Mechanically induced polyamorphism in a one-dimensional coordination polymer.

We created different amorphous structures of a coordination polymer by applying mechanical shear forces. One-dimensional Cu(TfN)(bip) (1, TfN = bis(trifluoromethanesulfonyl)imide, bip = 1,3-bis(1-imidazolyl)propane) melted at 245 °C and underwent a glass transition at -10 °C by a static cooling process. 1 formed another amorphous state with a distinct glass transition point of 70 °C under oscillatory shear stress.

Effects of Methyl Substitution on the Ultrafast Internal Conversion of Benzene.

The effects of methyl substitution on the ultrafast internal conversion from the S(B, ππ*) state to the S state of benzene were studied using ultrafast extreme-ultraviolet photoelectron spectroscopy and electronic structure calculations. The quantum yield of the internal conversion to the S state reached ∼0.69 in benzene, while lower values of 0.

Platinum-Group Metal High-Entropy Selenides for the Hydrogen Evolution Reaction.

The selenides of platinum-group metals (PGMs) are emerging as promising catalysts for diverse electrochemical reactions. To date, most studies have focused on single metal or bimetallic systems, whereas the preparation of a high-entropy (HE) selenide consisting of five or more PGM elements holds the promise to further enhance catalytic performance by introducing abundant active sites with various local coordination environments and electronic structures. Herein, we report for the first time the synthesis of PGM-based HE-Selenide (HE-Se) nanoparticles with a unique amorphous structure.

The Nature of Structural Defects in ZIF-8 Revealed with H and P MAS NMR and X-Ray Absorption Spectroscopy.

The metal-organic frameworks (MOFs) attract interest as potential catalysts whose catalytic properties are driven by defects. Several methods have been proposed for the defects-inducing synthesis of MOFs. However, the active species formed on the defective sites remain elusive and uncharacterized, as the spectroscopic fingerprints of these species are hidden by the regular structure signals.

Mixed Crystalline Covalent Heptazine Frameworks with Built-in Heterojunction Structures towards Efficient Photocatalytic Formic Acid Dehydrogenation.

Covalent heptazine frameworks (CHFs) are widely utilized in the recent years as potential photocatalysts. However, their limited conjugated structures, low crystallinity and small surface areas have restricted the practical photocatalysis performance. Along this line, we report herein the synthesis of a kind of mixed crystalline CHF (m-CHF-1) with built-in heterojunction structure, which can efficiently catalyze the formic acid dehydrogenation by visible light driven photocatalysis.

Increased CO/N selectivity by stepwise fluorination in isoreticular ultramicroporous metal-organic frameworks.

Exploration of porous adsorbents with high CO/N selectivity is of great significance for reducing CO content in the atmosphere. In this study, a series of isoreticular ultramicroporous fluorinated metal-organic frameworks (MOFs) were prepared to explore the benefits of fluorinated ultramicropores in improving CO/N selectivity. Gas adsorption measurements revealed that the increase in the number of fluorine atoms in a ligand molecule leads to the increased CO uptakes and CO/N selectivity.

First synthesis of RuSn solid-solution alloy nanoparticles and their enhanced hydrogen evolution reaction activity.

Solid-solution alloys based on platinum group metals and p-block metals have attracted much attention due to their promising potential as materials with a continuously fine-tunable electronic structure. Here, we report on the first synthesis of novel solid-solution RuSn alloy nanoparticles (NPs) by electrochemical cyclic voltammetry sweeping of RuSn@SnO NPs. High-angle annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy maps confirmed the random and homogeneous distribution of Ru and Sn elements in the alloy NPs.

How to measure work functions from aqueous solutions.

The recent application of concepts from condensed-matter physics to photoelectron spectroscopy (PES) of volatile, liquid-phase systems has enabled the measurement of electronic energetics of liquids on an absolute scale. Particularly, vertical ionization energies, VIEs, of liquid water and aqueous solutions, both in the bulk and at associated interfaces, can now be accurately, precisely, and routinely determined. These IEs are referenced to the local vacuum level, which is the appropriate quantity for condensed matter with associated surfaces, including liquids.

