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Published: 14 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103049

Abstract:
Four synthetic farnesyl diphosphate analogues were enzymatically converted with three bacterial sesquiterpene synthases, including β-himachalene synthase (HcS) and ( Z )-γ-bisabolene synthase (BbS) from Cryptosporangium arvum , and germacrene A synthase (SmTS6) from Streptomyces mobaraensis . These enzyme reactions not only yielded several previously unknown compounds, showing that this approach opened the door to a new chemical space, but substrates with blocked or altered reactivities also gave interesting insights into the cyclisation mechanisms and the potential to catalyse reactions with different initial cyclisation modes.
Ibrahima Fa Bamba, , Jérôme Marrot, Patrick Atheba, Gildas Gbassi, David Landy, William Shepard, Mohamed Haouas, Emmanuel Cadot
Published: 14 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102684

Abstract:
Host-guest complexes between native cyclodextrins (α-, β- and γ-CD) and hybrid Lindqvist-type polyoxovanadates (POVs) [V6O13((OCH2)3C-R)2]2– with R=CH2CH3, NO2, CH2OH and NH(BOC) were studied in aqueous solution. 6 crystal structures determined by SCXRD analysis revealed the nature of the R group strongly influences the host–guest conformation. In all systems isolated in the solid-state, the organic groups R are embedded within the CD cavities, involving only a few weak supramolecular contacts. The interaction between hybrid POVs and the macrocyclic organic hosts have been studied in solution using ITC, cyclic voltammetry and NMR methods (1H NMR, and 2D DOSY, and ROESY). This set of complementary techniques provides clear insights about the strength of interactions and the binding host-guest modes occurring in aqueous solution, highlighting a dramatic influence of the functional group R on the supramolecular properties of the POV (association constant K1:1 vary from 0 to 2 000 M-1 ) while isolated functional organic groups exhibit only very weak intrinsic affinity with CDs. Electrochemical and calorimetric investigations suggest that the driving force of the host-guest association involving larger CDs (β- and γ-CD) is mainly related to the chaotropic effect. In contrast, the hydrophobic effect supported by weak attractive forces appears as the main contributor for the formation of α-CD-containing host-guest complexes. In any cases, the origin of driving forces is clearly related to the ability of the macrocyclic host to desolvate the exposed moieties of the POVs.
Michael Andresini, Arianna Tota, Leonardo Degennaro, James A. Bull,
Published: 14 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102619

Abstract:
Recent years have seen a marked increase in the occurrence of sulfoximines in the chemical sciences, often presented as valuable motifs for medicinal chemistry. This has been prompted by both pioneering works taking sulfoximines containing compounds into clinical trials and the concurrent development of powerful synthetic methods. This review covers recent developments in the synthesis of sulfoximines concentrating on developments since 2015. This includes extensive developments in both S-N and S-C bond formations. Flow chemistry processes for sulfoximine synthesis are also covered. Finally, subsequent transformations of sulfoximines, particularly in N-functionalization are reviewed, including N–S, N–P, N–C bond forming processes and cyclization reactions.
, Sien Liu, Bangyue He, Hongyi Li, Xiaofeng Zhang, Yaping Shang
Published: 14 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102734

Abstract:
The Rh-catalyzed method for ortho-C(sp2)-H functionali-zation reaction of 8-aminoquinoline-derived benzamides with aliphatic acid fluorides in-situ generated from the corresponding acid has been developed. This reaction goes through 8-aminoquinoline-directed ortho-C(sp2)-H a cylation and concomitant intramolecular nucleophilic acyl substitution of amide group with newly installed enol moiety to produce alkylidene phthalides that are key structural components in a wide array of bioactive compounds and also versatile synthetic intermediates. This approach exhibits high stereo-selectivity for Z-isomers, and tolerates a variety of functional groups and aliphatic carboxylic acids with diverse structural scaffolds.
Bernhard S. Birenheide, Felix Krämer, Lea Bayer, Paul Mehlmann, ,
Published: 13 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103251

Abstract:
A retro-style arcade machine needs an oxidant or a proton to be inserted to start playing and to switch the donating capabilities of novel phosphine ligands orthogonally and reversibly. Rh-catalysed hydrosilylation showed that these triggers can influence either the rate of conversion and/or the product distribution. The Japanese kanji for “iron” highlights the ferrocene moiety in the ligands′ metal complexes. More information can be found in the Communication by F. Dielmann, F. Breher et al. (DOI: 10.1002/chem.202101969).
Magdalena Roth,
Published: 13 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102600

Abstract:
Fluorogenic hybridization probes allow the detection of RNA and DNA sequences in homogeneous solution. Typically, one target molecule activates the fluorescence of a single probe molecule. This limits the sensitivity of nucleic acid detection. Herein, we report a self-immolative molecular beacon (iMB) that escapes the one-target/one-probe paradigm. The iMB probe includes a photoreductively cleavable N-alkyl-picolinium (NAP) linkage within the loop region. A fluorophore at the 5’-end serves, on the one hand, as a reporter group and, on the other hand, as a photosensitizer of a NAP-linker cleavage reaction. In the absence of target, the iMB adopts a hairpin shape. Quencher groups prevent photo-induced cleavage. The iMB opens upon hybridization with a target, and both fluorescent emission as well as photo-reductive cleavage of the NAP linker can occur. In contrast to previous chemical amplification reactions, iMBs are unimolecular probes that undergo cleavage leading to products that have lower target affinity than the probes before reaction. Aided by catalysis, the method allowed the detection of 5 pm RNA target within 100 min.
Thorben Sieling, Thorben Petersen, Torben Alpers, Jens Christoffers, Thorsten Klüner,
Published: 12 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102346

