Unidirectional adsorbate motion on a high-symmetry surface: "walking" molecules can stay the course

Step edges and low-symmetry faces of metal crystals can restrict the diffusive motion of adsorbates, yet they offer little flexibility with regards to the location and/or direction of the guided motion. We show inherently unidirectional motion of an organic molecule on a high-symmetry thermodynamic-equilibrium metal surface [Cu(111)]. Sequential placement of the substrate linkers of 9,10-dithioanthracene prevents it from rotating or veering off course. A combination of low temperature scanning tunneling microscopy and density functional theory simulations provide atomistic insight.     

Synthesis and studies of 1,4,5,8,9,12,13,16-octamethoxytetraphenylene

[structure: see text] The synthesis of 1,4,5,8,9,12,13,16-octamethoxytetraphenylene (6) is accomplished in five steps from 3,6-dimethoxy-2-nitroaniline (8). Its inclusion property and the electrochemical data of the corresponding tetraquinone 7 are presented.     

Organic reactions in frozen water: Michael addition of amines and thiols to the dehydroalanine side chain of nocathiacins

Nocathiacins are densely functionalized cyclic thiazolyl peptide natural products with potent in vitro and in vivo antibacterial activity against a variety of gram-positive bacteria, including a number of multiple drug-resistant strains. Attempts to prepare Michael adducts using known conditions resulted in the formation of complex mixture of products. In order to overcome this problem, we developed unique conditions in which Michael addition of amine and thiol nucleophiles to the dehydroalanine moiety of nocathiacins was successfully achieved in frozen water. Under these conditions, the Michael addition was highly chemoselective, very efficient and provided good isolated yields of the desired products.     

Electron electric dipole moment induced by octet-colored scalars

An appended sector of two octet-colored scalars, each an electroweak doublet, is an interesting extension of the simple two Higgs doublet model motivated by the minimal flavor violation. Their rich CP violating interaction gives rise to a sizable electron electric dipole moment, besides the quark electric dipole moment via the two-loop contribution of Barr–Zee mechanism.     

A computational study of the optical response of strongly coupled metal nanoparticle chains

We study the optical response of strongly coupled metal nanoparticle chains using rigorous multiple scattering calculations. The collective resonant frequency of silver nanosphere chains and the coupling between chains are considered. The coupling between silver nanoparticle chains are understood by the transmission and reflection calculations of 2D periodic arrays of nanospheres. The results are in agreement with recent experiments. The splitting of plasmon resonance modes for different polarizations of the incident light are explored. Our results show that the transverse mode resonant wavelength is very sensitive to the inter-chain distance. Results on the effect of disorder are also presented.     

Landau-Yang theorem and decays of a Z' boson into two Z bosons

We study the decay of a Z' boson into two Z bosons by extending the Landau-Yang theorem to a parent particle decaying into two Z bosons. For a spin-1 parent the theorem predicts that (1) there are only two possible couplings and (2) the normalized differential cross section depends on kinematics only through a phase shift in the azimuthal angle between the two decay planes of the Z boson. When the parent is a Z' the two possible couplings are anomaly induced and CP violating, respectively. At the CERN Large Hadron Collider their effects could be disentangled when both Z bosons decay leptonically.     

Ruthenium-catalyzed asymmetric epoxidation of olefins using H2O2, part II: catalytic activities and mechanism

Asymmetric epoxidation of olefins with 30 % H2O2 in the presence of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2 has been studied in detail (pybox = pyridine-2,6-bisoxazoline, pyboxazine = pyridine-2,6-bisoxazine, pydic = 2,6-pyridinedicarboxylate). 35 Ruthenium complexes with sterically and electronically different substituents have been tested in environmentally benign epoxidation reactions. Mono-, 1,1-di-, cis- and trans-1,2-di-, tri-, and tetra-substituted aromatic olefins with versatile functional groups can be epoxidized with this type of catalyst in good to excellent yields (up to 100 %) with moderate to good enantioselectivies (up to 84 % ee). Additive and solvent effects as well as the relative rate of reaction with different catalysts have been established. It is shown that the presence of weak organic acids or an electron-withdrawing group on the catalyst increases the reactivity. New insights on the reaction intermediates and reaction pathway of the ruthenium-catalyzed epoxidation are proposed on the basis of density functional theory calculation and experiments.     

A study on the spectral characteristics of surface enhanced Raman scattering based on far‐field extinction and near‐field electromagnetic field intensity of 2D nanostructures

A new solid‐state electrochemical patterning technique was applied to fabrication of high‐resolution silver bowtie antennas and hexagonal arrays. These silver nanofeatures were used to investigate the relation among surface enhanced Raman scattering (SERS) enhancement factor (EF), extinction, local electromagnetic (EM) field maxima of the features. It is found that spectral extinction property or the plasmonic resonance of a given SERS substrate alone is not sufficient for determining optimal EF; the number of points of high local EM field, or ‘hot spots’, and the distribution of those high‐field spots, too, play a role. Copyright © 2014 John Wiley & Sons, Ltd.