Dynamic Covalent Properties of a Novel Indolo[3,2-b]carbazole Diradical

This work describes the synthesis and properties of a dicyanomethylene-substituted indolo[3,2-b]carbazole diradical ICz-CN. This quinoidal system dimerises almost completely to (ICz-CN)₂, which contains two long C(sp³)−C(sp³) σ-bonds between the dicyanomethylene units. The minor open-shell ICz-CN component in the solid-state mixture was identified by EPR spectroscopy. Cyclic voltammetry and UV–visible spectroelectrochemical data, as well as comparison with reference monomer ICz-Br reveal that the nature of the one-electron oxidation of (ICz-CN)₂ at ambient temperature and ICz-CN at elevated temperature is very similar in all these compounds due to the prevailing localization of their HOMO on the ICz backbone. The peculiar cathodic behaviour reflects the co-existence of (ICz-CN)₂ and ICz-CN. The involvement of the dicyanomethylene groups stabilizes the close-lying LUMO and LUMO+1 of (ICz-CN)₂ and especially ICz-CN compared to ICz-Br, resulting in a distinctive cathodic response at low overpotentials. Differently from neutral ICz-CN, its radical anion and dianion are remarkably stable under ambient conditions. The UV/Vis(–NIR) electronic transitions in parent (ICz-CN)₂ and ICz-CN and their different redox forms have been assigned convincingly with the aid of TD-DFT calculations. The σ-bond in neutral (ICz-CN)₂ is cleaved in solution and in the solid-state upon soft external stimuli (temperature, pressure), showing a strong chromism from light yellow to blue–green. Notably, in the solid state, the monomeric diradical species is predominantly formed under high hydrostatic pressure (>1 GPa).     

Heterogenization of titanium(IV) complexes with amine bis(phenolate) ligands onto SBA‐15: exploring their catalytic epoxidation and electrochemical behaviour

This paper describes the synthesis and characterization of titanium catalysts supported onto SBA‐15 via chemical bonding. This was done by first modifying the support with amine bis(phenol) groups as functional linkers and hexamethyldisilizane as capping agent to mask the remaining silanol groups on the silica surface. Finally, titanium tetraisopropoxide was immobilized by reaction with the modified SBA‐15. All the materials were characterized using X‐ray diffraction, X‐ray fluorescence, nitrogen adsorption‐desorption, Fourier transform infrared, UV‐visible diffuse reflectance and solid‐state nuclear magnetic resonance spectroscopies, and solid‐state electrochemical techniques. The titanium materials were tested as cyclohexene epoxidation catalysts. The stability and reusability of the catalysts were also examined using voltammetry measurements. Copyright © 2016 John Wiley & Sons, Ltd.     

Study on the hydrolytic degradation of the segmented GL-b-[GL-co-TMC-co-CL]-b-GL copolymer with application as monofilar surgical suture

The hydrolytic degradation of Monosyn™, a segmented copolymer derived from glycolide, trimethylene carbonate and ε-caprolactone, has been evaluated in buffered aqueous media at different pH and temperature. Degradation processes have been followed by considering mass loss and molecular weight profiles as well as the changes on ¹H NMR and FTIR spectra, morphology and both calorimetric and mechanical properties during exposure to the selected media and temperature.     

Reactivity of Chiral Sesquiterpene Synthons Obtained by the Degradation of Maslinic Acid from Olive‐Pressing Residues

Maslinic acid, a naturally occurring compound isolated from the solid wastes of olive‐oil pressing, was fragmented through the C‐ring via oxidative procedures to obtain two structural fragments. The chemical behaviors of cis‐decalin, from the D and E rings, and of trans‐decalin fragments, from the A and B rings, were investigated in depth using several chemical and enzymatic reactions. These decalin chiral synthons are interesting intermediates to semisynthesize phenanthrene‐ and drimane‐type compounds and natural tricyclic triterpenes.     

