Creating Pyrethrin Mimetic Phosphonates as Chemical Genetics Tools Targeting the GDSL Esterase/Lipase TcGLIP to Investigate Pyrethrin Biosynthesis.

Pyrethrins from Tanacetum cinerariifolium are natural pesticides that exhibit high knockdown and killing activities against flying insects such as disease-spreading mosquitoes. Despite the increasing demand for pyrethrins, the mechanism of pyrethrin biosynthesis remains elusive. To elucidate it, we for the first time created pyrethrin mimetic phosphonates targeting the GDSL esterase/lipase (GELP or TcGLIP) underpinning pyrethrin biosynthesis. The compounds were synthesized by reacting mono-alkyl or mono-benzyl-substituted phosphonic dichloride with pyrethrolone, the alcohol moiety of pyrethrin I and II, and then p-nitrophenol. n-Pentyl (C5) and n-octyl (C8)-substituted compounds were the most potent of the (S)p,(S)c, and (R)p,(S)c diastereomers, respectively. The (S)-pyrethrolonyl group is more effective than the (R)-pyrethrolonyl group in blocking TcGLIP, consistent with the features predicted by TcGLIP models complexed with the (S)p,(S)c-C5 and (R)p,(S)c-C8 probes. The (S)p,(S)c-C5 compound suppressed pyrethrin production in T. cinerariifolium, demonstrating potential as a chemical tool for unravelling pyrethrin biosynthesis.

Tin(II)-Based Metal-Organic Frameworks Enabling Efficient, Selective Reduction of CO2 to Formate under Visible Light.

Certain metal complexes are known as high-performance CO2 reduction photocatalysts driven by visible light. However, most of them rely on rare, precious metals as principal components, and integrating the functions of light absorption and catalysis into a single molecular unit based on abundant metals remains a challenge. Metal-organic frameworks (MOFs), which can be regarded as intermediate compounds between molecules and inorganic solids, are potential platforms for the construction of a simple photocatalytic system composed only of Earth-abundant nontoxic elements. In this work, we report that a tin-based MOF enables the conversion of CO2 into formic acid with a record high apparent quantum yield (9.8 % at 400 nm) and >99 % selectivity without the need for any additional photosensitizer or catalyst. This work highlights a new MOF with strong potential for photocatalytic CO2 reduction driven by solar energy.

Supramolecular multi-electron redox photosensitisers comprising a ring-shaped Re(i) tetranuclear complex and a polyoxometalate.

Redox photosensitisers (PSs) play essential roles in various photocatalytic reactions. Herein, we synthesised new redox PSs of 1 : 1 supramolecules that comprise a ring-shaped Re(i) tetranuclear complex with 4+ charges and a Keggin-type heteropolyoxometalate with 4- charges. These PSs photochemically accumulate multi-electrons in one molecule (three or four electrons) in the presence of an electron donor and can supply electrons with different reduction potentials. PSs were successfully applied in the photocatalytic reduction of CO2 using catalysts (Ru(ii) and Re(i) complexes) and triethanolamine as a reductant. In photocatalytic reactions, these supramolecular PSs supply a different number of electrons to the catalyst depending on the redox potential of the intermediate, which is made from the one-electron-reduced species of the catalyst and CO2. Based on these data, information on the reduction potentials of the intermediates was obtained.

Layered ß-ZrNBr Nitro-Halide as Multifunctional Photocatalyst for Water Splitting and CO2 Reduction.

Developing mixed-anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide-based photocatalyst is still in shortage. Here we report a layered nitro-halide ß-ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO2 reduction under visible-light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro-halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of ß-ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro-halide, which opens a new avenue for fabricating efficient artificial photosynthesis.

Alumina-Supported Alpha-Iron(III) Oxyhydroxide as a Recyclable Solid Catalyst for CO2 Photoreduction under Visible Light.

Photocatalytic conversion of CO2 into transportable fuels such as formic acid (HCOOH) under sunlight is an attractive solution to the shortage of energy and carbon resources as well as to the increase in Earth's atmospheric CO2 concentration. The use of abundant elements as the components of a photocatalytic CO2 reduction system is important, and a solid catalyst that is active, recyclable, nontoxic, and inexpensive is strongly demanded. Here, we show that a widespread soil mineral, alpha-iron(III) oxyhydroxide (α-FeOOH; goethite), loaded onto an Al2 O3 support, functions as a recyclable catalyst for a photocatalytic CO2 reduction system under visible light (λ>400 nm) in the presence of a RuII photosensitizer and an electron donor. This system gave HCOOH as the main product with 80-90 % selectivity and an apparent quantum yield of 4.3 % at 460 nm, as confirmed by isotope tracer experiments with 13 CO2 . The present work shows that the use of a proper support material is another method of catalyst activation toward the selective reduction of CO2 .

