NMR parameters of two tricyclododecadienes—strained hydrocarbons with close distance between perpendicularly or parallelly arranged double bonds

Quantum chemical calculations of the hypothetical tricyclo[5.5.0.0^{4, 10}]dodeca‐1(7),4(10)‐diene with a perpendicular arrangement of double bonds and of the known tricyclo[4.2.2.2^{2, 5}]dodeca‐1,5‐diene isomer with the parallel arrangement yield, in agreement with expectations, greater stability of the latter molecule. They reproduce the available experimental results for chemical shifts and coupling constants for the latter molecule. Large calculated values of σ_Csp2 and those of ¹J_C?C for both dienes are not due to nonplanar distortions on the double bonds but due to the close distances between them. The calculated NMR parameters of the hypothetical diene could be useful for its future identification as the calculated values of the parameters for 1 are larger than those for 2. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrodeposition Sample Introduction for Ultra Trace Determinations of Platinum Group Elements (Pt,Pd, Rh,Ru) in Road Dust by Electrothermal Atomic Absorption Spectrometry

A novel method for the determination of the platinum group elements (PGEs: Pt, Pd, Rh, Ru) in environmental samples by electrothermal atomic absorption spectrometry (ET-AAS) was developed. Sample preparation involved complete microwave-assisted acid digestion of the matrix with HNO₃-HF-HClO₃/HClO₄mixtures in a high-pressure Teflon bomb. Traces of PGEs were deposited on the inner wall of a graphite tube in a flow-through cell of 1 ml volume. A flow system for this preconcentration was constructed. For the electrodeposition, a three-electrode arrangement was used. The geometry of the cell, flow rate during electrodeposition, deposition potential and electrolyte composition were optimized. After the deposition step, the graphite tube was placed into the graphite furnace and an atomization program applied. Detection limits (LOD, 3σ_{total procedure blank}, peak area) of 3.6, 0.5, 0.3 and 5.9 ng were obtained for Pt, Pd, Rh and Ru, respectively, reflecting preconcentration factors of 416, 503, 423 and 46, respectively. The detection limits were restricted by variations in the blank. Precision of replicate determination was typically 21% RSD at a concentration 25-fold above the LOD for a 100-mg sample mass. Reasonable agreement was found between results for CW7 road tunnel dust literature and for CRM NIES No. 8 Vehicle Exhaust Particulates. Calibration was achieved via the method of standard additions.     

Distribution of scattering poles near the real axis

Nous étudions le spectre de l'opérateur de Schrödinger avec potentiel périodique. L'approximation consiédérée consiste à supposer que les puits de potentiels sont suffisam-ment éloignés. Nous démontrons l'existence de développements de Rayleigh-Schrödinger pour les valeurs propres de Floquet non égénérées. Nous étudions ensuite les effets tunnels en donnant le développement asymptotique de la largeur des bandes spectrales. En presence d'un champ magnétique constant, la reduction de Fioquet ne fonctionne plus. Nous montrons que l'étude est équivalente a celle d'un opérateur pseudo-différentiel de type Harper.     

New perspectives in VLSI design automation: deterministic packing by Sequence Pair

In the paper we consider a problem of packing rectangular blocks on a plane, which is known as Block Packing Problem (BPP). This problem is a central issue of the modern VLSI chips design methods. Basing on a new interpretation of the Sequence-Pair representation of the packing solution-space, which is based on Complementary Mirror Constraint Graphs (CMCG), we develop the efficient method of neighborhood exploration. This method might be able to improve the efficiency of other neighborhood-based search methods, such as simulated annealing or tabu search, as well as, to construct efficient heuristics. We illustrate application of the developed method by constructing a heuristic algorithm for solving BPP and comparing its efficiency and effectiveness to the algorithms commonly used so far.     

From Open Quantum Systems to Open Quantum Maps

For a class of quantized open chaotic systems satisfying a natural dynamical assumption we show that the study of the resolvent, and hence of scattering and resonances, can be reduced to the study of a family of open quantum maps, that is of finite dimensional operators obtained by quantizing the Poincaré map associated with the flow near the set of trapped trajectories.     

3-Alkoxymethyl-1-(1R,2S,5R)-(−)-menthoxymethylimidazolium salts-based chiral ionic liquids

A new group of imidazolium salt-based chiral ionic liquids have been prepared and characterized. The chiral ionic liquids obtained are stable in air, in contact with water and popular organic solvents. Their physicochemical properties, single-crystal X-ray structures, antimicrobial activities, and antielectrostatic effects have been determined. The chiral ionic liquids synthesized have proven to represent not only potential new solvents in asymmetric synthesis but also effective disinfectants with antielectrostatic activity.     

Synthesis,spectroscopic studies,and crystal structure of 2,6-diacetylpyridinediphenylhydrazone perchlorate and its complexing ability toward the lanthanides

2,6-diacetylpyridinediphenylhydrazone perchlorate was prepared and characterized by spectroscopic (IR, ESI–MS, UV–Vis, ¹H NMR) and analytical data and its crystal structure was determined by single X-ray analysis. The lanthanum(III), praseodymium(III), and neodymium(III) perchlorate complexes of 2,6-diacetylpyridinediphenylhydrazone were prepared in a direct reaction of the ligand with appropriate metal perchlorates. The spectroscopic and analytical data indicate 1:2 metal to ligand stoichiometry. In all the complexes the hydrazones act as monodeprotonated terdentate NNN donor chelators. The same lanthanum(III) complex was also obtained in a one-step condensation reaction between 2,6-diacetylpyridine and phenylhydrazine in the presence of lanthanum(III) perchlorate.     

Influence of substituents in vinyl groups on reactivity of parylene during polymerization process

The MCSCF calculations indicate that both triplet and singlet state of biradical di-para-xylylene can exist during polymerization of parylene in gas phase and both can potentially react with vinyl molecules. The singlet-state open-shell dimer turned out to exhibit multiconfigurational character. In the case of triplet state of the dimer two mechanisms of the reactions with various species containing vinyl groups have been examined at the B3LYP/6-31G level. The kinetic and thermodynamical barriers have been estimated for the reaction path involving the π-bond cleavage as well as for the route describing the hydrogen atom transfer. It was found that the overall reactions are thermodynamically favorable, whereas appropriate kinetic barriers for certain derivatives are very small (close to 0 kcal/mol) which in turn makes allowances for easy reactivity under accessible conditions. The calculated mechanisms indicate the influence of substituents in vinyl groups for reactivity of parylene during LPCVD process.