Ultrasonically enhanced extraction of bioactive principles from Quillaja Saponaria Molina

A study of ultrasonic enhancement in the extraction of bioactive principles from Quillaja Saponaria Molina (Quillay) is presented. The effects influencing the extraction process were studied through a two-level factorial design. The effects considered in the experimental design were: granulometry, extraction time, acoustic Power, raw matter/solvent ratio (concentration) and acoustic impedance.It was found that for aqueous extraction the main factors affecting the ultrasonically-assisted process were: granulometry, raw matter/solvent ratio and extraction time. The extraction ratio was increased by Ultrasonics effect and a reduction in extraction time was verified without any influence in the product quality. In addition the process can be carried out at lower temperatures than the conventional method.As the process developed uses chips from the branches of trees, and not only the bark, this research contributes to make the saponin exploitation process a sustainable industry.     

Thermal analysis of polymer layered silicate nanocomposites

It has been shown, for three different polymer layered silicate (PLS) nanocomposite systems, how differential scanning calorimetry (DSC) can identify the different reactions of homopolymerisation and of crosslinking that occur in the intra- and extra-gallery regions of these nanocomposites, respectively, and hence how DSC can be used to assess the cure conditions for optimising their nanostructure. The PLS nanocomposites are based upon: (i) diglycidyl ether of bisphenol-A (DGEBA) cured with a polyoxypropylene diamine; (ii) DGEBA cured with an –NH₂ terminated hyperbranched polymer (HBP); and (iii) tri-glycidyl p-amino phenol (TGAP) cured with a diamine. In each case, the existence of both intra- and extra-gallery reactions in the DSC cure curves, and whether they occur simultaneously or sequentially, and in what order, are identified and correlated with the nanostructure as observed by small angle X-ray scattering and transmission electron microscopy. In particular, it is shown that the intra-gallery reaction must precede the extra-gallery for significant exfoliation to occur. In accordance with this scenario, the TGAP/diamine system displays the greatest degree of exfoliation, the DGEBA/diamine system the least, with the DGEBA/HBP system intermediate. For those systems in which significant exfoliation occurs, the DSC cure curves also allow the optimum cure conditions, such as the isothermal cure temperature, to be determined.     

Energy Transfer in Aminonaphthalimide‐Boron‐Dipyrromethene (BODIPY) Dyads upon One‐ and Two‐Photon Excitation: Applications for Cellular Imaging

Aminonaphthalimide–BODIPY energy transfer cassettes were found to show very fast (k_EET≈10¹⁰–10¹¹ s^?1) and efficient BODIPY fluorescence sensitization. This was observed upon one‐ and two‐photon excitation, which extends the application range of the investigated bichromophoric dyads in terms of accessible excitation wavelengths. In comparison with the direct excitation of the BODIPY chromophore, the two‐photon absorption cross‐section δ of the dyads is significantly incremented by the presence of the aminonaphthalimide donor [δ≈10 GM for the BODIPY versus 19–26 GM in the dyad at λ_exc=840 nm; 1 GM (Goeppert–Mayer unit)=10^?50 cm⁴ s molecule^?1 photon^?1]. The electronic decoupling of the donor and acceptor, which is a precondition for the energy transfer cassette concept, was demonstrated by time‐dependent density functional theory calculations. The applicability of the new probes in the one‐ and two‐photon excitation mode was demonstrated in a proof‐of‐principle approach in the fluorescence imaging of HeLa cells. To the best of our knowledge, this is the first demonstration of the merging of multiphoton excitation with the energy transfer cassette concept for a BODIPY‐containing dyad.     

On the Lindenstrauss-Rosenthal theorem

We present a homological principle that governs the behaviour of couples of exact sequences of quasi-Banach spaces. Three applications are given: (i) A unifying method of proof for the results of Lindenstrauss, Rosenthal, Kalton, Peck and Kislyakov about the extension and lifting of isomorphisms inc ₀,ι _∞,ι _p andL _pfor 0<p≤1; (ii) A study of the Dunford-Pettis property in duals of quotients ofL _∞-spaces; and (iii) New results on the extension ofC(K)-valued operators. The research has been supported in part by DGICYT project BFM 2001-0813.