Isomeric ruthenium terpyridine complexes [Ru(trpy)(L)Cl]n+ containing the unsymmetrically bidentate acceptor L=3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine. Synthesis, structures, electrochemistry, spectroscopy and DFT calculations

The isomeric title complexes were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and L. Crystal structure analyses of the perchlorate hemihydrates, electrochemical and spectroscopic (NMR, UV/VIS, EPR) studies, supported by DFT calculations, reveal distinct differences between the isomeric redox series [1]n+(tetrazine-Nt trans to Cl) and [2]n+(pyrazolyl-Np trans to Cl; n= 0, 1, 2). The latter system with the pi acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidation, lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidised (RuIII) state. According to partially resolved EPR spectra of one-electron reduced neutral compounds and they have the unpaired electron predominantly in the tetrazine ring of L.     

Solution-based chemical synthesis of boehmite nanofibers and alumina nanorods

This article reports an easy chemical method of synthesizing boehmite nanofibers by a modified sol-gel process involving aluminum isopropoxide precursor. Nanorods of gamma-alumina have been successfully prepared after dehydration of the viscous sol at 600 degrees C for 4 h in air. The boehmite nanofibers and gamma-alumina nanorods were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy for surface chemistry and functional groups, scanning electron microscopy, high-resolution transmission electron microscopy with selected area electron diffraction, and energy-dispersed spectroscopy for morphology and structure identification. The length of the boehmite nanofibers was found to be more than 10 mum with a crystalline lattice structure. The mechanism of formation of the boehmite nanofibers included the preferential growth along the longitudinal axis due to interaction between the solvent molecules and the surface OH- groups of hydrogen bonds. It is also suggested that the boehmite nanofibers may have formed due to the inherent instability of the planar structure of the boehmite lattice. The diameter of the gamma-alumina nanorods was found to be less than 10 nm with a varying length in the range of 50-200 nm. Boehmite to gamma-Al2O3 transformation was attributed to the loss of water molecules by internal condensation of protons and hydroxyl ions.     

XRD and bulk magnetic studies on Ni-Cd and Ti doped Ni-Cd ferrites

For the ferrites Ni _x Cd_1–x Fe₂O₄ (x=0.3, 0.4,1) the lattice parameter, grain size, electrical resistivity, initial permeability, Curie temperature and squareness of the magnetization curve were measured. The results are discussed in terms of the model of the canted spin structure taking into account the domain structure of the polycrystalline ferrite.     

Synergetic extraction and spectrophotometric determination of iron (II) in steel

Summary A simple and rapid method is described for synergetic extraction and spectrophotometric determination of iron(II). The Fe(II)--furildioxime-pyridine complex extracted into chloroform has a characteristic pink color measurable at 570 nm. Iron is also separated from associated elements and the results of the analysis of synthetic mixtures and standard steel samples are reported.

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Zusammenfassung Eine einfache und rasche Methode zur Extraktion und Bestimmung von Eisen(II) wurde beschrieben. Der Komplex Fe(II)--Furildioxim-Pyridin wird mit Chloroform extrahiert. Seine charakteristische rosa Farbe ist bei 570 nm meßbar. Eisen läßt sich so auch von Begleitelementen trennen. Die Analysenergebnisse für synthetische Gemische und Standard-Stahlproben werden mitgeteilt.

     

Monoterpenoids—V: (+)-Carvone from (+)-car-3-ene

A stereoselective conversion of the readily available (+)-car-3-ene into (+)-carvone by two different routes is described. This is the first report on synthesis of carvone from car-3-ene.     

Studies on the colloidal properties of papain with titanium dioxide sol

Summary The coagulation concentration for a titania sol decreases if the concentration of a mixture of electrolytes and papain decreases. If the concentration of papain is increased then lesser amount of electrolytes is needed to coagulate the sol. If glycine is added as an additional substance then the value decreases more rapidly. There is no significant change in the p_H and the electrical conductance of the sol by the addition of papain or electrolytes. There is a little change, when glycine is added as an additional substance. These observations are explained due to the formation of negative papain ions in a low p_H region. The possibility of the adsorption or the release of the counter ions is ruled out.The authors wish to thank Dr.R. C. Mehrotra, Professor and the Head of the Chemistry Department for providing all the facilities for this work. We are also thankful to the Ministry of Education, Government of India, for the award of a research scholarship to one of us (V.K.S.).     

Stability-Indicating HPLC Method for the Determination of Metadoxine as Bulk Drug and in Pharmaceutical Dosage Form

A sensitive and reproducible method is described for the quantitative determination of metadoxine in the presence of its degradation products. The method was based on high performance liquid chromatographic separation of the drug from its degradation products on the reversed phase, kromasil column [C₁₈ (5-micron, 25 cm × 4.6 mm, i.d.)] at ambient temperature using a mobile phase consisting of methanol and water (50: 50, v/v). Flow rate was 1.0 mL min^?1 with an average operating pressure of 180 kg cm^?2 and t _R was found to be 2.85 ± 0.05 min. Quantitation was achieved with UV detection at 286 nm based on peak area with linear calibration curves at concentration range 10–100 μg mL^?1. This method has been successively applied to pharmaceutical formulation. No chromatographic interference from the tablet excipients was found. The method was validated in terms of precision, robustness, recovery and limits of detection and quantitation. Drug was subjected to acid, alkali and neutral hydrolysis, oxidation, dry heat, wet heat treatment and photo and UV degradation. As the proposed method could effectively separate the drug from its degradation products, it can be employed as stability indicating one. Moreover, the proposed HPLC method was utilized to investigate the kinetics of the acidic, alkaline and oxidative degradation processes at different temperatures and their respective apparent pseudo first order rare constant, half-life and activation energy was calculated with the help of Arrhenius plot. In addition the pH-rate profile of degradation of metadoxine in constant ionic strength buffer solutions with in the pH range 2–11 was studied.     

A class of exact solutions for doubly anharmonic oscillators

The solution of a difference equation in the form of an infinite continued fraction is used to obtain a class of exact solutions for the eigenfunctions and eigenvalues of doubly anharmonic oscillators described by potentials of the type (1/2)²x²+(1/4)x⁴+(1/6)x⁶, n>0, provided certain constraints on the couplings are satisfied. The class is denumerably infinite but not complete.     

Effects of structural imperfections on the dynamic mechanical response of main-chain smectic elastomers

We examine the influence of structural imperfections on mechanical damping in polydomain smectic main-chain liquid crystalline elastomers (MCLCE) subjected to small strain oscillatory shear. The mechanical loss factor tan δ = G″(ω)/G′(ω) exhibits a strong maximum (tan δ ≈ 1.0) near the smectic-isotropic (clearing) transition. “Optimal” elastomers that exhibit minimal equilibrium swelling in a good solvent are compared with highly swelling “imperfect elastomers” that contain higher concentrations of structural imperfections such as pendant chains. For the imperfect elastomers, tan δ is markedly enhanced in the isotropic state because of relaxation of pendant chains and other imperfections. However, within the smectic state, the magnitude of tan δ and its temperature dependence are similar for optimal and imperfect elastomers at ω = 1 Hz. The prominent loss peak near the clearing transition arises from segment-level relaxations that are insensitive to the details of chain connectivity. Smectic MCLCE can be tailored for applications as vibration-damping materials by manipulating the clearing transition temperature through the backbone structure or by deliberate introduction of structural imperfections such as pendant chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3267–3276, 2007