Abstract:
Knowledge of the structure of the electrical double layer in ionic liquids is crucial for their applications in electrochemical technologies. We report the synthesis and applicability of an imidazolium-based amphiphilic ionic liquid with a perdeuterated alkyl chain for studies of electric potential-dependent rearrangements, and changes in the microenvironment in a monolayer on a Au(111) surface. Electrochemical measurements show two states of the organization of ions on the electrode surface. In situ IR spectroscopy shows that the alkyl chains in imidazolium cations change their orientation depending on the adsorption state. The methylene- d 2 stretching modes in the perdeuterated SAIL display a reversible, potential-dependent appearance of a new band. The presence of this mode also depends on the anion in the SAIL. Supported by quantum chemical calculations, this new mode is assigned to a second n as (CD 2 ) band in alkyl-chain fragments embedded in a polar environment of the anions/solvent present in the vicinity of the imidazolium cation and electrode. It is a measure of the potential-dependent segregation between polar and non-polar environments in the layers of a SAIL closest to the electrode.
, Diane Delbègue, Nicolas Louvain, Pierre-Emmanuel Lippens
Published: 10 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102470

Abstract:
The amount of silicon in anode materials for Li-ion batteries is still limited by the huge volume changes during charge-discharge cycles. Such changes lead to the loss of electrical contacts, as well as mechanical and surface electrolyte interphase (SEI) instabilities, strongly reducing the cycle life. Core-shell structures have attracted a vast research interest due to the possibility of modifying some properties with a judicious choice of the shell. It is, for example, possible to improve the electronic conductivity and ionic diffusion, or buffer volume variations. This review gives a comprehensive overview of the recent developments and the different strategies used for the design, synthesis and electrochemical performance of silicon-based core-shells. It is based on a selection of the main types of silicon coatings reported in the literature, including carbon, inorganic, organic and double-layer coatings, Finally, a summary of the advantages and drawbacks of these different types of core-shells as anode materials for Li-ion batteries and some insightful suggestions in regards to their use are provided.
Alexandra Mavridi Printezi, Arianna Menichetti, Moreno Guernelli,
Published: 10 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102479

Abstract:
Melanin-like nanomaterials have found application in a large variety of high economic and social impact fields as medicine, energy conversion and storage, photothermal catalysis and environmental remediation. These materials have been used mostly for their optical and electronic properties, but also for their high biocompatibility and simplicity and versatility of preparation. Beside this, their chemistry is complex and it yields structures with different molecular weight and composition ranging from oligomer, to polymer as well as nanoparticles (NP). The comprehension of the correlation of the different compositions and morphologies to the optical properties of melanin is still incomplete and challenging, even if it is fundamental also from technological point of view. In this minireview we focus on scientific papers, mostly recent ones, that indeed examine the link between composition and structural feature and photophysical and photochemical properties proposing this approach as a general one for future research.
, Yanxiong Liu, Baoru Wang, Longchun Bian, Yu Qin, Chunqiong Wang, Qiue Cao
Published: 10 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102631

Abstract:
The morphology of nanomaterials (geometric shape and dimension) play a significant role in its various physical and chemical properties. Thus, it is essential to link morphology with performance in specific applications. For this purpose, the morphology of copper metal-organic polyhedra (Cu-MOP) can be modulated through distinct assemble process, which facilitates the exploration of the relationship between morphology and catalytic performance. In this work, the assemblies of Cu-MOP with three different morphologies (nanorods, nanofibers and nanosheets) were facilely prepared by the variation of solvent mixture of N, N-dimethylformamide (DMF) and methanol, revealed the important role of the interaction between the surface group and the solvent on the morphology of these assemblies. Cu-MOP nanofibers exhibited the highest mimetic peroxidase enzyme activity over the Cu-MOP nanosheets and nanorods, which have been utilized in the detection of glucose. Cu-MOPs assemblies with tunable morphology accompanied with adjustable mimic peroxidase activity, had great potential applications in the field of bioanalytical chemistry and biomedicals.
Marta Meneghello, Christophe Léger,
Published: 10 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102702

Abstract:
Only two enzymes are capable of directly reducing CO2 : the CO dehydrogenase, which produces CO at a [NiFe4S4 ] active site, and the formate dehydrogenase, which produces formate at a W/Mo active site. Both metalloenzymes are very rapid, energy-efficient and specific in terms of product. They have been connected to electrodes with two different objectives. A series of studies used protein film electrochemistry to learn about different aspects of the reactivity of these enzymes (reactivity with substrates, inhibitors…). Another series focused on taking advantage of the catalytic performance of these enzymes to build biotechnological devices, from CO2-reducing electrodes to full photochemical devices performing artificial photosynthesis. Here, we review all these works.
Chengdong Wang, Yingjie Guo, , Zheng Wang, Kuiling Ding
Published: 10 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102847

Abstract:
An efficient nickel-catalyzed regioselective hydroarylation of 1,3-dienes with aryl halides and a silane has been developed, affording a range of allylic arenes in good to excellent yields under mild conditions. This method exhibits broad substrate scope, and excellent functional group tolerance. Late-stage modification of complex architectures was demonstrated.
Lei Kang,
Published: 10 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102597

Abstract:
Van der Waals (vdW) deep-UV (DUV) nonlinear optical (NLO) crystal is an important material system recently developed. Herein, we reviewed its concept and original intention, and then summarized the discovery process of related materials, including the role of A-site cations and the resulting two-/one-dimensional vdW DUV NLO systems. Finally, we evaluated the practical DUV NLO performance and prospected the opportunities and challenges.
Published: 9 September 2021
Chemistry – A European Journal, Volume 27; https://doi.org/10.1002/chem.202185162

Abstract:
Although the field of MOF-polymer hybrid membranes and their application in gas storage and separation, catalysis, sensing, etc. is evolving quickly, many opportunities and challenges remain. This minireview summarizes recent advances in the optimization of the hybrid membrane structure and looks at the expansion of applications: the homogeneity, compatibility and structure-performance relationship between MOF and polymer, and membranes with dynamic structures that could be modulated by external stimuli so as to play a role in smart devices. For more information, see the Minireview by B. Chen et al. on page ff12940.
Dmitriy M. Volochnyuk, Alina O. Gorlova,
Published: 9 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102108

