Studies on vibrational,thermal, optical,dielectric and mechanical properties of a molecular salt: 2-Methylimidazolium hydrogen succinate

Good quality single crystal of 2-methylimidazolium hydrogen succinate (2MISA) was grown by slow evaporation solution growth method. The grown crystal was investigated using various characterization techniques to study its properties. Single crystal of 2MISA was confirmed by single crystal XRD. The high resolution X-ray diffraction curve shows the structural perfection of the grown crystal. Factor group analysis predicts 153 possible modes of vibrations. IR and Raman measurements confirm the functional groups present in the title crystal. From the UV–vis spectrum the optical bandgap and refractive index were evaluated. The PL spectrum of the title compound shows green emission. Dielectric tensorial behavior of the grown single crystal was studied with varying frequencies. The thermal stability of 2MISA was analyzed using TGA/DTA measurements, which infer the thermally stability. Mechanical stability of the grown crystal was studied by Vickers hardness tester.     

Theoretical and experimental analysis on spectral,hyperpolarizability and dielectric properties of semi-organic nonlinear optical crystal: Potassium boromalate hydrate (PBH)

Semi-organic potassium boromalate hydrate KBC₈H₈O₁₀·H₂O (PBH) salt was synthesized by reflux method and grown as single crystals by slow evaporation technique. The single crystal X-ray diffraction, Fourier transform infra red (FT-IR) and Fourier transform Raman spectral analyses were carried out to confirm the grown crystals. The factor group analysis was performed and the possible vibrational modes were predicted for PBH. The first order hyperpolarizability value calculated by quantum chemical calculations is well supported by the results obtained from Kurtz–Perry powder technique. The transparency in the entire blue, green and IR region makes it a valid candidate for the NLO applications. From the dielectric studies it is inferred that conductance predominates at low frequency region due to the exchange of electrical charges at crystal surface which results in the local displacement of electrons in the direction of the applied field.     

Influence of Al concentration on electrical, structural and optical properties of Al-As codoped p-ZnO thin films

We report the influence of Al concentration on electrical, structural, optical and morphological properties of Al-As codoped p-ZnO thin films using RF magnetron sputtering. Al-As codoped p-ZnO films with different Al concentrations were fabricated using As back diffusion from the GaAs substrate and sputtering Al₂O₃ mixed ZnO targets (1, 2 and 4 at%). The grown films were investigated by Hall effect measurement, X-ray diffraction (XRD), electron probe microanalysis (EPMA), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and atomic force microscopy (AFM) to study the electrical, structural, optical and morphological properties of the films. From the XRD, it was observed that both full-width at half-maximum (FWHM) and c-axis lattice constant have similar trends with respect to Al concentration. Hall measurements showed that the hole concentration increases as the Al concentration increases from 10¹⁵ to 10²⁰ cm⁻³. The increase in hole concentration upon codoping was supported by the red shift in the near-band-edge (NBE) emission observed from room temperature PL spectra. The proposed p-type mechanism due to As_Zn-2V_Zn complex was confirmed by low temperature PL and XPS analysis. The low FWHM, resistivity and peak-to-valley roughness observed by XRD, Hall measurement and AFM, respectively, suggest that 1 at% Al-doped ZnO:As film is the best codoped film.     

Condensation of propargylic alcohols with indoles and carbazole in [bmim][PF6]/Bi(NO3)3·5H2O: a simple high yielding propargylation method with recycling and reuse of the ionic liquid

Propargylation of a variety of substituted indoles as well as mono- and di-propargylation of carbazole are achieved in 80–94% isolated yields by employing catalytic amounts (10 mol %) of the readily available Bi(NO₃)₃·5H₂O in [bmim][PF₆] ionic liquid (IL), with repeated recycling and reuse of the IL.     

Synthesis and structural and DNA binding studies of mono‐ and dinuclear copper(II) complexes constructed with ─O and ─N donor ligands: Potential anti‐skin cancer drugs

Mononuclear and dinuclear copper(II) complexes with thiophenecarboxylic acid, [Cu(3‐TCA)₂(2,2′‐bpy)] ( 1 ), [Cu(3‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 2 ), [Cu(5‐Me‐2‐TCA)₂(H₂O)(2,2′‐bpy)] ( 3 ) and [Cu₂(2,5‐TDCA)(DMF)₂(H₂O)₂(2,2′‐bpy)₂](ClO₄)₂ ( 4 ) (where 3‐TCA = 3‐thiophenecarboxylic acid; 3‐Me‐2‐TCA = 3‐methyl‐2‐thiophenecarboxylic acid; 5‐Me‐2‐TCA = 5‐methyl‐2‐thiophenecarboxylic acid; 2,5‐TDCA = thiophene‐2,5‐dicarboxylic acid; 2,2′‐bpy = 2,2′‐bipyridyl; DMF = N,N‐dimethylformamide), were synthesized. Compounds 1 – 4 were extensively characterized using both analytical and spectroscopic methods. Additionally, the solid‐state structures of 1 and 4 were unambiguously established from single‐crystal X‐ray diffraction studies. The hexacoordinated Cu(II) centre in 1 (CuO₄N₂) is a distorted octahedral geometry whereas the pentacoodinated 4 (CuO₃N₂) has distorted square pyramidal geometry. Compounds 1 and 4 exhibit intermolecular hydrogen bonding which leads to the formation of two‐ and three‐dimensional supramolecular architectures, respectively. Spectrophotometric and computational investigations suggest that these compounds bind with DNA in minor groove binding such that K_b = 4.9 × 10⁵ M^?1 and K_sv = 3.4 × 10⁵ M^?1, and binding score of ?5.26 kcal mol^?1. The binding affinity of these complexes to calf thymus DNA is in the order 2 > 3 > 4 > 1 . Methyl‐substituted thiophene ring increases the DNA binding affinity whereas unsubstituted thiophene ring DNA binding rate is reduced. The methyl group on the thiophene ring would sterically hinder π–π stacking of the ring with DNA base pairs, and subsequently they are involved in hydrophobic interaction with the DNA surface rather than partial intercalative interaction. Compounds 1 – 4 show pronounced activity against B16 mouse melanoma skin cancer cell lines as measured by MTT assay yielding IC₅₀ values in the micromolar concentration range. The compounds could prove to be efficient anti‐cancer agents, since at a concentration as low as 2.1 μg ml^?1 they exerted a significant cytotoxic effect in cancer cells whereas cell viability was not affected in normal cells.     

