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Selective aerobic oxidation of activated primary alcohols into acids or aldehydes is developed in ionic liquids. The newly developed catalytic systems are recycled and reused for three runs without any significant loss of catalytic activity.

The micellization of six cationic Gemini surfactants with various counterions and their interaction with DNA in aqueous solution is examined by isotheral titration microcalorimetry and conductivity measurements. The conclusion states that the interactions of all the surfactants with DNA is dependent on the DNA concentration and may be associated with each micelle interacting with more than one DNA molecule.

The extent of the sensibility of cysteine residues in proteins to alkylating or altering reagents varies greatly. The aspects which participate in the interaction can be determined by positioning the residues in particular areas of a protein with an identified conformation. Sensitivity toward 5,5'-dithiobis(2-nitrobenzoic acid) and 4,4'-dipyridyl disulfide is observed in certain residues, which are presumed to be unavailable to solvent. Faster reactivity is observed in the native protein than in the unfolded protein by the residues seen in the area of the entrance of the fatty acid to the inner areas of the protein.

The ultraviolet radiation-induced cytosine-to-thymine mutation which arise from the incorporation of adenine opposite the cytosine of dipyrimidine photoproducts was investigated. The viability of the tautomer bypass and deamination bypass mechanisms proposed as explanations for this event was examined. The results showed that replicative bypass of the TU dimer results in the exclusive incorporation of adenine opposite the TU dimer, which is consistent with the tautomer-bypass and deamination-bypass mechanisms.

The article presents a new approach, which can be employed for simultaneous tailoring of the evolution of phases and the distribution of dopants in the glassy phase for controlling the luminescence of the multiple active centers. The approach is shown to be extremely beneficial for the fabrication of a multifunctional light source.

Research has been conducted on beta-(N-tosyl)amino diazo carbonyl compounds. The authors describe the preparation of these compounds via nucleophilic condensation of N-tosylimines with acyldiazomethanes.

Achieving long-persistent phosphorescence in polymers is a challenge even at low temperatures. In this work, long-persistent phosphorescence (>1 s) is observed in nonconjugated polyurethane derivatives at 77 K, which is among the longest reported phosphorescent lifetimes for an organic polymer. The mechanism for this unusual behavior has been shown by steady-state photophysical characterization and time-resolved emission spectra to arise from the formation of intra- and/or intermolecular carbonyl clusters at low temperature. The lifetime of long-persistent phosphorescence is increased by the introduction of an aromatic monomer into the nonconjugated polyurethane chains. This is attributed to intra- and/or intermolecular n-p* transitions from electron-rich carbonyl groups to the conjugated aromatic units, thereby enhancing the intersystem crossing rate. Coating an ultraviolet InGaAsN light-emitting diode with a polyurethane derivative as the emitter gives cryogenic afterglow with long-persistent phosphorescence that is observed for up to 7 s with the naked eye. [ABSTRACT FROM AUTHOR]

To illustrate the formation mechanism of imidazolium-based ionic liquids (ILs) from N-alkyl imidazoles and halogenated hydrocarbons, density functional theory calculations have been carried out on a representative system, the reaction of N-methyl imidazole with chloroethane to form 1-ethyl-3-methyl imidazolium chloride ([Emim]Cl) IL. The reaction is shown to proceed via an SN2 transition state with a free energy barrier of 34.4 kcal/mol in the gas phase and 27.6 kcal/mol in toluene solvent. The reaction can be remarkably promoted by the presence of ionic products and water molecules. The calculated barriers in toluene are 22.0, 21.7, and 19.9 kcal/mol in the presence of 1-3 ionic pairs of [Emim]Cl and 23.5, 21.3, and 19.4 kcal/mol in the presence of 1-3 water molecules, respectively. These ionic pairs and water molecules do not participate directly in the reaction but provide a polar environment that favors stabilizing the transition state with large charge separation. Hence, we propose that the synthesis of imidazolium-based ILs from N-alkyl imidazoles and halogenated hydrocarbons is an autopromoted process and a polar microenvironment induced reaction, and the existence of water molecules (a highly polar solvent) in the reaction may be mainly responsible for the initiation of reaction. [ABSTRACT FROM AUTHOR]