Abstract:
A review with 349 references discussing recent advances in the chemistry of saturated boronic acids, boronates, and trifluoroborates. Applications of the title compounds in design of boron-containing drugs are surveyed, with special emphasis on a-amino boronic derivatives. A general overview of saturated boronic compounds as the modern tools to construct C( sp 3 )–C and C( sp 3 ) – heteroatom bonds is given, including recent developments in the Suzuki – Miyaura and Chan – Lam cross-couplings, single-electron transfer processes including metallo- and organocatalytic photoredox reactions, and transformations of boron ‘ate’ complexes. Finally, an attempt to summarize the current state-of-art in the synthesis of saturated boronic acids, boronates, and trifluoroborates is made, with brief mentioning of the ‘classical’ methods (transmetallation of organolithium/magnesium reagents with boron species, anti-Markovnikov hydroboration of alkenes, and modification of alkenyl boron compounds) and special focus on the recent methodologies (boronation of alkyl (pseudo)halides, derivatives of carboxylic acids, alcohols, and primary amines, boronative C–H activation, novel approaches to alkene hydro­boration, and 1,2-metallate-type rearrangements).
Jannik Reimler,
Published: 9 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102749

Abstract:
A method for the selective tryptophan modification and labelling of tryptophan-containing peptides is described. Photoirradiation of acylsilanes generates reactive siloxycarbenes which undergo H­–N-insertion into the indole moiety of tryptophan to give stable silyl protected hemiaminals. This method is successfully applied to chemically modify various tryptophan containing oligopeptides. The method enables the selective introduction of alkynes to peptides that are eligible for further alkyne-azide click chemistry. In addition, the dansyl fluorophore can be conjugated to a peptide using this approach.
Carlo Diaferia, Elisabetta Rosa, Nicole Balasco, Teresa Sibillano, Giancarlo Morelli, Cinzia Giannini, Luigi Vitagliano,
Published: 9 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102007

Abstract:
Peptide-based hydrogels, originated by multiscale self-assembling phenomenon, have been proposed as multivalent tools in different technological areas. Structural studies and molecular dynamics simulations pointed out the capability of completely aromatic peptides to gelificate if hydrophilic and hydrophobic forces are opportunely balanced. Here we evaluated the effect produced by the introduction of a Cys residue in the heteroaromatic sequence of (FY)3 and in its PEGylated variant. The physicochemical characterization indicates that both FYFCFYF and PEG8-FYFCFYF are able to self-assemble in supramolecular nanostructures whose basic cross-β motif resembles the one detected in the ancestor (FY)3 assemblies. However, gelification occurs only for FYFCFYF at a concentration of 1.5 wt%. After cross-linking of cysteine residues, the hydrogel undergoes to an improvement of the rigidity compared to the parent (FY)3 assemblies as suggested by the storage modulus (G’) that increases from 970 to 3360 Pa. The mechanical properties of FYFCFYF are compatible with its potential application in bone tissue regeneration. Moreover, the avalaibility of a Cys residue in the middle of the peptide sequence could allow the hydrogel derivatization with targeting moieties or with biologically relevant molecules.
Di Wang, Guang-Hui Chen, Lv-Bing Yuan, Cheng-Cheng Feng, Jian Zhang, Lei Zhang
Published: 9 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103226

Abstract:
In this work, we report the first examples of inorganic macrocyclic tin-oxo clusters which are stabilized by sulfate ligands. As determined by X-ray diffraction and photoelectron spectroscopy analyses, the prepared inorganic Sn10-oxo cluster displays interesting mixed valence behaviors, with 8 Sn4+ located at the cyclic skeleton and two Sn2+ encapsulated in the center. When further introducing Ti4+ and In3+ ions to the synthetic systems, heterometallic Sn2Ti6 and SnIn5Ti6 complexes with Ti6(SO4)9 and SnIn5(SO4)12 macrocyclic skeletons were prepared whose configuration and packing models were affected by the ionic radius of incorporated metals. Moreover, comparative CO2 reduction experiments confirm that such heterometallic composition can significantly improve the catalytic activities of these inorganic macrocyclic oxo clusters. This work represents a milestone in constructing inorganic tin complexes and also macrocyclic metal oxo clusters with tunable configurations and properties.
Leonhard Winter, Radha G. Bhuin, Florian Maier,
Published: 9 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102492

Abstract:
The interaction of molecules, especially hydrocarbons, at the gas/ionic liquid (IL) surface plays a crucial role in supported IL catalysis. The dynamics of this process is investigated by measuring the trapping probabilities of n- butane, iso- butane and 1‑butene on a set of frozen 1‑alkyl-3‑methylimidazolium-based ILs [C n C 1 Im]X, where n = 4, 8 and X - = Cl - , Br - , [PF 6 ] - and [Tf 2 N] - . The decrease of the initial trapping probability with increasing surface temperature is used to determine the desorption energy of the hydrocarbons at the IL surfaces. It increases with increasing alkyl chain length n and decreasing anion size for the ILs studied. We attribute these effects to different degrees of alkyl chain surface enrichment, while interactions between the adsorbate and the anion do not play a significant role. The adsorption energy also depends on the adsorbing molecule: It decreases in the order n -butane > 1‑butene > iso- butane, which can be explained by different dispersion interactions.
Qian Liang, Haifeng Yue, Weishan Zhou, Qiang Wei, Qiang Ru, Yuan Huang, Hongtao Lou, Fuming Chen, Xianhua Hou
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102015

Abstract:
The large number of lithium batteries have been retiring from the market of energy storage. Thus, the recycling of the used electrode materials is becoming urgent. In this study, the industrial machinery processing was used to recover the crystal structure of the waste LiCoO 2 materials with the combination of small-scale equipment repair technology. The results show that the crystal parameters of the repaired LiCoO 2 material become small, the unit cell volume is reduced, and the crystal structure tends to be stable. The Co-O bond length of 1.9134 nm, O-Co-O bond angle of 94.72º, the (003) interplanar spacing of 0.467 nm indicate the excellent recovery level of the repaired LiCoO 2 . In addition, the electrochemical performance of the repaired LiCoO 2 material is greatly improved, compared with the waste material. The capacity of the repaired electrode material can be maintained at 120 mAh g -1 after 100 cycles at the current density of 0.2 C. The promising rate performance of the repaired electrode material demonstrates the stable structure. This research work provides a large-scale method for the direct recovery of LiCoO 2 with the reduction of unnecessary energy and reagent consumption, which will be beneficial to the environmental protection.
Jia-Chang Zhuang, Wen-Juan Wei, , Ning Song, Yun-Zhi Tang, Ding-Chong Han, Yu-Kong Li
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102550

