Orbital alignment in photodissociation probed using strong field ionization

The photodissociation of molecules often produces atomic fragments with polarized electronic angular momentum, and the atomic alignment, for example, can provide valuable information on the dynamical pathways of chemical reactions unavailable by other means. In this work, we demonstrate for the first time that orbital polarization in chemical reactions can be measured with great sensitivity using strong field ionization by exploiting its extreme nonlinearity.     

Prospect for characterizing interacting soft colloidal structures using spin-echo small angle neutron scattering

Spin-echo small angle neutron scattering (SESANS) provides a new experimental tool for structural investigation. Due to the action of spin-echo encoding, SESANS measures a spatial correlation function in real space, as opposed to the structure factor S(Q), I(Q), in momentum (Q) space measured by conventional small angle neutron scattering. To establish the usefulness of SESANS in structural characterization, particularly for interacting colloidal suspensions, we have previously conducted a theoretical study of the SESANS correlation functions for model systems consisting of particles with uniform density profiles [X. Li, C.-Y. Shew, Y. Liu, R. Pynn, E. Liu, K. W. Herwig, G. S. Smith, J. L. Robertson, and W.-R. Chen J. Chem. Phys. 132, 174509 (2010)]. Within the same framework, we explore in the present paper the prospect of using SESANS to investigate the structural characteristics of colloidal systems consisting of particles with nonuniform intraparticle mass distribution. As an example, a Gaussian model of interacting soft colloids is used to investigate the manifestation of structural softness in a SESANS measurement. The exploration shows a characteristically different SESANS correlation function for interacting soft colloids, in comparison to that of a uniform hard sphere system. The difference arises from the Abel transform imbedded in the mathematical formalism bridging the SESANS spectra and the spatial autocorrelation function.     

Selectivity control in alkylidene carbene-mediated C-H insertion and allene formation

Regioselectivity of alkylidene carbene-mediated C-H insertion was explored utilizing electronic, conformational, steric, and stereoelectronic effects. Relying on these factors, highly regio- and chemoselective carbene insertion reaction of C-H bonds in different environments could be obtained. The observed selectivity clearly indicates that an electronic effect plays a more important role than steric effect. In general, C-H bonds in conformationally rigid cyclic environments are less reactive than those in acyclic systems toward carbene insertion, and in this situation, a competing intermolecular reaction between alkylidene carbene and trimethylsilyldiazomethane led to the formation of allenylsilanes. The formation of allenylsilane becomes more favorable as the concentration of reaction becomes higher, as well as the C-H bonds undergoing insertion becomes electronically and conformationally deactivated.     

DFT and CASPT2 study on the mechanism of ethylene dimerization over Cr(II)OH+ cation

In this work, the ethylene coordination and dimerization mechanism over Cr(II)OH(+) cation were systematically investigated using density functional theory (DFT) and complete active space second-order perturbation theory (CASPT2). It was found that Cr(II)OH(+) cation can coordinate with up to four ethylene molecules which gives seven possible stable Cr(II)OH(+)·(C(2)H(4))(n) (n = 1-4) π-complexes. We investigated whether ethylene dimerization over Cr(II)OH(+) cation proceeds through either a carbene mechanism or a metallacycle mechanism. The potential energy surfaces were characterized using four different functionals (M06L, BLYP, B3LYP, and M06). It was found that the potential energy profiles calculated at the M06 level agreed well with the CASPT2 energy profiles. Since the intermediates involved in the proposed catalytic cycles showed different ground spin states, a reaction pathway involving a spin crossing between two potential energy surfaces was observed. The minimum-energy crossing points (MECPs) that connect the two potential energy surfaces were successfully located. The two-state metallacycle reaction pathway with the formation of chromacyclopentane as the rate-determining step was found to be energetically more favorable than the carbene reaction pathway. 1-Butene was formed from the chromacyclopentane by a two-step reductive elimination pathway through a chromium(IV) hydride intermediate.     

Photoreversible cellular imaging using photochrome-conjugated fullerene silica nanoparticles

Photochromic compound-conjugated fluorescent fullerene-silica nanoparticles prepared by the reverse-microemulsion method was utilized for photoswitchable cellular imaging by repeatable irradiation of ultraviolet and visible light.     

A three-way synergy of triple-modified Bi2WO6/Ag/N-TiO2 nanojunction film for enhanced photogenerated charges utilization

We demonstrate a general strategy to prepare Bi(2)WO(6)/Ag/N-TiO(2) film with double visible-light-active components bridged by Ag nanoparticles as an electron shuttle, which exhibits enhanced photocatalytic activity and photoelectrochemical performance under visible light.     

A reagentless and disposable electronic genosensor: from multiplexed analysis to molecular logic gates

Reagentless, sensitive and multiplexed analysis of gyrB and K-ras gene biomarkers is achieved based on the proximity changes of two different redox-tags to the electrode surface upon DNA hybridizations, and the presence of the two gene biomarkers also acts as inputs and activates the logic gate.     

Wrapping the walls of n-TiO2 nanotubes with p-CuInS2 nanoparticles using pulsed-electrodeposition for improved heterojunction photoelectrodes

The CuInS(2) (CIS) nanoparticles were wrapped uniformly throughout the inner and outer walls of TNTs (TNT) by using square wave pulsed-electrodeposition. This structure enables the CuInS(2)-TiO(2) (CIS-TNT) to exhibit p-n junction diode behavior and enhanced photoelectrochemical properties.     

Kinetic resolution of aromatic β-amino acids by ω-transaminase

Racemic aromatic β-amino acids have been kinetically resolved into (R)-β-amino acids with high enantiomeric excess (>99%) by a novel ω-TA with ca. 50% conversion.     

Precursor-directed fungal generation of novel halogenated chaetoglobosins with more preferable immunosuppressive action

Precursor-fed cultivation of endophytic Chaetomium globosum 1C51 afforded nine novel "unnatural" halogenated chaetoglobosins including those with more preferable immunosuppressive activity.