Kinetics and Thermodynamics of Solvolysis of a Cationic and an Anionic Chlorocobalt (III) Complex in Water–Ethanol Mixtures

Rate constants and derived thermodynamic activation parameters are reported for solvolysis of trans-[Co(3Mepy)₄Cl₂]⁺ and [Co(CN)₅Cl]^3– ions in water-rich mixtures of water with ethanol at various temperatures and are analyzed by initial- and transition-state contributions. The variation of enthalpies and entropies of activation with solvent composition show extrema in composition ranges where the physical properties of the mixtures, influenced by changes in solvent structures, also show extrema. From the application of a free-energy cycle to the process of the initial state going to the transition state, it is concluded for the solvolysis of both complexes that the Co(III) species in the transition state is more stable in water + ethanol mixtures than in the initial state.     

Equilibrium geometry and gas‐phase proton affinity of 2‐thiouracil derivatives

The ground‐state geometries of uracil, 6‐hydroxy‐uracil, and 6‐hydroxy‐, 6‐amino‐, 6‐methyl‐, 6‐trifluoro‐, and 6‐phenyl‐2‐thiouracil were optimized at the Hartree–Fock level. The molecular structures were fully optimized using the 6‐31G and 6‐31G* basis sets. The effect of substituents on the geometry and electronic structural features of 2‐thiouracils were examined. The perturbation effects of the OH and NH₂ groups are by far more pronounced on the geometric features and the dipole moment magnitude and direction of 2‐thiouracil. The potential energy per atom criteria was used to compare the relative tightness of binding in the studied series. Proton affinity and deprotonation enthalpy on each of the possible sites in 2‐thiouracil and its derivatives have been calculated at the 6‐31G/MP2 level of theory. The obtained results show that thiouracils behave as bases where they possess a high tendency to abstract protons. Substituents in the 6‐position have the general effect of enhancing the basicity strength of the thiocabonyl site in the order Ph < CH3 ≈ NH2 < OH. The CF3 group has the effect of reducing considerably the basicity strength and enhances the acidity strength at both N1 and N3. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Synthesis and efficiency of 5-(2-hydroxyphenylazo)-indazoles as new reagents for the determination of vanadium

Summary Four azo compounds based on 5-aminoindazole have been synthesized and characterized by elemental analysis as well as different spectroscopic techniques. The potentiality of the prepared compounds as new chromophoric reagents for the spectrophotometric determination of VO ₂ ⁺ was studied by extensive investigation of optimum conditions favouring the formation of the coloured complexes. The effect of interfering ions on the determination of VO ₂ ⁺ was investigated.Beer's law is obeyed in the concentration range of 1.0–12 µg/ml. The detection limits are 0.8, 0.9, 0.7, and 1.1 µg/ml using reagent1a,1b,1c, and1d, respectively. The standard deviations of the proposed method are 0.098, 0.111, 0.089, and 0.078. The molar absorptivities are 5.8, 6.7, 6.1, and 8.2×10³l·mol^–1·cm^–1 for1a–d, respectively, whereasSandell sensitivities are found to be 0.0187, 0.0163, 0.0174, and 0.0146 µg·cm^–2 using the same reagents. The ability of using these reagents as metallochromic reagents in complexon III titrations was also studied.

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Synthese und Leistungsfähigkeit von 5-(Hydroxyphenylazo)-indazolen als neue Reagentien zur Bestimmung von Vanadium

Zusammenfassung Vier von 5-Aminoindazol abgeleitete Azoverbindungen wurden synthetisiert und mittels Elementaranalyse sowie mit Hilfe verschiedener spektroskopischer Techniken charakterisiert. Die Einsatzmöglichkeiten der Verbindungen als Reagentien zur spektrophotometrischen Bestimmung von VO ₂ ⁺ wurde durch ausführliche Untersuchungen zur Ermittlung der optimalen Bedingungen für die Ausbildung der gefärbten Komplexe ausgetestet. Der Einfluß von Fremdionen auf die Ergebnisse wurde ebenfalls untersucht. DasBeer'sche Gesetz wird im Konzentrationsbereich von 1.0–12µg/ml befolgt. Die Nachweisgrenzen liegen bei 0.8, 0.9, 0.7 und 1.1 µg/ml für die Reagentien1a–d. Die entsprechenden Standardabweichungen betragen 0.098, 0.111, 0.089 und 0.078. Die Komplexe zeigen molare Extinktionen von 5.8, 6.7, 6.1 und 8.2×10³l·mol^–1·cm^–1 und Empfindlichkeiten nachSandell von 0.0187, 0.0163, 0.0174 und 0.0146 für die jeweiligen Verbindungen1a–d. Die Verwendungsmöglichkeit der neuen Verbindungen als metallochrome Reagentien bei Titrationen mit Komplexon III war ebenfalls Gegenstand der Untersuchungen.

     

Solochrome Green V as a new analytical reagent

Summary The acid-base properties of Solochrome Green V have been studied with the object of testing its use as a metal indicator or colorimetric reagent. The pK values of the three steps of ionisation of the free acid were evaluated. The dye has proved to be a suitable indicator in EDTA titrations of zinc and manganese as well as a colorimetric reagent for the microdetermination of zinc. The method is highly sensitive that by its application 0.05 ppm Zn can be determined with fair accuracy.     