Nanoscale chemical imaging of a dynamic molecular phase boundary has broad implications for a range of problems in catalysis, surface science, and molecular electronics. While scanning probe microscopy (SPM) is commonly used to study molecular phase boundaries, its information content can be severely compromised by surface diffusion, irregular packing, or three-dimensional adsorbate geometry. Here, we demonstrate the simultaneous chemical and structural analysis of N-N'-bis(2,6-diisopropylphenyl)-1,7-(4'-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) molecules by UHV tip-enhanced Raman spectroscopy. Both condensed and diffusing domains of PPDI coexist on Ag(100) at room temperature. Through comparison with time-dependent density functional theory simulations, we unravel the orientation of PPDI molecules at the dynamic molecular domain boundary with unprecedented ~4 nm spatial resolution. [ABSTRACT FROM AUTHOR]

The Ni-P incorporated citric acid (CA) catalysts with different CA/Ni molar ratios (x) were successfully prepared. The introduction of CA can change the structure of the catalyst precursor by complexing, and therefore affect the catalyst pore structures. The incorporation of CA into bulk Ni-P catalyst leads to a dramatic increase in surface area and pore volume. As compared to the Ni-P sample, the surface area of CA(2.0)-Ni-P increases 8.3 times. CA can also promote the formation of smaller, highly dispersed Ni2P particles, favoring more nickel phosphide phase. The DBT conversion of the CA(2.0)-Ni-P catalyst reached 96%, which increased by 34% as compared to the Ni-P sample. [ABSTRACT FROM AUTHOR]

Thedesign of active, robust, and nonprecious electrocatalystswith both H2and O2evolution reaction (HERand OER) activities for overall water splitting is highly desirablebut remains a grand challenge. Herein, we report a facile two-stepmethod to synthesize porous Co-P/NC nanopolyhedrons composed of CoPx(a mixture of CoP and Co2P) nanoparticlesembedded in N-doped carbon matrices as electrocatalysts for overallwater splitting. The Co-P/NC catalysts were prepared by direct carbonizationof Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation.Benefiting from the large specific surface area, controllable poretexture, and high nitrogen content of ZIF (a subclass of metal–organicframeworks), the optimal Co-P/NC showed high specific surface areaof 183 m2g–1and large mesopores, andexhibited remarkable catalytic performance for both HER and OER in1.0 M KOH, affording a current density of 10 mA cm–2at low overpotentials of −154 mV for HER and 319 mV for OER,respectively. Furthermore, a Co-P/NC-based alkaline electrolyzer approached165 mA cm–2at 2.0 V, superior to that of Pt/IrO2couple, along with strong stability. Various characterizationtechniques including X-ray absorption spectroscopy (XAS) revealedthat the superior activity and strong stability of Co-P/NC originatedfrom its 3D interconnected mesoporosity with high specific surfacearea, high conductivity, and synergistic effect of CoPxencapsulated within N-doped carbon matrices. [ABSTRACT FROM AUTHOR]

Weinvestigated the strong coupling between the excitons of ZnO nanowires(NWs) and the localized surface plasmons (LSPs) of individual Ag nanoparticles(NPs) by monochromated electron energy loss spectroscopy (EELS) inan aberration-corrected scanning transmission electron microscopy(STEM) instrument. The EELS results confirmed that the hybridizationof the ZnO exciton with the LSPs of the Ag NP created two plexcitons:the lower branch plexcitons (LPs) with a symmetrical dipole distributionand the upper branch plexcitons (UPs) with an antisymmetrical dipoledistribution. The spatial maps of the LP and UP excitations revealthe nature of the LSP–exciton interactions. With decreasingsize of the Ag NP the peak energies of the LPs and UPs showed a blue-shiftand an anticrossing behavior at the ZnO exciton energy was observed.The coupled oscillator model explains the dispersion curve of theplexcitons and a Rabi splitting energy of ∼170 meV was deduced.The high spatial and energy resolution STEM-EELS approach demonstratedin this work is general and can be extended to study the various couplinginteractions of a plethora of metal–semiconductor nanocompositesystems. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman scattering (TERS)and optically excited tip-enhanced fluorescence (TEF) of a self-assembledporphyrin monolayer on Ag(111) are studied using an ultrahigh vacuumscanning tunneling microscope (UHV-STM). Through selectively excitingdifferent Q-bands of meso-tetrakis- (3,5-ditertiarybutylphenyl)-porphyrin(H2TBPP), chemical information regarding different vibronicexcited states is revealed by a combination of theory and experiment;namely, TERS and time-dependent density functional theory (TDDFT)simulations. The observed TEF spectra suggest a weak coupling of H2TBPP to the substrate due to the bulky t-butyl groups anda possible alternative excited state decay path. This work demonstratesthe potential of combining TERS and TEF for studying surface-mountedporphyins on substrates, thus providing insight into porphyrin-sensitizedsolar cells and catalysis. [ABSTRACT FROM AUTHOR]

