The structure and modified properties of a self-dimerised Cu(II) inclusion complex in γ-cyclodextrins.

Inclusion structures incorporating more than one guest molecule are elusive because confinement alters their molecular properties. We report the solid-state characterization of an inclusion complex comprising two γ-cyclodextrins and two [Cu(2-pyridinemethanolate)(2-pyridinemethanol)]PF6 units. Quantum calculation reveals that interfragment charge transfer occurs. The confined Cu fragment and the unincluded "linear chain [Cu(2-pyridinemethanolate)(2-pyridinemethanol)]PF6" exhibit different properties.

Design of a MOF based on octa-nuclear zinc clusters realizing both thermal stability and structural flexibility.

An octa-nuclear zinc (Zn8) cluster-based two-fold interpenetrated metal-organic framework (MOF) of [(CH3)2NH2]2[Zn8O3(FDC)6]·7DMF (denoted as Zn8-as; H2FDC = 9H-fluorene-2,7-dicarboxylic acid; DMF = N,N-dimethylformamide) was synthesized by the reaction of a hard base of a curved dicarboxylate ligand (H2FDC) with the borderline acid of Zn(II) under solvothermal conditions. Zn8-as shows significant crystal volume shrinkage upon heating, yielding a solvate-free framework of [(CH3)2NH2]2[Zn8O3(FDC)6] (Zn8-de). Zn8-de displays gated adsorption for C2H2 and type-I adsorption for CO2, attributed to the framework flexibility and the different interactions between the gas molecules and the host framework.

Guest-selective and reversible magnetic phase switching in a pseudo-pillared-layer porous magnet.

A novel porous magnet consisting of cationic two-dimensional (2-D) layers extended by FeIII-CN-NiII linkages and pseudo-pillar dianions was synthesized. The size-selective guest adsorption behaviour of water and methanol molecules originates from the narrow bottle-neck-type pores in the flexible pseudo-pillared-layer structure, which results in the switching of the magnetic phases from antiferromagnetic to ferromagnetic, involving significant changes in the interlayer distance.

Coordination Geometry Changes in Amorphous Cyanide-Bridged Metal-Organic Frameworks upon Water Adsorption.

Amorphous coordination polymers and metal-organic frameworks (MOFs) have attracted much attention owing to their various functionalities. Here, we demonstrate the tunable water adsorption behavior of a series of amorphous cyanide-bridged MOFs with different metals (M[Ni(CN)4]: MNi; M = Mn, Fe, and Co). All three compounds adsorb up to six water molecules at a certain vapor pressure (Pads) and undergo conversion to crystalline Hofmann-type MOFs, M(H2O)2[Ni(CN)4]·4H2O (MNi-H2O; M = Mn, Fe, and Co). The Pads of MnNi, FeNi, and CoNi for water adsorption is P/P0 = 0.4, 0.6, and 0.9, respectively. Although the amorphous nature of these materials prevented structural elucidation using X-ray crystallography techniques, the local-scale structure around the N-coordinated M2+ centers was analyzed using L2,3-, K-edge X-ray absorption fine structure, and magnetic measurements. Upon hydration, the coordination geometry of these metal centers changed from tetrahedral to octahedral, resulting in significant reorganization of the MOF local structure. On the other hand, Ni[Ni(CN)4] (NiNi) containing square-planar Ni2+ centers did not undergo significant structural transformation and therefore abruptly adsorbed H2O in the low-pressure region. We could thus define how changes in the bond lengths and coordination geometry are related to the adsorption properties of amorphous MOF systems.

One-Step Synthesis of an Adaptive Nanographene MOF: Adsorbed Gas-Dependent Geometrical Diversity.

