Tuning the structure and the mechanical properties of epoxy-silica sol-gel hybrid materials

A new route for the synthesis of a monolithic porous hybrid organic-inorganic material composed of silica and an epoxy resin is reported. This ormosil material is prepared by supercritical drying of a gel obtained by a one-pot procedure and using ethanol as the only solvent. The microscopic analysis reveals that the material presents an open network of micrometric pores. The characteristics of the pore structure strongly depend on the ratio between silica and epoxy. While in most cases the structure is formed by homogeneous hybrid primary particles, a foam-like structure is observed for a specific composition, which seems related to a phase-separation effect. The material presents rubber-like behavior under compression. Moreover, the compression modulus can be continuously tuned along two orders of magnitude through the variation of the silica-epoxy ratio, allowing the preparation of a material with tailored mechanical properties.MATGAS is acknowledged for allowing the use of their supercritical drying facilities. Dr Daniel Crespo (Departament de Física Aplicada, Escola d'Enginyeria de Telecomunicació i Aeronàutica de Castelldefels, Universitat Politècnica de Catalunya) is acknowledged for his help in the DMA tests. SOPREMA (France), the Spanish Ministerio de Economía y Competitividad (Grant No.ENE-2012-36368-C02-02) and the Generalitat de Catalunya (Grant No. 2014SGR1643) are acknowledged by their financial support. support.Peer Reviewe

Cocrystallization of antifungal compounds mediated by halogen bonding

The application of halogen bonding in pharmaceutical chemistry remains a challenge. In this work, novel halogen-bonded cocrystals based on azole antifungal active pharmaceutical ingredients (APIs) and the ditopic molecule 1,4-diiodotetrafluorobenzene are reported. Their crystal structural features, spectroscopic properties, and thermal stability were studied. The components are bound through I···N from the triazole moieties present in all of the compounds. The molecular electrostatic potential (MEP) surfaces and quantum theory of atoms in molecules (QTAIM) calculations are used to rationalize the presence of hydrogen and halogen bonds in the resulting structures and their energetic analysis. The relative halogen bond ability of the different groups of voriconazole, fluconazole, and itraconazole was analyzed using MEP surfaces, demonstrating this approach to be an interesting tool to predict halogen-bonding preferences

Effect of Ce and Mn co-doping on photocatalytic performance of sol-gel TiO2

Co-doped titanium dioxide was synthesized by doping with manganese (Mn) and cerium (Ce) through a sol-gel method for the degradation of diclofenac (DCF). The synthesized products were successfully characterized by X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Nitrogen physisorption at 77 K, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance (UV-DRS), photoluminescence spectroscopy (PL) and total organic carbon (TOC). It was shown that co-doping increased the specific surface area, improved the visible light absorption and extended the lifetime of photogenerated charge carriers. Furthermore, the results of the photocatalytic experiments show that the photodegradation rate of diclofenac can be approached by pseudo first-order kinetics and it followed the Langmuir-Hinshelwood model very well. The co-doped catalyst with 0.6 % Mn and 1 % Ce molar ratios appeared to be the most photoactive catalyst with 94 % of DCF removal and an apparent rate constant of 0.012 min-1.Peer ReviewedPostprint (published version

Crystal defects and spin tunneling in single crystals of Mn12 clusters

The question addressed in this paper is that of the influence of the density of dislocations on the spin tunneling in Mn12 clusters. We have determined the variation in the mosaicity of fresh and thermally treated single crystals of Mn12 by analyzing the widening of low angle x-ray diffraction peaks. It has also been well established from both isothermal magnetization and relaxation experiments that there is a broad distribution of tunneling rates which is shifted to higher rates when the density of dislocations increases

A practical synthetic route to enantiopure 6-substituted cis-decahydroquinolines

Starting from 4-substituted cyclohexanones, a practical synthetic route to enantiopure 6-substituted cis-decahydroquinolines has been developed, the key steps being a stereoselective cyclocondensation of an unsaturated δ-keto ester derivative with (R)-phenylglycinol and the stereoselective hydrogenation of the resulting tricyclic oxazoloquinolone lactams