Abstract:
The multifunctional two-dimensional (2D) organic-inorganic hybrid perovskites have potential applications in many fields, such as, semiconductor, energy storage and fluorescent device etc. Here, a 2D Ruddlesden-Popper (RP) perovskite (IPA) 2 (FA)Pb 2 I 7 ( 1 , IPA + = C 3 H 9 NI + , FA + = CN 2 H 5 + ) is determined for its photophysical properties. Strikingly, 1 reveals a solid reversible phase transition with T c of 382 K accompanied by giant entropy change of 40 J·mol -1 ·K -1 . Further optical investigations indicate that 1 reveals a narrow direct bandgap (2.024 eV) attributed to the slight bending of I-Pb-I edge and inorganic [Pb 2 I 7 ] n layer and a superior photoluminescence (PL) emission with super long lifetime of 0.1607 ms. It is believed that this work will pave an avenue to further design multifunctional semiconductors that combines energy storage and photoelectric etc.
Jingfang Zhou,
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102533

Abstract:
Herein, we report a detailed structural, electric, thermal and optical analysis of a titanium and tantalum phosphate LiNaTiTa 2 P 2 O 13 . The title compound is comprised of typical ReO 3 -type layers constituted by corner-sharing TiO 6 and TaO 6 octahedra, bridged by PO 4 tetrahedra, which is closely related to monophosphate niobium bronzes. The existence of pentagonal tunnels, hosting the Li + and Na + ions, endow LiNaTiTa 2 P 2 O 13 a moderate ion transportation behavior (4.67×10 -4 S/cm at 823 K). In addition, the successful substitution of Nb for Ta in LiNaTiTa 2 P 2 O 13 results in the optical absorption red-shift towards visible range with a narrowing band gap, which may provide a route of isomorphic replacement to band engineering for photo-catalysis.
, Leo D. M. Nicholls
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103197

Abstract:
The combination of a peptide catalyst and a gold catalyst is presented for enantioselective addition reactions between allenamides and branched aldehydes. The two catalysts act in concert to provide γ,δ-enamide aldehydes bearing a fully substituted, benzylic stereogenic center – a structural motif common in many natural products and therapeutically active compounds – with good yields and enantioselectivities. The reaction tolerates a variety of alkyl and alkoxy aldehydes and the products can be elaborated into several chiral building blocks bearing either 1,4- or 1,5- functional group relationships. Mechanistic studies showed that the conformational features of the peptide are important for both the catalytic efficiency and stereochemistry, while a fine balance of acid/base additives is key for ensuring formation of the desired product over undesired side reactions.
Krishnamoorthy Sathiyan, Ronen Bar-Ziv, Vered Marks, Dan Meyerstein,
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103040

Abstract:
Photocatalytic hydrogen production is proposed as a sustainable energy source. Simultaneous reduction and oxidation of water is a complex multistep reaction with high overpotential. Photocatalytic processes involving semiconductors transfer electrons from the conduction band to the valence band. Sacrificial substrates that react with the photochemically formed holes in the conduction band are often used to study the mechanism of H2 production, as they scavenge the holes and hinder the charge carrier recombination. The desired sacrificial agent is one forming a radical that is a fairly strong reducing agent, and that its oxidized form is not a good electron acceptor that might suppress the hydrogen evolution reaction (HER). In an acidic medium, methanol was found better to fulfill both these requirements than ethanol and 2-propanol in the TiO2 -(M0 -NPs) (M = Au or Pt) system, while in an alkaline medium, the alcohols exhibit a reverse order of activity. Moreover, we report that CH2(OH)2 is by far the most efficient sacrificial agent in a non-trivial mechanism in acidic media. Our study provides general guidelines for choosing an appropriate sacrificial substrate and helps to explain the variance in the performance of alcohol scavengers-based photocatalytic systems.
Achim Füngerlings, Adarsh Koul, Maik Dreyer, Anna Rabe, Dulce M. Morales, Wolfgang Schuhmann, Malte Behrens,
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102829

Abstract:
In a combined experimental and theoretical study we assess the role of Co incorporation on the OER activity of LaCo x Fe 1− x O 3 . Phase pure perovskites were synthesized up to x = 0.300 in 0.025/0.050 steps. HAADF STEM and EDX analysis points towards FeO2 -terminated (001)-facets of LaFeO3, in accordance with the stability diagram obtained from density functional theory calculations with a Hubbard U term (DFT+ U ). Linear sweep voltammetry shows a reduction of the OER overpotential and a nonmonotonic trend wtih x , with double layer capacitance measurements indicating an intrinsic nature of activity. This is supported by DFT+ U results that show reduced overpotentials for both Fe and and Co reaction sites with the latter reaching values of 0.32-0.40 V, ~0.3 V lower than for Fe. This correlates with a stronger reduction of the binding energy difference of the *O and *OH intermediates towards an optimum value of 1.6 eV for x =0.25, the OH deprotonation being the potential limiting step in most cases. Significant variations of the magnetic moments of both surface and subsurface Co and Fe during the OER demonstrate that the beneficial effect is a result of a concerted action involving many surrounding ions, which extends the concept of the active site.
Martin Hejda, Daniel Duvinage, Enno Lork, Antonín Lyčka, Zdeněk Černošek, Jan Macháček, Sergey Makarov, Sergey Ketkov, Stefan Mebs, Libor Dostál, et al.
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103181

