Three polymorphic Cd(II) coordination polymers obtained from the solution and mechanochemical reactions of 3-cyanopentane-2,4-dione with Cd(II) acetate.

We previously reported that monomeric and polymeric metal complexes are obtained from solution and mechanochemical reactions of 3-cyano-pentane-2,4-dione (CNacacH) with 3d metal acetates (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II)). A common feature found in all complexes was that their structural base is trans-[M(CNacac)(2)]. Here, we report that the reactions of CNacacH with Cd(II) acetate in the solution and solid states afford different coordination polymers composed of trans-[Cd(CNacac)(2)] and cis-[Cd(CNacac)(2)] units, respectively. From a methanol solution containing CNacacH (L) and Cd(OAc)(2)⋅2 H(2)O (M), a coordination polymer (Cd-1) in which trans-[Cd(CNacac)(2)] units are three-dimensionally linked was obtained. In contrast, two different coordination polymers, Cd-2 and Cd-3, were obtained from mechanochemical reactions of CNacacH with Cd(OAc)(2)⋅2 H(2)O at M/L ratios of 1:1 and 1:2, respectively. In Cd-2, cis-[Cd(CNacac)(2)] units are two-dimensionally linked, whereas the units are linked three-dimensionally in Cd-3. Furthermore, Cd-1 and Cd-2 converted to Cd-3 by applying an annealing treatment and grinding with a small amount of liquid, respectively, in spite of the polymeric structures. These phenomena, 1) different structures are formed from solution and mechanochemical reactions, 2) two polymorphs are formed depending on the M/L ratio, and 3) structural transformation of resulting polymeric structures, indicate the usability of mechanochemical method in the syntheses of coordination polymers as well as the peculiar structural flexibility of cadmium-CNacac polymers.

Adsorption and separation of poly-aromatic hydrocarbons by a hydrogen-bonded coordination polymer.

A residual-host prepared by thermal removal of naphthalene (NA) from the inclusion compound [Ni(SCN)(2)(isonicotinic acid)(2)]·(NA)(0.5) was found to function as an adsorbent for aromatic molecules and exhibit method-dependent selectivity.

Tridymite-like host clathrate [K(H2O)n][CuZn(CN)4]: crystal structure, guest molecular motion and properties.

A new clathrate [K(H(2)O)(n)][CuZn(CN)(4)] has been synthesized and its host structure has been determined by the single-crystal X-ray diffraction method. It has a [CuZn(CN)(4)](-) tridymite-like 3D framework host, formed with tetrahedral Cu(I) and Zn(II) ions and cyanide bridges and includes water molecules as guests, together with K(+). This tridymite-like structure is the first structural variation of the [CuZn(CN)(4)](-) 3D framework, whose only known structure has been a cristobalite-like structure. The new host shows properties never seen in the previous cristobalite-like structure host. It absorbs and desorbs water as a guest and the water content (n) varies between 1.2 and 11.2 at room temperature, by adjusting the conditions where the clathrate is placed. The desorption of the water causes deformation of the host structure and this deformation is recovered by the absorption of water. The water can be replaced with methanol and acetonitrile by their absorption instead of water. Solid-state (2)H-NMR spectra revealed the molecular motion of the water, methanol and acetonitrile guests in a temperature range between 123 K and 300 K.

Formation of 1 D and 3 D coordination polymers in the solid state induced by mechanochemical and annealing treatments: bis(3-cyano-pentane-2,4-dionato) metal complexes.

Bis(3-cyano-pentane-2,4-dionato) (CNacac) metal complex, [M(CNacac)(2)], which acts as both a metal-ion-like and a ligand-like building unit, forms supramolecular structures by self-assembly. Co-grinding of the metal acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with CNacacH formed a CNacac complex in all cases: mononuclear complex was formed in the cases of Mn(II), Cu(II) and Zn(II), whereas polymeric ones were formed in the cases of Fe(II), Co(II) and Ni(II). Subsequent annealing converted the mononuclear complexes of Mn(II), Cu(II) and Zn(II) to their corresponding polymers as a result of dehydration of the mononuclear complexes. The resultant Mn(II), Fe(II), Co(II), Ni(II) and Zn(II) polymeric complexes had a common 3 D structure with high thermal stability. In the case of Cu(II), a 1 D polymer was obtained. The Mn(II), Cu(II) and Zn(II) polymeric complexes returned to their original mononuclear complexes on exposure to water vapour but they reverted to the polymeric complexes by re-annealing. Co-grinding of metal chlorides with CNacacH and annealing of the mononuclear CNacac complexes prepared from solution reactions were also examined for comparison. [Mn(CNacac)(2)(H(2)O)(2)], [M(CNacac)(2)(H(2)O)] (M=Cu(II) and Zn(II)) and [M(CNacac)(2)](infinity) (M=Mn(II), Fe(II) and Zn(II)) are new compounds, which clearly indicated the power of the combined mechanochemical/annealing method for the synthesis of varied metal coordination complexes.

Crystal structure and dynamic properties of a bimetallic cyano complex Cd(C4H8O2)Cu(CN)3 with an interpenetrating 3D framework containing a 1,4-dioxane bridging ligand as a rotor.

