Exploring physical and chemical properties in new multifunctional indium-, bismuth-, and zinc-based 1D and 2D coordination polymers.

Main group element coordination polymers (MGE-CPs) are important compounds for the development of multifunctional materials. However, there has been a shortage of studies regarding their structural, optical, catalytic, mechanical, and antibacterial properties. This work presents an exhaustive study of a set of crystalline MGE-CPs obtained from bismuth and indium metals and iminodiacetate, 1,2,4,5-benzenetetracarboxylate, and 2,2'-bipyridine as building blocks. An in-depth topological analysis of the networks was carried out. Additionally, nanoindentation studies were performed on two representative low-dimensional compounds in order to find the relationships between their structural features and their intrinsic mechanical properties (hardness and elasticity). The solid-state photoluminescence (SSPL) properties were also studied in terms of excitation, emission, lifetimes values, and CIE chromaticites. Moreover, the heterogeneous catalytic activities of the compounds were evaluated with the cyanosilylation reaction using a set of carbonylic substrates under solvent-free conditions. Finally, the inhibitory effect of the Bi-CPs on the growth of microorganisms such as Escherichia coli, Salmonella enterica serovar Typhimurium, and Pseudomonas aeruginosa, which are associated with relevant infectious diseases, is reported.

Cytocompatibility, biofilm assembly and corrosion behavior of Mg-HAP composites processed by extrusion.

In this work the cytocompatibility of pure magnesium and Mg-xHAP composites (x=5, 10 and 15wt%) fabricated by powder metallurgy routes has been investigated. The materials were produced from raw HAP powders with particle mean sizes of 6µm (S-xHAP) or 25µm (L-xHAP). The biocompatibility study has been performed for MC3T3 cells (osteoblasts/osteoclasts) and L929 fibroblasts. The results indicate that S-Mg (pure magnesium), S-10HAP and L-10HAP composites are the materials with the best biocompatibility. The ability of S. aureus bacteria to assemble biofilms was also evaluated. Biofilm formation assays showed that these materials are not particular prone to colonization and biofilm assembly is strain dependent. The corrosion resistance of S-Mg, S-10HAP and L-10HAP materials immersed in the media used for the cells culture has also been analyzed. Different trends in the corrosion resistance have been found: S-Mg and S-10HAP show a very high resistance to corrosion whereas the corrosion of L-10HAP steadily increases with time.

Processing and mechanical characteristics of magnesium-hydroxyapatite metal matrix biocomposites.

Magnesium/hydroxyapatite composites were produced by conventional extrusion and their mechanical behavior studied under uniaxial compression at room temperature. The results evidence the capability of the HA for strengthening the Mg material, lowering its microstructural anisotropy and inhibiting deformation twinning. They also reveal that the ECAP processing is effective for improving the grain structure and reducing the crystallographic texture of these composites, giving rise to a significant enhancement of their yield strength and microhardness although the ultimate compressive stress worsens. The analysis of the strain hardening rate of the flow curves demonstrates that the HA addition and the ECAP processing are also effective in inhibiting non-basal dislocation slip.

Crystal phase competition by addition of a second metal cation in solid solution metal-organic frameworks.

Herein we report a synthetic study focused on the preparation of solid-solution metal-organic frameworks, MOFs, with the use of two kinds of linkers. In particular, we have explored the system composed by zinc, cobalt, 1,2,4-triazole and 4,4'-hexafluoroisopropylidenebisbenzoic acid (H2hfipbb). During this study, four new MOFs have been isolated, denoted TMPF-88 [M3(hfipbb)2(triazole)2(H2O)], TMPF-90 [M2(triazole)3(OCH2CH3)], TMPF-91 [M2(hfipbb)(triazole)2(H2O)] and TMPF-95 [M5(hfipbb)4(triazole)2(H2O)] (TMPF = transition metal polymeric framework, M = Zn, Co, or mixture of them). The study demonstrates that the addition of a second metal element during the MOF synthesis has a major effect in the formation of new phases, even at very high Zn/Co metal ratios. Furthermore, we show that during the MOF formation reaction, there is a competition among different crystal phases, where kinetically favoured phases of various compositions crystallize in short reaction times, precluding the formation of the pure solid-solution phases of other energetically more stable MOFs.

Synthesis, crystal structure, and biological activity of a Pt-dipyridamole salt.

