An improved Darcian analysis for chemically reacted Maxwell liquid toward convectively heated moving surface with magnetohydrodynamics

Journal of Thermal Analysis and Calorimetry - Heat transportation analysis subjected to porous medium consideration has increased because of industrial and engineering utilization. Typical examples...     

A proposed unsteady bioconvection model for transient thin film flow of rate-type nanoparticles configured by rotating disk

Journal of Thermal Analysis and Calorimetry - The revolution in nanotechnology has made new developments toward enhancement of energy resources which play a substantial role in the growth of...     

Synthesis, Characterization, and Electrochemistry of Ruthenium Porphyrins Containing a Nitrosyl Axial Ligand

Two ruthenium nitrosyl porphyrins have been synthesized and characterized by spectroscopic and electrochemical methods. The investigated compounds are represented as [(TPP)Ru(NO)(H(2)O)]BF(4) and (TPP)Ru(NO)(ONO) where TPP is the dianion of 5,10,15,20-tetraphenylporphyrin. (TPP)Ru(NO)(ONO) crystallizes in the tetragonal space group I4, with a = 13.660(1) ?, c = 9.747(1) ?, V = 1818.7(3) ?(3), and Z = 2, 233 K. The most chemically interesting feature of the structure is that the nitrosyl and O-bound nitrito groups are located axial and trans to one another. Both complexes undergo an irreversible reduction at the metal center which is accompanied by dissociation of the axial ligand trans to NO. The addition of 1-10 equiv of pyridine to [(TPP)Ru(NO)(H(2)O)]BF(4) in CH(2)Cl(2) containing 0.1 M TBAP leads to the formation of [(TPP)Ru(NO)(py)](+), a species which is reversibly reduced at E(1/2) = -0.29 V. The electrochemical data indicate that (TPP)Ru(NO)(ONO) can also be converted to [(TPP)Ru(NO)(py)](+) in CH(2)Cl(2) solutions containing pyridine but only under specific experimental conditions. This reaction does not involve a simple displacement of the ONO(-) axial ligand from (TPP)Ru(NO)(ONO) but occurs after reduction of (TPP)Ru(NO)(ONO) to (TPP)Ru(NO)(py) followed by reoxidation to [(TPP)Ru(NO)(py)](+).     

Organoplatinum(IV) compounds : II. Preparation and characterization of trimethylplatinum(IV) compounds with chelating nitrogen donor ligands. The crystal and molecular structure of iodotrimethyl[bis(3,5-dimethyl-1-pyrazolyl)methane]platinum(IV)

Compounds of the types Me₃PtX(NN) (where X = Cl, I, OAc, NO₃; NN = bis(1-pyrazolyl)methane (pz₂CH₂), bis(3,5-dimethyl-1-pyrazolyl)methane ((Me₂pz)₂CH₂), or bis(2-pyridyl)methane (py₂CH₂)), [Me₃Pt(NNN)][PF₆] (where NNN=tris(1-pyrazolyl)methane (pz₃CH), or tris(2-pyridyl)methane (py₃CH)), and [Me₃Pt((Me₂pz)₂CH₂(py)][PF₆] have been prepared and characterized by elemental analyses and ¹H and ¹³C NMR spectroscopy; the structure of Me₆PtI[(Me₂pz)₂CH₂] (1) has also been determined by X-ray crystallography. Crystals of 1 are orthorhombic, space group Pcmn with four molecules in a unit cell of dimensions a 11.936(5), b 14.462(4), c 10.138(5) Å. The structure was solved by the heavy-atom method and refined by full-matrix least-squares calculations to R = 0.022 for 1719 observed data. The molecule has crystallographic mirror symmetry. The Pt atom has octahedral geometry with one methyl group trans to iodine and two methyl groups trans to the N atoms of the bidentate ligand (Pt---I 2.843(1), Pt---N, 2.236(4), Pt---C 2.077(6) (trans to I) and 2.032(5) Å (trans to N)).     