A mutasynthetic strategy is introducedfor the mycosynthesis ofnaphthalene-based molecules (mutadalesols A–F) with directedsubstitution patterns and new frameworks by generating and using the ΔpksTLmutant strain of Daldinia eschscholzii.(±)-Mutadalesol A and its (+)-enantiomer are cytotoxic, andits (−)-enantiomer inhibits Toll-like receptor 5 (TLR5). Thein-culture reactability of fungal oligoketide intermediates with 5-aminonaphthalen-1-ol(ANL) is demonstrated, shedding light on bioorthogonal accesses tounnatural molecule libraries valuable in drug discovery pipelines. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy (TERS) provides chemical information for adsorbates with nanoscale spatial resolution, single-molecule sensitivity, and, when combined with scanning tunneling microscopy (STM), Ångstrom-scale topographic resolution. Performing TERS under ultrahigh-vacuum conditions allows pristine and atomically smooth surfaces to be maintained, while liquid He cooling minimizes surface diffusion of adsorbates across the solid surface, allowing direct STM imaging. Low-temperature TER (LT-TER) spectra differ from room-temperature TER (RT-TER), RT surface-enhanced Raman (SER), and LT-SER spectra because the vibrational lines are narrowed and shifted, revealing additional chemical information about adsorbate–substrate interactions. As an example, we present LT-TER spectra for the rhodamine 6G (R6G)/Ag(111) system that exhibit such unique spectral shifts. The high spectral resolution of LT-TERS provides intramolecular insight in that the shifted modes are associated with the ethylamine moiety of R6G. LT-TERS is a promising approach for unraveling the intricacies of adsorbate–substrate interactions that are inaccessible by other means. [ABSTRACT FROM AUTHOR]

An innovative plasma reactor, which generates hybrid surface/packed-bed discharge (HSPBD) plasmas, was employed for the degradation of benzene. The HSPBD reactor was found to display remarkably better benzene degradation, mineralization, and energy performance than surface or packed-bed discharge reactors alone. The degradation efficiency, CO2 selectivity, and energy yield in the HSPBD reactor were 21%, 11%, and 3.9 g kWh-1 higher, respectively, than in a surface discharge reactor and 30%, 21%, and 5.5 g kWh-1 higher, respectively, than in a packed-bed discharge reactor operated at 280 J L-1. Particularly, the benzene degradation in the HSPBD reactor exhibited an unambiguous synergistic enhancement rather than a simple additive effect using the surface discharge and packed-bed discharge reactors. Moreover, in the HSPBD reactor, the formation of byproducts, such as NO2, was suppressed, while O3 was promoted. The use of N2 as the carrier gas was found to be effective for benzene degradation because of the fast reaction rate of N2(A³Σu+) with benzene, and oxygen species derived from the dissociation of O2 were found to be significant in the mineralization process. Thus, the addition of O2 to N2 allows for efficient degradation of benzene, and the optimized amount of O2 was determined to be 3%. [ABSTRACT FROM AUTHOR]

