Atom probe tomography (APT) can measure the composition of complex materials with up to atomic resolution by ionizing and desorbing atomic and molecular fragments at high electric fields from a surface. In molecular structures, the desorption products are often whole molecular ions, which can fragment on the way to the detector, providing insight into their atomic composition. We study the postdesorption fragmentation of n-tetradecane as an example of organic molecules and compare it to experimental APT results. We find that strong electric fields cause the monocation to fragment asymmetrically, preferentially producing ethyl and propyl carbocations. The dication of n-tetradecane was found to be only metastable even in the absence of an external field and was found to fragment easily in an applied field.

Proper use of shape-selectivity effects requires (1) spatially resolved locations of active sites and (2) an optimized ratio between molecular and pore diameters. While effective pore diameters depend...

Despite their wide application in everyday laboratory work and industry, mechanistic investigations of electrochemical, photo redox, and photoelectroc…

Stereoselective ring opening metathesis polymerization (ROMP) of enantiomerically pure 2,3-dicarbomethoxynorborn-5-ene ((+)-DCMNBE) was accomplished by the action of cationic tetra- and pentacoordinated molybdenum imido alkylidene cyclic alkyl amino carbene (CAAC) complexes that are chiral at molybdenum. The same catalysts were also utilized to perform the ROMP of 2,3-dimethoxymethylnorborn-5-ene ((+)-DMMNBE). All complexes were moderately to highly active and showed high trans-isoselectivity, offering up to 97% trans-isotactic (it) repeat units. In all cases, tetracoordinated complexes were the active species, resulting in pentacoordinated transition states. A theoretical model was elaborated using the buried volume (% Vbur) values of all ligands from single-crystal X-ray analysis together with the structures of the density functional theory (DFT) generated molybdacyclobutane intermediates. The model demonstrates the steric effects of all ligands at molybdenum on the trans-isoselectivity of the reaction, as predicted by the turnstile mechanism, and includes a positive correlation between the bulky CAAC ligand with high values of % Vbur of the other ligands and a high trans-isoselectivity. It was also successfully extended to molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes, proved to be of sufficient accuracy with a root mean squared error (RMSE) of 6.19% and was verified by Monte Carlo cross-validation (MCCV).

University of Stuttgart Faculty of Chemistry   Professorship (W3) „Inorganic Coordination Chemistry” Institute of Inorganic Chemistry | to be appoi...

Supported single-site platinum hydride compounds are promising heterogeneous catalysts for organic transformations. Few methods exist to describe the structures of single-site Pt catalysts with atomic...

We provide a theoretical basis for phase diagrams that show the stability of species under different availability of electrons and protons in coupled redox and acid/base chemistry. The diagrams can b...

The field of machine learning potentials has experienced a rapid surge in progress, thanks to advances in machine learning theory, algorithms, and hardware capabilities. While the underlying methods a...

Room-temperature ionic liquids are an exciting group of materials with the potential to revolutionize energy storage. Due to their chemical structure and means of interaction, they are challenging to ...

Molybdenum alkylidyne N-heterocyclic carbene (NHC) complexes of the type [Mo(C-p-C6H4Y)(OC(R)(CF3)2)2 (L)(NHC)][B(ArF)4] (Y = OMe, NO2; R = CH3, CF3; L = none, pivalonitrile, tetrahydrofuran; NHC = 1,...