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Car-Parinello molecular dynamics (CPMD) simulations of the liquid imidazolium chloride/Al[Cl.sub.3] by inserting one pair of [[C.sub.2][C.sub.1]im] into liquid Al[Cl.sub.3] forming an acidic mixture is described. Large anions within the equilibrium phase are found for both simulations and these large anion species are formed to account for the lack of electrons present in the acidic melt.

Chiral, enantiopure metallo-supramolecular rhombs self-assemble in solution through coordination of bis-pyridyl-substituted ligands with (en)M(NO3)2. Characterization by nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy in solution and by electospray ionization Fourier transform ion cyclotron resonance (ESI-FT-ICR) mass spectrometry in the gas phase suggests that an equilibrium exists in water/methanol of a major 2:2 complex and a minor 3:3 complex of ligands and metal corners.

The deuteron quadrupole coupling constant of water together with dimethyl sulfoxide was studied using computer simulations.

A theoretical study of amide pseudorotaxane IR spectra in the harmonic approximation is carried out to examine the effect of axle substitution on the hydrogen bonds that are formed between axle and wheel. A clear relation observed between the NH stretch shifts and individual hydrogen bond energies is confirmed by correlations of the shared electron number with the NH stretch shift which is an indicator for individual hydrogen bond energies.

Molecular dynamics simulations with an all-atom model are used for studying the structural and dynamics properties of ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][P[F.sub.6]]). The studies have reproduced the phenomenon where electrical conductivity of ionic liquids has deviated from the Nernst-Einstein relation and it is shown to result from the correlated motion of cations and anions over time scales up to nanoseconds.

The density functional theory methods were used to study mechanistic details of catalytic dinitrogen reduction mediated by Schrok's molybdenum complex under ambient conditions. The results demonstrated that the [[Mo](NN[H.sub.3]).sup.+] complex easily loses ammonia even in the absence of a reductant.

Density functional theory (DFT) was conducted for examining the thermodynamic boundary conditions for dinitrogen reduction under mild and ambient conditions. The 80.6 kJ/mol is required for the dissociation of NH3 from the cationic complex [Mo]NNH3(super +).

A biomimetic complex, which mimics the arginine phosphonate diester interaction of the arginine fork, is investigated with respect to structure and energetics of stable configurations. Different tweezer guest structures are evaluated with respect to their temperature-dependent thermodynamical properties as products of the first association reaction step of the bisphosphonate tweezer template and the guanidinium moiety.

An approach is presented that allows NMR relaxation rates to be determined for a complex mixture, and it is applied to a dimethyl sulfoxide/water solution. The calculation of the spin-lattice relaxation times (T1) and relaxation rates (R1 = (T1)(super -1) is discussed.

Time-independent quantum chemical methods is employed to examine possible clusters for the stable supermolecules at mole fraction n(sub DMSO)= 0.25 and 0.33 in DMSO-water mixtures. Structure and interaction energetics indicated that the methyl-water interactions become more important upon solvation.

Abstract: Four different minima on the potential energy surface of a pseudorotaxane were subject of this computational study. The most stable structure is one with three hydrogen bonds (60–80kJ/mol) between axle and wheel. All functionals employed describe the next stable structure with a twofold hydrogen bond (30–50kJ/mol) where the axle is still located inside the wheel. For almost all functionals the energy of a structure with the axle inside the wheel and with one hydrogen bond (20–40kJ/mol) is only approximately another 10kJ/mol above the second most stable structure. The calculated stability of the complex where the axle is located outside the wheel is functional dependent, but it lies for all calculations between the second most and the least stable pseudorotaxane structure. MP2 calculations performed additionally confirm this stability trend, and the estimation of the dispersion interaction points to contributions between 15 and 55kJ/mol, corresponding to fractions of 20–50%. Thermochemical calculations show that a template as realized in this pseudorotaxane works as an entropic sink. From the analysis of the dipole moments we find that solvents could alter the situation tremendously. The frequency calculation reveals characteristic bands of which we analyze the N–H stretching modes found around 3500cm−1, the Cing modes found around 1670cm−1 and N–H bending modes found around 1480cm−1. While the N–H stretching bands are shifted by between 100 and 180cm−1, the Cbeing more intense, are only shifted by up to 60cm−1. [Copyright &y& Elsevier]