Ryosuke Miyake

Single-crystal membrane for anisotropic and efficient gas permeation.

Development of gas separation materials has been one of the basic requirements of industry. Microporous materials have adequate pores for gas separation and have contributed to the advancement of gas purification techniques. Because the simplest and most economical method would be membrane separation, various microporous membranes have been prepared and explored for their separation properties. However, a key issue remains as to how to generate defect-free membranes with practical gas permeance. Here we report the preparation of a well-oriented single-crystal membrane with high permeance by using a flexible single crystal of [Cu(2)(bza)(4)(pyz)](n) possessing one-dimensional (1D) penetration channels; this membrane exhibits anisotropic gas permeation through the 1D channels with high permselectivity for H(2) and CO(2). Although the diameter of the neck of the narrow channels is smaller than the kinetic diameters of the sample gases, various gases pass through the 1D channels. This report provides a new way of developing gas permeation membranes as sophisticated crystal devices for gas purification techniques.

A C60-templated tetrameric porphyrin barrel complex via zinc-mediated self-assembly utilizing labile capping ligands.

Coordination-driven self-assembly utilizing labile capping ligands has been exploited as a novel strategy for metallo-cage containers. Herein, we report a tetrameric porphyrin barrel complex [C60⊂Zn814(H2O)4(OTs)12](OTs)4 (2) (OTs = p-CH3C6H4SO3) formed from a tetrakis(bipyridyl)porphyrin ligand 1, Zn(OTs)2, and a template guest, C60 fullerene. The tetrameric-barrel 2 contains two kinds of bis(bpy) Zn(II) centers coordinated by TsO(-) anions which serve as labile capping ligands in the formation of the finite structure of 2.

Structural and Magnetic Study of O2 Molecules Arranged along a Channel in a Flexible Single-Crystal Host Family

We report the magnetic behaviors of O(2) molecules, which aligned in the channels of four types of single-crystal adsorbents, [M(2)(bza)(4)(pyz)](n) (bza = benzoate; pyz = pyrazine; M = Rh(II) (1a) and Cu(II) (1b)) and [M(2)(bza)(4)(2-mpyz)](n) (2-mpyz = 2-methylpyrazine; M = Rh(II) (2a) and Cu(II) (2b)). The X-ray single-crystal structures at various temperatures from 10 to 298 K were determined for O(2)-included crystals of 1a and 2a. All adsorbed O(2) molecules exhibited abnormal magnetic phases above 4 T in the temperature range around 55-105 K. The magnetic behaviors of adsorbed O(2) molecules between four inclusions were discussed. The existence of the metastable state, which was also suggested by hysteresis on the M-H curves, was revealed by analysis of the time course of the magnetization. Considering that the abnormal magnetic behavior occurred at relatively high temperatures and a low magnetic field, it was suggested that these behaviors were induced because of the changes of magnetic interaction of included O(2) aggregates involving transformation which is supported by the surrounding of the channels of the single-crystal hosts under the applied magnetic field.

Selective Ortho‐Hydroxylation–Defluorination of 2‐Fluorophenolates with a Bis(μ‐oxo)dicopper(III) Species

The bis(μ-oxo)dicopper(III) species [Cu(III) 2 (μ-O)2 (m-XYL(MeAN) )](2+) (1) promotes the electrophilic ortho-hydroxylation-defluorination of 2-fluorophenolates to give the corresponding catechols, a reaction that is not accomplishable with a (η(2) :η(2) -O2 )dicopper(II) complex. Isotopic labeling studies show that the incoming oxygen atom originates from the bis(μ-oxo) unit. Ortho-hydroxylation-defluorination occurs selectively in intramolecular competition with other ortho-substituents such as chlorine or bromine.

Large Entropic Effect in Flexible Crystalline Media for Gas Separation

To develop the application of the adsorption ability of our flexible single-crystal host [Cu(2)(bza)(4)(pyz)](n) (1) (bza = benzoate; pyz =pyrazine) possessing a 1D channel, we study the separation ability of a 1 packed column for various organic vapors and inorganic gases. A 1 packed column can detect various organic molecules with sharp signals although steric or nonpolar molecules give broad signals. Interestingly, 1 separates various organic mixtures even if the mixture contains nonpolar molecules. Comparing the separation properties with columns of other separation media, including zeolite, activated carbon, activated alumina, and silica gel, suggests that a 1 packed column separates various gaseous molecules under moderate conditions. Additionally, the eluted order of similar molecules, such as N(2)/O(2) and methanol/ethanol using the 1 packed column is different from the others (zeolite, activated carbon, activated alumina, and silica gel), which suggests a difference in the separation mechanism of 1. From GC measurements, the estimated changes in Gibbs free energy by gas adsorption, under diluted gas conditions, exhibits a large entropy dependence caused by regularity in the generated adsorption state, which enables the dynamic control of gas adsorption selectivity. Therefore, it is suggested that single-crystal host 1, because of its flexibility, can separate various gases by adjusting its channel structure according to the features of the guest gaseous molecules. This generates active controllability of the adsorption potential in addition to the intrinsic adsorption interaction.

