Magnetic and Mechanical Anisotropy in a Manganese 2-Methylsuccinate Framework Structure

Hybrid inorganic-organic framework materials exhibit unique properties that can be advantageously tuned through choice of the inorganic and organic components and by control of the crystal structure. We present a new hydrothermally prepared 3D hybrid framework, [Mn(2-methylsuccinate)](n) (1), comprising alternating 2D manganese oxide sheets and isolated MnO(6) octahedra, pillared via syn, anti-syn carboxylates. Powder magnetic characterization shows that the compound is a homospin Mn(II) ferrimagnet below 2.4 K. The easy-axis is revealed by single-crystal magnetic susceptibility studies and a magnetic structure is proposed. Anisotropic elastic moduli and hardness, observed through nanoindentation on differing crystal facets, were correlated with specific structural features. Such measurements of anisotropy are not commonly undertaken, yet allow for a more comprehensive understanding of structure-property relationships.

An open-framework zincoborate formed by Zn6B12O24 clusters

A novel zincoborate, Zn(H2O)B2O4.xH(2)O (xapproximate to0.12), I, with open architecture has been synthesized hydrothermally. The 3-dimensional structure is built up of Zn6B12O24 clusters formed by the capping of the polycyclic borate anion, B12O2412-, by Zn3O3 clusters. The open-framework structure of I has one-dimensional 8-membered channels wherein the water molecules reside. Formation of trimeric Zn3O3 clusters as well as the presence of boron in dual coordination, both triangular and tetrahedral, are important structural features of this new zincoborate.

Mechanical properties of a metal-organic framework containing hydrogen-bonded bifluoride linkers

We report the mechanical properties of a framework structure, Cu2F(HF)(HF2)(pyz)(4)](SbF6)(2)](n) (pyz = pyrazine), in which Cu(pyz)(2)](2+) layers are pillared by HF2- anions containing the exceptionally strong F-H center dot center dot center dot F hydrogen bonds. Nanoindentation studies on single-crystals clearly demonstrate that such bonds are extremely robust and mechanically comparable with coordination bonds in this system.

Rare-earth carboxylates, Ln(2)(III)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O Ln = Ce, Pr and Nd]: synthesis, structure and properties

A new series of inorganic-organic hybrid framework compounds, Ln(2)(mu(3)-OH)(C4H4O5)(2)(C4H2O4)]center dot 2H(2)O, (Ln = Ce, Pr and Nd), have been prepared employing a hydrothermal method. Malic acid and fumaric acid form part of the structure. The malate units connect the lanthanide centers forming Ln-O-Ln two-dimensional layers, which are cross-linked by the fumarate units forming the three-dimensional structure. Extra framework water molecules form a dimer and occupy the channels. The water molecules can be reversibly adsorbed. The dehydrated structure did not show any differences in framework structure/ connectivity. The presence of lattice water provides a pathway for proton conductivity. Optical studies suggest an up-conversion behavior involving more than one photon for a neodymium compound.

Probing the mobility of lithium in LISICON: Li+/H+ exchange studies in Li2ZnGeO4 and Li2+2xZn1-xGeO4

We investigated Li+/H+ exchange in the lithium ion conductors (LISICONS) [ Li2+2xZn1-xGeO4; x = 0.5 ( I) and x = 0.75 (II)] and their parent, gamma-Li2ZnGeO4. Facile exchange of approximately 2x lithium ions per formula unit occurs with both the LISICONS in dilute acetic acid, while the parent material does not exhibit an obvious Li+/H+ exchange under the same conditions. The results can be understood in terms of lithium ion distribution in the crystal structures: the parent Li2ZnGeO4, where all the lithium ions form part of the tetrahedral framework structure, does not exhibit a ready Li+/H+ exchange; LISICONS, where lithium ions are distributed between framework ( tetrahedral) and nonframework sites, undergo a facile Li+/H+ exchange of the nonframework site lithium ions. Accordingly, Li+/H+ exchange in dilute aqueous acetic acid provides a convenient probe to distinguish between the mobile and the immobile lithium ions in lithium ion conductors.

