Quantification of Noncovalent Interactions in Azide–Pnictogen, –Chalcogen,and –Halogen Contacts

The noncovalent interactions between azides and oxygen-containing moieties are investigated through a computational study based on experimental findings. The targeted synthesis of organic compounds with close intramolecular azide–oxygen contacts yielded six new representatives, for which X-ray structures were determined. Two of those compounds were investigated with respect to their potential conformations in the gas phase and a possible significantly shorter azide–oxygen contact. Furthermore, a set of 44 high-quality, gas-phase computational model systems with intermolecular azide–pnictogen (N, P, As, Sb), –chalcogen (O, S, Se, Te), and –halogen (F, Cl, Br, I) contacts are compiled and investigated through semiempirical quantum mechanical methods, density functional approximations, and wave function theory. A local energy decomposition (LED) analysis is applied to study the nature of the noncovalent interaction. The special role of electrostatic and London dispersion interactions is discussed in detail. London dispersion is identified as a dominant factor of the azide–donor interaction with mean London dispersion energy-interaction energy ratios of 1.3. Electrostatic contributions enhance the azide–donor coordination motif. The association energies range from −1.00 to −5.5 kcal mol⁻¹.     

‐Theory for Schrödinger systems

In this article, we study for the ‐realization of the vector‐valued Schrödinger operator . Using a noncommutative version of the Dore–Venni theorem due to Monniaux and Prüss, we prove that the ‐realization of , defined on the intersection of the natural domains of the differential and multiplication operators which form , generates a strongly continuous contraction semigroup on . We also study additional properties of the semigroup such as extension to L¹, positivity, ultracontractivity and prove that the generator has compact resolvent.     

On the lattice structure of kernel operators

Consider the lattice of bounded linear operators on the space of Borel measures on a Polish space. We prove that the operators which are continuous with respect to the weak topology induced by the bounded measurable functions form a sublattice that is lattice isomorphic to the space of transition kernels. As an application we present a purely analytic proof of Doob's theorem concerning stability of transition semigroups.     

SYNTHESIS OF CHIRAL THIOCARBAMOYLPHOSPHINES DERIVED FROM AMINO ACIDS1

Abstract

The methylester hydrochlorides of the (S)-amino acids L-alanine (la), L-phenylalanine (1b), L-valine (1c) and L-lysine (1d) were converted to the corresponding isothiocyanates 2a-d by thiophosgenation. 2a-d react with secondary phosphines and phosphine oxides to give the thiocarbamoylphosphines 3a-d and P-oxides 4a, b.     

Surface chemistry and nonadecanoic acid adsorbate layers on TiO2(100) surfaces prepared at ambient conditions

The surface and adsorbate chemistry of the TiO₂(100) surface prepared at high temperatures and ambient conditions were studied by means of angle resolved X-ray photoelectron spectroscopy (AR-XPS), Low Energy Electron Diffraction (LEED) and Atomic Force Microscopy (AFM) based nanoshaving studies. The TiO₂(100) surface shows a 1 × 1 structure with a 1 × 3 superstructure assigned to surface defects. A significant hydroxide surface concentration was revealed by means of AR-XPS measurements. The adsorbate formation of nonadecanoic acid (NDCA) from ethanolic solution led to disordered sub-monolayer surface coverage. The weak interaction between the carboxylic acid group and the TiO₂ surface is assumed to be a combination of the neutral to acid behavior of the TiO₂ surface and the stable hydroxide surface layer created under ambient conditions.     

Use of ultrasonic nebulizer with desolvator membrane for the determination of titanium and zirconium in human serum by means of inductively coupled plasma – mass spectroscopy

A technique for the determination of titanium and zirconium in human blood serum, after pressurized digestion utilizing ICP-MS coupled to an ultrasonic nebulizer (USN) and desolvating membrane is described. As no CRM for titanium is available, zirconium has been determined in order to demonstrate the accuracy of the technique, as the limits in blood are well known. Bone cement consists basically of a polymer, namely polymethylmethacrylate (PMMA). For better X-ray contrast some manufacturers use incorporated ZrO₂ with a volume fraction of 10 to 15%. Thus, the zirconium present in the PMMA matrix can be used as an indicator for the PMMA particulate debris.