Calculating intensities using effective Hamiltonians in terms of Coriolis-adapted normal modes

The calculation of rovibrational transition energies and intensities is often hampered by the fact that vibrational states are strongly coupled by Coriolis terms. Because it invalidates the use of perturbation theory for the purpose of decoupling these states, the coupling makes it difficult to analyze spectra and to extract information from them. One either ignores the problem and hopes that the effect of the coupling is minimal or one is forced to diagonalize effective rovibrational matrices (rather than diagonalizing effective rotational matrices). In this paper we apply a procedure, based on a quantum mechanical canonical transformation for deriving decoupled effective rotational Hamiltonians. In previous papers we have used this technique to compute energy levels. In this paper we show that it can also be applied to determine intensities. The ideas are applied to the ethylene molecule.     

Enantioselective Sulfoxidation Catalyzed by a Bisguanidinium Diphosphatobisperoxotungstate Ion Pair

The first enantioselective tungstate‐catalyzed oxidation reaction is presented. High enantioselectivities were achieved for a variety of drug‐like phenyl and heterocyclic sulfides under mild conditions with H₂O₂, a cheap and environmentally friendly oxidant. Synthetic utility was demonstrated through the preparation of (S)‐Lansoprazole, a commercial proton‐pump inhibitor. The active ion‐pair catalyst was identified to be bisguanidinium diphosphatobisperoxotungstate using Raman spectroscopy and computational studies.     

Effective Floquet Hamiltonians for dipolar and quadrupolar coupled N-spin systems in solid state nuclear magnetic resonance under magic angle spinning

Spin dynamics under magic angle spinning has been studied using different theoretical approaches and also by extensive numerical simulation programs. In this article we present a general theoretical approach that leads to analytic forms for effective Hamiltonians for an N-spin dipolar and quadrupolar coupled system under magic angle spinning (MAS) conditions, using a combination of Floquet theory and van Vleck (contact) transformation. The analytic forms presented are shown to be useful for the study of MAS spin dynamics in solids with the help of a number of simulations in two, three, and four coupled, spin-1/2 systems as well as spins in which quadrupolar interactions are also present.     

Polycarbosilane‐supported titanium(IV) catalyst for Knoevenagel condensation reaction

Polycarbosilane (PCS) was synthesized by the polycondensation of trichloromethylsilane and trimethoxyvinylsilane in the presence of sodium metal. PCS has a highly crosslinked structure, high ceramic yield and high surface area. Titanium metal ion was attached to the polycarbosilane and its catalytic activity was investigated. The Knoevenagel condensation reaction catalysed by titanium‐incorporated polycarbosilane is reported. The titanium‐incorporated PCS catalysed the reaction well and with a diverse set of substrates the reaction proceeded with good yield. PCS‐supported transition metal catalysts have been prepared for the first time and used successfully in the Knoevenagel condensation reaction. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of hybrid nanographite particles using fluidized bed system

Nanographite coated with ferromagnetic substances such as iron or iron oxide is a potential material for microwave absorption because of its favorable structural, magnetic, and electrical characteristics. In this paper, deposition on surfaces of acid functionalized and microwave-exfoliated nanographite particles with the use of fluidized bed system is reported. Acid functionalization improves iron adhesion and exfoliation reduces the flake thickness. The parameters influencing the deposition process are considered. It is demonstrated that Faraday’s laws of electrolysis can be used for these systems if the charge transfer from solid cathode to bed particles is uniform. This requirement is satisfied only above some critical values of suspension density, electrolyte concentration, and stirring rate. The optimized values of current density are required for each specific system, as low current density leads to non-uniform deposition with local nucleation, when high a current density induces too rapid nucleation and promotes iron hydroxo complex formation. Deposition time also should be optimized for any specific system, as the expected amount of deposit cannot be formed longer because of side reactions.     

New cholinesterase inhibiting steroidal alkaloids from the leaves of Sarcococca coriacea of Nepalese origin

From the leaves of Sarcococca coriacea two new steroidal alkaloids, epoxynepapakistamine-A [(20S)-20-(N-methylamino)-3beta-(tigloylamino)-5alpha-pregna-16alpha,17alpha-epoxy-2beta,4beta-di-O-acetate] (1), and epoxysarcovagenine-D [(20S)-20-(N-methylamino)-3beta-(tigloylamino)-5alpha-pregna-2-en-16alpha,17alpha-epoxy-4-one] (2), and two known compounds funtumafrine C [(20S)-20-(N,N-dimethylamino)-5alpha-pregna-3-one] (3) and N-methylfuntumine (4) were isolated. Their structures were elucidated on the basis of their spectral properties. The compounds 1, 3 and 4 were found to have cholinesterase inhibitory activity when tested for the inhibition of electric eel acetylcholinesterase and horse serum butyrylcholinesterase. They inhibited both enzymes in a concentration dependent fashion.     