Metal-Ion Metathesis in Metal-Organic Frameworks: A Synthetic Route to New Metal-Organic Frameworks

A porous metalorganic framework, Mn(H3O)(Mn4Cl)(3)(hmtt)(8)] (POST-65), was prepared by the reaction of 5,5',10,10',15,15'-hexamethyltruxene-2,7,12-tricarboxylic acid (H(3)hmtt) with MnCl2 under solvothermal conditions. POST-65(Mn) was subjected to post-synthetic modification with Fe, Co, Ni, and Cu according to an ion-exchange method that resulted in the formation of three isomorphous frameworks, POST-65(Co/Ni/Cu), as well as a new framework, POST-65(Fe). The ion-exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasmaatomic emission spectrometry (ICP-AES), powder X-ray diffraction (PXRD), and BrunauerEmmettTeller (BET) surface-area analysis. Single-crystal X-ray diffractions studies revealed a single-crystal-to-single-crystal (SCSC)-transformation nature of the ion-exchange process. Hydrogen-sorption and magnetization measurements showed metal-specific properties of POST-65.

Designing Novel Sulphate-based Ceramic Materials as Insertion Host Compounds for Secondary Batteries

Rechargeable batteries have propelled the wireless revolution and automobiles market over the past 25 years. Developing better batteries with improved energy density demands unveiling of new cathode ceramic materials with suitable diffusion channels and open framework structure. In this pursuit of achieving higher energy density, one approach is to realize enhanced redox voltage of insertion of ceramic compounds. This can be accomplished by incorporating highly electronegative anions in the cathode ceramics. Building on this idea, recently various sulphate- based compounds have been reported as high voltage cathode materials. The current article highlights the use of sulphate (SO4) based cathodes to realize the highest ever Fe3+/Fe2+ redox potentials in Li-ion batteries (LiFeSO4F fluorosulphate: 3.9V vs Li/Li+) and Na-ion batteries (Na2Fe2(SO4)(3) polysulphate: 3.8V vs Na/Na+). These sulphate-based cathode ceramic compounds pave way for newer avenues to design better batteries for future applications.

Fluorite and Mixed-Metal Kagome-Related Topologies in Metal-Organic Framework Compounds: Synthesis, Structure, and Properties

Two new three-dimensional metal-organic frameworks (MOFs) [Mn-2(mu(3)-OH)(H2O)(2)(BTC)]-2 H2O, I, and [NaMn(BTC)], II (BTC=1,2,4-benzenetricarboxylate = trimellitate) were synthesized and their structures determined by single-crystal X-ray diffraction (XRD). In I, the Mn-4 cluster, [Mn-4(mu(5)-OH)(2)(H2O)(4)O-12], is connected with eight trimellitate anions and each trimellitate anion connects to four different Mn-4 clusters, resulting in a fluorite-like structure. In II, the Mn2O8 dimer is connected with two Na+ ions through carboxylate oxygen to form mixed-metal distorted Kagome-related two-dimensional -M-O-M- layers, which are pillared by the trimellitate anions forming the three-dimensional structure. The extra-framework water molecules in I are reversibly adsorbed and are also corroborated by powder XRD studies. The formation of octameric water clusters involving free and coordinated water molecules appears to be new. Interesting magnetic behavior has been observed for both compounds. Electron spin resonance (ESR) studies indicate a broadening of the signal below the ordering temperature and appear to support the findings of the magnetic studies.

Synthesis, Structure, and Transformation Studies in a Family of Inorganic-Organic Hybrid Framework Structures Based on Indium

Eight new open-framework inorganic-organic hybrid compounds based on indium have been synthesized employing hydrothermal methods. All of the compounds have InO6, C2O4, and HPO3/HPO4/SO4 units connected to form structures of different dimensionality Thus, the compounds have zero- (I), two- (II, III, IV, V, VII, and VIII), and three-dimensionally (VI) extended networks. The formation of the first zero-dimensional hybrid compound is noteworthy In addition, concomitant polymorphic structures have been observed in the present study. The molecular compound, I, was found to be reactive, and the transformation studies in the presence of a base (pyridine) give rise to the polymorphic structures of II and III, while the addition of an acid (H3PO3) gives rise to a new indium phosphite with a pillared layer structure (T1). Preliminary density functional theory calculations suggest that the stabilities of the polymorphs are different, with one of the forms (II) being preferred over the other, which is consistent with the observed experimental behavior. The oxalate units perform more than one role in the present structures. Thus, the oxalate units connect two In centers to satisfy the coordination requirements as well as to achieve charge balance in compounds II, IV, and VI. The terminal oxalate units observed in compounds I, IV, and V suggest the possibility of intermediate structures. Both in-plane and out-of-plane connectivity of the oxalate units were observed in compound VI. The 31 compounds have been characterized by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and P-31 NMR studies.

