New insight in the template decomposition process of large zeolite ZSM-5 crystals: an in situ UV-Vis/fluorescence micro-spectroscopy study

A combination of in situ UV-Vis and confocal fluorescence micro-spectroscopy was used to study the template decomposition process in large zeolite ZSM-5 crystals. Correlation of polarized light dependent UV-Vis absorption spectra with confocal fluorescence emission spectra in the 400-750 nm region allowed extracting localized information on the nature and amount of chemical species formed upon detemplation at the single particle level. It has been found by means of polarized light dependent UV-Vis absorption measurements that the progressive growth of molecules follows the orientation of the straight channels of ZSM-5 crystals. Oligomerizing template derivatives lead to the subsequent build-up of methyl-substituted benzenium cations and more extended coke-like species, which are thermally stable up to ～740 K. Complementary confocal fluorescence emission spectra showed nearly equal distribution of these molecules within the entire volume of the thermally treated zeolite crystals. The strongest emission bands were appearing in the orange/red part of the visible spectrum, confirming the presence of large polyaromatic molecules.     

Phenolic constituents of Knautia arvensis aerial parts

A new C-6 flavone glycoside (6), together with seven known compounds, cryptochlorogenic acid (1), chlorogenic acid (2), 2-O-trans-caffeoylhydrocitric acid (3), isovitexin 7-beta-D-glucopyranoside (4), 7,4'-dihydroxy-5-methoxyflavone-6-C-beta-D-glucopyranoside (5), 3,5-O-dicaffeoylquinic acid (7) and 4,5-O-dicaffeoylquinic acid (8), were isolated from the aerial parts of Knautia arvensis. Their structures were elucidated by extensive spectroscopic methods including 1D- (1H, 13C and TOCSY) and 2D-NMR (DQF-COSY, HSQC, HMBC) experiments, as well as ESIMS analysis. Compounds 1, 3-5 and 8 are reported for the first time in Knautia arvensis.     

Numerical simulation of a strongly nonlinear Ait-Sahalia-type interest rate model

We are interested in the strong convergence of Euler-Maruyama type approximations to the solution of a class of stochastic differential equations models with highly nonlinear coefficients, arising in mathematical finance. Results in this area can be used to justify Monte Carlo simulations for calibration and valuation. The equations that we study include the Ait-Sahalia type model of the spot interest rate, which has a polynomial drift term that blows up at the origin and a diffusion term with superlinear growth. After establishing existence and uniqueness for the solution, we show that an appropriate implicit numerical method preserves positivity and boundedness of moments, and converges strongly to the true solution.     

Excess entropy in natural language: Present state and perspectives

We review recent progress in understanding the meaning of mutual information in natural language. Let us define words in a text as strings that occur sufficiently often. In a few previous papers, we have shown that a power-law distribution for so defined words (a.k.a. Herdan's law) is obeyed if there is a similar power-law growth of (algorithmic) mutual information between adjacent portions of texts of increasing length. Moreover, the power-law growth of information holds if texts describe a complicated infinite (algorithmically) random object in a highly repetitive way, according to an analogous power-law distribution. The described object may be immutable (like a mathematical or physical constant) or may evolve slowly in time (like cultural heritage). Here, we reflect on the respective mathematical results in a less technical way. We also discuss feasibility of deciding to what extent these results apply to the actual human communication.     

Numerical investigation of mid-infrared emission from Pr^{3+} doped GeAsGaSe fibre

The experimentally obtained luminescence characteristics of a praseodymium (Pr $^{3+})$ doped chalcogenide glass fiber are studied numerically using a rate equation approach. The numerical model includes both the radiative and non-radiative transition paths whilst it neglects the up-conversion processes. Photoluminescence spectra at mid-infrared wavelengths ranging from 3.5 to 6   ${\upmu }$ m were obtained by using two pump wavelengths: 1.55 and 1.94   ${\upmu }$ m. A good agreement between the experiment and theory is obtained for the photoluminescence decay profiles.     

Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies

The Ru‐catalysed C2?H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole‐based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on‐cycle intermediates do not possess a para‐cymene ligand and that the on‐cycle metalation occurs through an electrophilic attack by the Ru centre.     

Chiral Hemilabile P,N-Ligand-Assisted Gold Redox Catalysis for Enantioselective Alkene Aminoarylation

Enantioselective, intermolecular alkene arylamination was achieved through gold redox catalysis. Screening of ligands revealed chiral P,N ligands as the optimal choice, giving alkene aminoarylation with good yields (up to 80 %) and excellent stereoselectivity (up to 99 : 1 er). As the first example of enantioselective gold redox catalysis, this work confirmed the feasibility of applying a chiral ligand at the gold(I) stage, with the stereodetermining step (SDS) at the gold(III) intermediate, thus opening up a new way to conduct gold redox catalysis with stereochemistry control.     

“Orthogonal-Twisted-Arm” Ligands for The Construction of Metal–Organic Frameworks (MOFs): New Topology and Catalytic Reactivity

Extended tetratopic benzoic acid ligands with “orthogonal-twisted-arms” conformations were designed and synthesized for the construction of new MOF structures (OTA-MOF). Upon coordination with Cd²⁺ and Cu²⁺ cations, two well-defined new MOFs were prepared. X-ray single crystal structures were successfully obtained, demonstrating the formation of a new topology (4,4,4-c). The OTA2-MOF-Cu gave moderate stability in organic solvents and good gas sorption ability toward CO₂. This new MOF showed superior catalytic reactivity toward the epoxide-CO₂ cycloaddition, giving >50 folds yield enhancement over the controlled reaction without MOF. It is expected that this new ligand design, porous structure, and excellent CO₂ catalytic reactivity will make OTA-MOF promising new materials for applications in catalysis and separation.