Feasibility for chemometric energy dispersive X‐ray fluorescence and scattering (EDXRFS) spectroscopy method for rapid soil quality assessment

Soil quality assessment (SQA) is important for modulating agricultural productivity and thus requires simple and rapid analysis of soil (macro & micro) nutrients (here called soil quality indicators – SQIs). We report proof of concept of a chemometrics‐assisted energy dispersive X‐ray fluorescence and scattering (EDXRFS) spectroscopy technique for direct rapid analysis of SQIs. The EDXRFS method exploits, in addition to fluorescence, the X‐ray scatter peaks obtained non‐invasively from soils to develop a calibration strategy for quantitative analysis of SQIs in model clay soils doped with micronutrients (Fe, Cu, and Zn) and macronutrients (NO₃^?, SO₄^2?, and H₂PO₄^?). The soil samples and certified reference materials IAEA Soil‐7 and IAEA Soil‐1 (used to build spectral library for soil classification) were irradiated at various live times (to simulate different signal‐to‐noise ratios of analyte signals and analysis speed) in a teflon holder and were analyzed using a ¹⁰⁹Cd‐excited XRF spectrometer. Principal components analysis was used for spectral data compression and pattern recognition (including for those SQI spectral signatures without any visibly discernible characteristic X‐ray lines), whereas partial least squares regression and artificial neural networks were used to build a calibration and quantitative analysis strategy. The method furnishes soil micronutrient and macronutrient information simultaneously and rapidly (t = 200 s). To the best of the authors' knowledge, this is the first time that an XRF method has demonstrated spectroanalytical potential for quantitative macronutrients analysis in soils applicable to routine SQA. Coupling EDXRFS with multivariate chemometrics enables rapid and reliable assessment of chemical SQIs. Copyright © 2011 John Wiley & Sons, Ltd.     

Principal component analysis‐assisted energy dispersive X‐ray fluorescence spectroscopy for non‐invasive quality assurance characterization of complex matrix materials

The analytical challenges in direct quality assurance analysis of complex matrices (extreme matrix effects, spectral overlap, poor signal‐to‐noise ratio (SNR) for trace analytes, ‘dark matrix’, imprecise geometry, need for sample integrity) by energy dispersive X‐ray fluorescence (EDXRF) spectrometry necessitate development of novel techniques for material characterization. We demonstrate the utility of principal component analysis (PCA) in isotope‐excited EDXRF spectrometry of a complex matrix (in this case lubricating oil) in the context of a newly developed EDXRF and scattering (EDXRFS) technique. Lubricating oil quality may be interpreted in terms of its viscosity, anti‐wear, anti‐oxidation, and anti‐rust properties, which are detectable via B, Ca, Mg, Zn, Fe, Na additives (quality markers). Our method involves simultaneous non‐invasive acquisition of both fluorescence and scatter spectra from samples held in a propylene dish, and their modeling in a reduced multidimensional space for an interpretable overview that is analytically more useful than, and complementary to, fluorescence peak‐based quantitation of the additives; by this method, only Fe and Zn are directly detectable, but with SNR of the fluorescence peak 15–20 times poorer compared with analysis after sample digestion. Although Fe and Zn cannot distinguish the various lubricating oil brands, it can differentiate authentic from adulterated. The method was however found to be analytically useful when combined with PCA: various brands of lubricating oil were discriminated in addition to the detection of adulteration. PCA processing of the spectra showed that the most important quality assurance spectral signature information responsible for the success is contained in the scatter region (low‐Z elements). Evaluation of the performance of the method with respect to SNR (i.e. analysis time and therefore speed) showed that there was no significant difference in method performance of analysis live time in the range 100–1000 s, showing proof of concept for rapid characterization of complex matrix materials by PCA‐assisted EDXRFS. Copyright © 2012 John Wiley & Sons, Ltd.