Chromium‐metformin ternary complexes: Thermal,DNA interaction and Docking studies

Three chromium ternary complexes with metformin (met) as a primary ligand and bipyridine (bipy) or ortho‐phenylenediamine (opda) or ortho‐phenanthroline (phen) as secondary ligand were synthesized. These complexes [Cr (Cl)₂(Hmet)(bipy)]‐( 1 ), [Cr (Cl)₂(Hmet)(opda)]‐( 2 ) and [Cr (Cl)₂(Hmet)(phen)]‐( 3 ) were characterized by LC–MS, elemental analysis, molar conductance, thermal analysis, infrared spectroscopy, electronic spectroscopy. The geometrical structures have been found to be octahedral. Degradation pattern of the compounds is shown by thermal studies. The Kinetic parameters‐ energy of activation (E_a), enthalpy (ΔH), entropy (ΔS) and free energy changes (ΔG) have been determined by thermogravimetric data. Coats‐Redfern integration method with thirteen kinetic models was used to calculate the kinetic and thermodynamic parameters for the degradation of all the complexes. The stabilities of the complexes were obtained from their molecular orbital structures from which the quantum chemical parameters were calculated using the HOMO‐LUMO energies. UV–Visible absorption, fluorescence, and viscosity measurements have been conducted to assess the interaction of the complexes with CT DNA. The complexes showed absorption hyperchromism in its UV–Vis spectrum with DNA. The binding constants K_b from UV–Vis absorption studies were 3.1x10⁴, 4.4x10⁴, 5x10⁴ M^?1 for 1, 2, 3 respectively and Stern–Volmer quenching constants (K_sq) from fluorescence studies were 0.137, 0.532, 0.631 for 1, 2, 3 respectively. Finally, viscosity measurements revealed that the binding of the complexes with CT‐DNA could be surface binding, mainly due to groove binding. The activity of complexes towards DNA cleavage decrease in the order of 3 > 2 > 1.The light switching properties of the complexes were also evaluated. The complexes were docked in to B‐DNA sequence, 5′(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)‐3′ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.     

A facile approach to the synthesis of securinega alkaloids: stereoselective total synthesis of (−)-allonorsecurinine

A concise stereoselective total synthesis of alkaloid (−)-allonorsecurinine is described utilizing classical reactions such as Grignard, Aldol and Horner-Wittig reactions as the key steps.     

Synthesis of functionalized chromene and spirochromenes using l-proline-melamine as highly efficient and recyclable homogeneous catalyst at room temperature

An efficient and recyclable homogeneous catalyst is developed using commercially cheap l-proline and melamine for the synthesis of chromenes and spirochromenes (spirooxindoles) via multicomponent reactions at room temperature. Systematic studies were conducted in order to achieve desired reactivity and recyclability of the catalyst using various α-amino acids and aromatic amines as donor-acceptor pairs. Among the screened combinations, l-proline and melamine (3:1 ratio; 3 mol% on total weight) was found to be best catalyst to give the desired products with excellent yields (up to 99%) in very short times (1–15 min) at room temperature in DMSO as solvent. The catalyst was recovered by adding EtOAc and reused up to 5 cycles without losing the catalytic activity.     

Synthesis of Ge nanocrystals by atom beam sputtering and subsequent rapid thermal annealing

Ge nanocrystals embedded in an SiO₂ matrix were prepared by the atom beam co-sputtering (ABS) method from a composite target of Ge and SiO₂. The as-deposited films were rapid thermally annealed at the temperatures 700 and 800 °C in nitrogen ambience. The structure of the films was evaluated by using X-ray diffraction (XRD) and Raman spectroscopy. XRD results reveal that as-deposited films are amorphous in nature whereas annealed samples show crystalline nature. Raman scattering spectra showed a peak of Ge–Ge vibrational mode shifted downwards to 297 cm^?1, presumably caused by quantum confinement of phonons in the Ge nanocrystals. Rutherford backscattering spectrometry has been used to measure the thickness and Ge composition of the composite films. Size variation of Ge nanocrystals with annealing temperature has been discussed. The advantages of ABS over other methods are highlighted.     