The roles of the disulfide bridge, electrostatics, and hydrophobic/hydrophilic effects in the structural stability and conformational changes of six single-disulfide analogues of α-conotoxin GI(2−7;3−13) in aqueous solution are investigated by using molecular dynamics simulations with a fragment-based polarization model (J. Phys. Chem. A2008, 112, 9854.). It is found that the relative stabilities are largely determined by the dipole−dipole interactions between secondary structure-based fragments, revealing the favorable effect of polar residues on conformational stabilities. The loop size closely correlates to not only the thermodynamic stability but also the local geometry of disulfide bridge. The disulfide loops with no more than five residues [GI(2−7), GI(3−7), and GI(7−13)] choose the left-handed disulfide conformation, while the larger loops [with nine and 10 residues in GI(3−13) and GI(2−13)] and a smaller disulfide loop [GI(2−3) without intercysteine residue] prefer the right-handed configuration. In the left-handed analogues, the dihedral angles concerning disulfide bonds decrease subtly along with the enlargement of disulfide loops. A converse dihedral angle and loop size relationship is found in the right-handed isomers. These results are rationalized by the strain energy of the disulfide bond as well as the electrostatic and van der Waals interactions between cysteine pairs. The single-disulfide analogues also exhibit much higher conformational diversity than the native GI. The important role of the size of hydrophobic core in the conformational evolution is also demonstrated in terms of the radius of gyration of the hydrophobic region. The radial distribution functions show the significant solvent−solute hydrogen bonding, implying that the interplay between the intermolecular and the intramolecular interactions control the dynamic process of GI single-disulfide analogues. [ABSTRACT FROM AUTHOR]

The solution conformation of α-conotoxin GI and its two single disulfide analogues are simulated using a polarizable force field in combination with the molecular fragmentation quantum chemical calculation. The polarizability is explicitly described by allowing the partial charges and fragment dipole moments to be variables, with values coming from the linear-scaling energy-based molecular fragmentation calculations at the B3LYP/6−31G(d) level. In comparison with the full quantum chemical calculations, the fragmentation approaches can yield precise ground-state energies, dipole moments, and static polarizabilities for peptides. The B3LYP/6−31G(d) charges and fragment-centered dipole moments are introduced in calculations of electrostatic terms in both AmberFF03 and OPLS force fields. Our test calculations on the gas-phase glucagon (PDB code: 1gcn) and solvated α-conotoxin GI (PDB code: 1not) demonstrate that the present polarization model is capable of describing the structural properties (such as the relative conformational energies, intramolecular hydrogen bonds, and disulfide bonds) with accuracy comparable to some other polarizable force fields (ABEEM/MM and OPLS-PFF) and the quantum mechanics/molecular mechanics (QM/MM) hybrid model. The employment of fragment-centered dipole moments in calculations of dipole−dipole interactions can save computational time in comparison with those polarization models using atom-centered dipole moments without much loss of accuracy. The molecular dynamics simulations using the polarizable force field demonstrate that two single disulfide GI analogues are more flexible and less structured than the native α-conotoxin GI, in agreement with NMR experiments. The polarization effect is important in simulations of the folding/unfolding process of solvated proteins. [ABSTRACT FROM AUTHOR]

Piperylene sulfone was investigated as a recyclable dimethyl sulfide (DMSO) substitute for copper-catalyzed room temperature aerobic alcohol oxidation. Under the optimal conditions, various primary alcohols could be selectively converted into aldehydes in excellent yields with exceptionally high turnover frequency (over 31 h-1). The catalytic system also shows good compatibility with heteroatom-containing (S and N) substrates. Most importantly, the new developed catalytic system could also be recycled and reused for three runs with only slight loss of catalytic activity. [ABSTRACT FROM AUTHOR]

Aerobic Alcohol Oxidation. An efficient four-component system consisting of acetamido-TEMPO/Cu(ClO4)2/TMDP/DABCO in DMSO has been developed for room-temperature aerobic alcohol oxidation. Under the optimal conditions, various alcohols could be converted into their corresponding aldehydes or ketones in good to excellent yields. The newly developed catalytic system could also be recycled and reused for three runs without any significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

A series of β-(N-tosyl)amino diazo carbonyl compounds have been prepared by nucleophilic condensation of N-tosylimines with acyldiazomethanes. The diazo decomposition of these diazo carbonyl compounds under various catalytic conditions, including Rh(II) carboxylates, Cu(I) and Cu(II) complexes, PhCO[sub 2]Ag/Et[sub 3]N, TsOH, and SnC1[sub 2]·2H[sub 2]O, has been investigated. It was found that, in most cases, the diazo decomposition gave preferentially 1,2-aryl migration product, but 1,2hydride migration predominated when PhCO[sub 2]Ag/Et[sub 3]N was the catalytic system. Hammett correlation has been applied in the analysis of the electronic effects of 1,2-aryl migration. The factors that govern the migratory preference and the mechanistic aspects of the reaction are discussed. [ABSTRACT FROM AUTHOR]