Efficient Synthesis of N‐Oxide Derivatives: Substituted 2‐(2‐(Pyridyl‐N‐oxide)methylsulphinyl)benzimidazoles

Different substituted 2‐chloromethylpyridyl derivatives (6a–d) were oxidized with mCPBA to give the respective 2‐chloromethylpyridine‐N‐oxide derivatives (7a–d) at low temperature, which on condensation with 2‐mercapto‐1H‐benzimidazole (8a–c) in the presence of aprotic solvents give the 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfanyl]‐1H‐benzimidazole (9a–d) in good yield. Finally, 9a–d oxidized with mCPBA in chlorinated solvent gives a mixture of 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfonyl]‐1H‐benzimidazole (3a–d, 10%) and 2‐[[(pyridin‐2‐yl‐1‐oxide) methyl]sulfinyl]‐1H‐benzimidazole (4a–d, 90%) derivatives.     

Experimental characterization of hexatic smectic phases through electro-optic studies and dielectric relaxation spectroscopy

The electro-optic and complex dielectric behaviour of an antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl 4′-(n-butanoyloxyprop-1-oxy)biphenyl-4-carboxylate, having chiral SmC_A* and hexatic smectic phases, have been investigated. Complex dielectric permittivities were measured as a function of frequency, d.c. bias field and temperature. Spontaneous polarization was measured by the current reversal technique; tilt angle was measured under a polarizing microscope using a low frequency electric field. The electro-optic properties and dielectric behaviour of the material are compared with results obtained by DSC and polarizing optical microscopy. Dielectric relaxation processes in SmC_A* and hexatic smectic phases were determined. The dielectric strength at the SmC_A* to hexatic smectic phase transition is discussed in terms of coupling between the long range bond orientational order and smectic C director. It seems from the results of spontaneous polarization and dielectric relaxation spectroscopy that the material might possess an additional phase between the SmC_A* and hexatic smectic I* phases.     

X-ray diffraction analysis of the layer structure in a ferroelectric liquid crystal with a chiral nematic–chiral smectic C phase transition

A half-V-shaped switching ferroelectric liquid crystal (FLC) is a promising candidate for fast response displays. In the half-V FLC display, a liquid crystal with a chiral nematic–chiral smectic C phase transition is used, and the smectic layer is formed by cooling from N* to SmC* with an applied d.c. field. We studied the layer structure by means of X-ray measurements for two axes (ω and χ). By using a point-focused X-ray tube and optimizing the slit width, we succeeded in the two-axis measurement with a commercial X-ray system. The ω–χ profile of the half-V FLC showed two broad peaks in an arc-shaped high-intensity area. Our interpretation of this result is that the major part of the layer consists of a tilted-bookshelf structure and that the minor part consists of a near-bookshelf structure. Since optical microscopy observations on the half-V FLC cells showed a stripe-shaped texture, we consider that the coexistence of the tilted-bookshelf and the near-bookshelf structures forms the stripe-shaped patterns. The radius of the arc-shaped high-intensity area was nearly equal to the molecular tilt angle. This result can explain why the half-V FLC showed a desirable black appearance in spite of the stripe-shaped texture.     

Unperturbed Random Coil Dimensions of Two Tricopolypeptides Containing Glycine,Glutamic Acid,and Lysine

Two tricopolypetides with varying amounts of glycyl, ε-carbobenzoxy-L-lysyl, and γ-benzyl-L-glutamyl residues were synthesized and characterized by determining their intrinsic viscosity, refractive index increment, molecular weight, and second virial coefficient in the random coil solvent dichloraoacetic acid. The characteristic ratio (C∞) of the two polypetides was determined using the Brant-Flory equation. C∞ decreased from 8.1 to 4.8 on changing the content of glycine from 27.3 to 46.0 mole %. These values of C∞ are markedly higher than those expected from a consideration of the effect of glycine on random coil dimensions of copolypeptides.     

The difference of thermal stability between Fe-substituted palygorskite and Al-rich palygorskite

Sedimentary palygorskite (SP) and hydrothermal palygorskite (HP) were characterized by XRF, TG/DSC, and XRD. The total iron and dissociative iron in palygorskite were detected using spectrophotometry. The results showed that about 3.57 wt% of Fe₂O₃ was detected in SP in contrast with 0.4 wt% in HP. SP was a Fe-substituted palygorskite, and HP was an Al-rich palygorskite. The occurrence of Fe substitution in SP resulted in two mass loss steps of coordinated water and resulted in a larger d spacing. The SP showed greater thermal stability than the HP. It was proposed the change of (200) diffraction peak and (240) diffraction peak reflect changes of tetrahedral and octahedral structures in palygorskite.     