Abstract:
The aryltellurenyl cation [2-(tBuNCH)C6H4Te]+, a Lewis super acid, and the weakly coordinating carborane anion [CB11H12]–, an extremely weak Brønsted acid (pKa = 131.0 in MeCN), form an isolable ion pair complex [2-(tBuNCH)C6H4Te][CB11H12], in which the Brønsted acidity (pKa 7.4 in MeCN) of the formally hydridic B-H bonds is dramatically increased by more than 120 orders of magnitude. The electrophilic activation of B-H bonds in the carborane moiety gives rise to a proton transfer from boron to nitrogen at slightly elevated temperatures, as rationalized by the isolation of a mixture of the zwitterionic isomers 12- and 7-[2-(tBuN{H}CH)C6H4Te(CB11H11)] in ratios ranging from 62:38 to 80:20.
Luis M. Mateo, Luca Sagresti, Yusen Luo, Dirk M. Guldi, Tomas Torres, Giuseppe Brancato,
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103079

Abstract:
Tetracyanobuta-1,3-diene (TCBD) is a powerful and versatile electron-acceptor moiety widely used for the preparation of electroactive conjugates. While many reports addressing its electron-accepting capability have appeared in the literature, significantly scarcer are those dealing with its chemical modification, a relevant topic which allows to broaden the chemical space of this interesting functional unit. Here, we report on the first example of a high-yielding cyano-Diels-Alder (CDA) reaction between TCBD (i.e., where a nitrile group acts as a dienophile) and an anthryl moiety (i.e., acting as a diene). The resulting anthryl-fused−TCBD derivative, which structure was unambiguously identified by X-ray diffraction, shows high thermal stability, remarkable electron-accepting capability, and interesting electronic ground- and excited-state features, as characterized by a thorough theoretical, electrochemical and photophysical investigation. Moreover, a detailed kinetic analysis of the intramolecular CDA reaction transforming the anthryl−TCBD-based reactant into the anthryl-fused−TCBD product was carried out at different temperatures.
Clemence Bonnefoy, Emmanuel Chefdeville, Armen Pannosian, Gilles Hanquet, Frédéric R Leroux, Fabien Toulgoat,
Published: 8 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102809

Abstract:
Despite recent advances, trifluoromethoxylation remains a challenging reaction. Here we describe an efficient trifluoromethoxylative substitution, using an inexpensive and easy-to-handle reagent. By mixing DMAP with a slight excess of 1,4-dinitro-trifluoromethoxybenzene (DNTFB), a stable solution of trifluoromethoxide anion is obtained and can be used to perform a SN2 reaction without any silver additives. A precise study of the properties and behavior of this unusual stable solution of CF3O- species is also performed.
Martin Börner, Jennifer Klose, Matias Gutierrez Suburu, Cristian Strassert, Fangshun Yang, Kirill Monakhov, Bernd Abel,
Published: 7 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102079

Abstract:
The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed-ligand [Cr III 2 L(O 2 CR)] 3+ complexes (R = CH 3 ( 1 ), Ph ( 2 )) of a 24-membered binucleating hexa-aza-dithiophenolate macrocycle (L) 2− are presented. X-ray crystallographic analysis reveals an edge-sharing bioctahedral N 3 Cr( μ -SR) 2 ( μ 1,3 -O 2 CR)CrN 3 core structure with μ 1,3 -bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr 3+ ions leads to a high-spin ( S = 3) ground state. The coupling constants ( J = +24.2(1) cm −1 ( 1 ), +34.8(4) cm −1 ( 2 ), H = −2 J S 1 S 2 ) are significantly larger than in related bis - μ -alkoxido- μ -carboxylato structures. DFT calculations performed on both complexes reproduce both the sign and strength of the exchange interactions found experimentally. Frozen methanol-dichloromethane 1:1 solutions of 1 and 2 luminesce at 750 nm when excited into the 4 LMCT state on the 4 A 2 → 2 T 1 (ν 2 ) bands (λ exc = 405 nm). The absolute quantum yields ( Φ L ) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH 2 Cl 2 glasses, Φ L = 0.44±0.02% (for 1 ), Φ L = 0.45±0.02% (for 2 ).
, Yohan Gisbert, Seifallah Abid, Claire Kammerer
Published: 7 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103126

Abstract:
We report the synthesis of conceptually new prototypes of molecular winches with the ultimate aim to investigate the work performed by a single ruthenium-based molecular motor anchored on a surface by probing its ability to pull a load upon electrically-driven directional rotation. According to a technomimetic design, the motor was embedded in a winch structure, with a long flexible polyethylene glycol chain terminated by an azide hook to connect a variety of molecular loads. The structure of the motor was first derivatized by means of two sequential cross-coupling reactions involving a penta(4-halogenophenyl)cyclopentadienyl hydrotris(indazolyl)borate ruthenium(II) precursor and the resulting benzylamine derivative was next exploited as key intermediate in the divergent synthesis of a family of nanowinch prototypes. A one-pot method involving sequential peptide coupling and Cu-catalyzed azide-alkyne cycloaddition was developed to yield four loaded nanowinches, with load fragments encompassing triptycene, fullerene and porphyrin moieties.
Genesis Infante,
Published: 7 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103106

Abstract:
Sequential anionic intramolecular cyclizations and modelling were used for the first time to access unusual fused heterocyclic frameworks in excellent yields. 5- Exo - dig cyclizations yielded isoindolinone motifs and a subsequent 6- exo - and 7- endo - dig cyclization was directed to provide either fused isoquinoline- or azepine- frameworks. Regioselectivities were controlled by exploiting stereoelectronic effects via n C - → π* (Ph)­ interactions, and modelling studies provided reaction scope.
Ming Cui,
Published: 7 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102993

Abstract:
A copper-catalyzed conjugate silylation of various cyclobutenone derivatives with Me 2 PhSiZnCl·2LiCl or (Me 2 PhSi) 2 Zn· x LiCl ( x ≤ 4) to generate β-silylated cyclobutanones is reported. Trapping the intermediate enolate with ClP(O)(OPh) 2 affords silylated enol phosphates that can be further engaged in Kumada cross-coupling reactions to yield silylated cyclobutene derivatives.
, Alejandro Portugués, Delia Bautista
Published: 7 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103153