A Significant Two-Dimensional Structural Transformation in a Coordination Polymer that Changes Its Electronic and Protonic Behavior.

A 2D-to-2D (2D: two-dimensional) structural transformation accompanying significant bond rearrangement and coordination environment change is demonstrated in a coordination polymer (CP) comprised of copper(II) ions and terephthalate (BDC ) ligands for the first time. When immersed in water, a free-standing membrane of 2D Cu(BDC)(DMF) (Cu-1; DMF: N,N-dimethylformamide) transforms into 2D Cu(BDC)(H O) (Cu-2) while maintaining its highly oriented layered structure. In the 2D sheet, paddlewheel-type Cu dimers coordinated with four bidentate BDC ligands in a square-planar array in Cu-1 were released to form uniform aqua-bridged Cu chains, which are cross-linked with each other by unidentate BDC ligands, in Cu-2.

Cooperative Proton and Li-ion Conduction in a 2D-Layered MOF via Mechanical Insertion of Lithium Halides.

Ionic conduction in highly designable and porous metal-organic frameworks has been explored through the introduction of various ionic species (H , OH , Li , etc.) using post-synthetic modification such as acid, salt, or ionic liquid incorporation. Here, we report on high ionic conductivity (σ>10  S cm ) in a two-dimensionally (2D)-layered Ti-dobdc (Ti (Hdobdc) (H dobdc), H dobdc: 2,5-dihydroxyterephthalic acid) via LiX (X=Cl, Br, I) intercalation using mechanical mixing.

Observation of an Alternate Charge-Polarization State in a One-Dimensional Pt-Pt-I Chain Compound with a Bulky Pendant Ligand.

A one-dimensional (1D) halogen-bridged dinuclear-metal complex (MMX-chain) exhibits various electronic states based on a mixed-valence metal-dimer system. This report deals with the synthesis and physical properties of a new MMX-chain with a bulky pendant ligand, Pt (mcc-HexCS ) I (mcc-HexCS =trans-4-(methoxycarbonyl)cyclohexanedithiocarboxylate). The steric hindrance caused by the bulky substituent induces a strain in its 1D chain, achieving at ambient condition the first pure alternate charge-polarization (ACP) state (-Pt -Pt -I -Pt -Pt -I -), a kind of spin-Peierls state, as confirmed by X-ray diffraction and its conducting and magnetic properties.

Reversible ammonia uptake at room temperature in a robust and tunable metal-organic framework.

Ammonia is useful for the production of fertilizers and chemicals for modern technology, but its high toxicity and corrosiveness are harmful to the environment and human health. Here, we report the recyclable and tunable ammonia adsorption using a robust imidazolium-based MOF (JCM-1) that uptakes 5.7 mmol g of NH at 298 K reversibly without structural deformation.

High-Temperature Quantum Tunneling and Hydrogen Bonding Rearrangements Characterize the Solid-Solid Phase Transitions in a Phosphonium-Based Protic Ionic Liquid.

We report the complex phase behavior of the glass forming protic ionic liquid (PIL) d3-octylphosphonium bis(trifluoromethylsulfonyl)imide [C H PD ][NTf ] by means of solid-state NMR spectroscopy. Combined line shape and spin relaxation studies of the deuterons in the PD group of the octylphosphonium cation allow to map and correlate the phase behavior for a broad temperature range from 71 K to 343 K. In the solid PIL at 71 K, we observed a static state, characterized by the first deuteron quadrupole coupling constant reported for PD deuterons.

Reversible One- to Two- to Three-Dimensional Transformation in Cu Coordination Polymer.