A layered metal-organic framework (MOF) comprising extra-large nanographene sheets, HBCMOF, was successfully synthesized using a dicarboxylic acid derivative of hexa-peri-hexabenzocoronene (HBCLH2), and its structure was characterized by single-crystal X-ray diffraction analysis. The crystal structure shows that 2D layers composed of a dinuclear Zn2+ complex unit and HBCL are located on top of each other through multiple weak interlayer bonds, affording HBCMOF, having three dimensionally connected nanopores with large nanographene surfaces. The HBC-based nanographene sheets are anchored to the MOF framework via two zinc carboxylate linkages and therefore have an axial rotational freedom. The sorption isotherms of gaseous molecules such as carbon dioxide and hydrocarbons (acetylene, propane, propylene, benzene, and cyclohexane) on HBCMOF all displayed a hysteretic profile with reversible structural changes, as observed by in situ powder X-ray diffraction studies.

Nonanuclear Ni(ii) complexes in a [1-7-1] formation derived from asymmetric multidentate ligands: magnetic and electrochemical properties.

Nonanuclear Ni(ii) complexes, [Ni9(Ln)6(OH)6(H2O)6] (Ni9Ln, n = 1-4; H2Ln = 6-acetoacetyl-2-pyridinecarboxylic acid derivatives), were prepared via self-assembly using the asymmetric multidentate ligands H2Ln. A corner-sharing tetrahedron-type structure, [Ni7(µ3-OH)6]8+, and terminal mononuclear units constitute the nonanuclear structure in a [1-7-1] formation. The electrochemical and magnetic properties of Ni9Ln were modulated by the introduction of various substituents in H2Ln.

Coordination nano-space as stage of hydrogen ortho-para conversion.

The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)-para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o-p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o-p conversion.

Guest modulation of spin-crossover transition temperature in a porous iron(II) metal-organic framework: experimental and periodic DFT studies.

The synthesis, structure, and magnetic properties of three clathrate derivatives of the spin-crossover porous coordination polymer {Fe(pyrazine)[Pt(CN)4]} (1) with five-membered aromatic molecules furan, pyrrole, and thiophene is reported. The three derivatives have a cooperative spin-crossover transition with hysteresis loops 14-29 K wide and average critical temperatures Tc =201 K (1⋅fur), 167 K (1⋅pyr), and 114.6 K (1⋅thio) well below that of the parent compound 1 (Tc =295 K), confirming stabilization of the HS state. The transition is complete and takes place in two steps for 1⋅fur, while 1⋅pyr and 1⋅thio show 50 % spin transition. For 1⋅fur the transformation between the HS and IS (middle of the plateau) phases occurs concomitantly with a crystallographic phase transition between the tetragonal space groups P4/mmm and I4/mmm, respectively. The latter space group is retained in the subsequent transformation involving the IS and the LS phases. 1⋅pyr and 1⋅thio display the tetragonal P4/mmm and orthorhombic Fmmm space groups, respectively, in both HS and IM phases. Periodic calculations using density functional methods for 1⋅fur, 1⋅pyr, 1⋅thio, and previously reported derivatives 1⋅CS2 , 1⋅I, 1⋅bz(benzene), and 1⋅pz(pyrazine) have been carried out to investigate the electronic structure and nature of the host-guest interactions as well as their relationship with the changes in the LS-HS transition temperatures of 1⋅Guest. Geometry-optimized lattice parameters and bond distances in the empty host 1 and 1⋅Guest clathrates are in general agreement with the X-ray diffraction data. The concordance between the theoretical results and the experimental data also comprises the guest molecule orientation inside the host and intermolecular distances. Furthermore, a general correlation between experimental Tc and calculated LS-HS electronic energy gap was observed. Finally, specific host-guest interactions were studied through interaction energy calculations and crystal orbital displacement (COD) curve analysis.

Structure modulation of manganese coordination polymers consisting of 1,4-naphthalene dicarboxylate and 1,10-phenanthroline.

