Highlight Review Collection2019-2020

In this review, recent studies on the molecular design of polymer-based carriers forplasmid DNA (pDNA) delivery in vitro and in vivo are described. One pDNA moleculehas the advantages of the synthesis of multiple copies of messenger RNAs (mRNAs), shortinterfering RNAs (siRNAs), and non-coding RNAs (ncRNAs), as well as proteins. Fromthe viewpoint of in vitro pDNA delivery, molecular design for endosomal escape andnucleus localization is mainly reviewed. From the viewpoint of in vivo pDNA delivery,molecular design for biodistribution is mainly reviewed. Finally, molecular design fortherapeutic medicine by the present desirable technology using pDNA delivery is reviewed.

Keywords: Plasmid DNA delivery | Polymer-based carrier | Molecular designMolecular Design of Polymer-based Carriers for Plasmid DNA Delivery In Vitro and In VivoShoichiro AsayamaChem. Lett. 2020, 49, 1-9.https://www.journal.csj.jp/doi/abs/10.1246/cl.190696

Keywords: Metal-organic cages (MOCs) | Extended networks | Cage-to-frameworkMetal-Organic Cages (MOCs): From Discrete to Cage-based Extended ArchitecturesEl-Sayed M. El-Sayed and Daqiang Yuan*Chem. Lett. 2020, 49, 28-53.https://www.journal.csj.jp/doi/abs/10.1246/cl.190731

Vol. 49, No. 1

The review highlights possible ways for metal-organic cages (MOCs) to extend via their edges orvertices by high-order assembly. The further cageassembly is based on in situ generated cage oruses the stepwise assembly approach. Theextended networks can be infinite polycatenane,polyMOCs, polymers, metal-organic frameworks,covalent organic frameworks, and hydrogen-bonded organic frameworks.

S. Asayama

D. Yuan

The radical cation-induced cycloadditions of alkenes are useful for the synthesis of naturalproducts. The key is one-electron oxidation of alkene to give alkene radical cation. Thesecycloadditions have attracted renewed attention thanks to the recent development ofoxidants as an initiator. This Highlight Review summarizes initiators for [2 + 2]- and [4 +2]-cycloadditions leveraging the generation of the radical cation.

Keywords: Radical cation-induced cycloaddition | Initiator | One-electron oxidationInitiators for Radical Cation-induced [2 + 2]-and [4 + 2]-Cycloadditions of Electron-rich AlkenesTakahiro Horibe and Kazuaki Ishihara*Chem. Lett. 2020, 49, 107-113.https://www.journal.csj.jp/doi/abs/10.1246/cl.190790

Keywords: [NiFe]-hydrogenase | O2-tolerance | Reaction mechanismStructural Basis of the Function of [NiFe]-hydrogenasesKoji Nishikawa, Hideaki Ogata,* and Yoshiki Higuchi*Chem. Lett. 2020, 49, 164-173.https://www.journal.csj.jp/doi/abs/10.1246/cl.190814

Hydrogenases control the proton concentration in cells, which is an essential function forhydrogen metabolism in several microorganisms. Some [NiFe]-hydrogenases arecatalytically active under air and are thus of great interest for developing bio-inspiredsynthetic models and new devices for clean energy conversion. We provide an overview ofthe structural basis of the reaction mechanism of [NiFe]-hydrogenases.

Vol. 49, No. 2

K. Ishihara

H. Ogata Y. Higuchi

Rationally designed topological arrangement of multinuclear transition metal centers is offundamental importance to create diverse functions applicable to catalysts, electronic,photochemical, and magnetic materials, and molecular devices. This highlight reviewsummarizes recent progress of our research work on the synthesis of low-valent metalclusters constrained by linear tetradentate phosphine ligands,Ph2PCH2P(Ph)(CH2)nP(Ph)CH2PPh2 (n = 1–4) and Ph2PCH2P(Ph)N(Ph)P(Ph)CH2PPh2,mainly focusing on linear noble metal chains and rings and copper hydride clusters.

Keywords: Linear tetraphosphine | Noble metal chains | Copper hydride clustersTransition Metal Clusters Constrained by Linear Tetradentate Phosphine LigandsTakayuki Nakajima* and Tomoaki Tanase*Chem. Lett. 2020, 49, 386-394.https://www.journal.csj.jp/doi/abs/10.1246/cl.200041

Keywords: Organoseleniums | Oxidant | Transition metal-freeOrganoseleniums: Generated and Exploited in Oxidative ReactionsAditya Upadhyay, Monojit Batabyal, Kanika, and Sangit Kumar*Chem. Lett. 2020, 49, 395-408.https://www.journal.csj.jp/doi/abs/10.1246/cl.200015

Vol. 49, No. 4

In this highlight review, newer methods mainly relying on the oxidative approach, whichis sustainable and does not require pre-functionalized substrates to constructorganoseleniums, have been discussed. The organoselenium compounds serve as aneffective catalyst for the transformation of several organic transformations with the aid ofoxidants like peroxide and halogens. Catalytic properties of organoselenium toward theactivation of an abundant and greener oxidant such as oxygen is also highlighted.

T. Nakajima T. Tanase

S. Kumar

While host–guest binding is generally a very fast reaction, guest uptake/release sometimesbecomes slow particularly when the host cavity is separated from the outside by relativelynarrow openings. If the apertures are opened/closed, the host molecule can be used as anano-sized container just like a capped container in our daily life. This review focuses onthe recent development of the kinetic control of guest uptake/release based on theopen/close functions, etc., in addition to fundamental kinetic studies of host–guest binding.

