Redox-Neutral Metal-Free Three-Component Carbonylative Dearomatization of Pyridine Derivatives with CO2

The TBD (1,3,5-triazabicyclodec-5-ene) assisted three-component carbonylation of pyridine-2-methanamines is documented by means of CO₂ as a benign CO surrogate. The redox-neutral methodology enables the realization of densely functionalized imidazo-pyridinones in high yields (up to 93 %) and excellent chemoselectivity. Combined computational and experimental investigations revealed an unprecedented RCOCl/TBD concerted electrophilic activation of carbon dioxide.     

A DFT/TD DFT study of the structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion

The structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion were studied using a DFT and TD DFT methods with def2-TZVP basis set. It was shown that the type of functional used (B3-LYP or pbe0) implemented in TURBOMOLE package does not have essential influence on the geometry (small differences in bond length, valence and dihedral angles) of studied compounds in both ground and excited states. However, significant differences were obtained for the position of vertical absorption and emission transition but not for the oscillator strength of transition. Application of pbe0 functional seems to reproduce better the experimental spectrum.     

Use of Differential Derivative Spectrophotometry and Complexation with Palladium for the Assay of Three Phenothiazine Drugs in Tablets

Abstract

Two photometric methods have been described for the assay of three phenothiazine drugs, isothipendyl hydrochloride, dimethothiazine mesylate &; trimeprazine tartarate in their tablets. The first is the differential tartarate in their tablets. The first is the differential spectro-photometric method &; based on the measurement of the absorbance (Δ A-), first derivative (Δ D₁?) or second derivative (Δ D₂?) values of the sulphoxide product of phenothiazine versus the intact. The second is based on the absorbance measurement of the pink coloured complex formed in a ratio of two drug moles t o one palladium ion. All these values are following Beer's law, which pernits the phenothiazines determination in their tablets with high accuracy. Using t-test &; F-test the results of different methods are of equal accuracy and reproducibility. Both methods complement each ot her during the routine analysis and quality control of the investigated phenothiazine drugs.     

A novel mesophase formed by top-shaped molecules in the bulk and unsupported thin films: a molecular dynamics study

We have used molecular dynamics simulations to investigate the ordering of top-shaped molecules in bulk phases and in unsupported thin films. Each rigid anisotropic molecule was composed of 11 Lennard-Jones interaction centers (beads). In an attempt to enhance the nematic stability in preference to smectic, the three central beads were assigned a larger Lennard-Jones diameter than the tail beads, giving the molecule a shape resembling a top. The molecular model was found to exhibit an unusual bulk mesophase with long-range orientational order and with molecular center-of-mass positions arranged in parallel interdigitated layers, with layer spacing smaller than half the length of the long axis of a molecule. However, despite the toplike molecular shape, no nematic phase was observed in the pressure range studied. Unsupported films of the isotropic liquid were cooled in order to locate a triple point between the novel mesophase, vapor, and isotropic liquid. At temperatures slightly above the triple point, enhanced surface ordering of molecules was found to occur in the unsupported film. At temperatures slightly below the triple point, the preferred molecular alignment in the unsupported film was parallel to the interface, in violation of arguments that have been proposed based on the relative enthalpies of various cleavage planes for close-packed structures.     

A new family of ruthenium(II) polypyridine complexes bearing 5-aryltetrazolate ligands as systems for electrochemiluminescent devices

A new family of mono- and dinuclear ruthenium polypyridyl complexes containing 5-aryltetrazolate ligands such as the deprotonated form of 4-(1H-tetrazol-5-yl)benzonitrile (4-TBNH) and bis(1H-tetrazol-5-yl)benzene (BTBH(2)) have been synthesized and thoroughly characterized. The reactivity of the mononuclear species toward different electrophiles such as H(+) and CH(3)(+) has been investigated, and the effects of the resulting regioselective electrophilic attacks on the electronic and structural properties of the tetrazolate ligand have been studied by NMR ((1)H, (13)C) spectroscopy and X-ray crystal structures. Absorption and emission spectroscopy, together with an electrochemical and UV-vis-NIR spectroelectrochemical investigation of the uncoordinated ligand and complexes, has been performed, highlighting a rather good luminescence efficiency and a poor bridge-mediated electronic communication between the metal centers of the dinuclear complexes. The electrogenerated chemiluminescence (ECL) of the dinuclear species has been explored, and for one of these, an exceptionally high ECL efficiency has been observed, comparable to that of [Ru(bpy)(3)](2+), which is considered a standard in ECL studies.     

Vibrations of thin tolerance-periodic plates

In this contribution, linear-elastic thin plates with a tolerance-periodic structure in planes parallel to the plate midplane are considered. It is assumed that their averaged (macroscopic) properties are described by continuous, slowly-varying functions. Hence, plates of this kind can be treated as plates with a functionally graded structure. Here, free vibrations frequencies of a plate band are calculated within the proposed averaged model using the finite differences method. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

New polyethyleneglycol-functionalized texaphyrins: synthesis and in vitro biological studies

The synthesis of four new analogues of motexafin gadolinium (MGd), a gadolinium(III) texaphyrin complex in clinical trials for its anticancer properties, is described. These new derivatives contain either 1,2-diaminobenzene or 2,3-diaminonaphthalene subunits as the source of the imine nitrogens and bear multiple 2-[2-(2-methoxyethoxy)ethoxy]ethoxy (PEG) groups, on either meso aryl or beta-pyrrolic substituents, to increase their water solubility. All four analogues were found to be more active in vitro than the parent system MGd as judged from cell proliferation assays using the PC3 and A549 cell lines.     

On the normal approximation for random fields via martingale methods

We prove a central limit theorem for strictly stationary random fields under a sharp projective condition. The assumption was introduced in the setting of random sequences by Maxwell and Woodroofe. Our approach is based on new results for triangular arrays of martingale differences, which have interest in themselves. We provide as applications new results for linear random fields and nonlinear random fields of Volterra-type.     

II. “Spectroscopic Investigation of Charge Transfer Complexes of Osazone Intermediates Prepared From certain monosaccharides”

Monosaccharide osazones are utilized in the spectrophotometric determination of their parent compounds through charge transfer complexes (CTC) formation with three-electron acceptor reagents. These acceptors indlude iodine (as -π-acceptor) and chloranil (tetrachloro P-benzoquinone) & TCNE (tetracyano ethylene) as π-acceptors. The presence of two phenylhydrazone moieties in the osazone molecule imparts electron-donating properties toward electron-accepting reagents, yielding spectrophotometrically measurable complexes. However, the reaction of osazone intermediates with TCNE reagent gave tricyanovinyl derivative rather than CTC formation. The above complexes together with their corresponding intermediates were subjected to structure elucidation studies to confirm the results and conclusions obtained. These studies include IR, Raman spectra, H¹, C¹³-NMR, MS, ESR (electron spin resonance spectra) and microanalysis.     

A model for convection in the evolution of under-ice melt ponds

A model for convection in the evolution of under-ice melt ponds is presented. The system exhibits two competing effects namely, a temperature gradient which is destabilising and a salt gradient which is stabilising. Density is assumed to have a dependence quadratic in temperature and linear in concentration. A linear instability analysis and a nonlinear stability analysis are performed. The standard energy method does not yield unconditional stability so a weighted energy analysis is employed to achieve global results. The global stability bound is found to be independent of the salt field and a presentation of the region of possible subcritical instabilities is given. Received May 16, 2002 / Published online September 4, 2002 RID="a" ID="a" e-mail: Magdalen.Carr@durham.ac.uk Communicated by Brian Straughan, Durham