Failure-Experiment-Supported Optimization of Poorly Reproducible Synthetic Conditions for Novel Lanthanide Metal-Organic Frameworks with Two-Dimensional Secondary Building Units.

Invited for the cover of this issue are Daisuke Tanaka at Kwansei Gakuin University and co-workers at Kwansei Gakuin University, Hokkaido University, Kyoto University, Japan and KU Leuven, Belgium. The image is a depiction of exploring the desired crystal by decision tree analysis. Read the full text of the article at 10.1002/chem.202102404.

Failure-Experiment-Supported Optimization of Poorly Reproducible Synthetic Conditions for Novel Lanthanide Metal-Organic Frameworks with Two-Dimensional Secondary Building Units*.

Novel metal-organic frameworks containing lanthanide double-layer-based secondary building units (KGF-3) were synthesized by using machine learning (ML). Isolating pure KGF-3 was challenging, and the synthesis was not reproducible because impurity phases were frequently obtained under the same synthetic conditions. Thus, dominant factors for the synthesis of KGF-3 were identified, and its synthetic conditions were optimized by using two ML techniques. Cluster analysis was used to classify the obtained powder X-ray diffractometry patterns of the products and thus automatically determine whether the experiments were successful. Decision-tree analysis was used to visualize the experimental results, after extracting factors that mainly affected the synthetic reproducibility. Water-adsorption isotherms revealed that KGF-3 possesses unique hydrophilic pores. Impedance measurements demonstrated good proton conductivities (σ=5.2×10-4  S cm-1 for KGF-3(Y)) at a high temperature (363 K) and relative humidity of 95 % RH.

Redox-Active Tin Metal-Organic Framework with a Thiolate-Based Ligand.

Metal-organic frameworks (MOFs) and coordination polymers composed of thiolates as coordinating functional groups are interesting materials with unique optical and electronical properties. Herein, we report the preparation of KGF-4 and KGF-10, two Sn-MOF crystal structures with bonds between Sn and thiolate. KGF-10 was isolated as a pure phase and found to exhibit redox properties and a semiconducting band structure, as confirmed by first-principles (density functional theory) calculations.

Machine-Learning-Assisted Selective Synthesis of a Semiconductive Silver Thiolate Coordination Polymer with Segregated Paths for Holes and Electrons.

Coordination polymers (CPs) with infinite metal-sulfur bond networks have unique electrical conductivities and optical properties. However, the development of new (-M-S-)n -structured CPs is hindered by difficulties with their crystallization. Herein, we describe the use of machine learning to optimize the synthesis of trithiocyanuric acid (H3 ttc)-based semiconductive CPs with infinite Ag-S bond networks, report three CP crystal structures, and reveal that isomer selectivity is mainly determined by proton concentration in the reaction medium. One of the CPs, [Ag2 Httc]n , features a 3D-extended infinite Ag-S bond network with 1D columns of stacked triazine rings, which, according to first-principle calculations, provide separate paths for holes and electrons. Time-resolved microwave conductivity experiments show that [Ag2 Httc]n is highly photoconductive (φΣµmax =1.6×10-4  cm2 V-1 s-1 ). Thus, our method promotes the discovery of novel CPs with selective topologies that are difficult to crystallize.

Ipso -Type Regiocontrolled Benzannulation for the Synthesis of Uniquely Substituted α-Arylnaphthalenes: Application to the First Total Synthesis of Chaihunaphthone.

A distinctive method for synthesizing a variety of multisubstituted α-arylnaphthalenes utilizing novel regiocontrolled ipso-type [4 + 2] benzannulation is presented. Ortho- and para-substituted 1-Ar1-1-Ar2-2,2-dichlorocyclopropylmethanols (AACM) were transformed to the corresponding ipso-type α-arylnaphthalenes. (i) The reaction of ortho-AACM using TiCl4 or SnCl4 (1.0 equiv) proceeded smoothly to afford ipso-type α-arylnaphthalenes (seven examples; 49-69% yield) exclusively, without producing conventional benzannulation isomers. (ii) Para-AACM also underwent the reaction successfully to afford the desired ipso-type α-arylnaphthalenes (14 examples; 39-98% yield) without producing conventional benzannulation isomers. (iii) In contrast, meta-AACM underwent the previously reported conventional benzannulation. (iv) The present method exhibited sufficient substrate generality for application to ortho- and para-substituted AACM substrates bearing Me-, Cl-, and MeO- groups. (v) The six key structures were unambiguously confirmed by X-ray structure analyses. (vi) A plausible reaction mechanism for the present ipso-type reaction is proposed and supported by three careful cross-over and comparable experiments. To demonstrate the utility of the present reaction, we achieved the first total synthesis of chaihunaphthone, a uniquely (highly congested) substituted and less accessible natural lignan lactone with three contiguous trimethoxy substituents (total eight steps, overall 6.4% yield).