Keywords: Host–guest binding | Kinetic control | Molecular containerControl of Guest Binding Kinetics in Macrocycles and Molecular CagesShigehisa Akine* and Yoko SakataChem. Lett. 2020, 49, 428-441.https://www.journal.csj.jp/doi/abs/10.1246/cl.200017

Keywords: Mixed-valence | Stimuli-responsive | Supramolecular chemistryStimuli-responsive Mixed-valence Architectures: Synthetic Design and Interplay between Mobile and Introduced ChargesKeishiro Tahara* and Masaaki Abe*Chem. Lett. 2020, 49, 485-492.https://www.journal.csj.jp/doi/abs/10.1246/cl.200069

Mixed valency is a well-known phenomenonin which charge distributions change viaintervalence charge transfer. A basicunderstanding of the interface between mixedvalency and other charge-involvedphenomena remains poor. This HighlightReview describes new mixed-valencesubspecies with stimuli-responsiveness andinterplay between mobile charges and chargesnewly introduced by light and ions.

S. Akine

Vol. 49, No. 5

K. Tahara M. Abe

Benzophenone imine and its derivatives are useful ammonia equivalents for synthesizingprimary amines, readily achieving the selective formation of primary amines and obtainingeasily deprotectable imines as the product. These advantages have led to the developmentof various C–N bond-forming reactions in recent years. In this Highlight Review, wesummarize the progress related to their reaction patterns.

Keywords: Benzophenone imine | Amination | Primary aminesRecent Progress towards the Use of Benzophenone Imines as an Ammonia EquivalentYuta Kondo, Hiroyuki Morimoto,* and Takashi Ohshima*Chem. Lett. 2020, 49, 497-504.https://www.journal.csj.jp/doi/abs/10.1246/cl.200099

Keywords: Chemical kinetics | Reaction path network | Reaction mechanismRate Constant Matrix Contraction Method for Systematic Analysis of Reaction Path NetworksYosuke Sumiya and Satoshi Maeda*Chem. Lett. 2020, 49, 553-564.https://www.journal.csj.jp/doi/abs/10.1246/cl.200092

H. Morimoto T. Ohshima

This paper reviews the rate constant matrixcontraction (RCMC) method, a kineticmethod developed for the network of paths ofchemical reaction elementary steps. RCMCenables quick evaluation of population ofchemical species involved at a specific timewithout explicit time-evolution of the rateequations. RCMC is also utilized in thekinetics-based navigation which dramaticallyaccelerates the automated reaction path search.Its theoretical backgrounds and applicationexamples to various chemical reactions arepresented.

S. Maeda

Several fabrication technologies for molecular level ultra-thin films, from organic toorganic–inorganic hybrids, are introduced using the surface imaging technology ofscanning probe microscopy (SPM). Electrochemical scanning tunneling microscopy (EC-STM), atomic force microscopy (AFM) and the related techniques enable the observationof the surface of 2D materials in near real-time and in real-space. The combination of 2Dmaterials and SPM technology opens up a new avenue of surface and material science,despite its many restrictions.

Keywords: Scanning probe microscopy | 2D nanomaterials | On-site polymerizationConstruction and Scanning Probe Microscopy Imaging of Two-dimensional NanomaterialsMasashi Kunitake* and Shinobu UemuraChem. Lett. 2020, 49, 565-573.https://www.journal.csj.jp/doi/abs/10.1246/cl.200080

Head-to-tail dipole-dipole arrays of isoxazole rings lead tosupramolecular helical assemblies. The cooperativesupramolecular polymerization characterized by a two-steppolymerization consisting of nucleation and elongation isdriven by the multiple dipole array as well as the induceddipoles in the supramolecular organization. The helicalsupramolecular assemblies are fabricated with the aid ofmultiple dipole–dipole interactions. The chiroptical properties,such as CD and CPL, are determined by the right-handed andleft-handed helicities of the supramolecular organizations. TheAIE and AIEE features of the platinum complex are inherentin the supramolecular assemblies, which results inluminogenic micelles. In this review, these aspects are brieflydescribed, emphasizing the importance of the intermoleculardipole-dipole interactions in supramolecular chemistry.

Keywords: Isoxazole | Supramolecular polymerization | Helical assemblySupramolecular Polymerization and Functions of Isoxazole Ring MonomersTakeharu Haino* and Takehiro HiraoChem. Lett. 2020, 49, 574-584.https://www.journal.csj.jp/doi/abs/10.1246/cl.200031

T. Haino

M. Kunitake

The ability to control structure and function of metal-organic cages by a light stimulusoffers many possibilities. For example, to prevent product inhibition in catalysis, to releasea drug at a specific site, or to alter material properties. This Highlight Review describes thedifferent strategies that have been used to make metal-organic cages change their structurein response to light and furthermore, discusses major challenges and future perspectives.

Keywords: Metal-organic cages | Coordination cages | Molecular switchesLight-switchable Metal-Organic CagesSander J. WezenbergChem. Lett. 2020, 49, 609-615.https://www.journal.csj.jp/doi/abs/10.1246/cl.200076

Keywords: Metal–organic frameworks | Polymers | Host–guest systemsPolymers in Metal–Organic Frameworks: From Nanostructured Chain Assemblies to New Functional MaterialsTakashi Kitao and Takashi Uemura*Chem. Lett. 2020, 49, 624-632.https://www.journal.csj.jp/doi/abs/10.1246/cl.200106

Vol. 49, No. 6

S. J. Wezenberg

Recent developments in controlling polymerassemblies using metal–organic frameworks(MOFs) are covered in this highlight review.The characteristic features of MOFs are theirhighly tailorable and well-defined nanoporousstructures that can be utilized for specificpolymer nanoconfinement. This methodologyallows us to regulate assembly structures ofpolymers for the fundamental study of polymerproperties, as well as construction of functionalMOF–polymer nanohybrids.

