No abstract

According to high level calculations, the upper part of the previously published FT-ICR lithium cation basicity (LiCB at 373 K) scale appeared to be biased by a systematic downward shift. The purpose of this work was to determine the source of this systematic difference. New experimental LiCB values at 373 K have been measured for 31 ligands by proton-transfer equilibrium techniques, ranging from tetrahydrofuran (137.2 kJ mol(-1)) to 1,2-dimethoxyethane (202.7 kJ mol(-1)). The relative basicities (ΔLiCB) were included in a single self-consistent ladder anchored to the absolute LiCB value of pyridine (146.7 kJ mol(-1)). This new LiCB scale exhibits a good agreement with theoretical values obtained at G2(MP2) level. By means of kinetic modeling, it was also shown that equilibrium measurements can be performed in spite of the formation of Li(+) bound dimers. The key feature for achieving accurate equilibrium measurements is the ion trapping time. The potential causes of discrepancies between the new data and previous experimental measurements were analyzed. It was concluded that the disagreement essentially finds its origin in the estimation of temperature and the calibration of Cook's kinetic method.

The copper-free Sonogashira cross-coupling reaction consisting of oxidative addition, cisÀtrans isomerization, deprotonation, and reductive elimination was computationally modeled using the DFT B97D/cc-pVDZ method for reaction between phenyl bromide and phenylacetylene. Tetrakis(triphenylphosphano)palladium was used as a catalyst and sec-butylamine as a base. The reaction mechanism was studied in dichloromethane solution. Oxidative addition proceeds through the biligated pathway, and the catalytically active palladium species is Pd(PPh 3 ) 3 . Amines, present in the reaction mixture, can inhibit oxidative addition by coordinating to Pd(PPh 3 ) 3 .' ASSOCIATED CONTENT b S Supporting Information. Geometries and energies for all discussed structures are deposited. This material is available free of charge via the Internet at http://pubs.acs.org.

While metal oxide nanoparticles (NPs) are one of the most commonly used nanomaterials, the theoretical models used to analyze and predict their behavior have been mostly based on just the chemical composition or the extrapolation from small metal oxide clusters' calculations. In this study, a set of novel, theoretical full-particle descriptors for modeling, grouping or read-across of metal oxide NP properties and biological activity was developed based on the force-field calculation of the potential energies of whole NPs. The capability of these nanodescriptors to group the nanomaterials acoording to their biological activity was demonstrated by Principal Component Analysis (PCA). The grouping provided by the PCA approach was found to be in good accordance with the algal growth inhibition data of well characterized nanoparticles, synthesized and measured inside the consortia of the EU 7FP framework MODERN project.

Mechanism of an efficient and easily applicable catalytic system for the copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction, consisting of phosphane‐ligated CuI carboxylates and apolar/aprotic solvent was investigated by means of 1H NMR reaction monitoring techniques, isotope exchange studies, and DFT calculations (at the M06L/6‐311++G(d,p)//B97D/cc‐pVDZ (SDD) level of theory). Kinetic analysis indicates 1st order kinetics with respect to [Azide] and nonlinear positive order in [Cu]. H/D scrambling between alkynes reveals a quickly reached equilibrium existing between CuI–carboxylates and CuI–acetylides and that proton transfer processes are mediated by acetate/acetic acid system. According to the computational results, the Cu–triazolide forms a dinuclear structure that equalizes the copper atoms in the catalytic complex.