Two- and Three-Dimensional Open-Framework Uranium Arsenates: Synthesis, Structure, and Characterization

Hydrothermal reactions between uranium salts and arsenic pentoxide in the presence of two different amines yielded six new uranium arsenate phases exhibiting open-framework structures, ethylenediamine (en): [C2N2H9]-[(UO2)(ASO(4))] I; [C2N2H10][(UO2)F(HASO(4))]2 center dot 4H(2)O, II; [C2N2H9][U2F5(HASO(4))(2)], III; [C2N2H9][UF2(ASO(4))], IV; diethylenetriamine (DETA), [C4N3H16][U2F3(ASO(4))(2)(HAsO4)] V; and [C4N3H16][U2F6(AsO4)(HAsO4)], VI. The structures were determined using single crystal studies, which revealed two- (I, II, V) and three-dimensional (III, IV, VI) structures for the uranium arsenates. The uranium atom, in these compounds, exhibits considerable variations in the coordination (6 to 9) that appears to have some correlation with the synthetic conditions. The water molecules in [C2N2H10][(UO2)F(HAsO4)](2 center dot)4H(2)O, II, could be reversibly removed, and the dehydrated phase, [C2N2H10][(UO2)F(HAsO4)](2), IIa, was also characterized using single crystal studies. The observation of many mineralogical structures in the present compounds suggests that the hydrothermal method could successfully replicate the geothermal conditions. As part of this study, we have observed autunite, Ca[(UO2)(PO4)](2)(H2O)(11), metavauxite, [Fe(H2O)(6)][Al(OH)(H2O)(PO4)](2), finarite, PbCU(SO4)(OH)(2), and tancoite, LiNa2H[Al(PO4)(2)(OH)], structures. The repeated observation of the secondary building unit, SBU-4, in many of the uranium arsenate structures suggests that these are viable building units. Optical studies on the uranium arsenate compound, [C4N3H16][U2F6(AsO4)(HASO(4))), VI, containing uranium in the +4 oxidation state indicates a blue emission through an upconversion process. The compound also exhibits antiferromagnetic behavior.

Synthesis, structure, transformation studies and catalytic properties of open-framework cadmium thiosulfate compounds

Five new thiosulfate based inorganic-organic hybrid open-framework compounds have been synthesized employing mild reaction conditions. Of the five compounds, [Na-2(H2O)(8)][Cd(C10H8N2)( S2O3)(2)]center dot 2H(2)O, I and [Cd-2(C10H8N2)(2)(HS2O3)(2)(S2O3)(2)][(C10H9N2)(2)(C10H8N2)(2)]center dot 8H(2)O, II have one-dimensional (1D) structures and [Cd(C10H8N2)(H2O)(2)(S2O3)]center dot 2H(2)O, III, [Cd-2(C10H8N2)(3)(S2O3)(2)], IV and [Cd-2(C10H8N2)(2.5)(S2O3)(2)], V have three- dimensional (3D) structures. The 1D structures are somewhat related, formed by the bonding between tetrahedral Cd centers (CdN2S2) and 4,4'-bipyridine (bpy) units. The inter-chain spaces are occupied by the hanging thiosulfate units in both the cases along with Na(H2O)(6) chains in I and free bpy units in II. The three 3D structures have one-dimensional cadmium thiosulfate chains linked by bpy units. Interpenetration has been observed in all the 3D structures. The 3D structures appear to be related and can be derived from fgs net. Transformation studies on the 1D compound, [Na-2(H2O)(8)][Cd(C10H8N2)(S2O3)(2)]center dot 2H(2)O, I, indicated a facile formation of [Cd(C10H8N2)(H2O)(2)(S2O3)]center dot 2H(2)O, III. Prolonged heating of I gave rise to a 3D cadmium sulfate phase, [Cd-2(C10H8N2)(2)(H2O)(3)(SO4)(2)]center dot 2H(2)O, VI. Compound VI has one-dimensional cadmium sulfate chains formed by six-membered rings connected by bpy units to form a 3D structure, which appears to resemble the topological arrangement of III. Transformation studies of III indicates the formation of IV and V, and at a higher temperature a new 3D cadmium sulfate, [Cd(C10H8N2)(SO4)], VII. Compound VII has a 4 x 4 grid cadmium sulfate layers pillared by bpy units. All the compounds were characterized by PXRD, TGA, IR and UV-visible studies. Preliminary studies on the possible use of the 3D compounds (III-VII) in heterogeneous cyanosilylation of imines appear to be promising.