T. Uemura

Rh(II)-based metal–organic polyhedra(MOPs) represent a novel class of porousmetal–coordination complexes with robuststructures and unsaturated open metal sites.The rich coordination and covalentchemistries of Rh(II)-based MOPs make thema promising platform for constructingfunctional materials. Herein, we highlight thedevelopment and advances of Rh(II)-basedMOPs, as well as their applications fromdiscrete units to supramolecular materials.

Keywords: Metal–organic polyhedra (MOPs) | Discrete porous structures | Supramolecular materialsRh(II)-based Metal–Organic PolyhedraJun Zhao and Xuzhou Yan*Chem. Lett. 2020, 49, 659-665.https://www.journal.csj.jp/doi/abs/10.1246/cl.200152

Keywords: Metalloproteomics | Molecular mechanisms | ICP-MSMetalloproteomic Approaches for Matching Metals to Proteins: The Power of Inductively Coupled Plasma Mass Spectrometry (ICP-MS)Xiaohan Xu, Haibo Wang, Hongyan Li, and Hongzhe Sun*Chem. Lett. 2020, 49, 697-704.https://www.journal.csj.jp/doi/abs/10.1246/cl.200155

Metal/metalloid complexes have been commonly utlized in medicine for therapeutics anddiagnostics. Inductively coupled plasma mass spectrometry (ICP-MS) has been widelyapplied to unveil the molecular mechanisms of metallodrugs. This review focuses on themost recent applications of ICP-MS based metalloproteomic approaches in characterizingpotential protein targets of anticancer and antibacterial metallodrugs and subsequentlyexploring their molecular mechanisms.

X. Yan

H. Sun

G-quadruplexes (G4s) are formed in the guanine-rich sequences and found in biologically-significant regions of the genomic DNA, including the telomere, located at the end of theeukaryotic chromosome, the promoter regions of oncogenes. In this review, we focus onthe functional G4 ligands, which not only bind to the G4 structure but also have somefunction.

Keywords: G-quadruplexes | Functional G4 ligands | Selective alkylationFunctional G-Quadruplex Binding MoleculesFumi Nagatsugi* and Kazumitsu OnizukaChem. Lett. 2020, 49, 771-780.https://www.journal.csj.jp/doi/abs/10.1246/cl.200214

Keywords: Lanthanide complexes | Luminescence | Helicate structureHelicate Lanthanide Complexes: The Luminescent ElementsMiki Hasegawa* and Hitomi OhmagariChem. Lett. 2020, 49, 845-854.https://www.journal.csj.jp/doi/abs/10.1246/cl.200184

Vol. 49, No. 7

Luminescent lanthanide (Ln) complexes basedon chelate effect will be introduced by using aseries of hexadentate bipyridine derivatives astheir ligand moieties. The molecule forms asingle helicate molecular structure with a Ln-coordination. Molecular distortion and variousderivation induce the intent luminescence andcharacteristic molecular conformation whichdepend on atmospheres or media. It would be asupportive case to design novel units of Lncomponents for emission.

F. Nagatsugi

M. Hasegawa

The total synthesis of epilupinine as the simplest natural product with a fused ring systemis introduced in this highlight review. Due to the simple fused ring system, total synthesisof epilupinine has been attempted by various different approaches, and various methodsfor constructing the octahydro-2H-quinolizine (quinolizidine) skeleton have beendeveloped.

Keywords: Epilupinine | Total synthesis | Quinolizidine alkaloidTotal Synthesis of Epilupinine: Synthetic Strategy of Fused Bicyclic Skeleton Containing NitrogenTomohiro Tsutsumi and Kosuke Namba*Chem. Lett. 2020, 49, 963-969.https://www.journal.csj.jp/doi/abs/10.1246/cl.200340

Keywords: Aryl/Alkyl halides | Sulfur dioxide | Photoinduced conditionsSulfonylation of Aryl/Alkyl Halides with Sulfur Dioxide under Photoinduced ConditionsYuewen Li and Jie Wu*Chem. Lett. 2020, 49, 1066-1070.https://www.journal.csj.jp/doi/abs/10.1246/cl.200386

Vol. 49, No. 8

Recent advances in the sulfonylation of aryl/alkyl halides with sulfur dioxide underphotoinduced conditions are summarized in this report. The transformations usually proceedsmoothly with the insertion of sulfur dioxide via radical processes under mild conditions.Under ultraviolet irradiation, no metal catalysts are needed for the photoinducedsulfonylation of aryl/alkyl halides with sulfur dioxide, while a photoredox catalyst isnecessary for the sulfonylation of aryl/alkyl halides with sulfur dioxide under visible lightirradiation. During the transformation, excellent chemoselectivity and stereoselectivity areobserved for the final outcome.

K. Namba

Vol. 49, No. 9

J. Wu

Peptides are advantageous as a delivery tool becauseof the ease of their functional design and synthesis –this review highlights approaches for intracellulardelivery of biomacromolecules using peptides withdistinct modes of action.