Ni(II)-Mediated Self-Assembly of Artificial β-Dipeptides Forming a Macrocyclic Tetranuclear Complex with Interior Spaces for In-Line Molecular Arrangement

Metal-mediated self-assembly of bioinspired molecular building blocks shows promise as an excellent strategy to provide well-defined metal arrays and nanoscopic metallo-architectures in a programmable way. Herein, we report Ni(II)-mediated self-assembly of artificial beta-dipeptides (1) which were prepared from a newly designed beta-amino acid bearing a propanediamine ligand as the side chain. The beta-dipeptide (1) has thus two sets of ligands, that is, each building block serves as a tridentate ligand with a bidentate propanediamine unit and an amide carbonyl group. Both C- and N-terminal tridentate ligands in 1 bind to two Ni(II) ions independently, and consequently, four beta-dipeptides are circularly arranged in a head-to-tail fashion to form a macrocyclic tetranuclear Ni(II) complex, Ni414(ClO4)8(H2O)10. The cyclic structure was determined by X-ray analysis and ESI-TOF mass spectrometry. The resulting unique twisted-boat structure allows the formation of isolated spaces for in-line hydrogen-bonded arrangement of water and anion molecules within a hole and two grooves rich in hydrogen bonding groups.

Concerted ligand exchange and the roles of counter anions in the reversible structural switching of crystalline peptide metallo-macrocycles.

To understand reversible structural switching in crystalline materials, we studied the mechanism of reversible crystal-to-crystal transformation of a tetranuclear Ni(II) macrocycle consisting of artificial β-dipeptides. On the basis of detailed structural analyses and thermodynamic measurements made in a comparison of pseudo-isostructural crystals (NO3 and BF4 salts), we herein discuss how ligand-exchange reactions take place in the crystal due to changes in water content and temperature. Observations of the structural transformation of NO3 salt indicated that a pseudo crystalline phase transformation takes place through concerted ligand-exchange reactions at the four Ni(II) centers of the macrocycle with hydrogen bond switching. A mechanism for this ligand exchange was supported by IR spectroscopy. Thermodynamic measurements suggested that the favorable compensation relationship of the enthalpy changes due to water uptake and structural changes are keys to the reversible structural transformation. On the basis of a comparison with the pseudo-isostructural crystals, it is apparent that the crystal packing structure and the types of counter anions are important factors for facilitating reversible ligand exchange with single crystallinity.

Molecular Nanostamp Based on One-Dimensional Porphyrin Polymers

Surface design with unique functional molecules by a convenient one-pot treatment is an attractive project for the creation of smart molecular devices. We have employed a silane coupling reaction of porphyrin derivatives that form one-dimensional polymer wires on substrates. Our simple one-pot treatment of a substrate with porphyrin has successfully achieved the construction of nanoscale bamboo shoot structures. The nanoscale bamboo shoots on the substrates were characterized by atomic force microscopy (AFM), UV-vis spectra, and X-ray diffraction (XRD) measurements. The uneven and rigid nanoscale structure has been used as a stamp for constructing bamboo shoot structures of fullerene.

Switch of channel geometry by 1D component slide responding to slight structural stimuli of adsorbed guest

The adsorption behavior of a flexible single-crystal host [Cu2(bza)4(pyz)]n was studied for a planar triangular molecule and investigated for large host structural changes including a switch of channel geometry responding to included guest molecules.

Gas-adsorbing ability of tris-ethylenediamine metal complexes (M = Co(III), Cr(III), Rh(III), Ir(III)) as transformable ionic single crystal hosts

We previously reported that a single crystal of [Co(en)3]Cl3 shows gas adsorbency for various gases and organic vapors accompanying channel expansion in its crystal structure. To investigate the possibility of a single crystal of tris-ethylenediamine metal complex as an ionic single-crystal host for vapor adsorption, a series of adsorbencies of single crystals of [MIII(en)3]Cl3 (M = Co 1, Cr 2, Rh 3, Ir 4) were studied. All complexes have channels in their crystal structures, which dynamically and reversibly change size with vapor adsorption and show similar vapor adsorbency similar to the adsorption behavior of [Co(en)3]Cl3.