coordination, and amorphous phases.

    Metal oxynitrides are expected to show unique chemical and physical properties suitable for various applications. However, there is a huge unexplored chemical space due to their thermal instability and high reaction temperature required in conventional bulk synthesis. In this account, we will overview recent studies on thermally nonequilibrium thin film synthesis of oxynitrides, especially focusing on exploration of metastable phases. Fullsize Image
     
Article for Frontiers of Molecular Science
  • Yoshio Ando, Takumi Fukazawa, Ken Ohmori, Keisuke Suzuki
    2021 Volume 94 Issue 4 Pages 1364-1376
    Published: April 15, 2021
    Released: May 13, 2021
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    In connection with our synthetic study toward the dimeric pyranonaphthoquinone antibiotics, actinorhodin (1) and β-naphthocyclinone (3), we describe herein the synthesis of a monomer, hemi-actinorhodin (6) as a model target. Several implications were gained, including (1) stereoselective synthesis of the pyranonaphthoquinone, (2) viable construction of the naphthazarin core, and (3) the final deprotection conditions.

    Synthesis of hemi-actinorhodin, a pyranonaphthoquinone possessing a naphthazarin core, has been achieved. Through this study, we gained useful insights for the synthesis of dimeric pyranonaphthoquinones; 1) stereoselective synthesis of the pyranonaphthoquinone, 2) viable construction of the naphthazarin core, and 3) the final deprotection conditions. Fullsize Image
     
 
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The Chemical Society of Japan Award for Creative Work for 2018
  • Yusuke Ishigaki, Yasuto Uchimura, Takuya Shimajiri, Takanori Suzuki
    2021 Volume 94 Issue 4 Pages 1385-1393
    Published: April 15, 2021
    Released: May 13, 2021
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    Molecules with an extreme structural parameter, such as an elongated C-C bond, have attracted much attention due to their special properties, which ordinary molecules do not have. Stabilized hexaphenylethanes are suitable compounds for seeking for the longest C-C bond. In addition to steric repulsion among the aryl groups (“front strain”) found in 1,1,2,2-tetraarylacenaphthenes (1), “scissor effects” cause expansion of the C1-C2 bond in 1,1,2,2-tetraarylpyracenes (2). A series of crystallographic analyses of 2 revealed that the substituent on the aryl group also affects the C1-C2 bond length. The “front strain” over the weakened bond is enhanced by the ring-fused structure in di(spiroacridan)pyracene (2A). The bond length of 1.771(3) Å determined by X-ray analysis at 93 K is one of the largest values for a Csp3-Csp3 bond, and increases to 1.791(3) Å when the single crystal is heated to 413 K. Further expansion over 1.80 Å was achieved by maximizing the front strain by fixing the spirodibenzocycloheptatriene units in an eclipsed manner in the core-shell-type dihydropyracylene (3B) [1.795(2) Å at 100 K, 1.806(2) Å at 400 K]. Several studies show that “bond expandability” is a newly discovered feature of an elongated covalent bond, which could be used for the future design of novel materials with a mechanical/thermal response.

    By the reductive ring closure of dicationic precursors, highly strained hexaphenylethanes with an extremely long C-C bond were obtained, in which the front strain among the aryl group is maximized with high eclipseness by fusing a ring structure. The fused ring also induces further bond elongation by scissor effect, which led us to discover the new feature of covalent bonds. Fullsize Image
     
 
  • Ikuya Matsumoto, Ryo Sekiya, Takeharu Haino
    2021 Volume 94 Issue 4 Pages 1394-1399
    Published: April 15, 2021
    Released: May 13, 2021
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    This article reports production protocols for nanographenes and the effect of the reaction conditions on their structures and optical properties. These fundamental studies are of value for exploring suitable reaction conditions for the production of nanographenes with desirable properties. Graphite, finely crushed graphite powders, and artificial graphite, all of which are commercially available, are employed. Nanographenes are produced by the acid-assisted oxidative cleavage of the parent carbons followed by neutralization and deionization. The use of dialysis membranes for the size separation of nanographenes offers nanographenes with a specific size distribution, thereby allowing their structures and optical properties to be compared. Experiments demonstrate that small amounts of acids (60 ml of conc. H2SO4 and 20 mL of 60% HNO3) and oxidation for 12 h promotes a more efficient and cost-effective production of nanographenes from 2 g of a carbon source. The functionalization of the nanographene edges with p-propargyloxybenzyl amine confirms that the armchair edge with two carboxy groups is the dominant edge structure, irrespective of the carbon source.