Keywords: Arginine-rich cell-penetrating peptide (CPP) | Attenuated cationic membrane-lytic peptide | Macropinocytosis-inducing peptidePeptide-assisted Intracellular Delivery of BiomacromoleculesShiroh Futaki,* Jan Vincent V. Arafiles, and Hisaaki HiroseChem. Lett. 2020, 49, 1088-1094.https://www.journal.csj.jp/doi/abs/10.1246/cl.200392

Keywords: Supramolecular extraction | Macrocycles | Molecular recognitionPractical Applications of Supramolecular Extraction with MacrocyclesAimin Li, Huijuan Zhai, Jilian Li, and Qing He*Chem. Lett. 2020, 49, 1125-1135.https://www.journal.csj.jp/doi/abs/10.1246/cl.200409

Supramolecular extraction refers to an application ofsupramolecular chemistry, in particular host-guestchemistry, toward extraction. It has led to newapproaches, inter alia, in so-called solvent extractionthat is of great importance for separation science andtechnology. The past two decades or so havewitnessed a rapid and spectacular development ofthis field and seen the implementation of manyapplications in the real world. This mini reviewarticle briefly overviews recent advances of tailoredmacrocyclic supramolecular extractants and focuseson their practical applications in hydrometallurgy,waste reprocessing and treatment, environmentalmonitoring and cleanup, corrosion inhibition, aswell as protein separation and purification.

S. Futaki

Vol. 49, No. 10

Q. He

Cyanide-bridged mixed-valence Co-Fe multi-nuclear complexes, which are considered as0D molecular Prussian blue analogues (PBAs),have variable molecular structures and flexibleelectronic states. In this highlight review, theredox chemistry of the 0D Co-Fe molecularPBAs will be focused on to explain theirelectronic states and bistability induced byintramolecular electron transfer. In addition,dimensionally controlled assembly of the Co-Fe molecular PBAs into low-dimensionalaggregates will be introduced.

Keywords: Multinuclear complexes | Electron transfer | Molecular magnetismMolecular Prussian Blue Analogues: From Bulk to Molecules and Low-dimensional AggregatesMasayuki NiheiChem. Lett. 2020, 49, 1206-1215.https://www.journal.csj.jp/doi/abs/10.1246/cl.200428

Keywords: Template synthesis | Layer-by-Layer assembly | MicromotorsProtein-based Smart Microtubes and Nanotubes as Ultrasmall BiomaterialsTeruyuki KomatsuChem. Lett. 2020, 49, 1245-1255.https://www.journal.csj.jp/doi/abs/10.1246/cl.200433

Micrometer- and nanometer-scale cylindrical hollow structures that are made of softmaterials, i.e., microtubes (MTs) and nanotubes (NTs), have attracted great interestbecause of their potential applications. This review highlights the latest research onprotein-based smart MTs and NTs as ultrasmall biomaterials. These practical cylinderswere prepared using an alternate layer-by-layer assembly of proteins into a track-etchedpolycarbonate membrane with the subsequent dissolution of the template. Variousfunctionalities can be introduced into the inner surface, cylindrical wall, and outer surface.A perspective of the practical use of protein tubules with a good biofriendly nature is alsodescribed.

T. Komatsu

M. Nihei

Catalytic C–H functionalizations have become powerful synthetic tools in organicsynthesis. Recently, a combination of transition-metal-catalyzed C–H activation andelectrochemical oxidation has become as an environmentally-benign strategy. Studiesregarding transition-metal-catalyzed oxidative C–H functionalization with the aid ofelectrochemical oxidation leading C–C, C–halogen, C–O, C–N, and C–P bonds are brieflysurveyed.

Keywords: C–H activation | Electrochemical reaction | Regioselective functionalizationNew Strategy for Catalytic Oxidative C–H Functionalization: Efficient Combination of Transition-metal Catalyst and Electrochemical OxidationFumitoshi Kakiuchi* and Takuya KochiChem. Lett. 2020, 49, 1256-1269.https://www.journal.csj.jp/doi/abs/10.1246/cl.200475

Keywords: Fluorescence | Platinum(II) metallacycles | Supramolecular polymersFluorescent Platinum(II) Metallacycle-cored PolymersYali Hou and Mingming Zhang*Chem. Lett. 2020, 49, 1312-1318.https://www.journal.csj.jp/doi/abs/10.1246/cl.200469

Fluorescent platinum(II) metallacycle-coredpolymers could be prepared by the linkage ofemissive metallacycles via non-covalentbonds, covalent bonds or dynamic covalentbonds. Through the incorporation of differentfunctional groups and rational selection ofdifferent connection methods, theirphotophysical properties, solubilities,processabilities can be finely tuned, whichgreatly influence their functions andapplications.

Vol. 49, No. 11

F. Kakiuchi

M. Zhang

Strained bow-shaped macrocycles, namely,molecular bows (MBs), are consisted of a rigid π-conjugated unit (bow-limb) with a flexible chain(bowstring) under tension joining both ends.Because of their unique topology, MBs not onlyexhibit unique properties induced by bent bow-limbs, but also play a vital role in the constructionof advanced materials, such as carbon nanotubesand catalysts. This highlight review surveys thehistory and recent progress in the synthesis andapplication of a wide range of MBs involvingbenzene, acenes, terphenylenes, perylene bisimide,porphyrins, pyrene, dibenzo[a,e]pentalene, andazulene, along with an overview of their generalstructural features and properties.