The title complex Cd(C(4)H(8)O(2))Cu(CN)(3) has a 3D twofold interpenetrating framework structure. The structural base of the framework is a planar hexagonal network complex of [Cu(CN)(3)Cd](infinity) ,which is formed with cyanides connecting the coordination sites of Cu(i) ions with a triangle planar form and the equatorial coordination sites of Cd(ii) ions with a trigonal bipyramid form. The networks are stacked and a 1,4-dioxane molecule coordinates to two Cd(ii) ions in alternate networks as a bridging ligand. The 1,4-dioxane ligand penetrates a hexagonal window of the network sandwiched between the bridged networks. This 1,4-dioxane bridge completes the 3D twofold interpenetrating framework structure. (2)H-NMR powder patterns of the deuterated complex Cd(C(4)D(8)O(2))Cu(CN)(3) revealed the dynamics of the 1,4-dioxane bridge as a rotor. Above 253 K, the 1,4-dioxane ligand undergoes rotational motion combined with a ring inversion between two chair conformations. The free energy of activation DeltaG(double dagger) for the ring inversion was calculated to be 41.4(7) kJ mol(-1) at 298 K.

Coordination framework hosts consisting of 4-pyridyl-substituted carboxylic acid (PCA) dimers and 1D chains of Ni2+ and SCN-: a rational structural extension toward coordination framework hosts with large rectangular cavities.

For the expansion of a rectangular cavity (RC) defined by two isonicotinic acid (isoH) dimers as bridging ligands and two SCN bridges, we conducted a structural extension based on the elongation of the bridging ligands by the replacement of isoH with longer 4-pyridyl-substituted carboxylic acid (PCA). For this purpose, the following three PCAs have been employed: trans-3-(4-pyridyl)propenoic acid (acrylH), 4-(4-pyridyl)benzoic acid (pybenH), and trans-3-(4-(4-pyridyl)phenyl)propenoic acid (pppeH). Self-assembly of Ni2+, SCN-, and each of four PCAs involving isoH, acrylH, pybenH, and pppeH in the presence of an aromatic guest gave four inclusion compounds formulated as [Ni(SCN)2(isoH)2].1/2(benz[a]anthracene) (1), [Ni(SCN)2(acrylH)2].1/2(benz[a]anthracene) (2), [Ni(SCN)2(pybenH)2].(pyrene) (3), and [Ni(SCN)2(pppeH)2](3/)(2).(benz[a]anthracene) (4). X-ray crystal structural determination of 1-4 revealed that the proposed structural extension was successful. Their crystal structures are layered structures of two-dimensional (2D) grid-type coordination frameworks (2D host layers) framed with bridging ligands of the corresponding PCA dimers and 1D chains consisting of Ni2+ ions and mu(1,3)-SCN- ions. The lengths of the PCA dimers are 12.269(5) A (isoH dimer), 16.890(4) A (acrylH dimer), 20.89(2) A (pybenH dimer), 25.387(3) A (pppeH dimer A), and 25.527(4) A (pppeH dimer B). Each 2D host layer has RCs defined by the two corresponding PCA dimers and the two SCN bridges. The dimensions of RCs are expanded in proportion to the increase in the lengths of the PCA dimers: 29.52 x 5.60-7.20 A2 (4) > 24.95 x 5.46-7.38 A2 (3) > 20.88 x 5.49-7.25 A2 (2) > 16.41 x 5.53-7.43 A2 (1). These expansions reflect the number of aromatic guests that can be included in RCs. RC of 1 include only one molecule of benz[a]anthracene, whereas RCs of 3 or 4 includes two molecules of pyrene or benz[a]anthracene, respectively. Comparison of the lengths between the PCA dimers and 4,4'-bipyridine-type ligands demonstrated that a design strategy-the preparation of a bridging ligand through self-assembly of two PCAs-is both efficient and particularly suitable for the preparation of very long bridging ligands.

Cu3(CN)4(NH3)2Hg(CN)2: a novel interpenetrating framework formed from Cu(I), Cu(II), Hg(II) and cyanide bridges.

The title compound, poly[diamminehexa-mu-cyano-dicopper(I)copper(II)mercury(II)], [Cu3Hg(CN)6(NH3)2]n, has a novel threefold-interpenetrating structure of three-dimensional frameworks. This three-dimensional framework consists of two-dimensional network Cu3(CN)4(NH3)2 complexes and rod-like Hg(CN)2 complexes. The two-dimensional network complex contains trigonal-planar Cu(I) (site symmetry m) and octahedral Cu(II) (site symmetry 2/m) in a 2:1 ratio. Two types of cyanide group form bridges between three coordination sites of Cu(I) and two equatorial sites of Cu(II) to form a two-dimensional structure with large hexagonal windows. One type of CN- group is disordered across a center of inversion, while the other resides on the mirror plane. Two NH3 molecules (site symmetry 2) are located in the hexagonal windows and coordinate to the remaining equatorial sites of Cu(II). Both N atoms of the rod-like Hg(CN)2 group (Hg site symmetry 2/m and CN- site symmetry m) coordinate to the axial sites of Cu(II). This linkage completes the three-dimensional framework and penetrates two hexagonal windows of two two-dimensional network complexes to form the threefold-interpenetrating structure.