Abstract:
New dinuclear Au(I), Au(II) and Au(III) complexes containing (CF 2 ) n bridging chains were obtained. Metallomacrocycles [Au 2 {μ-(CF 2 ) 4 }{μ-diphosphine}] show an uncommon figure-eight structure, whose helicity inversion barrier is influenced by aurophilic interactions and steric constraints imposed by the diphosphine. Halogenation of LAu(CF 2 ) 4 AuL (L = PPh 3 , PMe 3 , (dppf) 1/2 , (binap) 1/2 ) gave [Au(II)] 2 species, some of which display unprecedented folded structures with Au–Au bonds. Aurophilic interactions facilitate this oxidation process by preorganizing the starting [Au(I)] 2 complexes and lowering its redox potential. The obtained [Au(II)] 2 complexes undergo thermal or photochemical elimination of R 3 PAuX to give Au(III) perfluorinated auracycles. Evidence of a radical mechanism for these decomposition reactions was obtained.
Aurore Fraix, Cristina Parisi, Mimimorena Seggio,
Published: 6 September 2021
Chemistry – A European Journal, Volume 27; https://doi.org/10.1002/chem.202185061

Abstract:
Given the role of nitric oxide in human physiology and pathophysiology, its controlled delivery has therapeutic applications. Site- and dosage-controlled release of this free radical from caging compounds by light activation can determine its biological effects. NO release with concomitant fluorescence allows easy, real-time tracking of NO in a non-invasive fashion even in cells. For more details, see the Review by S. Sortino et al. on page 12714 ff.
Diana Müller, , Deepanjan Panda, ,
Published: 6 September 2021
Chemistry – A European Journal, Volume 27; https://doi.org/10.1002/chem.202185062

Abstract:
This Minireview provides a survey of carbazole-based ligands targeting G-quadruplexes. Thereby, a focus on solution NMR interaction studies has been made. Further, results of biophysical experiments such as cytotoxicity assays and fluorescent microscopy imaging are discussed. The obtained detailed insights in binding sites, binding modes and the correlation of structure and function may be useful for improving the ligands properties for application in cancer therapy, biomedical technology, and nanotechnology. For more information, see the Minireview by J. Dash, H. Schwalbe et al. on page 12726.
Hamidreza Arandiyan, Sajjad S. Mofarah, Yuan Wang, Claudio Cazorla, Deshetti Jampaiah, Magnus Garbrecht, Karen Wilson, Adam F. Lee, Chuan Zhao,
Published: 6 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102672

Abstract:
Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost-effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influences their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO 3 perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO 3 induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO 3 ; the former exhibit a low onset overpotential of 380 mV at 10 mA.cm -2 and a small Tafel slope of 70.8 mV.dec -1 . Oxygen vacancy formation is accompanied by mixed Ni 2+ /Ni 3+ valence states, which quantum-chemical DFT calculations reveal modify the perovskite electronic structure. Surface oxygen vacancy formation is relatively facile, and favoured over lattice vacancy formation, and increases the electronic conductivity of reduced LaNiO 3 , in accordance with the enhanced OER activity observed.
Fabrizio Creazzo,
Published: 6 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102356

Abstract:
Notwithstanding RuO 2 is one of the most active catalysts toward oxygen evolution reaction (OER), a plethora of fundamental details on its catalytic properties are still elusive, severely limiting its large-scale deployment. Herein, spin-polarized Density Functional Theory Molecular Dynamics (DFT-MD) simulations, coupled with advanced enhanced sampling methods in the well-tempered metadynamics framework, are applied to gain a global understanding of RuO 2 aqueous interface (explicit water solvent) in catalyzing the OER, and hence possibly help in the design of novel catalysts in the context of photochemical water oxidation. The present study quantitatively assesses the free-energy barriers behind the OER at the (110)-RuO 2 catalyst surface revealing plausible pathways composing the reaction network of the O 2 evolution. In particular, OER is investigated at room temperature when such a surface is exposed to both gas-phase and liquid-phase water. Albeit a unique efficient pathway has been identified in the gas-phase OER, a surprisingly lowest-free-energy-requiring reaction route is possible when (110)-RuO 2 is in contact with explicit liquid water. By estimating the free-energy surfaces associated to these processes, we reveal a water-assisted OER mechanism which involves a crucial proton-transfer-step assisted by the local water environment. These findings pave the way toward the systematic usage of those techniques for the fine assessment of the activity of catalysts, considering finite-temperature and explicit-solvent effects.
, Joshua Clark, Rifahath M. Neyyappadath, Cihang Yu, Alexandra M. Z. Slawin, David B. Cordes
Published: 6 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102819

Abstract:
Monoalkylated derivatives of the unusually polar all- cis 2,3,4,5,6- pentafluorocyclohexyl (Janus face) motif are prepared starting from an aryl hydrogenation of 2,3,4,5,6- pentafluorophenylacetate methyl ester 15 . The method used Zeng’s Rh(CAAC) carbene catalyst 4 in the hydrogenation following the protocol developed by Glorius. The resultant Janus pentafluorocyclohexylacetate methyl ester 16 was converted to the corresponding alcohol 18 , aldehyde 13 , bromide 29 and azide 14 through functional group manipulations, and some of these building blocks were used in Ugi-multicomponent and Cu-catalysed click reactions. NBoc protected pentafluoroarylphenylalanine methyl ester 35 was also subject to an aryl hydrogenation, and then deprotection to generate the Janus face β-pentafluorocyclohexyl-alanine amino acid 15 , which was incorporated into representative members of an emerging class of candidate antiviral compounds. Log P measurements demonstrate that the all- cis 2,3,4,5,6-pentafluorocyclohexyl ring system is more polar than a phenyl ring. In overview the paper introduces new building blocks containing this Janus ring and demonstrates their progression to molecules typically used in bioactives discovery programmes.
Xander Schaapkens, Roy N. van Sluis, Eduard O. Bobylev, ,
Published: 6 September 2021
Chemistry - A European Journal; https://doi.org/10.1002/chem.202102176