A Review of HER4 (ErbB4) Kinase,Its Impact on Cancer,and Its Inhibitors

HER4 is a receptor tyrosine kinase that is required for the evolution of normal body systems such as cardiovascular, nervous, and endocrine systems, especially the mammary glands. It is activated through ligand binding and activates MAPKs and PI3K/AKT pathways. HER4 is commonly expressed in many human tissues, both adult and fetal. It is important to understand the role of HER4 in the treatment of many disorders. Many studies were also conducted on the role of HER4 in tumors and its tumor suppressor function. Mostly, overexpression of HER4 kinase results in cancer development. In the present article, we reviewed the structure, location, ligands, physiological functions of HER4, and its relationship to different cancer types. HER4 inhibitors reported mainly from 2016 to the present were reviewed as well.     

Determination of Amitraz Pesticide by Adsorptive Stripping Voltammetry on the Hanging Mercury Drop Electrode

 A sensitive method for the determination of amitraz pesticide at nanomolar level by adsorptive stripping voltammetry at a hanging mercury drop electrode is described. The cyclic voltammograms demonstrate the adsorption of this compound on the mercury electrode. A systematic study of the various experimental parameters, that affect the stripping response, was carried out by differential pulse voltammetry. Using an accumulation potential of −0.50 V, and 30 s accumulation time, the limit of detection was found to be 2.3 × 10⁻⁹ mol L⁻¹ and the relative standard deviations (n = 5) was 2.2% at concentration level of 5.0 × 10⁻⁸ mol L⁻¹ of amitraz. The influence of diverse ions and some other pesticides was investigated. Finally, the method was applied to the determination of amitraz in spiked soil and water. The relative standard deviation is 4.5% for 5 determinations of amitraz in water and 3.2% for 5 determinations in soil. Received December 6, 2000. Revision March 1, 2001.     

Internal energy content of n-butylbenzene, bromobenzene, iodobenzene and aniline molecular ions generated by two-photon ionization at 266 nm. A photodissociation study

A technique to investigate photodissociation kinetics on a nanosecond time scale has been devised for molecular ions generated by multiphoton ionization (MPI) using mass-analyzed ion kinetic energy spectrometry. The branching ratio or rate constant has been determined for the photodissociation of the n-butylbenzene, bromobenzene, iodobenzene, and aniline molecular ions generated by MPI at 266 nm. The ion internal energies have been estimated by comparing the measured kinetic data with the previous energy dependence data. The analysis has shown that only those molecular ions generated by two-photon ionization contribute to the photodissociation signals. Around half of the available energy has been found to remain as molecular ion internal energy in the two-photon ionization process. Copyright 1999 John Wiley & Sons, Ltd.     

A Generalized Spatial Modulation System Using Massive MIMO Space Time Coding Antenna Grouping

Massive multiple input multiple output (MIMO), also known as a very large-scale MIMO, is an emerging technology in wireless communications that increases capacity compared to MIMO systems. The massive MIMO communication technique is currently forming a major part of ongoing research. The main issue for massive MIMO improvements depends on the number of transmitting antennas to increase the data rate and minimize bit error rate (BER). To enhance the data rate and BER, new coding and modulation techniques are required. In this paper, a generalized spatial modulation (GSM) with antenna grouping space time coding technique (STC) is proposed. The proposed GSM-STC technique is based on space time coding of two successive GSM-modulated data symbols on two subgroups of antennas to improve data rate and to minimize BER. Moreover, the proposed GSM-STC system can offer spatial diversity gains and can also increase the reliability of the wireless channel by providing replicas of the received signal. The simulation results show that GSM-STC achieves better performance compared to conventional GSM techniques in terms of data rate and BER, leading to good potential for massive MIMO by using subgroups of antennas.     

Glow discharge in microfluidic chips for visible analog computing

Here we present a novel visible analog computing approach for solving a wide class of shortest path problems. Using a microfluidic chip for computation, based on the lighting up of a glow discharge, the solution to maze search problems, the solution of a network shortest path and k-shortest paths problems and the practical application of finding the shortest paths between several landmarks from a street map are presented. The solution and visible display (in real time) for these problems shows only a small difference in practical problem solving time among problems with varying differences in size.     

Synthesis and Some Reactions of Quinoxalinecarboazides

Chlorination of ethyl(quinoxalin‐2(1H)one)‐3‐carboxylate 1 gave ethyl (2‐chloroquinoxaline)‐3‐carboxylate 2 ;thionation of 1 by P₂S₅ or 2 by thiourea yielded the same product 3 . Reaction of chloro compound 2 or thiocompound 3 with hydrazine hydrate gave pyrazolylquinoxaline 4 . The reaction of ester 1 with thiourea or hydrazine hydrate afforded pyrimido quinoxaline 5 or carbohydrazide 6 ; the reaction of 6 with carbon disulfide in basic medium followed by alkylation afforded oxadiazoloquinoxaline derivatives 7, 8a,b . Carboazide 9 was produced by reaction of 5 with nitrous acid. Compound 9 on heating in an inert solvent, with or without amines, in alcohols or hydrolysis in H₂O undergoes Curtius rearrangments to yield 10‐13 . Reaction of 13 with thiosemicarbazide gave triazoloquinoxaline 14 which on reaction with alkylhalides or hydrazine hydrate yielded 15a‐c while hydrolysis of 13 gave 3‐aminoquinoxalinone 16 which was used as an intermediate to produce 17‐20 .