Synthesis, growth, structure and characterization of a new semiorganic crystal

A new semiorganic single crystal, tris(allylthiourea)silver(I) nitrate was grown from an aqueous solution containing silver(I) nitrate and allylthiourea by slow evaporation solution growth technique at room temperature. The crystal belongs to trigonal system with centrosymmetric space group R3 and the cell parameters are, a = 12.5090(4) Å, b = 12.5090(4) Å, c = 21.7130(8) Å, V = 3348.89 Å³, and Z = 6. The various functional groups present in the molecule are confirmed by Fourier transformed infrared spectroscopy. High transmittance is observed in the visible region and band-gap energy is calculated by Kubelka–Munk algorithm. The structure and the crystallinity of the materials were further confirmed using powder X-ray diffraction analysis. Microhardness studies were also carried out to elucidate the mechanical behavior. Thermogravimetric and differential thermal analysis reveal the purity of the sample and no decomposition is observed up to the melting point.     

A novel four-component tandem protocol for the stereoselective synthesis of highly functionalised thiazoles

The reaction of bis(aroylmethyl) sulfides with aromatic aldehydes and ammonium acetate in 1:2:1 molar ratio under solvent-free microwave irradiation afforded predominantly a series of thiazoles, viz., 1-aryl-2-[5(Z)-5-arylmethylidene-2,4-diaryl-2,5-dihydrothiazol-2-yl]ethanones stereoselectively. This reaction presumably occurs via a Knoevenagel condensation-Michael addition-cyclocondensation-ring opening-ring closing Michael addition sequence. The intermediacy of (Z,Z)-2,2′-thiobis(1,3-diarylprop-2-en-1-ones) in the above transformation is demonstrated by their conversion to the thiazoles upon reaction with ammonium acetate under solvent-free microwave irradiation.     

On reducing Howard's semicircle for homogeneous shear flows

Howard's semicircle bound on the range of the complex wave velocity of an arbitrary unstable mode in the stability problem of homogeneous shear flows is further reduced. The reduction depends on the curvature of the velocity profile and the depth of the fluid layer.     

Growth and characterization of Fe3+-doped bis(thiourea)zinc(II) chloride crystals

Fe3+-doping at ～10 mol% in aqueous medium during crystal growth by slow evaporation solution method in bis(thiourea)zinc(II) chloride (BTZC) leads to form a new compound C2H8Cl2N4S2Zn0.93Fe0.07 (BTZCF) which crystallizes in orthorhombic structure with centrosymmetric space group Pnma though the parent compound BTZC crystallizes in noncentrosymmetric structure with space group Pn2(1)a. The interesting feature observed in this new crystal is that though it crystallizes in centrosymmetric structure, it exhibits positive SHG result (weak signal), quite likely due to possible surface effects or internal stress. The calculated first-order hyperpolarizability is 1.457×10(-30) esu which is ～5.5 times that of urea. Fe3+-doping enhances the transmittance to a significant extent. Comparison of the thermal analysis results by DSC reveals the incorporation of dopant into the crystalline matrix. The high resolution XRD studies reveal that the crystalline quality is improved considerably when the doping level is reached to ～10 mol%.     

Solution and Solid-State Photophysical Properties of Positional Isomeric Acrylonitrile Derivatives with Core Pyridine and Phenyl Moieties: Experimental and DFT Studies

The compounds I (Z)-2-(phenyl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile with one side (2,4,5-MeO-), one symmetrical (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(2,4,5-trimethoxyphenyl)acrylonitrile), II (both sides with (2,4,5-MeO-), and three positional isomers with pyridine (Z)-2-(pyridin-2- 3, or 4-yl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile, III–V were synthetized and characterized by UV-Vis, fluorescence, IR, H¹-NMR, and EI mass spectrometry as well as single crystal X-ray diffraction (SCXRD). The optical properties were strongly influenced by the solvent (hyperchromic and hypochromic shift), which were compared with the solid state. According to the solvatochromism theory, the excited-state (μ_e) and ground-state (μ_g) dipole moments were calculated based on the variation of Stokes shift with the solvent’s relative permittivity, refractive index, and polarity parameters. SCXRD analyses revealed that the compounds I and II crystallized in the monoclinic system with the space group, P2₁/n and P2₁/c, respectively, and with Z = 4 and 2. III, IV, and V crystallized in space groups: orthorhombic, Pbca; triclinic, P-1; and monoclinic, P2₁ with Z = 1, 2, and 2, respectively. The intermolecular interactions for compounds I–V were investigated using the CCDC Mercury software and their energies were quantified using PIXEL. The density of states (DOS), molecular electrostatic potential surfaces (MEPS), and natural bond orbitals (NBO) of the compounds were determined to evaluate the photophysical properties.     

