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abstracts
Several studies have aimed to better understand coordination polymers, which are structures based on a connection between a metal ion and an organic ligand that extends infinitely, forming a macro-structure1. The interest in this type of structure is mainly due to its properties, such as its pore-forming ability, presenting many potential applications2 like selective separations, catalysis and gas storage. It is interesting to study the structure of coordination polymers to focus in some particular future application. In these way, a coordination polymer was synthetized by simple mixture with isonicotinylhydrazine (INH) and 1,2,4,5-benzenetetracarboxylic acid (BTC) ligands and zinc metallic ion. Yellow single crystals were formed in solution and one was separated, measured and solved by single crystal X-ray diffraction. The crystal-data for the structure were collected using an Oxford GEMINI A-Ultra diffractometer with MoKα radiation (λ = 0.71073 Å) at room temperature and solved using SHELXL-97 program3. The compound crystallized in monoclinic crystalline system in space group P21/c, cell parameters: a=9.2502(6) Å, b= 15.0004(6) Å, c=9.2947(4) Å, β= 108.4590(6), V=1223,35 Å3 and Z=4. The final statistical parameters of the structure refinement were R=0.0326, wR=0.0835 and S=1,053. In this compound the BTC and INH ligands are coordinated like a bridge to two zinc ions. The BTC forms chelates by two carboxylate groups and INH coordinates by pyridine ring and by chelate at hydrazide group. This polymer extends in only one direction along a axis forming a 1D network. There is only one metallic zinc ion crystallographically independent on structure, it is in a distorted octahedral geometry with oxygen and nitrogen atoms of ligands and one coordinated water molecule in its coordination sphere. The 1D network formed by coordination polymers stabilizes the crystalline arrangement by hydrogen bonds between carboxylate and hydrazide groups and coordinated water molecules.
abstracts
Layered double hydroxides (LDHs) or hydrotalite-like compounds belong to a class of synthetic two-dimensional inorganic materials with lamellar structures, where the hydroxyl-hydrated compounds are formed by chemical substitution of divalent ion of the brucite-like octahedral layers by trivalent ions [1]. The LDH are represented by the general formula, Figure a , where M2+, M3+ are divalent and trivalent cation and Am- is interlayer anion responsible by charge balancing, the range of divalent and trivalent ions (x) varies normally between 0.17 a 0.33. According Montanari and co-works [2] compounds type ZnAl-hydrotalcites (ZnAl-HT) have relevant industrial interest; however the scientific literature concerning this material as catalysts or catalyst precursor is scarce. Based on this fact, in the present communication we will present a studied on how the variation in percentage of Zinc in a ZnMgAl-HT catalyst precursor can influence the formation of mixed oxides after calcination. The ZnMgAl-HTs, Figure b , y=5, 10,15,20,25,50,75 and 100% were prepared by co-precipitation and urea method. Mg-Zn/Al mixed oxides were prepared from calcinations of hydrotalcites precursors at 5000C for 4 hours. The material synthesized were characterized by X-ray powder diffraction, the measurements were carried out in Bruker D8 DaVinci diffractometer, equipped with CuKα radiation , LynxEye linear Position Sensitive Detector, Ni-filter. Data was collect between 8 and 800 in 2θ with step size of 0.020 and the count time of 0.05 per step. Soller slit 2.50 of divergence and 0.2 mm primary slit were used. For the ZnMgAl-HT samples the measurements were performed at different temperatures, range 25-12000C, heating rate 50C/min. It was observed differences among XRD patterns for y greater than 25% of Zn in urea method at 5000C, and for co-precipitation method just for the substitution at 50 and 75% of Zn. These results suggested that the increase in Zn percentage change the structure of calcinated samples.
abstracts
The p-sulfobenzoic (4-psb) acid may be used as precursors for different Metal Organic frameworks (MOFs) since they can display different coordination site on the metal with two different functional groups (carboxylate and sulfonate). Details of the crystal packing can be studied using the Reticular Chemistry like a power tool for the deconstruction process of crystal structure of this compounds formed [1]. Two crystal structures Zn-psb and Mn-psb with 4-psb ligand and Zn+2 and Mn+2 ions, respectively, were synthesized. Single crystal-data were collected using an Oxford GEMINI A-Ultra diffractometer with MoKα radiation (λ = 0.71073 Å) at room temperature (298 K). These structures were refined by SHELXL-97 program [2]. Both compounds crystallized in the triclinic system and space group P-1. Zn-psb structure shows a coordinated Zn atom with a slightly distorted octahedral geometry formed by four oxygen atoms from water molecules with averaged distances at 2.08 (2) Å and two oxygen atoms with distances at 2.12 (2) Å derived from the ligand. Mn-psb structure has coordinated Mn atom with a slightly distorted octahedral geometry formed by four oxygen atoms from sulfonate group coordinated with averaged distances at 2.19 (3) Å and two oxygen atoms from water molecules with distances at 2.17 (2) Å. Despite the structural similarities of the structures, a simple modification of the metal in the reaction leads to a tendency for different network. Thus, Zn-psb structure consists of a network-connected system binodal (3,8). This network is deposited in Reticular Chemistry Structural Resource as a network type tfz-d system with tilling of transitivity [2222] and signature 3[4^2.6^2] + 2[6^3]. However, the Mn-psb structure leads to formation of a regular network with pcu topologic type presenting tilling with transitivity [1111] and signature [4^6]. The system of cavities formed into networks are blocked by ligands in the crystal structure.
