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Ionization energies below 20 eV of 10 molecules calculated with electron propagator techniques employing Hartree-Fock orbitals and multiconfigurational self-consistent field orbitals are compared. Diagonal and nondiagonal self-energy approximations are used in the perturbative formalism. Three diagonal methods based on second-and third-order self-energy terms, all known as the outer valence Green's function, are discussed. A procedure for selecting the most reliable of these three versions for a given calculation is tested. Results with a polarized, triple < basis produce root mean square errors with respect to experiment of approximately 0.3 eV. Use of the selection procedure has a slight influence on the quality of the results. A related, nondiagonal method, known as ADC(3), performs infinite-order summations on several types of self-energy contributions, is complete through third-order, and produces similar accuracy. These results are compared to ionization energies calculated with the multiconfigurational spin-tensor electron propagator method. Complete active space wave functions or close approximations constitute the reference states. Simple field operators and transfer operators pertaining to the active space define the operator manifold. With the same basis sets, these methods produce ionization energies with accuracy that is comparable to that of the perturbative techniques.

Hydrogen peroxide electroreduction on both catalytically active Pt and inactive Au surfaces are studied by using both surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations. SERS measurements on Pt show the presence of Pt-OH at negative potentials, which suggests that hydroxide is formed as an intermediate during the electroreduction process. Additionally, the O-O stretch mode of H(2)O(2) is observed on Pt, which shifts to lower energy as potential is swept negatively, indicating that the O-O bond is elongated. For comparison, there is no variation in the energy of the same O-O mode on Au surfaces, and there is no observation of Au-OH. DFT calculations show that H(2)O(2) adsorption on Pt(110) results in the dissociation of O-O bond and the formation of Pt-OH bond. On Au, O-O bond elongation is calculated to occur only on the (110) face. However, the magnitude of the elongation is much smaller than that found on Pt(110).

We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2'-bipyridine and Na(2)CO(3). We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present detailed mechanistic investigations on the Cu(I)-mediated direct thiolation reactions. Both computational studies and experimental results reveal that the copper-thiolate complex [(L)Cu(SR)] (L: nitrogen-based bidentate ligand such as 2,2'-bipyridine; R: aryl or alkyl group) is the first reactive intermediate responsible for the observed organic transformation. Furthermore, our computational studies suggest a stepwise reaction mechanism based on a hydrogen atom abstraction pathway, which is more energetically feasible than many other possible pathways including β-hydride elimination, single electron transfer, hydrogen atom transfer, oxidative addition/reductive elimination, and σ-bond metathesis.

Electron propagator method with a multiconfigurational second-order perturbation theory wave function as the initial state in the fermion operator block Higher order decouplings of the dilated electron propagator with applications to 2 P Be − , 2 P Mg − shape and 2 S Be + (1s −1 ) Auger resonances Comment on "Ionization potentials and electron affinities from the extended Koopmans' theorem applied to energy derivative density matrices: The EKTMPn and EKTQCISD methods" [J.The multiconfigurational spin tensor electron propagator method ͑MCSTEP͒ is specifically designed to provide accurate determination of the low-lying principal vertical ionization potentials ͑IP's͒ and electron affinities ͑EA's͒ of atoms and molecules. In this paper we modify and extend our definition of an ''optimal'' small complete active space ͑CAS͒ for MCSTEP calculations. We then use MCSTEP to determine the vertical principal ionization potentials ͑IP's͒ below 19 eV of the small organic molecules methane, acetylene, ethylene, and ethane. The calculations are done using the standard Dunning-core-valence pVDZ and pVTZ basis sets. The results are compared with experiments as well as with some other forefront theoretical methods. The MCSTEP IP's are in very good to excellent agreement with experimental IP's.

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