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The density functional theory (DFT) method was used to study the effect of nanoconfinement on the energetics of Mg-MgH(sub 2) systems. It was observed that, as the level of loading increases, the net energy change in the hydrogen sorption/desorption processes decreases to a significant level when the loading approaches maximum.

Low-temperature spectroscopy and linear/logarithmic time scale flash photolysis facilitated the analysis of the photochemistry of cone visual pigment P521, purified and extracted from the lizard Gekko gekko. Spectral absorbances for meta I and meta II rhodopsin intermediates, contained in the cone pigment, were observed at 480 and 380 nanometers. Thermodynamic and kinetic data for fast and slow components, involved in the formation of meta I and meta II, indicated that photochemistry of the visual pigment P521.

In the investigation and alternative approach to the development of general force field for molecular simulations of hydrated crystalline compounds and their interfaces with fluid phases is discussed. It shows that the CLAYFF force field provides a general set of simple interatomic potentials that allows investigation into complex behavior of natural hydrated materials including hydroxides, oxyhyroxides, and clays.

A rational molecular design strategy for tuning the emission color of phosphorescent complexes by functionalization of the bis(2-phenylpyridine)(2-(2'-oxyphenyl)-2-oxazoline/oxazole)iridium(III) framework is reported. Five new complexes (2-6) have been synthesized in good yields and characterized by cyclic voltammetry, absorption, and photoluminescence studies, by time-dependent density functional theory (TD-DFT) calculations, and by single-crystal X-ray diffraction studies for complexes 2, 4, and 6. An interesting feature of the complexes is that the HOMO is localized on the Ir d-orbitals and the phenoxylate part of the "ancillary" ligand, while the LUMO is located on the pyridyl ring of the ppy ligands. A few other complexes containing 2'-oxyphenyl-2-oxazoline/oxazole ancillary ligands have been reported previously; however, until now there has not been a systematic investigation into manipulating this unusual frontier orbital distribution to tune the emissive properties. It is shown that exchanging the phenylpyridine (ppy) ligand for 2,4-difluoro-ppy gives a blue shift of 21-22 nm (from 1 to 2 and from 4 to 5), and the introduction of electron-withdrawing substituents (SO2Me, CF3) onto the phenoxylate ring of the (2'-oxyphenyl)-2-oxazole ligand results in a further blue shift of 13-20 nm. Combining these functionalizations gives sky-blue emission with λmax PL 476 and 479 nm for complexes 5 and 6 in dichloromethane solution. The solution quantum yields of all the complexes are within the range ΦPL 0.42-0.73. The observed lifetimes (τobs = 1.52-3.01 μs) and spectral profiles are indicative of phosphorescence from a mixture of ligand-centered and MLCT excited states. (TD-)DFT calculations are in close agreement with the observed photophysical and electrochemical properties of the complexes. Phosphorescent organic light-emitting diodes have been fabricated using complexes 2, 3, 5, and 6 as the emitter, doped in a 4,4'-bis(N-carbazolyl)biphenyl host, giving efficient emission in the blue-green region. Notably, complex 5 gives λmax EL 480 nm with a maximum brightness of 26150 cd m-2. [ABSTRACT FROM AUTHOR]

A novel chemical strategy for fabricating flexible, transparent, and conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films with a nanofibrillar morphology by in situ deposition on commercial plastic substrates has been developed. The key points of the strategy include (1) preimplanting surface sulfate groups (SO4−) onto the substrate surface by a confined photocatalytic oxidation (CPO) technique, which was critical both for improving the adhesion of the PEDOT with the substrate via static interactions and for inducing polymerization of EDOT onto the substrate surface, and (2) deliberately controlling the nanofibrillar network morphology by means of the reaction recipe and parameters, which was critical for balancing conductivity and transparency. On the basis of this design, with BOPP as a model substrate, PEDOT−BOPP composite films approximately 20 nm in thickness with a transparency as high as 90% and a conductivity of 300 S/cm were obtained. Moreover, XPS data demonstrated that the SO4−implanted on the substrate surface constituted the primary dopant of the deposited PEDOT, and peeling tests with 3M Scotch adhesive tape proved that the adhesion between the substrate and PEDOT was drastically enhanced. Combined with a photomask, a PEDOT micropattern on the polymer substrate could also be fabricated. [ABSTRACT FROM AUTHOR]

A series of new N-halamine epoxide precursors, 3-glycidyl-5,5-dialkylhydantoins (GH's), has been synthesized by a very facile and economic method. Cellulose surfaces can be treated with GH'sand rendered biocidal by exposure to halogen solutions after curing the treated material. The biocidal efficacy tests showed that the chlorinated treated cellulose surfaces were antimicrobial with contact times required for 6−7 log reductions of Staphylococcus aureusand Escherichia coliO157:H7 of 5−30 min. It was found in simulated washing tests that celluloses, such as cotton swatches, treated with 3-glycidyl-5,5-dimethylhydantoin were quite stable and could survive more than the equivalent of 50 repeated home launderings with very little loss. Upon loss of the biocidal property due to long-term use, the treated surfaces could be recharged by further exposure to dilute bleach to regain antimicrobial activity. In addition, since only water was used as a solvent for the synthesis of GH'sat room temperature, the reaction solution could be directly used as a treatment solution. Stability tests showed that the reaction solutions were relatively stable at room temperature and more stable at 5 °C over a period of at least 30 d. Preliminary experiments have shown that polyester swatches can also be treated with GH'sand be rendered biocidal upon treatment with household bleach. The entire process should be economical for commercial application. [ABSTRACT FROM AUTHOR]

The monomer and polymer of the compound 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triaza spiro4.5decane-2,4-dione have been prepared and bonded to the surfaces of silica gel particles and cellulose, and the monomer has been copolymerized with a polyurethane formulation. Treatment of these polymers with dilute sodium hypochlorite solutions renders them antimicrobial. The oxidative chlorine immobilized on the materials is stable for extended periods and can be regenerated upon eventual loss by further exposure to dilute chlorine bleaching solutions. Data are presented showing that the treated materials are biocidal against Gram-positive Staphylococcus aureusand Gram-negative Escherichia coliO157:H7. The new siloxane is superior to previous N-halamine siloxane technology in that the N-halamine moiety contains two nitrogen binding sites for chlorine, one of which is a very stable hindered amine site. [ABSTRACT FROM AUTHOR]

Cyclopropane is a prevalent structural unit in natural products and bioactive compounds. While the transition metal-catalyzed alkene cyclopropanation of functionalized compounds such as α-diazocarbonyl derivatives has been well established and provides straightforward access to cyclopropanes, cyclopropanation directly from the more stable and simpler methylene compounds has remained an unsolved challenge despite the highly desirable benefits of minimal prefunctionalization and increased operational safety. Herein we report an electrocatalytic strategy for the cyclopropanation of active methylene compounds, employing an organic catalyst. The method shows a broad substrate scope and excellent scalability, requires no metal catalyst or external chemical oxidant, and provides convenient access to several types of cyclopropane-fused heterocyclic and carbocyclic compounds. Mechanistic investigations suggest that the reactions proceed through a radical-polar crossover process to form the two new carbon-carbon bonds in the nascent cyclopropane ring.