Crystal structures and spectroscopic properties of polycyano-polycadmate host clathrates including a CT complex guest of methylviologen dication and aromatic donor.

A series of polycyano-polycadmate (PCPC) host clathrates including a CT complex of methylviologen dication (MV2+) and an aromatic donor as a guest were synthesized, and their crystal structures and spectroscopic properties were investigated. The PCPC host has a framework structure built with Cd2+ ions as coordination centres and cyanides as bridging ligands. This framework host has negative charge and includes a cationic guest together with an ordinary neutral guest. MV2+, which is a strong acceptor, was included as a cationic guest and an aromatic compound, which works as a donor, was included as a neutral guest. Crystal structures of seven clathrates, whose neutral guests were o-cresol, m-cresol, p-cresol, 1-methylnaphthalene, 1,2,4-trimethoxybenzene, pyrrole and aniline, were determined by single crystal X-ray diffraction methods. In all cases MV2+ and the neutral guest formed a CT complex with a face to face stacking structure and were included as a CT complex guest. However, depending on each clathrate the ratio of aromatic donor to MV2+ was different and several variations were found in their PCPC host structures. The clathrates had their own colour depending on their neutral guest. The plot of the CT transition energies estimated from optical CT bands against the ionization potentials of the neutral guests satisfied a linear relationship predicted by Mulliken theory. However, the CT transition energies observed in the clathrates showed a shift to lower energy by ca. 0.6 eV compared with those observed in corresponding acetonitrile solutions.

Inorganic-organic hybrid molecular architectures of cyanometalate host and organic guest systems: specific behavior of the guests.

Molecular architectures built of inorganic cyanometalate building blocks provide variegated host structures with several organic guest molecules. The strategies to derive novel structures are presented briefly. The formation of a charge-transfer (CT) complex as the guest inside the cavity and the photochemistry of the CT complexes are discussed. The chemical pressure that the guest experiences inside the cavity is also discussed based on the vibrational spectroscopic results.

Crystalline inclusion compounds constructed through self-assembly of isonicotinic acid and thiocyanato coordination bridges.

The synthesis, crystal structures, inclusion ability, and structural robustness of novel crystalline inclusion compounds of [Ni(SCN)2(isoH)2].xG (isoH = isonicotinic acid; G = aromatic guest) are described. The inclusion compounds are constructed by stacking identical 2D host layers that consist of SCN-, isoH, and Ni2+ with van der Waals contact separation. In the layer, two types of rectangular cavities (A-type and B-type) are formed, and the guests are included in the former cavity. The inclusion compounds were categorized into four stacking modes according to the difference in the stacking mode of the layers. A systematic investigation of the crystal structures of the 21 inclusion compounds clarified the close relationship between the molecular structure of the guest and the resultant stacking mode of the layers.

Design and structural extension of a supramolecular inclusion-compound host made by the formation of dimers of isonicotinic acid and thiocyanato coordinating bridges.

A new host design for an inclusion compound with a preference for large planar aromatic guest molecules has been proposed. Our host design includes a rectangular cavity made using a long and a short building block based on the concept of supramolecular chemistry. The long building block facilitates the inclusion of large guests, and the short building block prevents the formation of an interpenetrated structure, which is often observed in frameworks with large void spaces. The long building block is made when dimers of 4-pyridinecarboxylic acid (isoH) form through hydrogen bonding between the two carboxylic acid moieties. This isoH dimer can link two transition metal centers using the N atoms at both ends to act as a long building block. For the short building block, the thiocyanato ion was used. This makes a bent bridge between two metal centers to form a 1D double-chain [M(SCN)2]infinity complex. From the self-assembly of isoH, SCN- and Ni2+, a 2D network of [Ni(SCN)2(isoH)2]infinity, in which the 1D [Ni(SCN)2]infinity complexes are linked by the isoH dimers, is built up. The rectangular cavity is formed as a mesh within the 2D network. The crystal of our inclusion compound has a layered structure of 2D networks, and a 1D channel-like cavity penetrating the layered 2D networks is formed where guests may be included. Moreover, our host design has the advantage of easy extension of the host structure. Replacement of isoH with another component and use of three components is possible for making the long building block. In the latter case, a linear spacer having two carboxy groups is inserted into the isoH dimer to form a long building block with a trimer structure. Based on our host design, a series of new inclusion compounds were synthesized. The crystal structures of three compounds were determined by single crystal X-ray diffraction. These were a biphenyl inclusion compound [Ni(SCN)2(isoH)2].1/2C12H10 (the basic case), a 9,10-dichloroanthracene inclusion compound [Ni(SCN)2(acrylH)2].1/2C14H8Cl2, where isoH is replaced with 3-(4-pyridinyl)-2-propenoic acid (acrylH), and a perylene inclusion compound [Ni(SCN)2(isoH)2(fumaricH2)].1/2C20H12, whose long building block is a trimer inserted with fumaric acid (fumaricH2) as a linear spacer.