Structural and DC conduction studies on vacuum evaporated BaTiO3 thin films prepared from BaTiO3 nano particles synthesised by wet chemical method

BaTiO₃ nanoparticles prepared by wet chemical method were thermally grown onto well cleaned glass substrates under the vacuum of 2 × 10⁻⁵ Torr, using 12A4 Hind Hivac coating unit. An Al–BaTiO₃–Al sandwich structure has been used for electrical conduction properties in the temperature range 303–423 K. The composition of nanoparticles and thin films were identified by EDS spectrum. The structural studies have been performed by the X-ray diffraction (XRD) technique. The X-ray analysis showed that the nano particle has a tetragonal structure and deposited films at a lower thickness amorphous in nature, whereas the crystallinity increases with increase of thickness. In the DC conduction studies, the current–voltage characteristics of the films showed ohmic conduction in the low voltage region. In the higher voltage region, a space charge limited conduction (SCLC) takes place due to the presence of the trapping level. The activation energy was estimated and the values found to decrease with increasing applied voltage. The zero field value of the activation energy is found to be 0.31 eV. The free carrier mobility, carrier density and trap density values were calculated and reported in this paper.     

Adsorption of fatty acids on iron (hydr)oxides from aqueous solutions

The interaction of iron (hydr)oxides with fatty acids is related to many industrial and natural processes. To resolve current controversies about the adsorption configurations of fatty acids and the conditions of the maximum hydrophobicity of the minerals, we perform a detailed study of the adsorption of sodium laurate (dodecanoate) on 150 nm hematite (α-Fe(2)O(3)) particles as a model system. The methods used include in situ FTIR spectroscopy, ex situ X-ray photoelectron spectroscopy (XPS), measurements of the adsorption isotherm and contact angle, as well as the density functional theory (DFT) calculations. We found that the laurate adlayer is present as a mixture of inner-sphere monodentate mononuclear (ISMM) and outer-sphere (OS) hydration shared complexes independent of the solution pH. Protonation of the OS complexes does not influence the conformational order of the surfactant tails. One monolayer, which is filled through the growth of domains and is reached at the micellization/precipitation edge of laurate, makes the particles superhydrophobic. These results contradict previous models of the fatty acid adsorption and suggest new interpretation of literature data. Finally, we discovered that the fractions of both the OS laurate and its molecular form increase in D(2)O, which can be used for interpreting complex spectra. We discuss shortcomings of vibrational spectroscopy in determining the interfacial coordination of carboxylate groups. This work advances the current understanding of the oxide-carboxylate interactions and the research toward improving performance of fatty acids as surfactants, dispersants, lubricants, and anticorrosion reagents.     

Genetically Modified Starch as an Industrial Raw Material

Abstract

Starch is an important raw material for industrial applications, both for food and nonfood purposes. Of particular interest is the use of starch as a nonpetroleum chemical stock for the manufacture of biodegradable polymers. Annual EC starch production is nearing 10 million tons, with 80% from cereals and 20% from potatoes, and grows at 4?5% annually. The potential for genetically modified starch is considered very high. Such starch offers significant advantages: 1) chemical modifications, which are expensive and environmentally hazardous, are replaced; 2) novel carbohydrates can be produced.     

A water-soluble fluorescent fluoride ion probe based on Alizarin Red S-Al(III) complex

A new water-soluble fluorescent fluoride ion signaling system has been developed based on the ligand exchange mechanism in aqueous medium. This procedure is based on the exchange of two Alizarin Red S (ARS) molecules coordinated to Al(III) by fluoride ion without interference from other common anions. The binary complex of ARS with Al(III) provides a sensitive signaling system for fluoride ion in the concentration range from 5x10(-6) to 3x10(-4) M. The ligand exchange reaction of ARS-Al(III) complex with fluoride ion has been investigated by UV-vis and fluorescence spectroscopies combined with the AM1 semi-empirical quantum chemical calculations. The pale orange fluorescence (lambdamax=575 nm) exhibited by the complex upon excitation at 435 nm decreases in intensity with fluoride addition with a detection limit of 0.1 mg L-1.