A new class of pyrazolopyridine nucleus with fluorescent properties, obtained through either a radical or a Pd arylation pathway from N-azinylpyridinium N-aminides

The synthesis of dipyridopyrazole and pyridopyrazolopyrazine derivatives--both of which incorporate a 3-aryl moiety--can be achieved in moderate yields by intramolecular radical arylation of pyridinium N-aminides using tris(trimethylsilyl)silane and azobisisobutyronitrile. Improved results were obtained on using Pd direct arylation in conjunction with microwave irradiation. A preliminary study into the fluorescent properties of the target compounds is also reported.     

Probing the pyrolysis of ethyl formate in the dilute gas phase by synchrotron radiation and theory

The thermal decomposition of the atmospheric constituent ethyl formate was studied by coupling flash pyrolysis with imaging photoelectron photoion coincidence (iPEPICO) spectroscopy using synchrotron vacuum ultraviolet (VUV) radiation at the Swiss Light Source (SLS). iPEPICO allows photoion mass-selected threshold photoelectron spectra (ms-TPES) to be obtained for pyrolysis products. By threshold photoionization and ion imaging, parent ions of neutral pyrolysis products and dissociative photoionization products could be distinguished, and multiple spectral carriers could be identified in several ms-TPES. The TPES and mass-selected TPES for ethyl formate are reported for the first time and appear to correspond to ionization of the lowest energy conformer having a cis (eclipsed) configuration of the O = C (H)– O – C (H₂)–CH₃ and trans (staggered) configuration of the O= C (H)– O – C (H₂)– C H₃ dihedral angles. We observed the following ethyl formate pyrolysis products: CH₃CH₂OH, CH₃CHO, C₂H₆, C₂H₄, HC(O)OH, CH₂O, CO₂, and CO, with HC(O)OH and C₂H₄ pyrolyzing further, forming CO + H₂O and C₂H₂ + H₂. The reaction paths and energetics leading to these products, together with the products of two homolytic bond cleavage reactions, CH₃CH₂O + CHO and CH₃CH₂ + HC(O)O, were studied computationally at the M06-2X-GD3/aug-cc-pVTZ and SVECV-f12 levels of theory, complemented by further theoretical methods for comparison. The calculated reaction pathways were used to derive Arrhenius parameters for each reaction. The reaction rate constants and branching ratios are discussed in terms of the residence time and newly suggest carbon monoxide as a competitive primary fragmentation product at high temperatures.     

Condensation and Densification Mechanism of Sol-Gel TiO2 Layers at Low Temperature

Titanium dioxide films were prepared by the sol-gel process at low temperature under dry and humid conditions. The effect of solution parameters on the solution reactivity was studied. Layers deposited on silicon wafers as well as on organic substrates were characterized by Fourier Transform infrared spectoscopy and ellipsometry. Their mechanical quality was also tested. Results reported in this paper demonstrate the influence of the temperature and humidity during post-deposition treatment on the network development and densification. A suitable balance between both mechanisms led to hard and flexible coatings compatible with the thermal expansion of polymer substrates.     

The Influence of the Dispersion and Vertical Divergence on the Reflection Curve of a Double-crystal Arrangement

The influence of the dispersion and vertical divergence on the half width of the reflection curves was investigated using a double-crystal arrangement where the second crystal could be rotated about an axis parallel to the beam reflected by the first crystal. The experimentally measured dependence of the half width of the reflection curves on the angle of rotation φ is accurately confirmed by geometrical considerations.     

A Mean Square Chain Rule and its Application in Solving the Random Chebyshev Differential Equation

In this paper a new version of the chain rule for calculating the mean square derivative of a second-order stochastic process is proven. This random operational calculus rule is applied to construct a rigorous mean square solution of the random Chebyshev differential equation (r.C.d.e.) assuming mild moment hypotheses on the random variables that appear as coefficients and initial conditions of the corresponding initial value problem. Such solution is represented through a mean square random power series. Moreover, reliable approximations for the mean and standard deviation functions to the solution stochastic process of the r.C.d.e. are given. Several examples, that illustrate the theoretical results, are included.