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We report here on the design of inorganic-organic hybrid materials, which consist of layered double hydroxides (LDHs) as inorganic carrier and short single-stranded nucleic acids (ssDNA) as organic molecules. LDHs were prepared by the co-precipitation method followed by hydrothermal treatment. A model 12-nucleotide-long sequence was immobilized either by ion exchange or covalent grafting. Both the LDH composition and the nucleic acid-to-particle ratio were optimized throughout the synthesis to develop highly stable suspensions of the hybrid materials. Structural characterization revealed that the covalent attachment of the ssDNA was successfully achieved via silanization of the LDHs in aqueous suspension. Covalent linkage of the nucleic acids confers to this model nanoparticulate system promising properties and potential for applications as therapeutic agents. Fragments of nucleic acids could be introduced into living cells without release during the delivery process since LDHs slowly dissolve in the slightly acidic intracellular space. [ABSTRACT FROM AUTHOR]

In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe–LDH, heat treated in the 373–973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57 Fe Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and Fe Mössbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids. [ABSTRACT FROM AUTHOR]

Five- and six-membered cyclic α-amino acid anions with secondary nitrogen in the ring ( l-prolinate and dl-pipecolinate) were immobilised in CaFe-L(ayered)D(ouble)H(ydroxide) by the dehydration-rehydration method. The resulting organic-inorganic hybrids were characterised by various instrumental methods (powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray fluorescence with elemental mapping, and analytical techniques for determining the iron as well as the organic contents) and molecular modelling. The immobilised organocatalysts were tested in the cross-aldol dimerization-condensation reaction between benzaldehyde and acetone and found to be active and enantioselectivity in the dimerization was also observed. [ABSTRACT FROM AUTHOR]

A Cu(II)Fe(III)-layered double hydroxide is shown to efficiently catalyze 1,3-dipolar cycloadditions of organic azides to alkynes leading to valuable 1,2,3-triazoles. The benefits of continuous processing were exploited for reaction optimization and synthesis, and the production of triazoles was realized in an inherently safe and scalable manner. It was established that the catalytic activity of the as-prepared material can be derived from in situ reduction of Cu(II), generating lattice defects containing the catalytically active Cu(I) species. It was verified that oxidative homocoupling of the alkyne component was responsible for the conversion of Cu(II) to Cu(I), but a cooperation of certain structural items of the hydrotalcite-like material could also contribute to the outstanding catalytic efficiency. After a successful gram-scale triazole synthesis under high-pressure/high-temperature conditions, no destruction of the catalyst structure was found, suggesting that the layered double hydroxide acted as a highly robust catalytic system. [ABSTRACT FROM AUTHOR]

Syntheses of Ca(II)Sn(IV)-layered double hydroxides (LDHs) are attempted by the traditional co-precipitation as well as mechanochemical methods. Both the co-precipitation method and the one-step milling operation proved to be unsuccessful; these methods only produced physical mixtures of hydroxides and carbonates of the two metal ions. However, a two-step milling operation (dry milling followed by milling in the presence of minute amount of water) led to successful synthesis, verified by a range of characterisation methods. Surprisingly, it was found that ball-milling was not even necessary; the reaction proceeded on manual grinding of the components in an agate mortar with a pestle. The preparation of nanocomposites through intercalation of the anions of cystine or valine into Ca(II)Sn(IV)-LDH could also be achieved by the two-step milling method verified again by a range of instrumental methods. [ABSTRACT FROM AUTHOR]

In order to find highly active and selective oxygen-transfer catalysts with appreciable durability, Cu(II)–histidine complexes were covalently grafted onto a chlorinated polystyrene resin as copper-containing enzyme mimics. The Cu(II)-histidine complexes and the mobile polymer were to resemble the active center and the proteomic skeleton of the enzymes, respectively. The resulting heterogenized complexes were expected to be nearly so active and more durable catalysts that are easier to recycle than their homogeneous counterparts. The substances were tested in a superoxide radical anion dismutation reaction. Control for the syntheses was exerted by protecting either the N-terminal or the C-terminal of the covalently grafted l-histidine molecules. During the preparative work generally applied methods of synthetic organic chemistry (alkylation or esterification) were used. Various anchored complexes were prepared and characterized by classical analytical methods, different forms of spectroscopy as well as molecular modeling. The covalently grafted complexes having the protected amino acids as ligands displayed remarkably high activities in the superoxide dismutase (SOD) test reaction. [ABSTRACT FROM AUTHOR]