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The synthesis of iron(II) and cobalt(II) thiolates with single and double NH***S hydrogen bonds as models of rubredoxins, using X-ray analysis, 1H nuclear magnetic resonance and infrared spectra, is reported. Findings showed an isotropic contact shift of the NH protons through intramolecular hydrogen bond affirms that the NH***S hydrogen bonds shorten the M-S bond and positively shift the redox potential in an additivity relationship. The functional differences between single and double NH***S hydrogen bonds in Fe(II) and related Co(II) complexes are also discussed.

A channel-switching single crystal, which can change pore topology in maintaining single-solid morphology, is synthesized by the addition of a degree of freedom to the host crystal component by molecular design of the host component. The designable dynamic porous single-solid devices might generate new applications by the active controllability of anisotropic guest diffusivity on the basis of sorption and diffusion phenomena.

The combination of metal benzoate complexes and pyrazine derivatives has produced a series of one-dimensionally assembled complexes for examining the correlation between host gas adsorption ability and structural flexibility. Single-crystal X-ray analyses of nonincluded crystals and C[O.sub.2] inclusions for all hosts have shown that large structural changes have occurred through C[O.sub.2] absorption to increase the inner space for adsorption gases, depending on the substituents on the pyrazine ring.

A well-oriented single-crystal membrane with high permeance is prepared by using a flexible single crystal of [[Cu.sub.2][(bza).sub.4](pyz)].sub.n] possessing one-dimensional (1D) penetration channels, where the membrane has displayed anisotropic gas permeation through the 1D channels with high permselectivity for [H.sub.2] and C[O.sub.2]. The studies have provided a new way of developing gas permeation membranes as sophisticated crystal devices for gas purification methods.

The magnetic behaviors of [O.sub.2] molecules, which have aligned in the channels of four types of single-crystal adsorbents, are studied. The studies have shown that the abnormal magnetic behaviors are induced because of the changes of magnetic interaction of included [O.sub.2] aggregates involving transformation that is supported by the surrounding of the channels of the single-crystal hosts under the applied magnetic field.

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 structural determination of saturated adsorbed methane inside a metal-organic cavity by the forcible pressure swing adsorption method through a gas adsorption equilibrium state gives a methane inclusion crystal even at 298K. The single-crystal adsorbent is effective for crystallographic observation of the thermal activated guest forced into regular alignment in the crystal lattice, which can be used as a model of the supercritical fluid.