The chemistry of pyridine thiols and related ligands,Part 6. The crystal and molecular structure of [1,3–bis(diphenylphosphino)-propane][bis(pyridine-2–thiolato)]ruthenium(II). A comparison with solution phase behaviour

Reaction of cis-RuCl2(dppp)2 with pyridine-2–thiol (HpyS) in the presence of Et3N in dry benzene replaces both the chloro groups and a diphosphine molecule to form Ru(dppp)(pyS)2 (1) [dppp=Ph2P(CH2)3PPh2], whose crystal and molecular structure has been determined with the help of single crystal X-ray crystallography. The discrete molecules of (1) adopt a distorted octahedral structure containing chelating pyridine-2–thiolato and dppp ligands with trans-S, cis-N and cis-P atom dispositions. The important interatomic parameters are: Ru-S, 2.443(2), 2.339(2); Ru-N, 2.133(5), 2.129(5); Ru-P, 2.274(2), 2.279(2)Å; trans-bond angles, S-Ru-S, 153.89(6); N-Ru-P, 172.76(13), 163.51(14)°; bite angles: P-Ru-P, 90.71(6); N-Ru-S, 67.18(14), 67.72(14)°. The n.m.r. spectra (1H, 13C, 31P) of (1) are also reported in order to compare solution phase behaviour with the solid state structure. The 13C-n.m.r. spectrum of the complex shows the presence of non-equivalent phenyls in the Ph2P-moiety.     

Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)     

Oriented Growth of Nanocrystalline Gamma Ferric Oxide in Electrophoretically Deposited Films

Films of nanocrystalline γ-Fe₂O₃ were deposited on silicon substrates by using the technique of electrophoretic deposition. The precursor powder was nanocrystalline γ-Fe₂O₃, which was synthesized, using DC arc plasma in the oxygen ambient by vapour–vapour interaction in gas phase condensation; at a stabilized arc current of 40 A. This powder was characterized by X-ray diffraction, Transmission Electron Microscopy, Vibrating Sample Magnetometer and Mössbauer Spectroscopy. An increase in directional coercivity was observed in case of films deposited on silicon substrates, which is dramatically significant. Preferred orientation of almost similar sized nanocrystalline magnetic domains in deposited films is evident from the results of X-ray diffraction and Transmission Electron Microscopy results. The preferred alignment of the nanocrystallites seems to be responsible for the significant changes observed in magnetic properties of films.     

Content-addressable Holographic Digital Data Storage Based on Hybrid Ternary Modulation with a Twisted-Nematic Liquid-Crystal Spatial Light Modulator

We propose and demonstrate the use of hybrid ternary modulated digital pages for content-addressable holographic data storage. Display of binary data pages with equal number of ZEROs and ONEs by modulating both amplitude and phase of beams using twisted-nematic liquid crystal spatial light modulator, reduces strong de component and produces a more homogeneous spectral distribution at the recording plane. This technique facilitates better recording of all spatial frequencies, thus improving the discrimination capability of a content-addressable memory. Hence we get better results in associative recall in a holographic memory system, with very low number of false hits. An important advantage of the hybrid ternary modulation over pure phase data pages is that it offers a dark state for coding the undesired portion of the SLM while the search argument is small. The unique orientation of quarter wave plate and the analyzer blocks the light transmitted from OFF pixels leading to near total removal of dark signals. This in turn improves the system performance and reduces the number of false hits when the size of the search argument is small. Our experimental results show good discrimination capability and signal-to-noise ratio for a hybrid ternary modulation based content addressable memory.     

Quality control assessment of polyherbal formulation based on a quantitative determination multimarker approach by ultra high performance liquid chromatography with tandem mass spectrometry using polarity switching combined with multivariate analysis

An ultra high performance liquid chromatography with electrospray ionization tandem mass spectrometry method has been developed and validated for the simultaneous quantification of 28 major bioactive compounds in Mentat tablet, a complex Indian herbal medicine used in the treatment of neurological disorder and improvement of mental health. Multiple‐reaction monitoring scanning was employed for quantification in positive and negative ion switching mode. The analysis was accomplished on Waters ACQUITY UPLC BEH C₁₈ column with linear gradient elution of water/formic acid (0.1%) and acetonitrile/formic acid (0.1%) at a flow rate of 0.3 mL/min. The proposed method was validated with acceptable linearity (r², 0.9984–0.9999), precision (RSD, 0.22–2.11%), stability (RSD, 0.16–1.78%), and recovery (RSD ≤ 3.74%), under optimum conditions. The limits of quantitation ranged from 0.28 to 3.88 ng/mL. The method was successfully applied for simultaneous determination of 28 compounds in 20 batches of Mentat tablet. Hierarchical cluster analysis and principal component analysis were performed to evaluate the similarity and variation of the 20 samples based on the characteristics of 28 bioactive compounds. Results indicated that this method is rapid, sensitive, and reliable to show the quality of the Mentat tablet's composition, hence may be used for quality control of polyherbal formulations having similar markers/raw herbs.     