Abstract:
The sialic acid N-acetylneuraminic acid (Neu5Ac) and its derivatives are involved in many biological processes including cell-cell recognition and infection by influenza. Molecules that can recognize Neu5Ac might thus be exploited to intervene in or monitor such events. A key obstacle in this development is the sparse availability of easily prepared molecules that bind to this carbohydrate in its natural solvent; water. Here, we report that the carbohydrate binding pocket of an organic soluble [Pd2L4]4+ cage could be equipped with guanidinium-terminating dendrons to give the water soluble [Pd2L4][NO3]16 cage 7. It was shown by means of NMR spectroscopy that 7 binds selectively to anionic monosaccharides and strongest to Neu5Ac with Ka=24 M−1. The cage had low to no affinity for the thirteen neutral saccharides studied. Aided by molecular modeling, the selectivity for anionic carbohydrates such as Neu5Ac could be rationalized by the presence of charge assisted hydrogen bonds and/or the presence of a salt bridge with a guanidinium solubilizing arm of 7. Establishing that a simple coordination cage such as 7 can already selectively bind to Neu5Ac in water paves the way to improve the stability, affinity and/or selectivity properties of M2L4 cages for carbohydrates and other small molecules.
Published: 6 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102483

Abstract:
Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydro-genation process, involving several electron transfer steps, is inspi-re-d by oxidations occurring in the respiratory chain. An environmen-tally friendly and inexpensive iron catalyst together with a hydro-quinone/cobalt Schiff base hybrid catalyst as electron transfer medi-ator were used for the substrate-selective dehydrogenation reaction of various N -heterocycles. The method shows a broad substrate scope and de-livers important heterocycles in good to excellent yields.
, Marc Sallé, Olivier Siri, Simon Pascal, Maksym Dekhtiarenko, Mourad Elhabiri, Valérie Mazan, David Canevet, Magali Allain, Vincent Carré, et al.
Published: 3 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202103039

Abstract:
The development of methodologies to control on demand and reversibly supramolecular transformations from self-assembled metalla-structures requires the rational design of architectures able to answer to an applied stimulus. While solvent, concentration, guest, light, addition of a chemical have been largely explored to provide these transformations, the case of pH sensitive materials is less described. Herein, we report the first example of a pH-triggered dissociation of a coordination-driven self-assembled interlocked molecular link. It incorporates a pH sensitive benzobisimidazole-based ligand that can be selectively protonated on its bisimidazole moieties. This generates intermolecular electrostatic repulsions that reduces drastically the stability of the interlocked structure, leading to its dissociation without any sign of protonation of the basic pyridine moieties involved in the coordination bonds. Importantly, the dissociation process is reversible through addition of a base.
, Nicolas Mézailles, Nathalie Saffon-Merceron, Luca Demonti
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102836

Abstract:
In ample variety of transformations, the presence of silver as an additive or co-catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross-coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2 e – redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through Ag I /Ag III redox catalysis ( i.e. CEL coupling), namely: i ) easy Ag I /Ag III 2 e – oxidation mediated by air; ii ) bpy/phen ligation to Ag III ; iii ) boron-to-Ag III aryl transfer; and iv ) ulterior reductive elimination of benzotrifluorides from an [aryl−Ag III −CF 3 ] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K] + [Ag III (CF 3 ) 4 ] – ( K-1 ), [(bpy)Ag III (CF 3 ) 3 ] ( 2 ) and [(phen)Ag III (CF 3 ) 3 ] ( 3 ), is described. The utility of 3 in cross-coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [Ag III (aryl)(CF 3 ) 3 ] – intermediates. This work breaks with old stereotypes and misconceptions regarding the disability of Ag to undergo cross-coupling by itself.
, Keiji Nishikawa, Yuka Ito, Keiji Murayama, Ichiyo Hayashi, Takahiro Kakuta, Tomoki Ogoshi, Hiroyuki Asanuma
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102333

Abstract:
We herein report a circularly polarized luminescent (CPL) probe that can respond to chirality of nucleic acids. An achiral nanostructure was prepared by hybridization of symmetric serinol nucleic acid (SNA) containing pyrene-modified residues. When chiral oligomers were added that were complementary to the SNA, they induced helicity into the SNA nanowire. Efficient circular dichroism (CD) signal amplification was observed when pyrene was attached to uracil base through a rigid alkynyl linker. Both CPL signals and CD signals were observed that depended on the chirality of added acyclic threoninol nucleic acid ( a TNA) oligomer. This system can be used to convert chirality of chiral biomolecules into chiroptical signals.
Yikang Cong, Shengsheng Huang, Yan Mei,
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102209

Abstract:
Electrocatalytic water splitting has been considered as a promising strategy for the sustainable evolution of hydrogen energy and storage of intermittent electric energy. Efficient catalysts for electrocatalytic water splitting are urgently demanded to decrease the overpotentials and promote the sluggish reaction kinetics. Carbon-based composites, including heteroatom-doped carbon materials, metals/[email protected] composites, metal [email protected] composites, and atomically dispersed metal [email protected] composites have been widely used as the catalysts due to their fascinating properties. However, these electrocatalysts are almost powdery form, and should be cast on the current collector by using the polymeric binder, which would result in the unsatisfied electrocatalytic performance. In comparison, a self-supported electrode architecture is highly attractive. Recently, self-supported metal-organic frameworks (MOFs) constructed by coordination of metal centers and organic ligands have been considered as suitable templates/precursors to construct free-standing carbon-based composites grown on conductive substrate. MOFs-derived carbon-based composites have various merits, such as the well-aligned array architecture and evenly distributed active sites, and easy functionalization with other species, which make them suitable alternatives to non-noble metal-included electrocatalysts. In this review, we intend to show the research progresses by employment of MOFs as precursors to prepare self-supported carbon-based composites. Focusing on these MOFs-derived carbon-based nanomaterials, the latest advances in their controllable synthesis, composition regulation, electrocatalytic performances in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting (OWS) are presented. Finally, the challenges and perspectives are showed for the further developments of MOFs-derived self-supported carbon-based nanomaterials in electrocatalytic reactions.
Jongguk Kim, Ze Zhang, Jingyu Sun, Shudi Mo, Unhyok Yun, Huigwang Yun,
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102268

