Influence of proton transfer degree on the potential energy surface for two very short hydrogen bonds.

The influence of temperature on the proton location in hydrogen bonds has been systematically studied by neutron diffraction in only a few crystal structures. Two of these are the 1:1 complex of urea - phosphoric acid with an OHO hydrogen bond and 4-methylpyridine -pentachlorophenol with an OHN hydrogen bond. Based on these earlier determined crystal structures the potential energy surface (PES) at different temperatures has now been determined by DFT calculations at the B3LYP/6-31++G** level of theory using the Gaussian03 system.

Proton Transfer Dynamics in Crystalline Maleic Acid from Molecular Dynamics Calculations.

The crystal structure of maleic acid, the cis conformer of HOOC-CH═CH-COOH has been investigated by Car-Parrinello molecular dynamics (CPMD) and path integral molecular dynamics (PIMD) simulations. The interesting feature of this compound, compared to the trans conformer, fumaric acid, is that both intra- and intermolecular hydrogen bonds are present. CPMD simulations at 100 K indicate that the energy barrier height for proton transfer is too high for thermal jumps over the barrier in both the intra- and intermolecular hydrogen bonds.

Comparison of the proton-transfer paths in hydrogen bonds from theoretical potential-energy surfaces and the concept of conservation of bond order III. O-H-O hydrogen bonds.

The quantum-mechanically derived reaction coordinates (QMRC) for the proton transfer in O-H-O hydrogen bonds have been derived from ab initio calculations of potential-energy surfaces. A comparison is made between the QMRC and the corresponding bond-order reaction coordinates (BORC) derived by applying the Pauling bond order concept together with the principle of conservation of bond order. In agreement with earlier results for N-H-N(+) hydrogen bonds there is virtually perfect agreement between the QMRC and BORC curves for intermolecular O-H-O hydrogen bonds.

Proton-transfer dynamics in the (HCO3-)2 dimer of KHCO3 from Car-Parrinello and path-integrals molecular dynamics calculations.

The proton motion in the (HCO(3)(-))(2) dimer of KHCO(3) at 298 K has been studied with Car-Parrinello molecular dynamics (CPMD) and path-integrals molecular dynamics (PIMD) simulations. According to earlier neutron diffraction studies at 298 K hydrogen is disordered and occupies two positions with an occupancy ratio of 0.804/0.

Proton transfer in the intramolecular NHN+ bonds in proton sponges with different hydrogen bridge flexibility.

The proton transfer in the intramolecular NHN(+) hydrogen bonds of selected proton sponges has been studied using theoretical calculations of the potential energy surfaces (PES). The proton-transfer trajectory follows very closely the lowest energy path, derived as the quantum-mechanical reaction coordinates (QMRC). The bond order is not conserved in the transfer process.