Photoconductive Coordination Polymer with a Lead-Sulfur Two-Dimensional Coordination Sheet Structure.

Coordination polymers with metal-sulfur (M-S) bonds in their nodes have interesting optical properties and can be used as photocatalysts for water splitting. A wide range of inorganic-organic hybrid materials with M-S bonds have been prepared in recent years. However, there is a dearth of structural information because of their low crystallinity, which has hampered the understanding of their underlying chemistry and physics. Thus, we conducted a structural study of a novel, highly crystalline coordination polymer with M-S bonds. Theoretical calculations were performed to elucidate its photoconductivity mechanism. The photoconductive, three-dimensional coordination polymer [Pb(tadt)]n (denoted as KGF-9; tadt = 1,3,4-thiadiazole-2,5-dithiolate) was synthesized and confirmed to have a three-dimensional structure containing a two-dimensional Pb-S framework by single-crystal X-ray diffraction. We also performed diffuse-reflectance ultraviolet-visible-near-infrared spectroscopy, time-resolved microwave conductivity, and photoelectron yield spectroscopy measurements on the bulk powder samples, as well as first-principles calculations. Additionally, direct-current photoconductivity measurements were conducted on a single-crystal sample.

Coordination distortion induced water adsorption in hydrophobic flexible metal-organic frameworks.

Herein, we synthesized four isostructural flexible interdigitated hydrophobic metal-organic frameworks that differ only in their central metal ion. The water-adsorption properties are dependent on the metal species, which was revealed to be caused by coordination distortion around the metal ions.

A new design strategy for redox-active molecular assemblies with crystalline porous structures for lithium-ion batteries.

A new design strategy for high-performance organic cathode active materials for lithium-ion batteries is presented, which involves the assembly of redox-active organic molecules with a crystalline porous structure using mixed-stacked charge-transfer (CT) complexes. Hexahydroxytriphenylene was used as a donor molecule and 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile as an acceptor molecule to give a new porous CT complex (PCT-1) with a pseudo-hexagonal mixed columnar structure. X-ray diffraction measurements and sorption experiments demonstrated that the intercolumnar spaces in PCT-1 can incorporate various molecules accompanied by lattice expansion. A lithium metal battery containing PCT-1 as a cathode active material exhibited a high capacity of 288 mA h g-1 at 500 mA g-1, and this performance was attributed to a combination of the redox-active units and the porous structure of PCT-1.

Solvent-Vapor-Induced Reversible Single-Crystal-to-Single-Crystal Transformation of a Triphosphaazatriangulene-Based Metal-Organic Framework.

A triphosphaazatriangulene (H3 L) was synthesized through an intramolecular triple phospha-Friedel-Crafts reaction. The H3 L triangulene contains three phosphinate groups and an extended π-conjugated framework, which enables the stimuli-responsive reversible transformation of [Cu(HL)(DMSO)⋅(MeOH)]n , a 3D-MOF that exhibits reversible sorption characteristics, into (H3 L⋅0.5 [Cu2 (OH)4 ⋅6 H2 O] ⋅4 H2 O), a 1D-columnar assembled proton-conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10-3  S cm-1 at 95 % relative humidity and 60 °C.

Semiconductive Nature of Lead-Based Metal-Organic Frameworks with Three-Dimensionally Extended Sulfur Secondary Building Units.

Recently, metal-organic frameworks (MOFs) composed of sulfur secondary building units (sulfur-SBUs) have attracted significant attention as unique electronic materials with high conductivities and photo- and electrocatalytic properties. Herein we report the crystal structure of KGF-1, an example of a Pb-MOF composed of three-dimensionally extended sulfur-SBUs that displays molecular sieving behavior, visible-light absorption, and a semiconductor band structure and is a hydrogen-evolution photocatalyst.

Atomic Force Microscopy Study of the Influence of the Synthesis Conditions on the Single-Crystal Surface of Interdigitated Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) containing two or more types of metal ions exhibit promising new functionalities. To precisely control the distribution of metal ions, the relationship between the crystal-growth mechanism and the metal-ion type is important. Therefore, we investigated this relationship by using atomic force microscopy (AFM), which provided significant information about crystal-growth processes. We focus on interdigitated MOFs of the type: {[M(ip)(bpy)]⋅solvent}n (M=Zn or Cd, ip=isophthalate, bpy=4,4'-bipyridine, solvent=water or N,N-dimethylformamide). AFM images show two surface condition types that strongly depend on the solvent or synthetic conditions. We also demonstrate that the adsorption properties between different crystal surfaces are affected by the surface conditions. Finally, we synthesize solid-solution MOFs and observe their surface conditions. Such mechanistic insights will aid in the design of the adsorption properties of multi-metal MOFs.