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The Chemical Society of Japan Award for Creative Work for 2019
  • Tomoyuki Akutagawa
    2021 Volume 94 Issue 4 Pages 1400-1420
    Published: April 15, 2021
    Released: May 13, 2021
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    The thermally activated motional freedom of protons (H+), ions (M+), and molecules can be controlled using supramolecular approaches. In single crystals, motional freedom is enabled because of the small size of H+ and M+ (e.g., Li+ and Na+), and the thermally activated motion of small molecular units can yield molecular rotator structures in electrically conducting and magnetic crystals. The design of hydrogen-bonded networks and rotator–stator structures is a rational method to form functional dynamic molecular assemblies, and the thermally activated motional freedom of alkylamide (–CONHCnH2n+1) chains in discotic hexagonal columnar (Colh) and lamellar (La) liquid crystal phases enables the dipole inversion of polar N–H•••O= hydrogen-bonded chains, enabling a ferroelectric response to an applied external electric field. The thermally activated rotational freedom of neutral radicals in plastic crystals results in multifunctional dielectric, magnetic, and optical properties at the order–disorder phase transition. In hydrogen-bonded host–guest molecular crystals, dynamic structural transformations are coupled with highly reversibly guest adsorption–desorption in the crystalline state. Further, changes in the fluorescence colour of excited-state intramolecular proton transfer (ESIPT) systems can be exploited for solid-state molecular sensing, in which both dynamic molecular rotation and conformational transformations drastically affect the fluorescent responses.

    The thermally activated motional freedom of protons, ions, and molecules can be controlled using supramolecular approaches, which are combined with physical properties of proton conduction, ion conduction, dielectric switching, molecular rotator, collective rotation, ferroelectrics, molecular sorption, fluorescent chromism, and molecular sensing. Fullsize Image
     
Award Account
The Chemical Society of Japan Award for 2014
  • Kazuo Takatsuka
    2021 Volume 94 Issue 4 Pages 1421-1477
    Published: April 15, 2021
    Released: May 13, 2021
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    This account places a particular emphasis on recent progress in the theory and its applications of nonadiabatic electron dynamics in chemical science. After a brief description of the fundamental relevance of the breakdown of the Born-Oppenheimer approximation, we show examples of our extensive and systematic application of electron dynamics to highlight the significance and necessity of beyond-Born-Oppenheimer chemistry. The chemical subjects presented herewith cover (1) characteristic phenomena arising from nonadiabatic dynamics, (2) flow of electrons during chemical reactions and ionization dynamics, (3) symmetry breaking and its possible control in chemical reactions emerging from multi-dimensional nonadiabatic interactions, a special example which can cause possible breakdown of molecular mirror symmetry, (4) physical mechanism of charge separation in organic compounds and biomolecules, (5) essential roles of charge separation and elementary chemical reaction mechanisms in catalytic cycles of Mn oxo complexes up to Mn4CaO5 in water splitting dynamics (2H2O → 4H+ + 4e + O2), (6) chemical bonds and huge electronic state fluctuation in densely quasi-degenerate electronic manifolds, which make chemistry without the notion of potential energy surfaces, and so on. All these materials and issues have been chosen because they are not directly resolved by the method of energetics based on time-independent quantum chemistry. We thus have been exploring, developing, and cultivating a new chemical realm beyond the Born-Oppenheimer paradigm. This account is closed with a scope about the theory of simultaneous electronic and nuclear quantum wavepacket dynamics.

    Progress of the theory of nonadiabatic electron dynamics beyond the Born-Oppenheimer paradigm in chemical science is presented. We show that a new field of theoretical chemistry, namely, chemistry of nonadiabatic electron dynamics has been initiated and developed by illustrating some of our systematic applications to elementary molecular processes, chemical reactions, diffusive dynamics of densely quasi-degenerate electronic states, and so on. Fullsize Image
     
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