Crystal Structure and Structural Transformation of [(CH3)3NH]2[CuZn(CN)5]

A newly synthesized coordination polymer, [(CH₃)₃NH]₂[CuZn(CN)₅], was investigated using ¹³C and ⁶³Cu solid‐state NMR techniques and single‐crystal X‐ray diffractometry. It consists of a three‐dimensional (3D) net composed of tetrahedral Cu^I and Zn^II ions and CN^– ligands bridging between the two metal ions. (CH₃)₃NH⁺ ions are trapped in the inner space of the 3D net. Three coordination sites of each metal ion are used for the formation of the 3D net and the remaining site is occupied by a unidentate CN^– ligand. The structure of the 3D net is chiral and categorized as srs in the notation of the Reticular Chemistry Structure Resource (RCSR). In water vapor or open air at room temperature under ambient pressure, a powder of [(CH₃)₃NH]₂[CuZn(CN)₅] showed a structural transformation to [(CH₃)₃NH][CuZn(CN)₄] · 1.5H₂O, which is a known compound with a diamond‐like 3D net of [CuZn(CN)₄]^– composed of tetrahedral Cu^I and Zn^II ions and bridging CN^– ligands. ⁶³Cu solid‐state NMR spectroscopy revealed that the Cu‐CN‐Zn orientation of the bridging CN^– ligands was conserved after the structural transformation.     

Electrooxidative glycosylation through C-S bond cleavage of 1-arylthio-2,3-dideoxyglycosides. Synthesis of 2',3'-dideoxynucleosides

[reaction: see text] The electrooxidative glycosylation of newly designed 1-arylthio-substituted 2,3-dideoxyglycosides is described. The halide salt-mediated electrooxidation utilizing either of the alpha- or beta-thiodideoxyglycosides proceeded smoothly at -78 degrees C to give dideoxynucleosides in a beta-selective manner, presumably through a 1-halo-substituted glycosyl donor.     

Molecular simulation of condensation process of Lennard-Jones fluids confined in nanospace with jungle-gym structure

We report grand canonical Monte Carlo simulations for a Lennard-Jones (LJ) fluid modeled on methane confined in nanospace with jungle-gym-like (JG) cubic structure, which is typically found in porous coordination polymers. Pillars composing the cubic structure were modeled as structureless smooth solid rods made of LJ carbon. We examined the effects of pore size, pore geometry, rod thickness, and rod potential onto the condensation phenomena in the JG pore structure. The simulations clarified that the condensation pressure and adsorption amount in the JG structure were influenced by pore size and rod potential, while the transition type was determined by rod thickness. The characteristics of the JG structure lie in the sensitivity to the slight changes in pore size, rod thickness, and rod potential owing to the combination of the packing effect of molecules and the superposition effect of rod potentials.     

Fundamental properties of a touchable high‐power pulsed microplasma jet and its application as a desorption/ionization source for ambient mass spectrometry

Plasma‐based ambient desorption/ionization mass spectrometry (ADI–MS) has attracted considerable attention in many fields because of its capacity for direct sample analyses. In this study, a high‐power pulsed microplasma jet (HPPMJ) was developed and investigated as a new plasma desorption/ionization source. In an HPPMJ, a microhollow cathode discharge is generated in a small hole (500 µm in diameter) using a pulsed high‐power supply. This system can realize a maximum power density of 5 × 10⁸ W/cm³. The measured electron number density, excitation temperature and afterglow gas temperature of the HPPMJ were 3.7 × 10¹⁵ cm^‐3, 7000 K at maximum and less than 60 °C, respectively, which demonstrate that the HPPMJ is a high‐energy, high‐density plasma source that is comparable with an argon inductively coupled plasma while maintaining a low gas temperature. The HPPMJ causes no observable damage to the target because of its low gas temperature and electrode configuration; thus, we can apply it directly to human skin. To demonstrate the analytical capacity of ADI–MS using an HPPMJ, the plasma was applied to direct solid sample analysis of the active ingredients in pharmaceutical tablets. Caffeine, acetaminophen, ethenzamide, isopropylantipyrine and ibuprofen were successfully detected. Application to living tissue was also demonstrated, and isopropylantipyrine on a finger was successfully analyzed without damaging the skin. The limits of detection (LODs) for caffeine, isopropylantipyrine and ethenzamide were calculated, and LODs at the picogram level were achieved. These results indicate the applicability of the HPPMJ for high‐sensitivity analysis of materials on a heat‐sensitive surface. Copyright © 2014 John Wiley & Sons, Ltd.     

