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The uptake of inhalation anesthetics by three topologically identical frameworks is described. The 3D network materials, which possess square channels of different dimensions, are formed from the relatively simple combination of ZnII centres and dianionic ligands that contain a phenolate and a carboxylate group at opposite ends. All three framework materials are able to adsorb N2O, Xe and isoflurane. Whereas the framework with the widest channels is able to adsorb large quantities of the various guests from the gas phase, the frameworks with the narrower channels have superior binding enthalpies and exhibit higher levels of retention. The use of ligands in which substituents are bound to the aromatic rings of the bridging ligands offers great scope for tuning the adsorption properties of the framework materials. [ABSTRACT FROM AUTHOR]

Materials that display multiple stepped spin crossover (SCO) transitions with accompanying hysteresis present the opportunity for ternary, quaternary, and quinary electronic switching and data storage but are rare in existence. Herein, we present the first report of a four-step hysteretic SCO framework. Single-crystal structure analysis of a porous 3D Hofmann-like material showed long-range ordering of spin states: HS, HS0.67LS0.33, HS0.5LS0.5, HS0.33LS0.67, and LS. These detailed structural studies provide insight into how multistep SCO materials can be rationally designed through control of host-host and host-guest interactions. [ABSTRACT FROM AUTHOR]

Cyanidometallate complexes are highly versatile building units for the generation of functional porous materials. Here we report five new pillared Hofmann layer compounds incorporating the tetracyanidometallates [MoO(CN)4]2−and [MnN(CN)4]2−. These metalloligands, which are new to this class of materials, have been combined with divalent 1st-row transition metals to produce Hofmann layers that are linked into three-dimensional frameworks by ditopic bridging dipyridyls. We report the structures and anomalous thermal expansion properties of five new materials: [Mn(H2O)(bpy)½{MoO(CN)4(bpy)½}]·2H2O (1), [Mn(H2O)(bpy)½{MnN(CN)4(bpy)½}]·2H2O (2), [Fe(H2O)(bpy)½{MnN(CN)4(bpy)½}]·2H2O (3), [Co(H2O)(bpy)½{MnN(CN)4(bpy)½}]·2H2O (4) and [{Mn(H2O)2}½{Mn(bpa)2}½{MoO(CN)4(bpa)½}]·MeOH (5), (where bpy = 4,4′-bipyridine and bpa = 4,4′-bipyridylacetylene). [ABSTRACT FROM AUTHOR]

The subtle flexibility of the framework material Co(bpy)1.5(NO3)2'(guest) (bpy = 4,4'-bipyridine) (1 (guest)) is demonstrated quantitatively through in situ single-crystal X-ray diffraction measurements of guest desorption and sorption processes. Variable temperature unit cell determinations were employed to monitor the uptake and release of guest species, and full structural determinations have been carried out for the as-grown ethanol-loaded framework (1 (EtOH)), for the empty host framework (1), and for each of the five introduced guests (methanol: I (MeOH), acetone: I `(ACN), acetonitrile: 1(MeCN), tetrahydrofuran: 1 (THF), dichloromethane; I(DCM)). The framework consists of interdigitated two-dimensional bilayers of cobalt(ll) centers bridged by bpy ligands, with one-dimensional pores that account for approximately 20% of the total volume. The sorption of guest species of varying size and shape has revealed the framework's ability to adapt to different guests through a range of different framework flexibilities. [ABSTRACT FROM AUTHOR]

The nanoporous metal-organic framework Fe[sub2](azpy)[sub4](NCS)[sub4]·(guest) (azpy is frans-4,4&prime-azopyridine) displays reversible uptake and release of guest molecules and contains electronic switching centers that are sensitive to the nature of the sorbed guests. The switching of this material arises from the presence of iron(II) spin crossover centers within the framework lattice, the sorbed phases undergoing “half-spin” crossovers, and the desorbed phase showing no switching property. The interpenetrated framework structure displays a considerable flexibility with guest uptake and release, causing substantial changes in the local geometry of the iron(II) centers. The generation of a host lattice that interacts with exchangeable guest species in a switchable fashion has implications for the generation of previously undeveloped advanced materials with applications in areas such as molecular sensing. [ABSTRACT FROM AUTHOR]

The nanoporous metal-organic framework, Fe(bpe)2(NCS)[sub2]∙3(acetone), SCOF-4(Ac) (where bpe is 1,2-bis(4'-pyridyl)ethane), displays a two-step spin crossover (SCO) transition (65-155 K) that is sensitive to the presence of acetone guest molecules. Structural analyses have revealed a structural phase transition, from tetragonal (P421c) to orthorhombic (P2[sub1]2[sub1]2), associated with the spin transition that defines a checkerboard-like ordering of spin sites at the high-spin:low-spin plateau. The reversible desorption of the acetone guest species is accompanied by a complex series of structural phase transitions that describe a dramatic flexing of the structure. The thermal trapping of a metastable state with ∼20-25% high-spin character was observed both magnetically and structurally upon rapid quenching of SCOF-4(Ac) to 10 and 25 K, respectively. The light-induced excited spin state trapping (LIESST) effects for SCOF-4(Ac) show a 55% excitation of a metastable HS state at 10 K and a characteristic T(LIESST) value of 52 K. [ABSTRACT FROM AUTHOR]

The porous coordination framework material, Fe(NCS2(bped2·3EtOH, SCOF-3(Et) (where bped is DL-1,2-bis(4′-pyridyl)-1,2-ethanediol), displays a spin-crossover (SCO) transition that has been stimulated both thermally and by light irradiation. The one-step thermal SCO (70-180 K) is sensitive to the presence of molecular guests, with a more gradual transition (70-225 K) apparent following the desorption of ethanol molecules that hydrogen bond to the spin centers. Additional intraframework hydrogen-bonding interactions stabilize the vacant one-dimensional pore structure of the apohost, SCOF-3, despite a dramatic single- crystal to single-crystal (SC-SC) structural change upon removal of the guests. Comprehensive structural analyses throughout this transformation, from primitive orthorhombic (Pccn) to body-centered tetragonal (l4/mcm), reveal a flexing of the framework and a dilation of the channels, with an accompanying subtle distortion of the iron(II) coordination geometry. Photomagnetic measurements of the light-induced excited spin state trapping (LIESST) effect have been used to assess the degree of cooperativity in this system. [ABSTRACT FROM AUTHOR]

Describes the synthesis, characterization and reversible guest-exchange chemistry of a porous Cobalt(II)-hydroxide layer structure pillared with trans-1,4-cyclohexanedicarboxylate magnetic material that orders ferrimagnetically. In-situ single crystal and powder X-ray diffraction analyses; Decrease in interlayer spacing; Loss of two water molecules per formula unit; Single crystal structure of the fully dehydrated material.

Examines the adsorption dynamics of gases and vapors on a nanoporous metal organic framework material. Calculation of adsorption activation energies and pre-exponential factors; Absence of isotherm steps in ethanol adsorption; Correlation between activation energy and pre-exponential factors.