Facile one-pot template synthesis of isotypic Co(II), Ni(II) and Cu(II) complexes of a Schiff base derived from glyoxylic acid and ethyl carbazate

Journal of Thermal Analysis and Calorimetry - Glyoxylic acid and ethyl carbazate condense in situ in the reaction medium and react with metal nitrates of Co, Ni or Cu to yield isostructural metal...     

A facile domino protocol for the stereoselective synthesis of trans-2,3-dihydrobenzofurans and cis-5,6-dihydrofuro[2,3-d]pyrimidines

A facile protocol for the stereoselective construction of trans-2,3-dihydrobenzofurans and cis-5,6-dihydrofuro[2,3-d]pyrimidines from the reactions of 2,2′-sulfonylbis(1,3-diarylprop-2-en-1-ones) with cyclic 1,3-diketones, viz. cyclohexane-1,3-diones, barbituric acid, and 2-thioxodihydropyrimidine-4,6(1H,5H)-dione in the presence of DBU in ethanol is described. This transformation presumably occurs via domino Michael addition-proton exchange-annulation via intramolecular displacement sequence.     

Crystal growth,structure, crystalline perfection and characterization of zinc magnesium ammonium sulfate hexahydrate mixed crystals ZnxMg(1−x)(NH4)2(SO4)2·6H2O

Mixed crystals Zn_xMg_(1?x)(NH₄)₂(SO₄)₂·6H₂O of the two well-known Tutton's salts Zn(NH₄)₂(SO₄)₂·6H₂O and Mg(NH₄)₂(SO₄)₂·6H₂O were grown with varying molar proportions (x=0.10–0.90) by slow evaporation solution growth technique. The mixed crystal Zn_0.54Mg_0.46(NH₄)₂(SO₄)₂·6H₂O is crystallizing in monoclinic system with space group P2₁/c and cell parameters a=6.2217(4) Å, b=12.5343(7) Å, c=9.2557(6) Å, β=106.912(3)°. The coexistence of zinc and magnesium ions in the mixed crystal was confirmed by inductively coupled plasma (ICP), atomic absorption spectroscopy (AAS) and energy dispersive X-ray spectroscopy (EDS). Compositional dependence of lattice parameters follows Vegard's relations. Slight variations are observed in FT-IR and XRD of pure and mixed crystals. Comparison of crystalline perfection as evaluated by high-resolution X-ray diffraction (HRXRD) for mixed crystals of various proportions reveals a reasonably good crystalline perfection for the mixed crystal with nearly equimolar ratio of Zn and Mg. The surface morphology of the mixed crystals changing with composition was studied by scanning electron microscopy (SEM). UV–vis studies reveal that the transparency of the mixed crystals was not much affected.     

Synchronous fluorescence and excitation emission characteristics of transformer oil ageing

This paper describes the evaluation of synchronous fluorescence spectroscopy (SFS) and excitation emission matrix fluorescence (EEMF) spectroscopy as means of monitoring transformer oil degradation. When accelerated thermal ageing method is used, the onset of degradation of transformer oil on 17th day and transformer oil with polypropylene and cellulosic paper on 23rd and 27th days is sensitively reflected in the SFS and EEMF fluorescence spectral characteristics.     

Crystal growth,characterization and Density functional theory computations of supramolecular N‐carbamothioyl acetamide

Single crystals of N‐carbamothioylacetamide (NCTA) were grown by slow evaporation technique at constant temperature. The structure is elucidated by single crystal XRD analysis. The studies reveal that the molecule is associated with accommodating weak C–O···H, N–H···O, N–H···S, C–H···N, C···C and H···H stacking interactions which are responsible for the formation and strengthening of supramolecular assembly. Inter‐ and intramolecular hydrogen bonding interactions exhibit supramolecular architecture in the crystal packing. Two different types of architecture, i.e., a column like packing, and cluster network type of infrastructure are observed. Hirshfeld surfaces and Fingerprint plots were used to locate and analyze the percentage of hydrogen bonding interactions. The various functional groups present in the molecule are confirmed by FT‐IR analysis. Density functional theory computations of the vibrational spectrum, molecular geometry, HOMO‐LUMO energy gaps, NBO and hyperpolarizability (β) were successfully evaluated. Facts concerning with the size, shape, charge density distribution and site of chemical reactivity of the molecule have been obtained by mapping electron density with electrostatic potential (ESP).     

Crystal growth and characterization of potassium(I)-doped tetrakis(thiourea)nickel(II) chloride

The influence of alkali metal potassium(I)-doping on the properties of tetrakis(thiourea)nickel(II) chloride crystals has been investigated. The variation in the intensity observed in powder X-ray diffraction (XRD) of doped specimen and slight shifts in vibrational frequencies confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the alkali metal are observed by scanning electron microscopy. The incorporation of K(I)- into the crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The crystal is further characterized by UV–Vis and Kurtz powder technique.     

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

Single crystals of (chloro)tris(thiourea-κS)cadmium(II) picrate have been grown by slow evaporation of a mixed solvent system water–acetone containing thiourea, cadmium chloride, and picric acid. The yellow crystals belong to triclinic system with centrosymmetric space group P-1 and the corresponding lattice parameters are a = 7.4632(3) ?, b = 7.9567(3) ?, c = 17.4885(7) ?, α = 98.990(2)°, β = 100.137(2)°, γ = 95.275(2)°, and Z = 2. The vibrational patterns of the as-grown crystals are analyzed by FT-IR and FT-Raman spectral analyses. The optical absorption study was performed to analyze the optical transparency of CTTCP and the crystals were transparent in the visible region and have a lower optical cutoff at ~507 nm with band gap energy of 2.47 eV. TG–DTA thermal analysis shows that the crystal is stable up to ~208 °C and has a good chemical stability.     

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.