Combining Bayes Classification and Point Group Symmetry under Boolean Framework for Enhanced Protein Quaternary Structure Inference

Our ability to infer the protein quaternary structure automatically from atom and lattice information is inadequate, especially for weak complexes, and heteromeric quaternary structures. Several approaches exist, but they have limited performance. Here, we present a new scheme to infer protein quaternary structure from lattice and protein information, with all-around coverage for strong, weak and very weak affinity homomeric and heteromeric complexes. The scheme combines naive Bayes classifier and point group symmetry under Boolean framework to detect quaternary structures in crystal lattice. It consistently produces >= 90% coverage across diverse benchmarking data sets, including a notably superior 95% coverage for recognition heteromeric complexes, compared with 53% on the same data set by current state-of-the-art method. The detailed study of a limited number of prediction-failed cases offers interesting insights into the intriguing nature of protein contacts in lattice. The findings have implications for accurate inference of quaternary states of proteins, especially weak affinity complexes.

An eight-connected metal organic framework based on Cu(5) clusters: Synthesis, structure, magnetic and catalytic properties

A reaction of copper acetate, 5-nitroisophthalic acid in a water-methanol mixture under solvothermal condition results in a new metal-organic framework compound, [Cu(5)(mu(3)-OH)(2)(H(2)O)(6){(NO(2))-C(6)H(3)-(COO)(2)}(4)]center dot 5H(2)O, (1). The compound contains Cu5 pentameric cluster units connected by 5-nitro isophthalate (NIPA) moieties forming a CdCl(2)-like layer, which are further connected by another NIPA moiety forming the three-dimensional structure. The water molecules in (1) can be reversibly adsorbed. The removal of water accompanies a change in the colour as well as a structural re-organization. Magnetic studies suggest strong antiferromagnetie correlations between the Cu5 cluster units. The compound (1) exhibits heterogeneous Lewis acid catalysis for the cyanosilylation of imines with more than 95 % selectivity. Compound (1) has been characterized by IR, UV-vis, TGA, powder XRD studies.

Synthesis, Structure, and Magnetic Properties of a New Eight-Connected Metal-Organic Framework (MOF) based on Co-4 Clusters

A hydrothermal reaction of cobalt nitrate, 4,4'-oxybis(benzoic acid) (OBA), 1,2,4-triazole, and NaOH gave rise to a deep purple colored compound Co-4(triazolate)(2)(OBA)(3)], I, possessing Co-4 clusters. The Co-4 clusters are connected together through the tirazolate moieties forming a two-dimensional layer that closely resembles the TiS2 layer. The layers are pillared by the OBA units forming the three-dimensional structure. To the best of our knowledge, this is the first observation of a pillared TiS2 layer in a metal-organic framework compound. Magnetic studies in the temperature range 1.8-300 K indicate strong antiferromagetic interactions for Co-4 clusters. The structure as well as the magnetic behavior of the present compound has been compared with the previously reported related compound Co-2(mu 3-OH)(mu(2)-H2O)(pyrazine)(OBA)(OBAH)] prepared using pyrazine as the linker between the Co-4 clusters.

A Disulfide Stabilized beta-Sandwich Defines the Structure of a New Cysteine Framework M-Superfamily Conotoxin

The structure of a new cysteine framework (-C-CC-C-C-C) ``M''-superfamily conotoxin, Mo3964, shows it to have a beta-sandwich structure that is stabilized by inter-sheet cross disulfide bonds. Mo3964 decreases outward K+ currents in rat dorsal root ganglion neurons and increases the reversal potential of the Na(V)1.2 channels. The structure of Mo3964 (PDB ID: 2MW7) is constructed from the disulfide connectivity pattern, i.e., 1-3, 2-5, and 4-6, that is hitherto undescribed for the ``M''-superfamily conotoxins. The tertiary structural fold has not been described for any of the known conus peptides. NOE (549), dihedral angle (84), and hydrogen bond (28) restraints, obtained by measurement of (h3)J(NC') scalar couplings, were used as input for structure calculation. The ensemble of structures showed a backbone root mean square deviation of 0.68 +/- 0.18 angstrom, with 87% and 13% of the backbone dihedral (phi, psi) angles lying in the most favored and additional allowed regions of the Ramachandran map. The conotoxin Mo3964 represents a new bioactive peptide fold that is stabilized by disulfide bonds and adds to the existing repertoire of scaffolds that can be used to design stable bioactive peptide molecules.