The ethanol vapor adsorption behavior and the inclusion crystal structure of a 1D-transformable coordination polymer host were characterized. The adsorption jump was observed during phase transition or two-phase equilibrium with abnormal adsorption enthalpy caused by the nature of "mass induced phase transition." The included ethanol guests selectively form O-H...O hydrogen bonded pairs inside channels, suggesting selective construction of a specific cluster/aggregate in pores under control of thermodynamic factors and cooperative intermolecular interactions among the guest and channel surface.

For the purpose of investigating the correlation between host gas adsorption ability and structural flexibility, the combination of metal benzoate complexes [M(II)(2)(bza)(4)] (M(II) = Rh (a), Cu (b); bza = benzoate) and pyrazine derivatives (pyz = pyrazine (1), 2-mpyz = 2-methylpyrazine (2), 2,3-dmpyz = 2,3-dimethylpyrazine (3)) yields a series of one-dimensionally assembled complexes. The study of the adsorption properties of this series was examined for CO(2), H(2), N(2), O(2), and Ar gases at 195 K (CO(2)) or at 77 K (all others). The adsorption manners of these complexes are similar for each gas, while the pressure at which adsorption started or rapidly grew increased with a rise in the number of methyl groups in the case of adsorbable gases. The maximum amount of adsorption was a positive integer, e.g., 3 molecules per M(2) unit for 1 and 2 and 2 molecules per M(2) unit for 3 in the case of CO(2) adsorption for all complexes at 0.1 MPa of adsorbable gases. Structural transformation was observed accompanying gas adsorption. This transformation was observed when the adsorption amount reached 1 molecule per M(2) unit, suggesting a correlation of the adsorption amount and dynamic adsorption behavior. Single-crystal X-ray analyses of nonincluded crystals and CO(2) inclusions for all hosts (1-3) revealed that large structural changes occurred through CO(2) adsorption to increase the inner space for adsorption gases, depending on the substituents on the pyrazine ring. These facts were confirmed as a transition by DSC measurements using a mixed CO(2)/N(2) gas atmosphere. Solid-state (1)H and (2)H NMR studies of the crystalline sample of 1a and its partially deuterated samples of 1a' (deuterated phenyl group) and 1a'' (deuterated pyrazine) revealed rapid 180 degree-flip motions of the aromatic rings of the host skeletons, which form the walls of the channels. These "rotating" motions would help the diffusion of CO(2) molecules through a narrow channel at relatively low pressure. Indeed, the motions of phenyl groups and methyl-substituted pyrazine moieties of phenyl deuterated 3a were confirmed to be very slow by solid-state (1)H and (2)H NMR spectra, where the amount of adsorbed gas molecules was small for 3a at 0.1 MPa of CO(2).

Sheer magnetism: The phase transitions and magnetic behavior of included oxygen in a single crystal were studied at low temperature. The system exhibits three correlated structural and magnetic phases. The distinct middle‐temperature phase shows a one‐dimensional‐chain arrangement of oxygen trimers with an anomalous magnetization response to external magnetic fields.

Tris(ethylenediamine)cobalt(III) chloride, [Co III (en) 3 ]Cl 3 (en = ethylenediamine), is one of the most fundamental compounds of coordination chemistry. Although the wellknown ethylenediamine complexes may be regarded as well studied, research that considers their gas-adsorbent ability has not been reported. The racemic hydrated crystal of (AE )-[Co(en) 3 ]Cl 3 (1) includes H 2 O molecules within the onedimensional channels (see Figure 1).[1] Although the "zeolitic" behavior of 1 as a hydrate and dehydrate was reported in 1959,[2] the gas-adsorption ability of dried crystals of 1 was recently euphemistically indicated in 2002 and 2003 by a solidstate NMR spectroscopic study of n-alkanes under saturated vapor as well as of loaded Xe gas at high pressure.[3] Currently, porous materials based on metal complexes are very attractive research targets owing to their designable structure, unusual flexibilities, and projected tunable functions. [4] Dynamic porosity has been given much attention for the function of dynamic guest inclusion, [4][5][6] which can control guest reactivity and stability. [7] In the context of host dimensionality and binding forces for the component skeletons, currently the most actively investigated materials generally consist of polymeric skeletons with the assistance of van der Waals interpolymer interactions. Such structures should be well restricted in their transformability regarding the direction and range of motion by how the 3D architecture is constructed. Thus, an ionic crystal consisting of charged spherical components can be considered to possess extremely unrestricted transformability, which is regulated mostly by the minimization of the ionic-crystal energy under the various gas-adsorbing states. In this case, the Coulombic potential is rather "loose" in terms of binding interaction, which is generated in isotropic radial directions over a long distance proportional to r À1 (r = intermolecular distance), whereas that of van der Waals interactions is proportional to r À6 . Thus, there is a possibility that the ionic crystal can transform its crystal structure to sensitively adapt to the various adsorbedguest properties even by weak physisorption. Because crystal 1 seems to satisfy these requirements for the target-flexible ionic porosity, we focus on the gas adsorbency of ionic crystal 1. The purely van der Waals molecular crystal host is known for the cyclotriphosphazene inclusion compound. [8] Well-formed hydrated single crystals of 1 ([Co III (en) 3 ]Cl 3 ·4 H 2 O) were obtained as hexagonal rods by recrystallization from water. The structure has 1D channels running along the rod axis perpendicular to the hexagonal (001) plane, forming a channel crystal with 1D penetration pores (Figure 2). Single-crystal X-ray diffraction analysis demonstrated the 1D channel structure of 1 including a 1D water chain with the infinite connectivity of a trigonalbipyramidal periodic unit (Figure 3 a). After vacuum drying at 60 8C, single-crystal X-ray diffraction analysis can be perform...

The vapor absorbency of the series of alcohols methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol was characterized on the single-crystal adsorbents [M(II)2(bza)4(pyz)]n (bza = benzoate, pyz = pyrazine, M = Rh (1), Cu (2)). The crystal structures of all the alcohol inclusions were determined by single-crystal X-ray crystallography at 90 K. The crystal-phase transition induced by guest adsorption occurred in the inclusion crystals except for 1-propanol. A hydrogen-bonded dimer of adsorbed alcohol was found in the methanol- and ethanol-inclusion crystals, which is similar to a previous observation in 2 x 2EtOH (S. Takamizawa, T. Saito, T. Akatsuka, E. Nakata, Inorg. Chem. 2005, 44, 1421-1424). In contrast, an isolated monomer was present in the channel for 1-propanol, 1-butanol, and 1-pentanol inclusions. All adsorbed alcohols were stabilized by hydrophilic and/or hydrophobic interactions between host and guest. From the combined results of microscopic determination (crystal structure) and macroscopic observation (gas-adsorption property), the observed transition induced by gas adsorption is explained by stepwise inclusion into the individual cavities, which is called the "step-loading effect." Alcohol/water separation was attempted by a pervaporation technique with microcrystals of 2 dispersed in a poly(dimethylsiloxane) membrane. In the alcohol/water separation, the membrane showed effective separation ability and gave separation factors (alcohol/water) of 5.6 and 4.7 for methanol and ethanol at room temperature, respectively.