Reversible Pore Size Control of Elastic Microporous Material by Mechanical Force

Nanoporous materials, such as zeolites, activated carbons, and metal–organic frameworks (MOFs), are peculiar platforms in which a variety of guest molecules are stored, reacted, and/or separated. The size of the nanopores is essential to realize advanced functions. In this work, we demonstrate a very simple but innovative method for the control of nanopore size, that is, reversible and continuous control by mechanical force loaded to soft nanoporous materials. The elastic properties of several microporous materials, including zeolites, zeolite‐templated carbon (ZTC), activated carbon, and MOFs (e.g., ZIF‐8), are examined and it is found that ZTC is a material that is suitable for the aforementioned idea thanks to its extraordinary soft properties compared to the others. The original pore size of ZTC (1.2 nm) can be contracted to 0.85 nm by using a relatively weak loading force of 135 MPa, whereas the other microporous materials barely contracted. To demonstrate the change in the physical properties induced by such artificial deformation, in situ gas adsorption measurements were performed on ZTC with and without loading mechanical force, by using CO₂, CH₄, and H₂, as adsorbates. Upon the contraction by loading 69 or 135 MPa, CO₂ adsorption amount is increased, due to the deepening of the physisorption potential well inside the micropores, as proved by the increase of the heat of adsorption. Moreover, the adsorption amount is completely restored to the original one after releasing the mechanical force, indicating the fully reversible contraction/recovery of the ZTC framework against mechanical force. The experimental results are theoretically supported by a simulation using Grand Canonical Monte Carlo method. The similar adsorption enhancement is observed also on CH₄, whereas H₂ is found as an exception due to the weak interaction potential.     

Field-induced staggered magnetization and magnetic ordering in Cu2(C5H12N2)2Cl4

We present a 2D NMR investigation of the gapped spin-1/2 compound Cu2(C5H10N2D2)2Cl4. Our measurements reveal the presence of a magnetic field-induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence, and symmetry can be explained by an intradimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.     

On the valence states of cerium in CeO2

The absorption spectra below the 4d threshold of cerium in Ce metal, CeF₃ and CeO₂ compounds were measured by using a CDM (Constant Deviation Monochromator) at the Photon Factory, KEK. The difference in structure between these spectra is discussed. The structure appeared in CeO₂ were considered to be due to the tetravalent configuration of cerium (Ce⁴⁺) in the ground state.     

Symmetry-adapted-cluster/symmetry-adapted-cluster configuration interaction methodology extended to giant molecular systems: ring molecular crystals

The symmetry adapted cluster (SAC)/symmetry adapted cluster configuration interaction (SAC-CI) methodology for the ground, excited, ionized, and electron-attached states of molecules was extended to giant molecular systems. The size extensivity of energy and the size intensivity of excitation energy are very important for doing quantitative chemical studies of giant molecular systems and are designed to be satisfied in the present giant SAC/SAC-CI method. The first extension was made to giant molecular crystals composed of the same molecular species. The reference wave function was defined by introducing monomer-localized canonical molecular orbitals (ml-CMO's), which were obtained from the Hartree-Fock orbitals of a tetramer or a larger oligomer within the electrostatic field of the other part of the crystal. In the SAC/SAC-CI calculations, all the necessary integrals were obtained after the integral transformation with the ml-CMO's of the neighboring dimer. Only singles and doubles excitations within each neighboring dimer were considered as linked operators, and perturbation selection was done to choose only important operators. Almost all the important unlinked terms generated from the selected linked operators were included: the unlinked terms are important for keeping size extensivity and size intensivity. Some test calculations were carried out for the ring crystals of up to 10 000-mer, confirming the size extensivity and size intensivity of the calculated results and the efficiency of the giant method in comparison with the standard method available in GAUSSIAN 03. Then, the method was applied to the ring crystals of ethylene and water 50-mers, and formaldehyde 50-, 100-, and 500-mers. The potential energy curves of the ground state and the polarization and electron-transfer-type excited states were calculated for the intermonomer distances of 2.8-100 A. Several interesting behaviors were reported, showing the potentiality of the present giant SAC/SAC-CI method for molecular engineering.