2‐[N‐(X‐Chlorophenyl)carbamoyl]benzenesulfonamide (with X = 2 and 4)

The structures of 2‐[N‐(2‐chlorophenyl)carbamoyl]benzenesulfonamide and 2‐[N‐(4‐chlorophenyl)carbamoyl]benzenesulfonamide, both C₁₃H₁₁ClN₂O₃S, are stabilized by extensive intra‐ and intermolecular hydrogen bonds. In both structures, sulfonamide groups are hydrogen bonded via the N and O atoms and form chains of molecules. The carbamoyl groups are also hydrogen bonded, involving the O and N atoms, further strengthening the polymeric chains running along the c and a axes in the 2‐ and 4‐chloro derivatives, respectively. Carbamoylsulfonamide derivatives are novel compounds with a great potential for medicinal applications.     

Separation,preconcentration and speciation of chromium by solid phase extraction on immobilised ferron

A sensitive and simple method for determination of chromium species after separation and preconcentration by solid phase extraction (SPE) has been developed. For the determination of the total concentration of chromium in solution, Cr(VI) was efficiently reduced to Cr(III) by addition of hydroxylamine and Cr(III) was preconcentrated on a column of immobilised ferron on alumina. The adsorbed analyte was then eluted with 5?mL of hydrochloric acid and was determined by flame atomic absorption spectrometery. The speciation of chromium was affected by first passing the solution through an acidic alumina column which retained Cr(VI) and then Cr(III) was preconcentrated by immobilised ferron column and determined by FAAS. The concentration of Cr(VI) was determined from the difference of concentration of total chromium and Cr(III). The effect of pH, concentration of eluent, flow rate of sample and eluent solution, and foreign ions on the sorption of chromium (III) by immobilised ferron column was investigated. Under the optimised conditions the calibration curve was linear over the range of 2–400?µg?L^?1 for 1000?mL preconcentration volume. The detection limit was 0.32?µg?L^?1, the preconcentration factor was 400, and the relative standard deviation (%RSD) was 1.9% (at 10?µg?L^?1; n?=?7). The method was successfully applied to the determination of chromium species in water samples and total chromium in standard alloys.     

Ring-expansion of tertiary cyclic alpha-vinylamines by tandem conjugate addition to (p-toluenesulfonyl)ethyne and formal 3-aza-Cope rearrangement

A novel ring-expansion protocol is based on the conjugate additions of cyclic alpha-vinylamines to (p-toluenesulfonyl)ethyne, followed by aza-Cope rearrangements of the resulting zwitterions, to afford medium and large-ring cyclic amines under remarkably mild conditions.     

Triphenylene analogues with B2N2C2 cores: synthesis, structure, redox behavior, and photophysical properties

A series of alkyl (1-3), aryl (6), and benzo-annulated (4, 5) heteroaromatic triphenylene analogues with B(2)N(2)C(2) cores have been synthesized via chelation of pyridazine derivatives using difunctional Lewis acidic diborabiphenyl precursors. In contrast to triphenylene, NICS(1) calculations on 1 suggested high aromaticities for the central (-11.3 ppm) and outer borabenzene rings (-7.7 ppm), along with nonaromatic behavior for the pyridazine ring (-0.7 ppm). Crystal structure analyses supported this analysis. When the a- and c-faces of the pyridazine moiety were free of substitution (1, 3), planar structures resulted, but upon substitution, a twisted B(2)N(2)C(2) core was observed due to steric repulsion of neighboring hydrogen atoms (e.g., 5). The increase of steric bulk from H (1) to (i)Pr (3) in the planar species was found to result in a dimeric, head-to-tail herringbone packing motif, held together by close intermolecular B...N interactions of 3.39 Angstrom. One-electron reduction by Cp(2)Co was found to afford the radical anions of 3 and 5, which were characterized by broad, featureless singlets in the EPR spectra; [3](.)(-)[Cp(2)Co](+) was characterized by X-ray crystallography. While the planar structures (1-4) were observed to possess weak fluorescence (Phi(F) = 0.02-0.08) with either yellow-orange (ca. 555 nm) or green emission (521 nm), the twisted structures (5, 6) were found to be nonfluorescent.