Aqua(1,10-phenanthroline)(l-serinato)copper(II) Nitrate

The unit cell of the title complez, [Cu(C3H6NO3)-(C12H8N2)(H20)]NO3, contains two nitrate anions and two complex cations, each with two chiral centers, one in the serine molecule and the other at the Cu uion. Each Cu ion displays slightly distorted square-pyramidal coordination, with the water molecule in the apical position and the base defined by the aliphatic N atom and one of the O atoms from the aminocarboxylate ligand and the two N atoms from the phenanthroline molecule. The relative position of the apical water molecule generates the chiral center at the Cu ion. In both molecules, the five-membered chelate ring defined by atoms N1, C12, C11, N2 and Cu is roughly planar, while the ring defined by atoms N3, C13, C14, O1 and Cu has a distorted half-chair conformation

A Biomimetic Enantioselective Approach to the Decahydroquinoline Class of Dendrobatid Alkaloids

Frogs of the neotropical family Dendrobatidae produce a remarkably diverse array of biologically active alkaloids. One of the major classes of these amphibian alkaloids[1] are the decahydroquinolines, which have been isolated not only from skin extracts of dendrobatid and mantelline frogs,[2] but also from bufonid toads,[3] tunicates,[4] marine flatworms,[4b] and myrmicine ants.[5] They possess either a cis or trans decahydroquinoline ring fusion, with a side-chain substituent at both the C2 and C5 positions and, in the lepadin series,[4] an acylated hydroxy group at the C3 position. The most representative decahydroquinoline alkaloid is cis-195A (formerly called pumiliotoxin C), first isolated in 1969 from a Panamanian population of Dendrobates pumilio. [6] The source of amphibian alkaloids remains an unresolved and challenging question,[1] in particular after the discovery that some of these alkaloids also occur in ants, thus strengthening a dietary hypothesis for their origin in frogs.[5] Although there are no conclusive studies concerning the biosynthesis of these toxins and, consequently, little is known about the biosynthetic pathways, there has been speculation as to possible derivation from the polyketide route by aminocyclization of polycarbonyl intermediates (A), leading to either 2,5-disubstituted decahydroquinolines (C) or spiropiperidines (histrionicotoxins).[1a,b, 7] In accordance with this hypothesis, a plausible biosynthetic pathway to the decahydroquinoline class of dendrobatid alkaloids is depicted i

Preparation and Double Michael Addition Reactions of a Synthetic Equivalent of Nazarov Reagent

A synthetic equivalent of the Nazarov reagent, the silyl derivative 2, able to undergo base-catalyzed double Michael addition reactions with a,b-unsaturated carbonyl compounds, has been developed. The new reagent satisfactorily reacts with unsaturated indolo[2,3-a]quinolizidine lactams to give pentacyclic yohimbinone-type derivatives

Studies on the Enantioselective Synthesis of E-Ethylidene-bearing Spiro[indolizidine-1,3′-oxindole] Alkaloids

A synthetic route for the enantioselective construction of the tetracyclic spiro[indolizidine-1,3'-oxindole] framework present in a large number of oxindole alkaloids, with a cis H-3/H-15 stereochemistry, a functionalized two-carbon substituent at C-15, and an E-ethylidene substituent at C-20, is reported. The key steps of the synthesis are the generation of the tetracyclic spirooxindole ring system by stereoselective spirocyclization from a tryptophanol-derived oxazolopiperidone lactam, the removal of the hydroxymethyl group, and the stereoselective introduction of the E-ethylidene substituent by acetylation at the -position of the lactam carbonyl, followed by hydride reduction and elimination. Following this route, the 21-oxo derivative of the enantiomer of the alkaloid 7(S)-geissoschizol oxindole has been prepared

Stereoselective synthesis of cis-1,3-dimethyltetrahydroisoquinolines: formal synthesis of naphthylisoquinoline alkaloids

Starting from tricyclic lactam 2, which is easily accessible by cyclocondensation of -oxoester 1 with (R)-phenylglycinol, a three-step synthetic route to enantiopure 1-substituted tetrahydroisoquinolines, including 1-alkyl-, 1-aryl-, and 1-benzyl- tetrahydroisoquinoline alkaloids as well as the tricyclic alkaloid (-)-crispine A, has been developed. The key step is a stereoselective -amidoalkylation reaction using the appropriate Grignard reagent