Abstract:
Today, the threat of pathogenic bacterial infection worldwide that leads to the increase of mortality rate strongly demands the development of new antibacterial agents that can kill bacteria quickly and effectively. Although there are a lot of antibacterial agents that have been developed so far, few studies on the antibacterial ability of SnS have been investigated at 808 nm laser. Here, we synthesized SnS nanosheets with strong near-infrared absorption performance and excellent antibacterial performance via a simple hydrothermal synthesis route. The as-prepared SnS nanosheets showed excellent photothermal conversion efficiency (38.7%), photodynamic performance, and photostability, and at the same time 99.98% and 99.7% sterilization effect against Gram-negative Escherichia coli ( E. coli ) and Gram-positive Bacillus subtilis ( B. subtilis ) under near-infrared irradiation (808 nm, 1.5 W / cm 2 ). This study suggests that SnS nanosheets could be a promising candidate for antibacterial therapy owing to the synergetic effects of photothermal and photodynamic performance..
, Anthony J. Fernandes, Frederic Robert, Sandra Künzler, Thomas Müller
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102614

Abstract:
The structure determination of a series of biphenylsilyloxonium cations through NMR and XRD studies, supported by DFT calculations was carried out, allowing to get insights into the origin of the oxygen pyramidalization in biphenyl and binaphthylsilyl oxoniums. Low barrier of inversion in the oxygenyl series points toward a key role of the biaryl axis in the inversion of configuration at the oxygen center.
, Alireza Ariafard, Gerard van Koten
Published: 2 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202102687

Abstract:
Density functional theory computation indicates that bridge-splitting of [Pt II R 2 (μ-SEt 2 )] 2 proceeds via partial dissociation to form R 2 Pt a (μ-SEt 2 )Pt b R 2 (SEt 2 ), followed by coordination of N-donor bromoarenes (L-Br) at Pt a leading to release of Pt b R 2 (SEt 2 ), which reacts with a second molecule of L-Br, providing two molecules of PtR 2 (SEt 2 )(L-Br- N ). For R = 4-tolyl (Tol), L-Br = 2,6-(pzCH 2 ) 2 C 6 H 3 Br (pz = pyrazol-1-yl) and 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 Br, subsequent oxidative addition assisted by intramolecular N-donor coordination via Pt II Tol 2 (L- N,Br ), and reductive elimination from Pt IV intermediates, gives mer -Pt II (L- N,C,N )Br and Tol 2 . The strong σ-donor influence of Tol groups results in subtle differences in oxidative addition mechanisms when compared with related aryl halide oxidative addition to palladium(II) centres. For R = Me and L-Br = 2,6-(pzCH 2 ) 2 C 6 H 3 Br, a stable Pt IV product, fac -Pt IV Me 2 {2,6-(pzCH 2 ) 2 C 6 H 3 - N,C,N )Br is predicted, as reported experimentally, acting as a model for undetected and unstable Pt IV Tol 2 {L- N,C,N }Br undergoing facile Tol 2 reductive elimination. The mechanisms reported herein enable the synthesis of Pt II pincer reagents with applications in materials and bio-organometallic chemistry.
, Volodymyr Gvozdetskyi, Renhai Wang, Weiyi Xia, Feng Zhang, Zijing Lin, Kai-Ming Ho, Gordon Miller
Published: 1 September 2021
Chemistry – A European Journal; https://doi.org/10.1002/chem.202101948

Abstract:
Here we demonstrate the combination of theoretical computations followed by rapid experimental screening and in-situ diffraction studies as a powerful strategy for novel compounds discovery. When applied for the previously “empty” Na-Zn-Bi system, such an approach led to 4 novel phases. The compositional space of this system was rapidly screened via the hydride route method and the theoretically predicted NaZnBi (PbClF type, P4/nmm) and Na11Zn2Bi5 (Na11Cd2Sb5 type, P-1) phases were successfully synthesized, while other computationally generated compounds on the list were rejected. In addition, single crystal X-ray diffraction studies of NaZnBi indicate minor deviations from the stoichiometric 1:1:1 molar ratio. As a result, two isostructural (PbClF type, P4/nmm) Zn-deficient phases with similar compositions, but distinctly different unit cell parameters were discovered. The vacancies on Zn sites and unit cell expansion were rationalized from bonding analysis using electronic structure calculations on stoichiometric “NaZnBi”. In-situ synchrotron powder X-ray diffraction studies shed light on complex equilibria in the Na-Zn-Bi system at elevated temperatures. In particular, the high-temperature polymorph HT-Na3Bi (BiF3 type, Fm-3m) was obtained as a product of Na11Zn2Bi5 decomposition above 611 K. HT-Na3Bi cannot be stabilized at room temperature by quenching, and this type of structure was earlier observed in the high-pressure polymorph HP-Na3Bi above 0.5 GPa. The aforementioned approach of predictive synthesis can be extended to other multinary systems.
Víctor Laina‐Martín, ,
Published: 1 September 2021
Chemistry – A European Journal, Volume 27; https://doi.org/10.1002/chem.202184962

Abstract:
Inverse-electron-demand hetero-Diels-Alder reactions have been an important breakthrough for the synthesis of heterocyclic compounds. Among all their variants, the organocatalytic enantioselective version has been widely explored since the asymmetric construction of diversely functionalized scaffolds under reaction conditions encompassed within the green chemistry field is of great interest. A profound revision on the latest advances on the organocatalytic asymmetric inverse-electron demand hetero-Diels-Alder reaction is shown, showing in detail the mode of action of the organocatalysts. For more information, see the Minireview by J. Alemán et al. on page 12509.
Karunanidhi Murali, Luana A. Machado, Renato L. Carvalho, Dr. Leandro F. Pedrosa, Rishav Mukherjee, ,
Published: 1 September 2021
Chemistry – A European Journal, Volume 27; https://doi.org/10.1002/chem.202184961

Abstract:
Directing groups play an important role in synthetic chemistry, especially with regard to C−H bond activation. Synthetic routes for the successful synthesis and incorporation of directing groups which are frequently used in different C−H activation methodologies together with a discussion of advantages and disadvantages of different types of directing groups are provided in the Review article by E. N. Da Silva Júnior, D. Maiti et al on page 12453 ff.
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