Oxovanadium(IV), manganese(II) and manganese(III) carbodithioates exhibiting abnormal magnetic behaviour

Summary New carbodithioate complexes of the oxovanadium(IV), manganese(II) and manganese(III) ions have been prepared and studied by i.r. and electronic spectral and variable temperature magnetic susceptibility (77K to room temperature) measurements. The carbodithioate ligands, 4-methylpiperazine-1-carbodithioate (4-MPipzcdt) and 4-phenylpiperazine-1-carbodithioate (4-PPipzcdt), were derived from heterocyclic secondary amines. The VO(4-MPipzcdt)₂ and VO(4-PPipzcdt)₂ complexes possess C _4v symmetry; Mn(4-PPipzcdt)₂ is tetrahedral and Mn(4-PPipzcdt)₃ is octahedral. All exhibit abnormal room temperature magnetic moments and the variable temperature magnetic moments suggest antiferromagnetism for the oxovanadium(IV) and the manganese(II) complexes and the occurrence of low spin (³ T _1g ) high spin (⁵ E _g ) equilibrium in addition to antiferromagnetic interactions in the manganese(III) complex. The spin-spin exchange parameter (-2J) value for the VO(4-MPipzcdt)₂ complex has been calculated using variable temperature magnetic susceptibility data.     

Artificial neural networks applied to the classification of hair samples according to pigment and sex using non-invasive analytical techniques

In this study, we investigated the possibility of using an artificial neural network (ANN) to classify human hair samples according to pigment (original or bleached hair) and sex (female or male) from numerical data obtained by wavelength dispersive X-ray fluorescence (WDXRF) and by laser-induced breakdown spectroscopy (LIBS). The results were promising, showing that the developed ANNs are able to classify the pigment and donor sex of hair samples with 100% and 89.5% accuracy, respectively, in the test set using WDXRF data. For the LIBS data in the test set, 100% of the pigment classifications were correct, and 78.9% of the donor sex classifications were correct.     

Water-based biphasic media for exothermic reactions: green chemistry strategy for the large scale preparation of clofibric acid and analogues

A water-based biphasic reaction process has been developed for conducting exothermic reactions without organic solvents. This procedure is rapid, simple, and suitable for small scale synthesis as well as larger (multi-molar) scale reactions. The preparation of several hundred grams of clofibric acid and analogues by this eco-friendly and energy-efficient procedure is described. Smaller amounts of these compounds were prepared by the friction-activated ‘Grindstone Chemistry’ method described previously.     

Influence of cerium(IV) and manganese(II) on the oxidation of <Emphasis Type="Italic">D</Emphasis>-galactose by chromium(VI) in the presence of HClO<Subscript>4</Subscript>

The kinetics and mechanism of the oxidation of D-galactose by chromium(VI) in the absence and presence of cerium(IV) and manganese(II) were studied spectrophotometrically in aqueous perchloric acid media. The reaction is first order in both [D-galactose] and [H⁺]. The cerium(IV) inhibits the oxidation path, whereas manganese(II) catalyzes the reactions. The observed inhibitory role of cerium(IV) suggests the formation of chromium(IV) as an intermediate. In the manganese(II) catalyzed path, the D-galactose-manganese(II) complex was considered to be an active oxidant. In this path, the complex forms a ternary chromate ester with chromium(IV) which subsequently undergoes acid catalyzed redox decomposition (one-step three-electron transfer: Indian J. Chem., 2004, vol. 42A, p. 1060; Colloids and Surfaces, 2001, vol. 193, p. 1) in the rate determining step. On the basis of kinetic data, the mechanism of D-galactose oxidation is proposed for parent, the manganese(II) catalyzed and cerium(IV) — inhibited reactions. The activation parameters E _a = 59 kJ ΔH ^# = 57 kJ mol⁻¹, and ΔS ^# = −119 J K⁻¹ mol⁻¹ are calculated and discussed. Reaction products are also examined. Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 1, pp. 90–95. This article was submitted by the authors in English.     

Mueller matrix-based optimization of reflective type twisted nematic liquid crystal SLM at oblique incidences

Mueller matrix measurements were used to characterize the polarization properties of liquid crystal-based reflective type twisted nematic (TN) special light modulator (SLM) at oblique incidence of the laser beam. The experimentally obtained Mueller matrices were used to obtain the combination of polarization optics required to optimize it for phase only modulation. The results indicate that minimum intensity modulation is obtained with the use of a polarizer followed by a quarter wave plate (QWP) in polarization state generator (PSG) arm and a QWP followed by an analyzer in polarization state analyzer arm (PSA). Polarization parameters such as retardance, rotation and depolarization were calculated from the experimentally obtained Mueller matrices using polar decomposition method at different angle of incidences of the laser beam and the results has been discussed. The similarity between retardance and depolarization curve as a function of address voltage of TNSLM indicated that depolarization is mainly associated with errors in retardance values. Further, spectral Mueller matrix measurements were used to obtain intensity modulation response in the range of wavelengths 450-700 nm for broadband applications.     

Studies on lactams—V 3-azido-2-azetidinones

A convenient synthesis of -amino-β-lactams has been devised with the aim of preparing derivatives and analogs of penicillin and cephalosporin C. It has been found that -azido-β-lactams can be obtained from the reaction of -azido acid chlorides with imines in presence of triethylamine. The azido group undergoes facile catalytic reduction to afford -amino-β-lactams. The sequence of addition of the reactants influences the stereochemistry of the azido-β-lactam formed. The slow addition of azidoacetyl chloride to a solution of benzaliniline and triethylamine in methylene chloride favors the cis product, while the trans stereochemistry is favored when triethylamine is added to a mixture of the Schiff base and azidoacetyl chloride. Prolonged heating in presence of triethylamine did not result in the interconversion of cis- and trans- 1-phenyl-3-azido-4-(p-nitrophenyl)-azetidin-2-one.

1-Cholestanyl-3,3-dimethylazetidine-2-one has been prepared as an analog of the β-lactam-substituted steroid alkaloids reported recently.     

Compact and weakly compact weighted composition operators on weighted spaces of continuous functions

In this note we characterize the compact and weakly compact weighted composition operatorsW _, on certain weighted locally convex spacesCV _o(X, E) of vector-valued continuous functions induced by self maps ofX and the operator-valued mappings XB(E).The work of this author was supported in part by CSIR Grant 9/100/92-EMR-IThe work of this author was supported in part by UGC Grant F.8-7/91 (RBB-II)     

Cold microwave chemistry: synthesis using pre-cooled reagents

A novel experimental procedure for chemical reactions has been devised that involves mixing and then freezing the reagents (organic solvent-free) to a sub-zero temperature such as −30 °C. This frozen mixture is exposed to microwave irradiation for a brief period of time. The use of pre-cooled reagents may give a single product not obtained by traditional microwave irradiation at room temperature. Interestingly, such a product may provide information about mechanisms by identifying the first step of a multiple step reaction.