Nano Pt–TiO2 for an efficient one-pot photocatalytic synthesis of quinaldines from anilines and ethanol

Nanosized platinum particles loaded on the TiO₂ nanoparticles were prepared to assess its photocatalytic activity in simple one-pot synthesis of quinaldines from anilines in ethanol using UV light. The catalyst was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy, X-ray photoelectron spectra (XPS), Brunauer?CEmmer?CTeller surface area, atomic force microscope and diffuse reflectance spectra. XRD patterns revealed that the crystal structure of Pt?CTiO₂ resembled anatase phase of TiO₂. The UV?CVis spectra indicated an increase in absorption of visible light when compared to TiO₂. XPS analysis reveals that platinum particles are present mainly in metallic form. Furthermore, TEM analysis showed non-spherical-shaped Pt?CTiO₂ nanoparticles of the diameter 10?C30?nm. Upon irradiation in the presence of Pt?CTiO₂, aniline and oxidation products derived from ethanol undergo condensation?Ccyclization to afford quinaldines. Higher efficiency of Pt?CTiO₂ than Au?CTiO₂ in the conversion of aniline to quinaldines is due to the higher work function of Pt.     

Stability of stratified shear flows in channels with variable cross sections

For the instability problem of density stratified shear flows in sea straits with variable cross sections, a new semielliptical instability region is found. Furthermore, the instability of the bounded shear layer is studied in two cases: (i) the density which takes two different constant values in two layers and (ii) the density which takes three different constant values in three layers. In both cases, the dispersion relation is found to be a quartic equation in the complex phase velocity. It is found that there are two unstable modes in a range of the wave numbers in the first case, whereas there is only one unstable mode in the second case.     

Electrochemically nanopatterned conducting coronas of a conjugated polymer precursor: SPM parameters and polymer composition

Here we describe the formation of precisely controlled corona-type nanopatterns on electroactive polymer precursor films using scanning probe microscopy (SPM) methods. The binary composition of electroactive groups in the polymer triggers the formation of corona-type nanopatterns at particular voltages and tip writing speeds through the electrooxidation of the polymer precursor film. Various parameters such as tip speed and applied bias were explored in the nanopatterning process, and the formation of a conductive nanopattern was investigated using conducting atomic force microscopy (C-AFM). The formation of the nanopattern was attributed to the flow of electrons from the AFM tip to the polymer film in a controlled electric field distribution. We also report a new method to distinguish the polymer composition and distribution of a polymer blend film by characterizing biasing differences in the patterning of a polymer film.     

Kinetics and mechanism of the reaction of α‐phenoxypropanoic acids with sodium salt of N‐Chlorobenzene‐sulphonamide: EDTA catalysis

EDTA smoothly catalyses the oxidation cum chlorination of some 17 α‐phenoxypropanoic acids with sodium salt of N‐chlorobenzenesulphonamide in acidic solution. A ternary intermediate can be envisaged for describing the enhanced reactivity. Imperfections are observed in the linear Hammett relationship in the case of ? NO₂ substituents, irrespective of the position. The susceptibility constant, ρ(≈ + 1) indicates the development of an electron‐rich transition state. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 27–33, 2002     

Enhanced photodegradation of 2,4-dinitrophenol by n–p type TiO2/BiOI nanocomposite

Photocatalysis has recently been regarded as one of the most viable technologies for water treatment. Scholars all over the world are focusing on nanocomposites for water treatment for efficient and effective sanitization of bodies of water. Because of their high surface area, high chemical reactivity, excellent mechanical strength, low cost, and nanoscale composite materials have enormous potential to purify water in a various way. In this study, n-type TiO₂ was synthesized and tailored to produce a TiO₂/BiOI n–p nanocatalyst for enhanced photodegradation of 2,4-dinitrophenol (2,4-DNP) under UV-A and solar light respectively. Because of the formation of a heterojunction between BiOI and TiO₂, the photocatalytic activity in TiO₂/BiOI absorbs strongly in both the UV and visible regions and it has a lower recombination rate of the e^-/h⁺ pairs. Furthermore, the generation of OH^?, O₂^?– radicals during the oxidation process is attributed to the photodegradation of 2,4-DNP. The results revealed that the TiO₂/BiOI manifest outperformed BiOI and TiO₂ in terms of photocatalytic function. XRD, BET, HR-SEM-EDX with ECM, HR-TEM, FT-IR, PL, and UV-DRS techniques determined the photocatalyst composition. The HR-SEM images clearly showed that the particles are less than 27 ?nm in size. Thus, nanocomposite materials have played an important role in water purification.