Electrical conduction and dielectric properties of vanadium phosphate glasses doped with lithium

AC conductivity and dielectric studies on vanadium phosphate glasses doped with lithium have been carried out in the frequency range 0.2-100 kHz and temperature range 290-493 K. The frequency dependence of the conductivity at higher frequencies in glasses obeys a power relationship, σ_ac=Aω^s. The obtained values of the power s lie in the range 0.5≤s≤1 for both undoped and doped with low lithium content which confirms the electron hopping between V⁴⁺ and V⁵⁺ ions. For doped glasses with high lithium content, the values of s≤0.5 which confirm the domination of ionic conductivity. The study of frequency dependence of both dielectric constant and dielectric loss showed a decrease with increasing frequency while they increase with increasing temperature. The results have been explained on the basis of frequency assistance of electron hopping besides the ionic polarization of the glasses. The bulk conductivity increases with increasing temperature whereas decreases with increasing lithium content which means a reduction of the V⁵⁺.     

Laser spectroscopic investigation of salicylic acids hydrogen bonded with water in supersonic jets: Microsolvation effects for excited state proton dislocation

Geometric structures and excited-state proton dislocation of size-selected salicylic acid clusters (salicylic acid and 5-methoxysalicylic acid) with water were studied by using laser spectroscopic techniques. Fluorescence excitation, dispersed fluorescence, and infrared (IR) spectra of those clusters in supersonic jets were examined for both the electronic ground (S0) and first excited (S1) states. The geometric structures of the clusters were determined on the basis of the IR spectra of the OH stretch region with the help of quantum chemical calculations. The hydroxyl group of the water moiety in the clusters forms a ring involving the carboxylic group of the salicylic acid moiety. The IR spectra in S0 show that the intramolecular hydrogen bond in the salicylic acid moiety is still held upon cluster formation, but the phenolic OH stretch band intensity is remarkably weaken in the clusters. The IR spectra in the S1 state and dispersed fluorescence spectra indicated that the intramolecular excited state proton dislocation is hardly affected by the microsolvation with water, in contrast with the strong suppression of the dislocation in the self-solvation.     

Transformation of arctiin to estrogenic and antiestrogenic substances by human intestinal bacteria

After anaerobic incubation of arctiin (1) from the seeds of Arctium lappa with a human fecal suspension, six metabolites were formed, and their structures were identified as (-)-arctigenin (2), (2R,3R)-2-(3',4'-dihydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (3), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (4), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3"-hydroxy-4"-methoxybenzyl)butyrolactone (5), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dihydroxybenzyl)butyrolactone (6), and (-)-enterolactone (7) by various spectroscopic means including two dimensional (2D)-NMR, mass spectrometry, and circular dichroism. A possible metabolic pathway was proposed on the basis of their structures and the time course of the transformation. Enterolactones obtained from the biotransformation of arctiin and secoisolariciresinol diglucoside (SDG, from the seeds of Linum usitatissium) by human intestinal bacteria were proved to be enantiomers, with the (-)-(2R,3R) and (+)-(2S,3S) configurations, respectively. Compound 6 showed the most potent proliferative effect on the growth of MCF-7 human breast cancer cells in culture among 1 and six metabolites, while it showed inhibitory activity on estradiol-mediated proliferation of MCF-7 cells at a concentration of 10 microM. These results indicate that the transformation of 1 by intestinal flora might be essential for the manifestation of the estrogenic and antiestrogenic activity of 1.     

Inhibition of Pb-Leaching from Lead Crystal Glass by Coating with Films Prepared by the Sol-Gel Method

The chemical durability of lead glass tumblers (24% PbO) in a 4% (v/v) acetic acid solution before and after coating with sol-gel derived SiO2 films was assessed to determine the extent of reduction in Pb-leaching that can be achieved. It was found that by coating the internal surface of the glass tumblers with 1 ml of 10% TEOS solutions at 100°C and densifying the coating formed at 500°C for 1 h, it was possible to reduce Pb-leaching to about one quarter of that of the uncoated glass.     

Spectral and magnetic properties of phenylazo-6-aminouracil complexes

Complexes of Co(II), Ni(II) and Cu(II) with substituted phenylazo-6-aminouracils containing (-H, p-OH, p-CH(3), p-OCH(3) p-COOH) have been synthesized and characterized by elemental analysis, magnetic measurements and spectral measurements (IR, UV-Vis, ESR). Infrared spectra assigned the fundamental bands of the major groups, O-H, N-H, C-H, C=O, C=N, N=N, C-N and C-O (nu, delta and gamma modes of vibrations). The absence of nu(OH) and the appearance of nu(C=O) in the infrared spectra of the free ligands of 5-(p-tolyl and p-anisylazo)-6-aminouracil, assigned the keto structure, whereas in cases of 5-(phenyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracil ligands, the data showed strong nu(OH) and nu(C=O) bands to assign keto-enol tautomerisms. The modes of interactions between the ligands and the metals were discussed, where oxygen and nitrogen atoms (of amino-amide groups) are involved in chelation. The azo group was not involved in chelation for all the prepared complexes except those of copper complexes derived from 5-(phenyl, p-tolyl, p-hydroxyphenyl and p-carboxyphenylazo)-6-aminouracils. The room temperature effective magnetic moment values, the Nujol mull spectra and ESR proved that all the prepared complexes were of octahedral geometry, except the nickel complex derived from 5-(phenylazo)-6-aminouracil and cobalt complex derived from 5-(p-carboxy-phenylazo)-6-aminouracil were square planar.     

