Tetra‐μ‐acetato‐O:O′‐bis­[(7‐aza­indole‐N)­copper(II)]

The title complex, [Cu₂(C₂H₃O₂)₄(C₇H₆N₂)₂], shows a binuclear cage structure having an inversion centre. There are intramolecular N—H?O hydrogen bonds between the 7‐aza­indole ligands and the bridging acetate O atoms.     

Starter units of the biosynthesis of blepharismins: self-defense pigments of Blepharisma japonicum

The heterotrich ciliate Blepharisma japonicum produces red pigment blepharismins, which function as self-defense toxin against predators and as a photoreceptor for step-up photonegativity. The dibenzoperylenequinone moiety of blepharismins was shown to be biosynthesized via the polyketide pathway. In this paper, the starter units of the biosynthetic pathway of blepharismins were determined to be isovaleryl-CoA and butyryl-CoA by HPLC, LC/ESI-MS, and ¹H and ²H NMR analyses of the pigments obtained from feeding experiment of l-leucine or sodium butyrate in excess and deuterium-labeled l-leucine.     

Fully automated liquid chromatography-mass spectrometry determination of 17beta-estradiol in river water

Surface modified molecularly imprinted polymers (SM-MIPs) for 17beta-estradiol (E2), utilizing 6-ketoecradiol as a pseudo template were prepared. MIPs for E2 were synthesized using 4-vinyl pyridine and ethylene dimethacrylate as a functional monomer and cross-linking agent, respectively. MIPs selectively retained E2 and provided excellent chromatographic resolution from interfering compounds inherent in river water sample matrices. Therefore, freshly prepared MIPs were applied to quantitative mass spectrometric (negative electrospray ionization mode) detection of low levels of E2 in river water sample. In order to pre-concentrate the target compound for HPLC analysis, column switching was coupled with a pretreatment column packed with the MIPs. The repeatability of actual determinations of river water sample, in which background E2 was not detected, spiked with 50 ng/L of E2 was 2.2% RSD with a detection limit and qualification limit of 1.8 and 5.4 ng/L, respectively. Surface modification of MIP particlefs packed in the pretreatment column provided selective affinity and on-line concentration of low levels of E2 while simultaneously eliminating sample matrix interference, resulting in a significant increase in sensitivity and reproducibility for liquid chromatography-mass spectrometry analysis of E2 in river water sample.     

Effects of hydrophobic chain length on the characteristics of the micelles of octaoxyethylene tetradecyl C(14)E(8), hexadecyl C(16)E(8), and octadecyl C(18)E(8) ethers

Size, shape, and flexibility of micelles of octaoxyethylene tetradecyl C(14)E(8), hexadecyl C(16)E(8), and octadecyl C(18)E(8) ethers in dilute aqueous solutions were determined at finite surfactant concentrations c by static light scattering (SLS) and dynamic light scattering experiments at several temperatures T below the critical points. The SLS results were successfully analyzed with the aid of the thermodynamic theory formulated with wormlike spherocylinder model for SLS of micelle solutions. The analysis yielded the molar mass M(w) of the micelles as a function of c and the cross-sectional diameter d. The hydrodynamic radius R(H) and the radius of gyration S(2)(1/2) of the micelles as functions of M(w) were found to be also well-described by the corresponding theories for the wormlike spherocylinder or wormlike chain models. The results of the stiffness parameter lambda(-1) have revealed that the micelles are far from rigid rods but rather stiff compared with typical flexible polymers and they grow in size with increasing T to greater length for longer hydrophobic chains, i.e., alkyl groups of the surfactants. As the alkyl group becomes longer, the d value increased, while the spacings s between adjacent hexaoxyethylene chains on the micellar surface were found to remain substantially constant.     