In the present paper we present data on the synthesis, crystal structure and biological activity of bis(dipyridamole) tetrachloroplatinate(II).dipyridamole.dihydrate, [dpmH]2 PtCl4.dpm.2H2O. The crystals are Triclinic P1 with a = 11.490(2) A, b = 13.630(2) A, c = 15.81(1) A, a = 100.97(2) degrees, beta = 100.89(3) degrees, gamma = 112.35(1) degrees, Z = 1, M = 1885.9, Dx = 1.46 g/cm3, MoK alpha (lambda = 0.71069 A), mu = 0.0184 mm-1, R = 4.4%, Rw = 5.0%, 3231 (1 > 2 sigma (I)). The structure is stabilized by a hydrogen-bonding network. It was observed that although dpm alone is not able to alter the electrophoretic mobility of pUC8 DNA forms, the synthesized Pt-dpm compound substantially modifies the DNA conformation since it significantly alters the electrophoretic mobility of nicked and closed circular forms of pUC8 DNA. However, the alteration in mobility of pUC8 DNA induced by this compound upon binding is lower than that induced by cis-DDP. The analysis of the antiproliferative activity of the Pt-dpm salt against MDA-MB 468 (breast carcinoma) and HL-60 (leukemia) human cancer cells showed that this compound has ID50 values of 0.87 microM and 0.65 microM, respectively. Interestingly, it was found out that although the dpm molecule does not present any significant antiproliferative activity, the ID50 values of Pt-dpm are about 3-fold and 7-fold lower than those of cis-DDP and K2PtCl4, respectively. Altogether the biological data suggest that in Pt-dpm a synergic effect between cation and anion is produced.

Mechanical properties and corrosion behavior of Mg-HAP composites.

Mg and Mg-HAP composites containing 5, 10 and 15 wt% of hydroxyapatite have been produced following a powder metallurgy route that consists of mixing raw powders and consolidation by extrusion. The microstructure, texture, mechanical behavior and resistance to corrosion under a PBS solution have been studied. Addition of HAP increases the microhardness of the composites, however the yield strength under compression slightly decreases. Texture analyses reveal a fiber texture for pure Mg that is weakened increasing the HAP fraction. This texture promotes twinning and softening of Mg and Mg-5HAP during the initial deformation stages. Mg-10HAP and Mg-15HAP present a strain-hardening dependence showing no softening. The volume fraction of HAP particles weakens the texture and favors the activation of secondary slip systems. Corrosion experiments in PBS solution have shown that Mg-5HAP exhibits the best resistance to corrosion. Texture and porosity appear to be the main material features controlling the corrosion rates of Mg-HAP composites under the present conditions.

Effect of highly dispersed yttria addition on thermal stability of hydroxyapatite.

The capability of the colloidal method to produce yttria (Y(2)O(3)) dispersed hydroxyapatite (HA) has been investigated as an alternative method to the conventional method of mechanical mixing and sintering for developing HA-based materials that could exhibit controllable and enhanced functional properties. A water based colloidal route to produce HA materials with highly dispersed Y(2)O(3) has been applied, and the effect of 10 wt.% Y(2)O(3) addition to HA investigated by thermal analysis, X-ray diffraction and Fourier transform infrared spectroscopy. These measurements evidence a remarkable effect of this Y(2)O(3) addition on decomposition mechanisms of synthetic HA. Results show that incorporation of Y(2)O(3) as dispersed second phase is beneficial because it hinders the decomposition mechanisms of HA into calcium phosphates. This retardation will allow the control of the sintering conditions for developing HA implants with improved properties. Besides, substitution of Ca(2+) with Y(3+) ions appears to promote the formation of OH(-) vacancies, which could improve the conductive properties of HA favorable to osseointegration.

Fermi surface and magnetic structure of TmGa3.

We carry out measurements of the two-dimensional angular correlation of the positron annihilation radiation (2D-ACAR) to reconstruct the complex multisheet Fermi surface (FS) of the cubic rare-earth (RE) compound TmGa3. We discover a correlation between the antiferromagnetic structures and the nesting of the FS along the [110] directions. Moreover, we propose methods to estimate the density of states at the Fermi energy ( EF) and the electronic contribution to the specific heat [we obtain N(EF) = 13.6 states/Ryd cell and gamma = 2.4 mJ/mole K2].

In(2)(OH)(3)(BDC)(1.5) (BDC = 1,4-benzendicarboxylate): an In(III) supramolecular 3D framework with catalytic activity.

The new hybrid inorganic-organic polymer In(2)(OH)(3)[O(4)C(8)H(4)](1.5) has been hydrothermally obtained. Conditions for the synthesis are reported. The crystal structure of this material has been established by single-crystal X-ray diffraction: it is monoclinic, with space group P2(1)/c (Nomicron. 14), a = 6.772(1) A, b = 10.329(2) A, c = 20.152(3) A, beta = 97.573(3) degrees. The In atoms are octahedrally coordinated by three hydroxide groups and three different molecules of carboxylate ligand. The resulting polymeric 3D structure can be envisaged as having been generated from a honeycomb (6,3) 2D that is cross-linked by the BDC organic anions. Data of IR and TGA-DTA studies, as well as the results of reduction of nitroaromatics and selective oxidation of organic sulfide reactions catalyzed by the new material, are reported.