Synthesis and characterization of optically active and racemic forms of cyclometalated Rh(III) complexes. An experimental and theoretical emission study

The optically active cyclometalated Rh(III) complexes, delta[Rh(thpy4,5p(R,R)py)(2)TAP]Cl, lambda[Rh(thpy4,5p(S,S)py)(2)TAP]Cl, and delta[Rh(phpy4,5p(R,R)py)(2)TAP]Cl (where TAP = 1,4,5,8-tetraazaphenanthrene, thpy4,5p(R,R)py = (8R,10R)-2-(2'-thienyl)-4,5-pinenopyridine and phpy4,5p(R,R)py = (8R,10R)-2-(2'-phenyl)-4,5-pinenopyridine) have been prepared and characterized. Their photophysics has been examined in parallel with that of rac[Rh(thpy)(2)TAP]Cl and rac[Rh(phpy)(2)TAP]Cl. Their behaviors have been rationalized from results of TD-DFT calculations. The complexes with thienylpyridine (thpy) as cyclometalating ligands exhibit (3)CT (from thpy to TAP) and (3)LC(pi-pi) (centered on thpy) emissions in a solvent matrix at 77 K and one (3)CT luminescence at room temperature. In contrast, with phenylpyridine (phpy), the complexes show only one (3)CT emission (from phpy to TAP) at both temperatures.     

Copper-catalyzed rearrangement of oximes into primary amides

The atom-efficient and cost-effective rearrangement of oximes into primary amides is catalyzed by simple copper salts. The use of homogeneous Cu(OAc)₂ (1-2 mol %) was found to be effective for this transformation at 80 °C. The reaction was successful with either conventional or microwave heating. CuO and CuO/ZnO on activated carbon provided a competent reuseable heterogeneous catalyst which could be used in a batch process or in flow. Copper salts are much cheaper than the precious metals previously used for this rearrangement, and the reaction conditions are milder than those reported.     

Emerging blue‐UV luminescence in cerium doped YAG nanocrystals

Time‐resolved luminescence properties of Ce³⁺ doped Y₃Al₅O₁₂ (YAG) nanocrystals have been studied by means of vacuum‐ultraviolet excitation spectroscopy. It was discovered that additionally to the regular Ce³⁺ yellow‐green emission which is well‐known luminescence in YAG, new emission covering a broad spectral range from 2.7 eV to 3.5 eV was revealed in the luminescence spectra for all YAG:Ce nanocrystals studied. This blue‐UV emission has fast decay time about 7 ns as well as intensive well‐resolved excitation band peaking at 5.9 eV and, in contrast to green Ce³⁺ emission, practically is not excited at higher energies. The origin of the blue‐UV emission is tentatively suggested and discussed. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Notes: Polymer-Water Interaction in Emulsion Copolymerization of Vinyl Acetate

Abstract

In the case of copolymer latexes of vinyl acetate with maleic diesters, the amount of water bound to particles decreases with the increase of comonomer hydrophobicity. Increasing the concentration of bound water for more polar polymers determines a decrease of free water concentration. Therefore, the concentration of free surfactant and initiator in free water is higher and results in an increase of decomposition rate of potassium persulfate initiator. The increase of more polar copolymers hydration results in the increase of latex particle size.

     

Preparation of 5-Substituted 1H-Tetrazoles Catalyzed by Scandium Triflate in Water

Several 5-substituted 1H-tetrazoles were prepared in water or isopropanol/water mixtures using microwave heating. Good yields were obtained for the [2 + 3] cycloaddition of sodium azide with aryl nitriles, aliphatic nitriles, and vinyl nitriles when catalyzed by scandium triflate. The reactions were typically heated for 1 h at 160 °C in a 3:1 isopropanol/water mixture to obtain the best yields.     

Petrorhagiosides A – D,New γ‐Pyrone Derivatives from Petrorhagia saxifraga Link

Four novel γ‐pyrone (=4H‐pyran‐4‐one) metabolites, petrorhagiosides A–D, along with four known analogs, have been isolated from the MeOH extract of Petrorhagia saxifraga, a perennial herbaceous plant typical of Mediterranean vegetation. The structures of the new compounds were established on the basis of extensive spectroscopic analyses including 1D‐ an 2D‐NMR (¹H,¹H‐DQ‐COSY, TOCSY, HSQC, CIGAR‐HMBC, and HSQC‐TOCSY) experiments.     

Mathematical games and sampling inspection plans

Solutions to quality control by lot sampling through the game theory approach are presented, and the results are compared with those obtained by the classical statistical method. Single and double plans are considered and modeled as two-person zero-sum games, and optimal solutions are found. Most of the solutions are reminiscent of known statistical results and reinforce them by adding new features.     

v-triazolines. Part XIV . 1-aryl-5-dialkylaminomethyl-4-methylene-4,5-dihydro-v-triazoles

The cycloaddition of arylazides to 1-methyl- and 1-benzyl-2,5-dihydropyrrole affords pyrrolo[3,4-d]-v-triazole derivatives which react with methyl iodide, yielding the corresponding quaternary ammonium salts. On base-catalyzed elimination 1-aryl-5-dialkyl-aminomethyl-4-methylene-4,5-dihydro-v-triazoles are formed. Their structure and behaviour toward methoxide and secondary amines are discussed.     

Mechanism reduction of chemical reaction based on sensitivity analysis: development and testing of some new procedure

This paper proposes a procedure for simplifying the mathematical model of a chemical reaction by reducing the number of steps and species in the reaction scheme. This procedure is based on the sensitivity analysis of the model functional to the change in the model parameters. The application of this procedure makes it possible to accelerate and improve the construction of mathematical models for chemical reactions, as this does not require the calculation of sensitivity coefficients at various time points or sensitivity matrix analysis. This scheme was predicted the same behavior of the main reaction components as the detailed reaction scheme but includes much fewer steps. The efficiency of using this procedure was demonstrated by comparative results of modeling of formaldehyde oxidation and hydrogen oxidation in terms of detailed and reduced schemes. The sensitivity analysis was performed by Sobol’s method.     

Practical computational toolkits for dendrimers and dendrons structure design

Dendrimers and dendrons offer an excellent platform for developing novel drug delivery systems and medicines. The rational design and further development of these repetitively branched systems are restricted by difficulties in scalable synthesis and structural determination, which can be overcome by judicious use of molecular modelling and molecular simulations. A major difficulty to utilise in silico studies to design dendrimers lies in the laborious generation of their structures. Current modelling tools utilise automated assembly of simpler dendrimers or the inefficient manual assembly of monomer precursors to generate more complicated dendrimer structures. Herein we describe two novel graphical user interface toolkits written in Python that provide an improved degree of automation for rapid assembly of dendrimers and generation of their 2D and 3D structures. Our first toolkit uses the RDkit library, SMILES nomenclature of monomers and SMARTS reaction nomenclature to generate SMILES and mol files of dendrimers without 3D coordinates. These files are used for simple graphical representations and storing their structures in databases. The second toolkit assembles complex topology dendrimers from monomers to construct 3D dendrimer structures to be used as starting points for simulation using existing and widely available software and force fields. Both tools were validated for ease-of-use to prototype dendrimer structure and the second toolkit was especially relevant for dendrimers of high complexity and size.