Solid-state synthesis and characterization of novel aluminophosphates,A3Al2P3O12 (A = Na,K, Rb,Tl): influence of A+ ions on the coordination of aluminum

Four aluminophosphates, A3Al2P3O12 (A = Na, K (1), Rb (2), Tl (3)), have been synthesized by solid-state reactions and characterized by X-ray diffraction and NMR and IR spectroscopic techniques. Aluminum has trigonal bipyramidal coordination in the thallium compound and tetrahedral coordination in the others. Potassium, rubidium and thallium analogues have been structurally characterized by single-crystal X-ray diffraction and found to possess three-dimensional (Al2P3O12)3- anionic frameworks with channels occupied by A+ countercations. These frameworks are built from corner connections of PO4 tetrahedra with AlO4 tetrahedra in 1 and 2 and with AlO5 trigonal bipyramids in 3. Pertinent crystal data are as follows: for 1, orthorhombic space group Pna2(1), a = 8.685(2) A, b = 16.947(2) A, c = 8.458(3) A, Z = 4; for 2, orthorhombic space group Cmc2(1), a = 17.164(2) A, b = 8.6270(6) A, c = 8.8140(14) A, Z = 4; for 3, orthorhombic space group Pna2(1), a = 6.1478(15) A, b = 10.396(3) A, c = 17.787(5) A, Z = 4. Compound 3 is a rare example of an oxide possessing aluminum exclusively in trigonal bipyramidal coordination.     

Quantitative estimation of constituents in fly ash by lithium tetraborate fusion

Silica is removed from fly ash sample by hydroflourination for its effective determination gravimetrically and the remaining residue is subjected to lithium tetraborate (Li₂B₄O₇) fusion followed by dissolution in dilute nitric acid to obtain a clear solution in which elements including aluminum (Al), iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu) and zinc (Zn), have been determined by Flame Atomic Absorption Spectrometry (FAAS). Two fly ash samples analyzed by the proposed method have been received from the National Council of Cement and Building Materials (NCCBM), India (proposed CRM in future) and fly ash CRM 1633 (b) from NIST, USA. The validity of the method has been established by analyzing fly ash CRM 1633 (b) as reference standard. The standard deviation has been calculated for each measurement.     

First principle electronic structure calculations of ternary alloys Hg1−xMnxTe in zinc-blende structure

We have investigated the structural, electronic, magnetic and optical properties of Hg_1?xMn_xTe in the zinc-blende phase for 0≤x≤1. The calculations were performed by using the full potential linearized augmented plane wave plus local orbitals method within the framework of the density functional theory. The lattice constants of Hg_1?xMn_xTe at different Mn concentrations exhibit Vegard's law perfectly. For spin-up channel the Mn 3d bands are occupied and mixed with the Te 5p bands whereas for spin-down channel the Mn 3d bands are unoccupied. The values of the p–d exchange splitting energy, ?_x(pd) as produced by the Mn 3d states are given. The contribution of the valence band and the conduction band in the process of exchange and splitting is described by the exchange coupling constants N₀α and N₀β. Due to p–d hybridization the magnetic moment of the Mn atom reduces, which results in small local magnetic moments on the non-magnetic Hg and Te sites. The potential applications of Hg_1?xMn_xTe in infrared device have been discussed on the basis of its optical properties.     

Spectro Analytical,Computational and In Vitro Biological Studies of Novel Substituted Quinolone Hydrazone and it’s Metal Complexes

Some novel transition metal [Cu (II), Ni (II) and Co (II)] complexes of nalidixic acid hydrazone have been prepared and characterized by employing spectro-analytical techniques viz: elemental analysis, ¹H-NMR, Mass, UV–Vis, IR, TGA-DTA, SEM-EDX, ESR and Spectrophotometry studies. The HyperChem 7.5 software was used for geometry optimization of title compound in its molecular and ionic forms. Quantum mechanical parameters, contour maps of highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) and corresponding binding energy values were computed using semi empirical single point PM3 method. The stoichiometric equilibrium studies of metal complexes carried out spectrophotometrically using Job’s continuous variation and mole ratio methods inferred formation of 1:2 (ML₂) metal complexes in respective systems. The title compound and its metal complexes screened for antibacterial and antifungal properties, exemplified improved activity in metal complexes. The studies of nuclease activity for the cleavage of CT- DNA and MTT assay for in vitro cytotoxic properties involving metal complexes exhibited high activity. In addition, the DNA binding properties of Cu (II), Ni (II) and Co (II) complexes investigated by electronic absorption and fluorescence measurements revealed their good binding ability and commended agreement of K_b values obtained from both the techniques. Molecular docking studies were also performed to find the binding affinity of synthesized compounds with DNA (PDB ID: 1N37) and “Thymidine phosphorylase from E.coli” (PDB ID: 4EAF) protein targets.     

Metal-catalyzed aziridination of alkenes by organic azides: a mechanistic DFT investigation

Structural Chemistry - The DFT B3LYP/6–31G(d,p) approach is used to study alkene aziridination by azides through catalyzed routes involving a metal nitrenoid intermediate. The catalysts...     

Effects on the bifurcation and chaos in forced Duffing oscillator due to nonlinear damping

In this communication, the two-well Duffing oscillator with non-linear damping term proportional to the power of velocity is considered. We mainly focus our attention on how the damping exponent affects the global dynamical behaviour of the oscillator. In particular, we obtain analytically the threshold condition for the occurrence of homoclinic bifurcation using Melnikov technique and compare the results with the computational results. We also identify the major route to chaos and the regions of the 2D parameter space (consists of external forcing amplitude and damping coefficient) corresponding to the various types of asymptotic dynamics under linear (viscous or friction like) and nonlinear (drag like) damping. We also attempt to analyze how the basins of attraction patterns change with the introduction of nonlinear damping. We also present our analysis for the physically less-interesting cases where damping is proportional to the 3rd and 4th power of velocity for the sake of generalizing our findings and establishing firm conclusion.     

Design,synthesis and characterization of peptidyl boronate analogues as effective antimicrobial agents

Research on Chemical Intermediates - Antibiotic-resistant penicillin binding protein (PBPs) production is one of the reasons why bacteria develop resistance to β-lactam antibiotics, and this...