Molecular dynamics simulations with an all-atom model were carried out to study the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF(6)]. Analysis was carried out to characterize a number of structural and dynamic properties. It is found that the hydrogen bonds are weaker than expected, as indicated by their short lifetimes, which is due to the fast rotational motion of anions. Transport properties such as ion diffusion coefficients and ionic conductivity were also measured on the basis of long trajectories, and good agreement was obtained with experimental results. The phenomenon that electrical conductivity of ionic liquids deviates from the Nernst-Einstein relation was well reproduced in our work. On the basis of our analysis, we suggest that this deviation results from the correlated motion of cations and anions over time scales up to nanoseconds. In contrast, we find no evidence for long-lived ion-pairs migrating together.

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C3 wechselt die Seite: Die Thermolyse eines Trirutheniumkomplexes mit einem μ3‐Pentylidin‐ und einem μ3‐Pentin‐Liganden zu beiden Seiten der von den Metallatomen gebildeten Ebene führt ausschließlich zu einem μ3‐Ethylidin‐μ3‐octin‐Komplex. Bei dieser Reaktion wandert ein C3‐Fragment von einer Seite der Ru3‐Ebene auf die andere, was in einer Umverteilung von zwei C5‐ in ein C2‐ und ein C8‐Molekül resultiert.

First, different approaches to detect hydrogen bonds and to evaluate their energies are introduced newly or are extended. Supermolecular interaction energies of 256 dimers, each containing one single hydrogen bond, were correlated to various descriptors by a fit function depending both on the donor and acceptor atoms of the hydrogen bond. On the one hand, descriptors were orbital-based parameters as the two-center or three-center shared electron number, products of ionization potentials and shared electron numbers, and the natural bond orbital interaction energy. On the other hand, integral descriptors examined were the acceptor-proton distance, the hydrogen bond angle, and the IR frequency shift of the donor-proton stretching vibration. Whereas an interaction energy dependence on 1/r(3.8) was established, no correlation was found for the angle. Second, the fit functions are applied to hydrogen bonds in polypeptides, amino acid dimers, and water cluster, thus their reliability is demonstrated. Employing the fit functions to assign intramolecular hydrogen bond energies in polypeptides, several side chain CH...O and CH...N hydrogen bonds were detected on the fly. Also, the fit functions describe rather well intermolecular hydrogen bonds in amino acid dimers and the cooperativity of hydrogen bond energies in water clusters.