Regioselective Synthesis of Substituted Triazolium Salts <Emphasis Type="Italic">via</Emphasis> 1,3-Dipolar Cycloaddition Reactions

Summary. The regioselectivity of 1,3-dipolar cycloaddition reactions of 1-aza-2-azoniaallene salts with ,-unsaturated nitriles such as acrylonitrile or cyclohexylidene acetonitrile afforded only 1,2,4-triazolium salts via addition to the nitrile group, while the other expected pyrazolium salts were not observed. Moreover, 1-aza-2-azonia-allene salts reacted with other competitive systems such as -iminonitrile derivatives yielding only triazolium salts via addition to the nitrile and not to the imino group. Treatment of cumulene with 3-pyridylnitrile afforded the pyridinium salt. However, 2,3-dimethyl-5-(2,6-dimethoxyphenyl)-[1,2,4]triazole could be prepared from cumulene and 2,6-dimethoxybenzonitrile. Some reactions of nitriles with 1-aza-2-azonia-allene salts prepared from 1,2,3-indantrione and 9-acetylphenanthrene are discussed.     

The Complexation of Some Transition Metals by Acetoacetanilidehydrazo Ligands “Stability Constants”

Acid dissociation constants of acetoacetanilide abbreviated (AAA); Orthocarboxy-phenylhydrazoacetoacetanilide (o-CPHAAA); and orthocarboxy-phenylhydrazo-parachloro-acetoacetanilide (o-CPH-p-Cl-AAA) and chelate stability constants of the corresponding anions with Cu⁺², Ni⁺², CO⁺², Zn⁺², Mn⁺², and Cd⁺² ions are reported. The infra-red spectra of o-CPHAAA and o-CPH-p-Cl-AAA ligands and their chelates for copper and nickel are discussed.     

Synthesis of Some Novel 2‐Anilinothiophene, 2,3′‐Bithienyl and Thienylthiopyridine Derivatives Resistance to Penicillium Digitatum Effect the Fruit

Reaction of benzotriazol‐1‐yl acetone 1 with phenyl isothiocyanate followed with α‐chloroacetone or ethyl‐α‐chloroacetate afforded 2‐anilinothiophenes 3 or 4 , respectively. Treatment of 3 with malononitrile at different reaction conditions afforded 6 or 7 . Reaction of 1 with CS₂ in DMF and phenacylbromide afforded S‐alkylated thiophene 10 . Reactions of the latter compound with different active methylene nitriles afforded thienylthiopyridine derivatives 14 and 15 . Condensation of 10 with hydrazine hydrate afforded hydrazon derivative 16 . Reaction of thiophene 17 with formamide in DMF afforded 19 which converted to N‐thienylpyrimidine 20 when treated with malononitrile. The structure of the newly synthesized compounds has been established on the basis of their analytical and spectral data. The compounds were also investigated for antibacterial and antifungal activities.     

Reductive Elimination of Phenylsulfonyl Groups in the 3‐Position of Benzo[a]heptalene‐2,4‐diols

3‐(Phenylsulfonyl)benzo[a]heptalene‐2,4‐diols 1 can be desulfonylated with an excess of LiAlH₄/MeLi?LiBr in boiling THF in good yields (Scheme 6). When the reaction is run with LiAlH₄/MeLi, mainly the 3,3′‐disulfides 6 of the corresponding 2,4‐dihydroxybenzo[a]heptalene‐3‐thiols are formed after workup (Scheme 7). However, the best yields of desulfonylated products are obtained when the 2,4‐dimethoxy‐substituted benzo[a]heptalenes 2 are reduced with an excess of LiAlH₄/TiCl₄ at ?78→20° in THF (Scheme 10). Attempts to substitute the PhSO₂ group of 2 with freshly prepared MeONa in boiling THF led to a highly selective ether cleavage of the 4‐MeO group, rather than to desulfonylation (Scheme 13).     

Cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin

A new series of hexacoordinate cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin HL having formulae [LM(OAc)(H₂O)₂] · nH₂O (M = Co^II, Cu^II and Ni^II), [LMCl(H₂O)₂] · nH₂O (M = Co^II and Ni^II), [LCuCl(H₂O)]₂ · 2H₂O, [LCu(H₂O)₃](ClO₄) and [LCu(HSO₄)(H₂O)₂] were isolated and characterized by elemental analyses, molar conductivities and magnetic susceptibilities, and by i.r., electronic and e.s.r. spectral measurements, as well as by thermal (t.g. and d.t.g.) analyses. The i.r. spectra indicate that the ligand HL behaves as a monobasic tridentate towards the three divalent metal ions via an azo-N, carboxylate-O and thiohydantoin-O atom. The magnetic moments and electronic spectral data suggest an octahedral geometry for Co^II complexes, distorted octahedral geometry for both Ni^II and Cu^II complexes with a dimeric structure for [LCuCl(H₂O)]₂ · 2H₂O through bridged chloro ligands. The X-band e.s.r. spectra reveal an axial symmetry for the copper(II) complexes with unsymmetrical M_s = ± 1 signal and G-parameter less than four for the dimeric [LCuCl(H₂O)]₂ · 2H₂O. The thermogravimetry (t.g. and d.t.g.) of some complexes were studied; the order and kinetic parameters of their thermal degradation were determined by applying Coats–Redfern method and discussed.