Structural relaxation of PbO–WO3–P2O5 glasses

The structural relaxation of three compositional series of PbO–WO₃–P₂O₅ glasses with composition (0.5 ? x/2)PbO·xWO₃·(0.5 ? x/2)P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO·xWO₃·(0.5 ? x)P₂O₅, x = 0, 0.1, 0.2, and 0.3; and (0.5 ? x)PbO·xWO₃·0.5P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO₃ in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO₃ in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value.     

Preparation,structures, and reactivities of compounds with double bonding between the heavier group 5A elements

Abstract

The synthesis of diphosphenes (RP[dbnd]PR′), phosphaarsenes (RPxydAsR′), phosphastibenes (RP[dbnd]SbR′), and diarsenes (RAs[dbnd]AsR′) is discussed. X-ray crystallographic studies have been performed on representative double-bonded compounds. The reactivities and coordination chemistry of selected compounds have been explored.     

L-leucinium perchlorate: new molecular complex with nonlinear optical properties. Vibrational, calorimetric and theoretical studies

On the basis of prior X-ray crystallographic results published by J. Janczak and G. Perpetuo, detailed vibrational studies were performed. The FT-IR and Raman spectra at ambient temperature were measured. The NLO properties were determined with the Kurtz-Perry experiment. Theoretical vibrational spectra were calculated. A detailed potential energy distribution (PED) analysis was performed. Assignments of observed bands were made. On the basis of these results, the behaviour of hydrogen bonds in the investigated compound was analysed and discussed. The equilibrium geometry of L-leucinium perchlorate was obtained. The results were compared with experimental X-ray data. The DFT formalism was used in theoretical studies. Detailed TDDFT study of hyperpolarizbility of first and second order for the investigated molecule was performed. Results were compared with experiments. Theoretical population analysis was used to determine the local electron density and local charges in investigated molecule. Differential scanning calorimetric study (DSC) was performed.      

Two phosphonodehydrotripeptides: Boc0–Gly1–Δ(Z)Phe2–α‐Abu3PO3Me2 and Boc0–Gly1–Δ(Z)Phe2–α‐Nva3PO3Et2

The present paper reports the crystal structures of two short phosphonotripeptides (one in two crystal forms) containing one ΔPhe (dehydrophenylalanine) residue, namely dimethyl (3‐{[tert‐butoxycarbonylglycyl‐α,β‐(Z)‐dehydrophenylalanyl]amino}propyl)phosphonate, Boc⁰–Gly¹–Δ(Z)Phe²–α‐Abu³PO₃Me₂, C₂₁H₃₂N₃O₇P, (I), and diethyl (4‐{[tert‐butoxycarbonylglycyl‐α,β‐(Z)‐dehydrophenylalanyl]amino}butyl)phosphonate, Boc⁰–Gly¹–Δ(Z)Phe²–α‐Nva³PO₃Et₂, as the propan‐2‐ol monosolvate 0.122‐hydrate, C₂₄H₃₈N₃O₇P·C₃H₈O·0.122H₂O, (II), and the ethanol monosolvate 0.076‐hydrate, C₂₄H₃₈N₃O₇P·C₂H₆O·0.076H₂O, (III). The crystals of (II) and (III) are isomorphous but differ in the type of solvent. The phosphono group is linked directly to the last C_α atom in the main chain for all three peptides. All the amino acids are trans linked in the main chains. The crystal structures exhibit no intramolecular hydrogen bonds and are stabilized by intermolecular hydrogen bonds only.     

Two-Photon Solvatochromism II: Experimental and Theoretical Study of Solvent Effects on the Two-Photon Absorption Spectrum of Reichardt’s Dye

In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt’s dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy.     

Simultaneous quantitation of venlafaxine and its main metabolite,O‐desmethylvenlafaxine,in human saliva by HPLC

Venlafaxine is used for the treatment of major depression and generalized anxiety disorders. Because its active metabolite, O‐desmethylvenlafaxine, has also a similar activity, the purpose of this work was to develop a simple method for simultaneous quantitation of both drugs using HPLC with UV detection. The saliva was chosen as diagnostic material because of its easy accessibility and possibility of sampling by patients, for example, at home. The sample pretreatment by liquid–liquid extraction allows to separate both compounds from this diagnostic material with a high recovery, varying between 92.65 and 104.78%. The major advantage of the validated method lies in its sensitivity, reproducibility, and specificity for routine quantitation of the venlafaxine and O‐desmethylvenlafaxine in the human saliva. The low detection and quantification values (2.8–3.1 and 9.4–10.2 ng/mL, respectively) enable to quantify both species excreted with saliva at the nanogram level. The applicability of the method was verified by analysis of the saliva obtained from depressed women treated with venlafaxine. The results suggest that the method could be used for therapeutic drug monitoring in patients undergoing treatment with venlafaxine, especially when metabolic anomalies or low compliance are suspected, or in the case of polypharmacy.     

Applicability of Gd-doped BaZrO3, SrZrO3, BaCeO3 and SrCeO3 proton conducting perovskites as electrolytes for solid oxide fuel cells

Four proton conducting oxides of perovskite structure: BaZrO₃, SrZrO₃, BaCeO₃ and SrCeO₃ doped with 5 mol.% of gadolinium are compared in terms of crystal structure, microstructure, sinterability, water sorption ability, ionic transference number, electrical conductivity and stability towards CO₂. Relations between proton conductivity, structural and chemical parameters: pseudo-cubic unit cell volume, lattice free volume, tolerance factor, crystal symmetry and electronegativity are discussed. The grain boundary resistance is shown to be the limiting factor of total proton-conductivity for the materials examined. The highest proton conductivity was observed for BaCeO₃, however, it turned out to be prone to degradation in CO₂-containing atmosphere and reduction at high temperatures. On the other hand, Ba and Sr zirconates are found to be more chemically stable, but exhibit low electrical conductivity. Electrical conductivity relaxation upon hydration is used to calculate proton diffusion coefficient. Selected materials were tested as electrolytes in solid oxide fuel cells.      

Drop‐coating deposition Raman spectroscopy of porphyrins

We report an improvement of the Raman detection sensitivity of porphyrins by factor of 10⁵ using drop‐coating deposition Raman spectroscopy (DCDR). We were able to obtain Raman spectra from ~20 nM initial (deposited) concentrations of cationic and anionic porphyrin. This detection limit is comparable with or even better than that of surface‐enhanced Raman scattering spectroscopy using Ag nanoparticles. Moreover, DCDR spectrum of protoporphyrin IX, which is known as a marker in clinical diagnostics of cancer, was also obtained from 10 nM deposited concentration. To our knowledge, it is the first demonstration of the resonance DCDR spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Azines and Azoloazines,Part 1: Reactions of Triazolo[3,4‐a]phthalazine and Its Derivatives with Carbanions

Triazolo[3,4‐a]phthalazine as well as their chloro and nitro derivatives were subjected to the reactions with the carbanions typical for the vicarious nucleophilic substitution (VNS) of hydrogen. The reactions were strongly dependent on the substituents present on the triazolo[3,4‐a]phthalazine ring and resulted not only in the substitution of hydrogen but also in exchange of chlorine atom and pyridazine ring scission; the latter process dominated for the unsubstituted triazolophthalazine. Two of the products showed promising stimulating activity towards the central nervous system with no significant toxic effects.