Keywords: Macrocycles | Strained structures | Polyaromatic hydrocarbonsMolecular Bows—Strained Bow-shaped MacrocyclesYimin Liang, Min Tang, and Zhichang Liu*Chem. Lett. 2020, 49, 1329-1336.https://www.journal.csj.jp/doi/abs/10.1246/cl.200408

Keywords: Chirality | Self-sorting | CagesChiral Self-sorting in Cage-like CompoundsChuanlong Li, Yong Zuo, Yu-Quan Zhao, and Shaodong Zhang*Chem. Lett. 2020, 49, 1356-1366.https://www.journal.csj.jp/doi/abs/10.1246/cl.200477

Chiral self-sorting in cage-like compounds has beendrawing increasing attention in recent years. It is ofgreat importance in controlling the chirality of theformed cages and their chirality related properties.In this Highlight Review recent progress in thisresearch field is summarized. The examples includeboth metallocages and organic cages. A summary ofthese advances would be beneficial for getting abetter perspective on the fundamental principles inchiral self-sorting and provide guidance for thedesign of novel chiral porous materials from cage-like compounds.

Z. Liu

S. Zhang

This highlight review describes the deoxygenative coupling of carbonyl compounds,starting with a brief historical presentation of stoichiometric reactions (McMurry coupling),then highlighting the efforts to develop catalytic reactions, and finally several examples ofreactions without the use of transition metals. When available, intermolecular reactionsand cross-coupling reactions of two different carbonyl compounds are highlighted.

Keywords: Deoxygenative coupling | Carbonyl compounds | OlefinOlefin Synthesis by DeoxygenativeCoupling of Carbonyl Compounds: From Stoichiometric to CatalyticSobi Asako* and Laurean Ilies*Chem. Lett. 2020, 49, 1386-1393.https://www.journal.csj.jp/doi/abs/10.1246/cl.200540

Keywords: para-C-H Functionalization | Directing group | Cooperative catalysisTransition Metals and Transition Metals/Lewis Acid Cooperative Catalysis for Directing Group Assisted para-C–H FunctionalizationSheuli Sasmal, Uttam Dutta,* Goutam Kumar Lahiri,* and Debabrata Maiti*Chem. Lett. 2020, 49, 1406-1420.https://www.journal.csj.jp/doi/abs/10.1246/cl.200500

A paradigm shift in the realm of site-selectiveC–H functionalization has been witnessed inrecent era by employing directing groupassisted strategies. Recent years, directinggroup assisted para-C–H activation hasemerged as an attractive synthetic tool tooverride the steric/electronic controlled C–Hfunctionalization. This review highlights therecent advancements on these approaches toserve a quick overview on the field of para-selective C–H functionalization.

S. Asako L. Ilies

U. Dutta

G. K. Lahiri

D. Maiti

We review the application of fluorescence lifetime correlation analyses to elucidate theleaflet-specific lipid diffusion in a model cell membrane supported on glass. The resultsshowed that lipid diffusion in a proximal leaflet facing a glass surface is sensitive to thestrength of the electrostatic interaction between the lipid headgroup and the glass surfacewhereas that in the distal one is insensitive to it. This suggests that the interleaflet couplingis negligible in mono-unsaturated lipids.

Keywords: Fluorescence correlation spectroscopy | Lipid membrane | Interleaflet couplingLeaflet-specific Lipid Diffusion Revealed by Fluorescence Lifetime Correlation AnalysesTakuhiro Otosu* and Shoichi Yamaguchi*Chem. Lett. 2020, 49, 1473-1480.https://www.journal.csj.jp/doi/abs/10.1246/cl.200539

Vol. 49, No. 12

T. Otosu S. Yamaguchi

Progressive research of materials for Li-ion batteryopened up a new research field targeting Na-ionand K-ion batteries. The author’s research groupdemonstrated 3-volt class Na-ion battery and 4-voltclass brand-new K-ion battery. This articleoverviews our systematic studies of lithium-,sodium-, and potassium-driven redox systems alongwith an recent update towards high-energy Na-ionbatteries.

Keywords: Lithium battery | Sodium battery | Potassium batterySodium-driven Rechargeable Batteries: An Effort towards Future Energy StorageShinichi KomabaChem. Lett. 2020, 49, 1507-1516.https://www.journal.csj.jp/doi/abs/10.1246/cl.200568

S. Komaba

Soluble organic semiconductors have been widelyresearched for a wide range of application scenarios,such as organic field-effect transistors (OFETs),organic light-emitting diodes and solar cells. Due totheir unique characteristics and great potentials as aplatform for exploiting charge transport, two-dimensional (2D) organic crystals are emerging toinvestigate the device physics in OFETs, which isessential for functional device applications. Here, 2Dorganic crystalline films are briefly introduced fromthe deposition to the applications in electronic devices.

Typical ancillary ligands are anionic or neutral species. Cationic ones are exceptions and,when used, the positively charged groups are normally attached to the periphery and notclose to the donating atom. However, a series of experimental results, which arereviewed here, suggest that the utility in catalysis of cationic phosphines with no spacerbetween the phosphorus atom and the positively charged groups (α-cationic phosphines)might be broader than anticipated.