Viscosity Behavior of Some Synthetic Polypeptides at Low Concentration

The viscosity of poly(γ-benzyl L-glutamate)(PBLG), poly -carbobenzoxy-L-lysine (PCBL), polyglycine (PG), and fivetricopolypeptides (glu^x-lys^y -gly^z) was studied as a function of concentration at 25°C. The solvents used include two random coil solvents, a theta solvent and a helicogenic solvent. The Huggins plots of all the systems except polyglycine showed anomalously high reduced viscosity values at low concentration of solutions. A variation of 20°C in the temperature of some of the systems did not show any marked effect on the abnormality in the Huggins plots. Various factors likely to cause abnormality were considered; disentanglement of the polypeptide chains appeared to be the prime factor responsible for the anomalous rise in the reduced viscosity.     

Vinyl Polymerization Initiated by Peroxydiphosphate. XI. Polymerization of Methyl Methacrylate Initiated by Peroxydiphosphate-Tartaric Acid Redox System

The polymerization of methyl methacrylate was studied using the peroxydiphosphate and tartaric acid redox system as the initiator. The rate of polymerization increases with increasing peroxydiphosphate concentration and the initiator exponent was computed to be 0.5. The rate of polymerization increases with increasing monomer concentration and the monomer exponent was computed to be unity. The reaction was carried out at three different temperatures, and the overall activation energy was computed to be 3.80 kcal/mol. The effect of certain surfactants on the rate of polymerization has been investigated and a suitable kinetic scheme has been proposed.     

Thermogravimetric analysis of the copper silicate mineral dioptase Cu6[Si6O18]·6H2O

There have been a few studies on the thermal decomposition of dioptase Cu₆[Si₆O₁₈]·6H₂O. The results of these analyses are somewhat conflicting and the conclusions vary among these thermo-analytical studies. The objective of this research is to report the thermal analysis of dioptase from different origins and to show the mechanism of decomposition. Thermal decomposition occurs over a very wide temperature range from around 400 to 730 °C with the loss of water. Two additional mass loss steps are observed at around 793 and 835 °C with loss of oxygen. The infrared spectra of dioptase in the hydroxyl stretching region enables the hydrogen bond distances of water molecules in the dioptase structure to be calculated. The large variation in the hydrogen bond distances offers an explanation as to why the decomposition of dioptase with loss of water occurs over such a wide temperature range.     

Popcorn‐Shaped Magnetic Core–Plasmonic Shell Multifunctional Nanoparticles for the Targeted Magnetic Separation and Enrichment,Label‐Free SERS Imaging,and Photothermal Destruction of Multidrug‐Resistant Bacteria

Over the last few years, one of the most important and complex problems facing our society is treating infectious diseases caused by multidrug‐resistant bacteria (MDRB), by using current market‐existing antibiotics. Driven by this need, we report for the first time the development of the multifunctional popcorn‐shaped iron magnetic core–gold plasmonic shell nanotechnology‐driven approach for targeted magnetic separation and enrichment, label‐free surface‐enhanced Raman spectroscopy (SERS) detection, and the selective photothermal destruction of MDR Salmonella DT104. Due to the presence of the “lightning‐rod effect”, the core–shell popcorn‐shaped gold‐nanoparticle tips provided a huge field of SERS enhancement. The experimental data show that the M3038 antibody‐conjugated nanoparticles can be used for targeted separation and SERS imaging of MDR Salmonella DT104. A targeted photothermal‐lysis experiment, by using 670 nm light at 1.5 W cm^?2 for 10 min, results in selective and irreparable cellular‐damage to MDR Salmonella. We discuss the possible mechanism and operating principle for the targeted separation, label‐free SERS imaging, and photothermal destruction of MDRB by using the popcorn‐shaped magnetic/plasmonic nanotechnology.     

A CSD analysis on H-bond patterns from phosphoric triamides to their coordination compounds, new complexes with (tBuNH)3PO ligand (PO): Cl2Ph2Sn(PO)2 and Fe(PO)2(NO3)3

The phosphoryl donor ligand (^tBuNH)₃PO (PO) was used for preparation of new tin(IV), Cl₂Ph₂Sn(PO)₂ (1), and iron(III), Fe(PO)₂(NO₃)₃ (2), complexes. These complexes are the first examples of using a phosphoric triamide containing a secondary nitrogen atom, [RNH]₃P(O), for preparation of an organotin(IV) complex of the type ([RNH]₃P(O))₂X₂Ph₂Sn, X = halide, and an iron(III) complex. In 1, the Sn coordination geometry is octahedral with the pair of similar ligands in a trans orientation. The Fe center in 2 is seven-coordinated with the two phosphoramide ligands in a trans fashion, too. This article also reviews the structures of analogous complexes with phosphoric triamide ligands, deposited in the CSD, aiming to classify hydrogen bond patterns in this category of compounds. Moreover, it is tried to find a relationship between the H-bond patterns in complexes and the related free ligands.