Three new manganese coordination polymers, {[Mn2(1,4-NDC)2(phen)2](H2O)}n (1), [Mn2(1,4-NDC)2(phen)(H2O)]n (2) and {[Mn4(1,4-NDC)4(phen)4](DMF)2}n (3) (1,4-H2NDC = 1,4-naphthalene dicarboxylic acid; phen = 1,10-phenanthroline; DMF = N,N-dimethylformamide), have been synthesized solvo/hydrothermally. 1,4-NDC(2-) ligands adopt different coordination modes under different solvents and concentrations which promotes different crystal structure formation. X-ray crystal structural data reveal that compounds 1, 2 and 3 crystallize in monoclinic space groups C2/c, P21/c and C2/c, respectively. Compound 1 has Mn2 dimers connected by 1,4-NDC(2-) linkers, packing into a 2D structure in a grid pattern. Compound 2 has a three-dimensional (3D) structure which is constructed by Mn2 dimers and 1,4-NDC(2-) linkers. Each MnO4N2 node of compound 3 is linked to another by 1,4-NDC(2-) ligands to form a two-dimensional (2D) structure. Variable-temperature magnetic susceptibilities of compounds 1-3 exhibit overall weak antiferromagnetic coupling between the adjacent Mn(II) ions.

Bis[µ-3,5-bis-(pyridin-2-yl)pyrazolato]bis-[(hexa-fluoro-phosphato)copper(II)].

The title dinuclear complex mol-ecule, [Cu2(C13H9N4)2(PF6)2], lies about an inversion center. The Cu(II) atom shows a square-pyramidal coordination geometry with the basal plane formed by four N atoms of the two bis-chelating 3,5-bis-(pyridin-2-yl)pyrazolate ions and with one F atom of the hexa-fluoro-phosphate ion in the apical position. Mol-ecules are stacked in a column along the a axis through C-H⋯F hydrogen bonds. The columns are further linked by other C-H⋯F hydrogen bonds, forming a three-dimensional network.

Guest responsivity of a two-dimensional coordination polymer incorporating a cholesterol-based co-ligand.

To implement specific guest responsivity, a hydrophobic cholesterol-based co-ligand, cholest-5-en-3-yl-4-isonicotinate (Cholpy), was incorporated into a two-dimensional Hofmann-type Co(II)Ni(II) coordination polymer. The chemically programmed structure successfully demonstrated the unique guest response with remarkable chromatic changes.

Bis[µ-3,5-bis-(pyridin-2-yl)-1H-pyrazole]-bis-[di-bromido-iron(III)].

The title dinuclear complex, [Fe2Br4(C13H9N4)2], which lies on an inversion center, features two approximately planar bis-(pyridin-2-yl)pyrazole (bpypz(-)) ligands [maximum deviation = 0.082 (3) Å] and four bromide ions. Each Fe(III) ion is octa-hedrally coordinated by four N atoms of two bpypz(-) ligands and two Br ions. π-π stacking inter-actions [centroid-centroid distances = 3.7004 (17)-4.0123 (18) Å] are observed between pyridyl and pyrazole rings, and between pyridyl and pyridyl rings of adjacent complex mol-ecules.

Bis[µ-3,5-bis-(2-pyrid-yl)pyrazolato]bis-(hydrogensulfato)-dicopper(II) methanol disolvate.

The title compound, [Cu(2)(C(13)H(9)N(4))(2)(HSO(4))(2)]·2CH(3)OH, consists of discrete centrosymmetric dinuclear complex mol-ecules and methanol solvent mol-ecules. The Cu(II) atom shows a square-pyramidal coordination geometry and is bonded to four N atoms of the two bis-chelating 3,5-bis-(2-pyrid-yl)pyrazol-ate ions (bpypz(-)) and one O atom of the hydrogensulfate ion. The bpypz(-) ligands in the complex mol-ecule are virtually coplanar [dihedral angle between the mean ligand planes = 0.000(1)°] with the Cu(II) atom deviating in opposite directions from their best plane by 0.2080 (12) Å. π-π stacking inter-actions between the pyridyl and pyrazole rings [centroid-centroid distance = 3.391 (3) Å] and strong O-H⋯O hydrogen bonds between the hydrogensulfate ligands and the methanol mol-ecules assemble the mol-ecules into a one-dimensional polymeric structure extending along the a axis. The methanol mol-ecule acts both as an accepter and a donor in the hydrogen bonding.