Raman optical activity spectra and conformational elucidation of chiral drugs. The case of the antiangiogenic aeroplysinin-1

We present the determination of the conformational properties of aeroplysinin-1 in aqueous solution by means of a combined experimental and theoretical Raman optical activity (ROA) and vibrational circular dichroism (VCD) study. Aeroplysinin-1 is an antiangiogenic drug extracted from the sponge Aplysina cavernicola which has been proved to be a valuable candidate for the treatment of cancer and other antiangiogenic diseases. Our study shows that this molecule possesses the 1S,6R absolute configuration in aqueous solution, where only two conformers are present to a significant level. We discuss in detail the relationships between the chiro-optical ROA and VCD features, and the structural properties of various energy accessible conformers are described. The present work is one of the first studies in which both ROA and VCD have been used as complementary tools for the determination of absolute configuration and dominant solution-state conformations of an unknown therapeutically significant molecule.     

Thiophene–Diazine Molecular Semiconductors: Synthesis,Structural, Electrochemical,Optical, and Electronic Structural Properties; Implementation in Organic Field‐Effect Transistors

New transportation : New thiophene‐based semiconductors have been produced and studied by electrochemistry, various spectroscopic methods, and structural and morphological techniques in conjunction with model chemistry. Their electrical properties have been analyzed by implementation in field‐effect transistor devices (see figure).

     

Infeasibility spheres for finding robust solutions of blending problems with quadratic constraints

The blending problem is studied as a problem of finding cheap robust feasible solutions on the unit simplex fulfilling linear and quadratic inequalities. Properties of a regular grid over the unit simplex are discussed. Several tests based on spherical regions are described and evaluated to check the feasibility of subsets and robustness of products. These tests have been implemented into a Branch-and-Bound algorithm that reduces the set of points evaluated on the regular grid. The whole is illustrated numerically.     

Stable Tetrabenzo-Chichibabin's Hydrocarbons: Tunable Ground State and Unusual Transition between Their Closed-Shell and Open-Shell Resonance Forms

Stable open-shell polycyclic aromatic hydrocarbons (PAHs) are of fundamental interest due to their unique electronic, optical, and magnetic properties and promising applications in materials sciences. Chichibabin's hydrocarbon as a classical open-shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin's hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure and geometry in the ground state were studied by various experiments (steady-state and transient absorption spectra, NMR, electron spin resonance (ESR), superconducting quantum interference device (SQUID), FT Raman, X-ray crystallographic etc.) and density function theory (DFT) calculations. 1-CS and 2-OS exhibited tunable ground states, with a closed-shell quinoidal structure for 1-CS and an open-shell biradical form for 2-OS. Their corresponding excited-state forms 1-OS and 2-CS were also chemically approached and showed different decay processes. The biradical 1-OS displayed an unusually slow decay to the ground state (1-CS) due to a large energy barrier (95 ± 2.5 kJ/mol) arising from severe steric hindrance during the transition from an orthogonal biradical form to a butterfly-like quinoidal form. The quick transition from the quinoidal 2-CS (excited state) to the orthogonal biradicaloid 2-OS (ground state) happened during the attempted synthesis of 2-CS. Compounds 1-CS and 2-OS can be oxidized into stable dications by FeCl(3) and/or concentrated H(2)SO(4). The open-shell 2-OS also exhibited a large two-photon absorption (TPA) cross section (760 GM at 1200 nm).     

Fracture strength testing of a self-passivating tungsten alloy at the micrometre scale

The brittle fracture strength of a self-passivating W-Cr10-Ti2 alloy (in wt.%) was measured through un-notched cantilever bending at the microscopic scale. The material behaved purely elastic and fractured catastrophically in an unstable fashion. An average nominal strength of 5.9 GPa was measured. The scatter in strength was shown to be significantly higher than the sum of all random errors indicating an inherent variability of the material’s strength. The measurements from 28 tests followed a Weibull distribution with a modulus of m = 12. Results from a size effect study at the microscopic scale were successfully predicted through Weibull scaling. Extrapolation into the macroscopic range overestimated the measured three-point bend strength, which is likely due to the presence of large-scale heterogeneities. The test technique sampled a material thickness of only several micrometres and is hence suitable for future ion irradiation studies.     

A green alternative method for analysis of ivermectin and moxidectin in environmental water samples using automatized preconcentration previous MEEKC

Antiparasitic drugs derived from macrocyclic lactones (MLs) are widely used in livestock activities around the world. An increasing concern for local authorities is the environmental pollution as a consequence of veterinary drugs widely used in rural areas. The purpose of environmental analysis is to monitor low levels of pollutant analytes in a large number of samples. Also, due to the lipophilic characteristic of these lactones, long‐chain solvents are usually required for performing sample treatment before and during the analysis. Therefore, sensitive, specific, robust, and environmentally friendly analytical methods are still required. In this paper, a new automatized preconcentration methodology followed by microemulsion electrokinetic chromatography analysis was developed for the simultaneous separation and determination of the most used MLs, ivermectin (IVM) and moxidectin (MXD) in environmental water. XAD‐4 resin was employed as an adsorbent for the preconcentration process and ethanol was used as the eluent. In contrast to traditional analysis for IVM and MXD, in this methodology nonpolluting solvents were involved during the whole process and therefore, it could be considered as a contribution to green analytical chemistry. Under optimal experimental conditions, LOD obtained for IVM and MXD were of 3 × 10^?3 and 3.6 × 10^?3 μg/L, respectively.