Synthesis and comparison of the structure–property relationships of symmetric and asymmetric water‐soluble poly(p‐phenylene)s

Sodium salts of water‐soluble polymers poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(hexyloxy)‐1,4‐phenylene]} ( P1 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dodecyloxy)‐1,4‐phenylene]} ( P2 ), poly{[2,5‐bis(3‐sulfonatopropoxy)‐1,4‐phenylene]‐alt‐[2,5‐bis(dibenzyloxy)‐1,4‐phenylene]} ( P3 ), poly[2‐hexyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P4 ), and poly[2‐dodecyloxy‐5‐(3‐sulfonatopropoxy)‐1,4‐phenylene] ( P5 )] were synthesized with Suzuki coupling reactions and fully characterized. The first group of polymers ( P1 – P3 ) with symmetric structures gave lower absorption maxima [maximum absorption wavelength (λ_max) = 296–305 nm] and emission maxima [maximum emission wavelength (λ_em) = 361–398 nm] than asymmetric polymers P4 (λ_max = 329 nm, λ_em = 399 nm) and P5 (λ_max = 335 nm, λ_em = 401 nm). The aggregation properties of polymers P1 – P5 in different solvent mixtures were investigated, and their influence on the optical properties was examined in detail. Dynamic light scattering studies of the aggregation behavior of polymer P1 in solvents indicated the presence of aggregated species of various sizes ranging from 80 to 800 nm. The presence of alkoxy groups and 3‐sulfonatopropoxy groups on adjacent phenylene rings along the polymer backbone of the first set hindered the optimization of nonpolar interactions. The alkyl chain crystallization on one side of the polymer chain and the polar interactions on the other side allowed the polymers ( P4 and P5 ) to form a lamellar structure in the polymer lattice. Significant quenching of the polymer fluorescence upon the addition of positively charged viologen derivatives or cytochrome‐C was also observed. The quenching effect on the polymer fluorescence confirmed that the newly synthesized polymers could be used in the fabrication of biological and chemical sensors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3763–3777, 2006     

Development and validation of an ultra high performance liquid chromatography electrospray ionization tandem mass spectrometry method for the simultaneous determination of selected flavonoids in Ginkgo biloba

A rapid and sensitive ultra high performance liquid chromatography electrospray ionization tandem mass spectrometry method was developed and validated for the simultaneous determination of 13 flavonoids in leaf, stem, and fruit extracts of male and female trees of Ginkgo biloba to investigate gender‐ and age‐related variations of flavonoids content. Chromatographic separation was accomplished on an Acquity UPLC BEH C₁₈ column (50 mm × 2.1 mm id, 1.7 μm) in 5 min. Quantitation was performed using negative electrospray ionization mass spectrometry in multiple reaction monitoring mode. The calibration curves of all analytes showed a good linear relationship (r² ≥ 0.9977) over the concentration range of 1–1000 ng/mL. The precision evaluated by an intra‐ and interday study showed RSD ≤ 1.98% and good accuracy with overall recovery in the range from 97.90 to 101.09% (RSD ≤ 1.67%) for all analytes. The method sensitivity expressed as the limit of quantitation was typically 0.25–3.57 ng/mL. The results showed that the total content of 13 flavonoids was higher in the leaf extract of an old male Ginkgo tree compared to young female Ginkgo trees.     

Structural and phonon dynamical properties of perovskite manganites: (Tb, Dy, Ho)MnO3

A shell model has been used to study the structure, phonon dynamics and phase coexistence of perovskite manganites RMnO₃ (R=Tb, Dy, Ho). The calculated crystal structure, Raman and IR frequencies and specific heats are found to be in good agreement with the available experimental data. The phonon density of states, elastic constants, elastic stiffness, shear constants and phonon dispersion curves have been computed for these manganites. A zone center imaginary A_u mode is revealed in these phonon dispersion curves, which indicates the occurrence of the metastability of the perovskite phase. The Gibbs free energy values calculated as a function of temperature and pressure for RMnO₃ in the orthorhombic phase, when compared with those of the hexagonal phase, reveal the possibility of coexistence of these two phases in the present multiferroic manganites under ambient conditions.     

Single enzyme nanoparticle for biomimetic CO<Subscript>2</Subscript> sequestration

Nanoparticle technology is being increasingly used in environmental sciences. We prepared single enzyme nanoparticle (SEN) by modifying the surface of carbonic anhydrase (CA) with a thin layer of organic/inorganic hybrid polymer. SEN-CA appears to be improving the stability of free enzyme. CA, as ubiquitously found enzyme, is involved in gaseous CO₂ sequestration and is being looked as a promising candidate for combating global warming. We report here physical characterization of SEN-CA using transmission electron microscope (TEM), Fourier-transform infrared analysis (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray (EDX). Average size of SEN-CA particles appears to be in the range of 70–80 nm. We also report the effect of SEN formation on the kinetic parameters of free CA such as Michaelis–Menten constant (K _m), maximum reaction velocity (V _max), and storage stability of free CA and SEN-CA. The V _max of SEN-CA (0.02857 mmol/min/mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. K _m has decreased from 6.143 mM for SEN-CA to 1.252 mM for free CA. The stabilization of CA by SEN formation results in improved the half-life period (up to 100 days). The formation of carbonate was substantiated by using gas chromatography (GC). The conversion of CO₂ to carbonate was 61 mg of CaCO₃/mg of CA and 20.8 mg of CaCO₃/mg of CA using SEN-CA and free CA, respectively.