Vol. 48, No.1Keywords: Cationic phosphines | Catalysis |Ligand designApplications of α-Cationic Phosphines as Ancillary Ligands in Homogeneous CatalysisLeo D. M. Nicholls and Manuel Alcarazo*Chem. Lett. 2019, 48, 1-13.https://www.journal.csj.jp/doi/abs/10.1246/cl.180810

M. Alcarazo

Keywords: Semiconductor/dielectric interface | Two-dimensional organic films |Organic field-effect transistor (OFET)Two-dimensional Organic Materials andTheir Electronic ApplicationsHengyuan Wang, Qijing Wang,* and Yun Li*Chem. Lett. 2019, 48, 14-21.https://www.journal.csj.jp/doi/abs/10.1246/cl. 180811

Q. Wang Y. Li

Understanding the mechanistic pathways for theformation of high-valent metal-oxo intermediates hasbeen of critical subjects in bioinorganic researchbecause they have been proposed as key intermediatesin dioxygen activation paradigm of O2-activatingenzymes. In this review, we discuss the peroxide bondcleavage processes of iron-(hydro/alkyl)peroxocomplexes induced by endogenous and exogenousfactors.

Selones, since their first report in 1963, have attractedsignificant interest with respect to their bonding,structure and more importantly as an ancillary ligandfor complexation with various metals. Starting as ananalogue of N-heterocyclic carbene (NHC), selonesare considered as promising molecules in chemistrywith numerous applications in various importantprocesses. Herein, a brief overview of selone, itsgenesis and relevance in contemporary chemistry isgiven, particularly focusing on its syntheses, reactivityand applications.

Vol. 48, No.2Keywords: Antioxidant activity | Selenium | StructuresRecent Developments in the Chemistry of NHC-based Selones: Syntheses, Applications and ReactivitySangeeta Yadav, Rajesh Deka, and Harkesh B. Singh*Chem. Lett. 2019, 48, 65-79.https://www.journal.csj.jp/doi/abs/10.1246/cl.180748

Keywords: Peroxide bond cleavage | Homolysis | HeterolysisPeroxide Bond Cleavage of Nonheme Iron-(Hydro/Alkyl)Peroxo Complexes Induced by Endogenous and Exogenous FactorsHyeri Jeon and Seungwoo Hong*Chem. Lett. 2019, 48, 80-85.https://www.journal.csj.jp/doi/abs/10.1246/cl.180831

H. B. Singh

S. Hong

This highlight review describes our contribution in the field of biomimetic andtechnomimetic molecular machines specially designed to be studied as single molecules onsurfaces. Prototypes of molecular wheels, vehicles, gears and motors will be describedfrom their design to the study of their controlled motions using ultra-high-vacuum low-temperature scanning tunneling microscopes.

Recently, visible light-induced generation of a hybrid Pd-radical species were reported toenable some unprecedented transformations via the photoexcited-state of the palladiumcomplex, which could not be achieved under traditional thermal conditions. This highlightreview discusses the recent progress in this sort of novel synthetic method.

Vol. 48, No.3Keywords: Visible light | Palladium catalysis | RadicalVisible Light-induced Palladium-catalysis in Organic SynthesisWen-Jun Zhou,* Guang-Mei Cao, Zhan-Peng Zhang, and Da-Gang Yu*Chem. Lett. 2019, 48, 181-191.https://www.journal.csj.jp/doi/abs/10.1246/cl.190006

Keywords: Polyaromatic hydrocarbons | Sandwich complexes | Scanning tunneling microscopyBiomimetic and Technomimetic Single Molecular MachinesClaire Kammerer, Guillaume Erbland, Yohan Gisbert, Toshio Nishino, Kazuma Yasuhara, and Gwénaël Rapenne*Chem. Lett. 2019, 48, 299-308.https://www.journal.csj.jp/doi/abs/10.1246/cl.181019

W.-J. Zhou D.-G. Yu

Vol. 48, No.4

G. Rapenne

In the present review, the dyes encapsulated insmectites and layered double hydroxides aresummarized from the viewpoints of dye stabilizationand possible mechanisms for the stabilization towarddecolorization are discussed. In addition, thestabilization of photochemically formed isomer of aphotochromic spiropyran, by the interactions withsmectite is also presented.

Vol. 48, No.5Keywords: Photofunctional materials | Dye | Nanoporous materialsThe Improved Stability of Molecular Guests by the Confinement into NanospacesAranee (Pleng) Teepakakorn, Tetsuo Yamaguchi, and Makoto Ogawa*Chem. Lett. 2019, 48, 398-409.https://www.journal.csj.jp/doi/abs/10.1246/cl.181026

M. Ogawa

Vol. 48, No.7

Fusion is a relatively new concept to produce unique members of the porphyrin family. Arepresentative compound formed by fusion is N-fused porphyrin, which is synthesizedfrom N-confused porphyrin. N-Fused porphyrin has an unusually narrow HOMO–LUMOenergy gap and exhibits absorption in the near infrared region up to 1100 nm. Moreover,N-fused porphyrin serves as a versatile mono-negative tridentate ligand, which can bind avariety of metal centers tightly. While inner-core fusion is rare in tetrapyrrolicporphyrinoids, it becomes more common in expanded porphyrins, where a variety ofnovel structures are produced unanticipatedly.

Keywords: Porphyrin | Metal complex | Expanded porphyrinN-Fused Porphyrin: A Maverick Member of the Porphyrin FamilyMotoki Toganoh and Hiroyuki Furuta*Chem. Lett. 2019, 48, 615-622.https://www.journal.csj.jp/doi/abs/10.1246/cl.190250

H. Furuta

The chemistry of anilido phosphine complexes hasbeen popularized since 2003 when N-arylation of theparent o-anilinophosphine was made possible. ThisHighlight Review summarizes the cumulative progressmade in nickel chemistry, paying particular attention tooxidative addition, reductive elimination, CO insertion,olefin insertion, β-hydrogen elimination, metatheticalreaction, arene C-H activation, and their collaborativeapplications to Kumada-type cross coupling catalysis.