Wave propagation in a porous composite beam: Porosity determination,location and quantification

A wave-based method is developed to quantify the defect due to porosity and also to locate the porous regions, in a composite beam-type structure. Wave propagation problem for a porous laminated composite beam is modeled using spectral finite element method (SFEM), based on the modified rule of mixture approach, which is used to include the effect of porosity on the stiffness and density of the composite beam structure. The material properties are obtained from the modified rule of mixture model, which are used in a conventional SFEM to develop a new model for solving wave propagation problems in porous laminated composite beam. The influence of the porosity content on the group speed and also the effect of variation in theses parameters on the time responses are studied first, in the forward problem. The change in the time responses with the change in the porosity of the structure is used as a parameter to find the porosity content in a composite beam. The actual measured response from a structure and the numerically obtained time responses are used for the estimation of porosity, by solving a nonlinear optimization problem. The effect of the length of the porous region (in the propagation direction), on the time responses, is studied. The damage force indicator technique is used to locate the porous region in a beam and also to find its length, using the measured wave propagation responses.     

Some ABO3 oxides with defect pyrochlore structure

Studies on the formation, structures and properties of the ternary oxides TlNbO₃, TlTaO₃ and BiVO_3+x occurring in A₂B₂O_7-y defect pyrochlore structure are reported. The reaction of Tl₂ CO₃ with Nb₂O₅/Ta₂O₅ initially leads to the formation of TlNbO_3+x [x ～ 0.3] and TlTaO_3+x [x ～ 0.4]. On further heating, the phases lose oxygen forming TlTaO₃ and TlNbO₃. The occurrence of ABO₃ oxides having Tl⁺, Pb²⁺ or Bi³⁺ as the A cation in defect pyrochlore structure in preference to the perovskite structure is attributed to the formation of a “trap-mediated” A-A bond through 6s² electrons.     

Worst case analysis of a graph coloring algorithm

In this paper, we show that a graph coloring heuristic developed by Brélaz may use n colors to color a 3-colorable graph with O(n) vertices.     

Energy transfer to neutral pions in high energy nuclear interactions

The fraction of energy transferred to the neutral pions ( \( K_{\pi ^ \circ } \) ), in an interaction of high energy (> 20 GeV) N-particles (nucleons and pions) with atomic nuclei, is estimated from the data collected, using a total absorption spectrometer (TAS) and a multiplate cloud chamber. The average value of \( K_{\pi ^ \circ } \) ( \( \bar K_{\pi ^ \circ } \) ) is found to be 0·12 ± 0·01 in the energy range 20–100 GeV (ē₀ = 35 GeV) and 0·19 ± 0·02 in the region of > 100 GeV (ē₀ = 206 GeV). The value of \( \bar K_{\pi ^ \circ } \) obtained in different experiments and its dependence on the primary energy are discussed. An increase in \( \bar K_{\pi ^ \circ } \) in pion-nucleus collisions with the energy of the pion or an increase in the ratio of pions to protons, at 800 gm./cm.², in the energy range of a few tens of GeV to a few hundred GeV or both is to be invoked to explain the energy dependence of \( \bar K_{\pi ^ \circ } \) observed in this investigation.     

Synthesis and NMR spectral studies of N-chloroacetyl-2,6-diarylpiperidin-4-ones

A series of 2,6-diarylpiperidin-4-ones having electron withdrawing chloroacetyl group at the heterocyclic nitrogen were synthesized. Unambiguous characterizations of the synthesized compounds were achieved by one-dimensional ((1)H NMR and (13)C NMR) and two-dimensional (HOMOCOSY, NOESY and HSQC spectra for compounds 8 and 9 and HOMOCOSY spectrum only for 10) NMR spectroscopic data. The conformational preferences of N-chloroacetyl-2,6-diarylpiperidin-4-ones with and without alkyl substituent at C-3 and C-5 (8-14) have also been discussed using the spectral studies. The spectral data and extracted coupling constant values suggest that the compounds 8, 12 and 14 adopt flattened boat conformation whereas the remaining compounds exist in twist-boat conformations in solution with coplanar orientation of the chloroacetyl moiety present at the heterocyclic nitrogen. The substituent parameters for the chloroacetyl moiety on the heterocyclic ring carbons have also been derived and discussed elaborately on the basis of their steric, electronic and gamma-eclipsing interaction. This substituent at the nitrogen causes a substantial change on the chemical shifts of ring carbons and the associated protons.