The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single‐Crystalline Ordered Mesoporous Nb‐TiO2 and Plate‐like Nb‐TiO2 with Ordered Mesoscale Dimples

Highly ordered mesoporous niobium‐doped TiO₂ with a single‐crystalline framework was prepared by using silica colloidal crystals with ca. 30 nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb‐doped TiO₂. The XPS measurements of Nb‐doped TiO₂ showed the presence of Nb⁵⁺ and correspondingly Ti³⁺. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate‐like TiO₂ with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.     

First-principles study of hydrogen adsorption in metal-doped COF-10

Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H(2) molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H(2) molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10.     

Theoretical Study of Clathrate Hydrates with Multiple Occupation

In this work, the electronic, structural, dynamic andthermodynamic properties of structure II, H and tetragonalAr clathrate hydrates have been calculated and the effectof multiple occupancy on their stability has been examinedusing first-principles and lattice dynamics calculations.The dynamic properties of these clathrates have beeninvestigated depending on the number of guest moleculesin a clathrate cage. It has been found that selectedhydrate structures are dynamically stable. The calculatedcell parameters are in agreement with experimental data.We also report the results of a systematic investigationof cage-like water structures using first-principles calculations. Ithas been observed that Ar clusters can be stabilized indifferent water cages and the stability is strongly dependenton the number of argon atoms inside the cages.     

Effect of boron non-stoichiometry on B-site in perovskite type structure ScBxRh3 and CeBxRh3 on charges of atoms on A-site: study by X-ray photoelectron and nuclear magnetic resonance spectroscopies

The solid solutions of ScBRh₃-ScRh₃ and CeBRh₃-CeRh₃ are synthesized by the arc melting method, where RBRh₃ and RRh₃ (R=rare earth element) have perovskite and AuCu₃ type structures, respectively. The binding energy of Sc 2p_3/2 for ScB_xRh₃ increases with the boron concentration. The Knight shift of ⁴⁵Sc observed by nuclear magnetic resonance spectroscopy decreases with increase of boron concentration. The decrement of the Knight shift corresponds the Sc 4s electron density at the Fermi level. The intensity ratio of f²: f¹: f⁰ of Ce 3d XPS spectrum changes with boron concentration of CeB_xRh₃. It is concluded that in both cases of ScB_xRh₃ and CeB_xRh₃ the charge on the atoms on A-site changes with the concentration of the atoms on B-site, where the atoms are not directly bound.     

Ni-catalyzed alkylative dimerization of vinyl grignard reagents using alkyl fluorides

Alkyl halides underwent unique cross-coupling reaction with vinylmagnesium chloride in the presence of Ni catalyst to give 2-alkyl-3-butenyl Grignard reagent (1) in high yields. This reaction proceeded efficiently at 25 degrees C in THF using primary and secondary alkyl fluorides. On the other hand, PhCH=CHMgBr gave double alkylative vinyl coupling product 4 in good yield as the sole coupling product. Alkyl fluorides react as the most suitable alkylating reagent in comparison to the corresponding chlorides, bromides, and iodides.     

Computational design of tetrahedral silsesquioxane-based porous frameworks with diamond-like structure as hydrogen storage materials

A novel type of three-dimensional (3D) tetrahedral silsesquioxane-based porous frameworks (TSFs) with diamond-like structure was computationally designed using the density functional theory (DFT) and classical molecular mechanics (MM) calculations. The hydrogen adsorption and diffusion properties of these TSFs were evaluated by the methods of grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results reveal that all designed materials possess extremely high porosity (87–93 %) and large H₂ accessible surface areas (5,268–6,544 m² g^?1). Impressively, the GCMC simulation results demonstrate that at 77 K and 100 bar, TSF-2 has the highest gravimetric H₂ capacity of 29.80 wt%, while TSF-1 has the highest volumetric H₂ uptake of 65.32 g L^?1. At the same time, the gravimetric H₂ uptake of TSF-2 can reach up to 4.28 wt% at the room temperature. The extraordinary performances of these TSF materials in hydrogen storage made them enter the rank of the top hydrogen storage materials so far.