Although importance of fluctuation for proteinreactions has been sometimes pointed out, there hasbeen no evidence showing contribution to proteinreactions. This highlight review describes theexperimental measurements of conformationalfluctuations for short-live species during proteinreactions. The correlations between the fluctuationsand the reactivities are described.

Vol. 48, No.8Keywords: Protein reaction | Time-resolved detection | FluctuationEnhanced Conformational Fluctuations during Protein ReactionsMasahide TerazimaChem. Lett. 2019, 48, 802-810.https://www.journal.csj.jp/doi/abs/10.1246/cl.190195

Keywords: PNP pincer | NP chelate |C-H activationChemistry of Anilido Phosphine Complexes of NickelXue-Ru Zou, Shu-Mei Liao, Kuo-Wei Huang,* and Lan-Chang Liang*Chem. Lett. 2019, 48, 811-819.https://www.journal.csj.jp/doi/abs/10.1246/cl.190216

M. Terazima

L.-C. Liang K.-W. Huang

Ultrathin gold nanowires and nanorods with diameterssmaller than the critical dimension for quantization (∼2nm), are a new class of anisotropic nanostructures. Thishighlight review will focus on the current status andfuture prospects of their controlled syntheses, acharacterization of their atomic structures andphysicochemical and thermodynamic properties, andtheir usage in the fabrication of advanced devices.

Keywords: Ultrathin gold nanowires | Ultrathin gold nanorods | Aspect ratioUltrathin Gold Nanowires and NanorodsRyo Takahata and Tatsuya Tsukuda*Chem. Lett. 2019, 48, 906-915.https://www.journal.csj.jp/doi/abs/10.1246/cl.190313

To date, the most effective iridium anticancercompounds are those with “piano-stool” structures andwhich usually incorporate a variety of N-, O-, S- and P-bidentate ligands. These compounds can be easilyfunctionalized by changing the bidentate ligands, theancillary ligands and increasing the aromaticity of thearene substituent, all in the hope to optimize theiractivities and allow the determination of structureactivity relationships. However, research towards C-donor ligands has only just emerged in the past 5 years,with cyclometalated and N-heterocyclic carbene iridiumcomplexes showing significant increases in potencytowards a range of cancer cell lines. This mini-reviewhighlights the recent and ongoing research in C-donoriridium organometallic complexes, and herein wediscuss their importance as potential anticancer drugs.

Keywords: Anticancer | Bioinorganic chemistry | Iridium arene complexesOrganometallic Iridium Arene Compounds: The Effects of C-Donor Ligands on Anticancer ActivityRianne M. Lord* and Patrick C. McGowanChem. Lett. 2019, 48, 916-924.https://www.journal.csj.jp/doi/abs/10.1246/cl.190179

R. M. Lord

T. Tsukuda

In just a few years, the power conversion efficiencies ofperovskite solar cells (PSCs) have exceeded 24%,demonstrating the potential for industrialization.However, the lead toxicity and instability still present asmajor obstacles for commercialization. We review theresearch progress all-inorganic cesium lead-free halidePSCs and highlight their viability to replace lead halidePSCs.

Keywords: Perovskite solar cell | Lead-free | StabilityProgress of All-inorganic CesiumLead-free Perovskite Solar CellsXiaotong Li, Jinbo Wu, Shenghao Wang,*and Yabing Qi*Chem. Lett. 2019, 48, 989-1005.https://www.journal.csj.jp/doi/abs/10.1246/cl.190270

Y. B. Qi S. Wang

Both amyloid-β (Aβ) and metal ions are implicated in the pathology of Alzheimer’sdisease (AD). Research efforts elucidating the pathogenic roles of these two biologicalcomponents denote a connection between them. This highlight review presents the currentunderstanding of Aβ and metal ions in AD and their relationship prompting a hybridconcept: metal-bound Aβ (metal–Aβ).

Keywords: Amyloid-β | Metal ions | Metal–amyloid-βIntertwined Pathologies of Amyloid-β and Metal Ions in Alzheimer’s Disease: Metal–Amyloid-βGeewoo Nam and Mi Hee Lim*Chem. Lett. 2019, 48, 951-960.https://www.journal.csj.jp/doi/abs/10.1246/cl.190281

M. H. Lim

Skeletal transformations of heteroaromatic compoundswhile cleaving their endocyclic bonds have beenemerging as new synthetic tools in modern organicchemistry. Especially, endocyclic insertion of aheteroatom into a heteroaromatic core is a game-changing approach to exotic classes of heterocycliccompounds. In this Highlight Review is summarizedrecent progress of ring-expanding and ring-openingreactions of benzofurans and indoles.

Keywords: Aromatic metamorphosis | Benzofuran | IndoleRing-expanding and Ring-opening Transformations of Benzofurans and Indoles with Introducing HeteroatomsHayate Saito and Hideki Yorimitsu*Chem. Lett. 2019, 48, 1019-1028.https://www.journal.csj.jp/doi/abs/10.1246/cl.190393

H. Yorimitsu

Semiconducting small molecules capable of self-organizing into well-definednanostructures have a great potential in organic electronics. In this article we reviewhydrogen-bond-directed supramolecular organization of barbiturated oligothiophenes andthe application of the resulting one-dimensional nanostructures to solution processablebulk heterojunction organic photovoltaic cells. Through this article we illustrate thatthrough a proper molecular design we can utilize directional hydrogen bonding units as apotent tool to organize π-conjugated molecules into 1D nanostructures optoelectronicallyactive at the device level.