A reversible transformation between 1D, 2D, and 3D is demonstrated for the first time in coordination polymers comprising Cu ions and bidentate terephthalate (BDC ). 1D uniform chains were reversibly transformed into 2D layers with the construction of Cu-paddlewheels by eliminating water molecules. 2D/3D reversible transformation was achieved by removing/rebinding N,N-dimethylformamide coordinated to the paddlewheels.

Synthesis and application of a F-labeled fluorescent nucleoside as a dual-mode probe for i-motif DNAs.

Because of their stable orientations and their minimal interference with native DNA interactions and folding, emissive isomorphic nucleoside analogues are versatile tools for the accurate analysis of DNA structural heterogeneity. Here, we report on a bifunctional trifluoromethylphenylpyrrolocytidine derivative () that displays an unprecedented quantum yield and highly sensitive F NMR signal. This is the first report of a cytosine-based dual-purpose probe for both fluorescence and F NMR spectroscopic DNA analysis.

Accurate vertical ionization energy and work function determinations of liquid water and aqueous solutions.

The absolute-scale electronic energetics of liquid water and aqueous solutions, both in the bulk and at associated interfaces, are the central determiners of water-based chemistry. However, such information is generally experimentally inaccessible. Here we demonstrate that a refined implementation of the liquid microjet photoelectron spectroscopy (PES) technique can be adopted to address this.

Chemoselective hydrogenation of heteroarenes and arenes by Pd-Ru-PVP under mild conditions.

Monometallic (Pd, Ru or Rh) and bimetallic (Pd-Ru) alloy NPs catalysts were examined for the hydrogenation of quinoline. Pd-Ru alloy catalyst showed superior catalytic activity to the traditional Rh catalyst. The characterization of Pd-Ru catalysts, HAADF-EDX mapping and XPS analysis suggested that the alloy state of PdRu catalysts remained unchanged in the recovered catalyst.

Nucleosomes and Epigenetics from a Chemical Perspective.

Nucleosomes, which are the fundamental building blocks of chromatin, are highly dynamic, they play vital roles in the formation of higher-order chromatin structures and orchestrate gene regulation. Nucleosome structures, histone modifications, nucleosome-binding proteins, and their functions are being gradually unravelled with the development of epigenetics. With the continuous development of research approaches such as cryo-EM, FRET and next-generation sequencing for genome-wide analysis of nucleosomes, the understanding of nucleosomes is getting wider and deeper.

Histidine-conjugated DNA as a biomolecular depot for metal ions.

Histidine is a versatile amino acid residue that plays a critical role in the active sites of many metalloenzymes. DNA is an attractive biomolecular scaffold owing to its chemical and thermal stability and easy accessibility. Herein, we report histidine-conjugated DNA oligonucleotides, which were synthesized by combining DNA alphabets and natural metal-binding amino acids, as novel biohybrid materials and demonstrate their use as molecular depots for various metal ions.

Soluble Guanylate Cyclase Stimulators and Activators: Where are We and Where to Go?

Soluble Guanylate Cyclase (sGC) is the intracellular receptor of Nitric Oxide (NO). The activation of sGC results in the conversion of Guanosine Triphosphate (GTP) to the secondary messenger cyclic Guanosine Monophosphate (cGMP). cGMP modulates a series of downstream cascades through activating a variety of effectors, such as Phosphodiesterase (PDE), Protein Kinase G (PKG) and Cyclic Nucleotide-Gated Ion Channels (CNG).

Hydrogen in Palladium and Storage Properties of Related Nanomaterials: Size, Shape, Alloying, and Metal-Organic Framework Coating Effects.

One of the key issues for an upcoming hydrogen energy-based society is to develop highly efficient hydrogen-storage materials. Among the many hydrogen-storage materials reported, transition-metal hydrides can reversibly absorb and desorb hydrogen, and have thus attracted much interest from fundamental science to applications. In particular, the Pd-H system is a simple and classical metal-hydrogen system, providing a platform suitable for a thorough understanding of ways of controlling the hydrogen-storage properties of materials.