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Abstract: We provide reaction and activation energies for 28 hydrogen abstraction reactions. Hydrogens are abstracted from biphenyl, acenaphthylene, naphthalene and phenanthrene by methyl radical and hydrogen radical. We compute reaction energies and activation energies using eight functionals, three non-hybrid (BP86, TPSS and PBE) and five hybrid (B3LYP, B3PW91, TPSSh, PBE0 and HCTH407). These DFT data are compared to the energies obtained by means of the composite method G3(MP2)-RAD, which was designed to handle radical species with a high accuracy. A classification of four abstraction sites is done based on topological and energetics criteria. Furthermore, we show that PBE0 is the functional of choice when one considers hydrogen abstraction from PAH by or . [Copyright &y& Elsevier]

The very low barrier (of the order of 1 kJ mol−1) to proton transfer in the (H2O)OH− complex is accurately computed by the coupled-cluster method including single and double excitations plus perturbative corrections for triple excitations [CCSD(T)]. By virtue of the coupled-cluster R12 method [CCSD(T)-R12], which employs explicitly correlated wave functions, results are obtained close to the limit of a complete basis set of atomic orbitals (AOs). The basis-set superposition error is avoided by applying the full function counterpoise approach to the three fragments OH−, H+, and OH−. The most accurate computed value for the proton barrier amounts to δ=0.9±0.3 kJ mol−1, which is 4–5 times this value below the lowest vibrational energy level. The three lowest vibrational energy levels are calculated from a one-dimensional potential energy curve describing the position of the bonding proton between the two OH− fragments. The electronic binding energy with respect to dissociation into H2O and OH− is estimated to De=109±10 kJ mol−1 at the level of explicitly correlated CCSD(T)-R12 theory. [Copyright &y& Elsevier]

We report on gas phase UV action spectroscopy and photodynamics of [Ag 3 (1MT-H/1MU-H) 2 ] + comprised of a linear silver string and two deprotonated 1-methyl-thymine/uracil (1MT/1MU) ligands. We applied pump–probe femtosecond laser photofragmentation in an electrospray ion trap mass spectrometer and high-level ab initio calculations at the level of approximate coupled-cluster singles-doubles theory. The experimental UV band at 283/275 nm is assigned to a red shifted 1 ππ ∗ nucleobase located transition. Relaxation of the 1 ππ ∗ state occurs with time constants of 0.2/1.1 ps and 0.2/4.2 ps for the 1MT and 1MU complexes, respectively, on a similar ultrafast time scale as non-metalated uracil derivatives. [ABSTRACT FROM AUTHOR]

Abstract: We have computed the atomization energies of nineteen C3H x molecules and radicals using explicitly-correlated coupled-cluster theory including corrections for core–core and core–valence correlation, scalar and spin–orbit relativistic effects, and anharmonic vibrational zero-point energies. Equilibrium geometries were obtained at the coupled-cluster level [CCSD(T) model] in a correlation-consistent polarized core–valence quadruple-zeta basis set, using a spin-restricted Hartree–Fock reference wave function, and including all electrons in the correlation treatment. Applied to a set of selected CH x and C2H x systems, our approach yields highly accurate atomization energies with a mean absolute deviation of 1.4kJ/mol and a maximum deviation of 4.2kJ/mol (for dicarbon) from the Active Thermochemical Tables (ATcT) values. The explicitly-correlated coupled-cluster approach provides energies near the basis-set limit of the CCSD(T) model, which is the coupled-cluster model with single and double excitations (CCSD) augmented with a perturbative correction for triple excitations (T). To obtain even more accurate atomization energies than those presented here, it would be required to include full triple excitations (CCSDT) and corrections for excitations beyond triples, as for instance done in the CCSDT(Q) model, which includes a perturbative correction for quadruple excitations (Q). [Copyright &y& Elsevier]

The calculation of parity-violating interactions has been implemented within the framework of nonrelativistic density-functional theory. Different exchange–correlation functionals have been tested for H2O2 and are compared with Hartree–Fock and complete-active-space multiconfigurational self-consistent field calculations. At all levels of theory, p-type Gaussian basis functions are found to be important. [Copyright &y& Elsevier]

Abstract: The interaction energy of dihydrogen with the C12H24O6 crown ether (18-crown-6) is calculated at the level of second-order Møller–Plesset (MP2) perturbation theory and amounts to 5.7kJmol−1. This value is six times smaller than the value of 34kJmol−1 reported in Micropor. Mesopor. Mater. 89 (2006) 138, which was obtained from pseudopotential density functional calculations and interpreted as being ‘in a marginal range between physisorption and chemisorption’. A value of 34kJmol−1 seems unreasonable, however. [Copyright &y& Elsevier]