Keywords: Self-assembly | Organic photovoltaics | Hydrogen bondSupramolecular Organization and Photovoltaic Properties of Barbiturated OligothiophenesHayato Ouchi, Xu Lin, and Shiki Yagai*Chem. Lett. 2019, 48, 1009-1018.https://www.journal.csj.jp/doi/abs/10.1246/cl.190296

Vol. 48, No.9

S. Yagai

Despite the tremendous advances in the field of C–H borylations of arenes over the pastdecade and a half, controlling the site-selectivity has remained a central challenge thatrequires resolving. In recent years, innovative catalytic strategies have set the stage for therealization of control over the site-selectivity in the C–H borylation of arenes. ThisHighlight Review examines strategic key advances for the site-selective C–H borylation ofarenes with a particular focus on the catalyst-controlled site-selectivity that has so farremained unattainable using standard catalyst systems.

Keywords: C–H borylation | Iridium | Site-selectiveCatalyst-enabled Site-selectivity in the Iridium-catalyzed C–H Borylation of ArenesYusuke Kuroda and Yoshiaki Nakao*Chem. Lett. 2019, 48, 1092-1100.https://www.journal.csj.jp/doi/abs/10.1246/cl.190372

Y. Nakao

Keywords: Pillar[n]arenes | Conformation | Planar chiralityConformation and Planar Chirality of Pillar[n]arenesShixin Fa, Takahiro Kakuta, Tada-aki Yamagishi, and Tomoki Ogoshi*Chem. Lett. 2019, 48, 1278-1287.https://www.journal.csj.jp/doi/abs/10.1246/cl.190544

Vol. 48, No.10

Because of the rotational ability of theparaphenylene units, pillar[n]arenes haveabundant conformers in principle, among whichthe two enantiomers with all substituentsarranging in the same direcation are most stable,offering the posibility to separate the planar chiralpillar[n]arenes. The enantiopure planar chiralpillar[n]arenes can be used in many applications.

T. Ogoshi

This Highlight Review sheds light on a neglected aspect of alkylnitriles in syntheticorganic chemistry. The chemical inertness and highly polar nature of alkylnitriles haveparticular utility as a reaction solvent. Alkylnitriles, however, also serve as potentialbuilding blocks for constructing carbon frameworks of interest. Two decades ofexploratory studies of this elusive reaction revealed competent catalytic systems that allowfor catalytic and enantioselective coupling of alkylnitriles with electrophiles.

Keywords: Acetonitrile | Asymmetric catalysis | C–C bond formationA Thirst for Enantioselectivity in Catalytic Addition of AlkylnitrilesNaoya Kumagai* and Masakatsu Shibasaki*Chem. Lett. 2019, 48, 1322-1327.https://www.journal.csj.jp/doi/abs/10.1246/cl.190609

Keywords: Polycyclic aromatic hydrocarbons | Phosphorus heterocycles | Organophosphorus materialsThe Renaissance of Bridged Triarylphosphines: Towards Organophosphorus Molecular BowlsTobias A. Schaub, Kevin Padberg, and Milan Kivala*Chem. Lett. 2019, 48, 1358-1367.https://www.journal.csj.jp/doi/abs/10.1246/cl.190601

Vol. 48, No.11

Phosphorus in a bowl: Introducing bridgingunits into triarylphosphines affords bowl-shapedheteroaromatics — a class of compounds withauspicious attributes for supramolecularchemistry and organic electronic applications. Inthis Highlight Review this emerging field ofresearch is reviewed starting from its origins inthe 1990s to a recent renaissance that renewed theinterest in these fascinating compounds.

N. Kumagai M. Shibasaki

M. Kivala

The installation of novel and artificial functions to proteins through modifications of theirchemical structure is an emerging research field covering chemistry, biology, and medicine.Because the reactions must proceed with high chemo- and regio-selectivity under mildconditions in aqueous solvents, developing chemical methods for precise proteinmodifications affording homogenous products is a great challenge in organic synthesis.Here we review selected recent examples of synthetically-inspiring chemical proteinmodifications. The chemistry discussed here will lead to novel methodologies for theefficient synthesis of broad range of organic molecules.

Keywords: Protein modifications | Chemoselectivity | Functional group-toleranceSynthetic Methodology-driven Chemical Protein ModificationsKatsuya Maruyama and Motomu Kanai*Chem. Lett. 2019, 48, 1421-1432.https://www.journal.csj.jp/doi/abs/10.1246/cl.190652

Keywords: Phthalocyanine | Photofunction | SpectroscopyPhotofunctionalization of PhthalocyaninesKazuyuki IshiiChem. Lett. 2019, 48, 1452-1461.https://www.journal.csj.jp/doi/abs/10.1246/cl.190637

The last few decades have seen rapiddevelopment in molecular science and technology.In this review, photofunctionalization ofphthalocyanines (Pcs) is introduced from theviewpoint of biological applications and advancedmaterials, such as fluorescence probes,photodynamic therapy photosensitizers,photocontrollable magnetic materials,photoconductors, and heat shielding materials.These would be useful model cases for molecularfunctionalization.

M. Kanai

Vol. 48, No.12

K. Ishii