Theoretical study of 3d‐metal mononitrides using DFT method

3d‐Metal mononitrides are studied using the density functional theory method. The lowest spin state for these dimers is obtained using the B3LYP hybrid functional with the 6‐311+G* basis set. The equilibrium geometries, vibrational frequencies, binding energies, Mulliken, and natural orbital population analysis charges, natural orbital electronic configuration, electron affinity, and ionization potential are obtained. Mulliken as well as natural orbital population analysis charges indicate that for all dimers, in cations most of the positive charge localized on the transition metal atom where in anions most of the negative charge localized on nitrogen atom. The binding energies for 3d‐metal mononitrides are higher than those for monocarbides and monoxides. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

呋喃西林水溶液在光和热作用下的稳定性

The influence of both light and heat on the stability of nitrofurazone aqueous solution was studied. Results show that in either heating experiments or the exposure to light at high temperatures, the degradation rate obeyed zero-order kinetics. The total rate constant ktotal caused by both light and heat can be divided into two parts: ktotal =kdark klight, where kdark and klight are the degradation rate constants caused by heat and light, respectively. The klight can be expressed as klight=Alight*exp(-Ea,light/RT)*E, where E is the illuminance of light, and Alight and Ea,light both are experimental constants. The values of these kinetic parameters were determined based on the experiments in the dark and upon exposure to three different light sources. Results show that the values of Alight and Ea, light varied with the light source. To save time, labor, and drugs, exponential heating experiments were employed and compared with the isothermal experiments. Results indicated that kinetic parameters obtained by exponential heating experiments are comparable to those obtained by isothermal experiments either in the dark or upon exposure to light.     

Study on the formation of the ketonic defects in the thermal degradation of ladder-type poly(p-phenylenes) by vibrational spectroscopy

We have investigated the thermal degradation in air by Fourier transform infrared spectroscopy of a ladder-type copolymer containing fluorene units in the backbone (Me-LPF), to reveal the formation of the ketonic defects. As thermal treatment of Me-LPF film at 200 degrees C in air proceeds, a new group of complex absorption bands due to degradation products arises in the range between 1800 and 1600 cm(-1). The observed overlapping bands were separated and assigned by utilizing the second-derivative IR spectral analysis, which can narrow the peak width to one-third of the originals and thereby eases the analysis. The degraded products were assigned as fluorenone (1718 cm(-1)) and benzophenone (Ar-(C=O)-Ar) (1665 cm(-1)), formed by the oxidation of the backbone, and acylphenone (Ar-(C=O)-R) (1685 cm(-1)) from the side chain. The fluorenone was found to be the major component among the degraded products in the main chain, and the time and temperature dependence indicated that the oxidation is a kind of autocatalytic radical-chain process. The oxidation can reach a very high degree (approximately 30% for 6 h oxidation at 240 degrees C estimated by absorption of the alkyl). Our results suggest the possibility of the oxidation of the 9-bialkylfluorene sites. We propose that the degradation of the alkyl in the side chain can help the radicals to propagate in the chain reaction.     

Theoretical study of the electronic spectrum of binuclear gold(I) complexes

The electronic structure and the spectroscopic properties of [Au₂(CS₃)₂]^?2, [Au₂(pym‐2‐S)₂] (pym = pyrimidethiolate), [Au₂(dpm)₂]⁺² (dpm = bis(diphosphino)methane) were studied using density functional theory (DFT) at the B3LYP level. The absorption spectrum of these binuclear gold(I) complexes was calculated by single excitation time‐dependent (TD) method. All complexes showed a ¹(5dσ* → 6pσ) transition associated with a metal–metal charge transfer, which is strongly interrelated with the gold–gold distance. Furthermore, we have calculated the frequency of the gold–gold vibration (ν_Au2) on the above complexes. The values obtained are theoretically in agreement with experimental range. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

A massively parallel electrochemical approach to the miniaturization of organic micro- and nanostructures on surfaces

This paper describes a simple and convenient strategy for reducing the dimensions of organic micro-and nanostructures on metal surfaces. By varying electrochemical desorption conditions, features patterned by dip-pen nanolithography or micro contact printing and made of linear alkanethiols or selenols can be gradually desorbed in a controlled fashion. The process is referred to as electrochemical whittling because the adsorbate desorption is initiated at the exterior of the feature and moves inward as a function of time. The whittling process and adsorbate desorption were studied as a function of substrate morphology, adsorbate head and tail groups, and electrolyte solvent and salt. Importantly, one can independently address different nanostructures made of different adsorbates and effect their miniaturization based upon ajudicious selection of adsorbate, applied potential, and supporting electrolyte. Some of the physical and chemical origins of these observations have been elucidated.     

Four Novel Eremophilanolides from Ligularia sagitta

Four new eremophilanolides, isolated from Ligularia sagitta, were identified as (1β,3β,6β,8β,10β)‐6‐acetoxy‐3‐(angeloyloxy)‐1,10‐epoxy‐8‐hydroxyeremophil‐7(11)‐en‐8,12α‐olide ( 1 ), (1β,3β,6β,8β,10β)‐3‐(angeloyloxy)‐1,10‐epoxy‐6,8‐dihydroxyeremophil‐7(11)‐en‐8,12α‐olide ( 2 ), (1β,3β,6β,8β,10β)‐3‐(angeloyloxy)‐1,10‐epoxy‐8‐ethoxy‐6‐hydroxyeremophil‐7(11)‐en‐8,12α‐olide ( 3 ), and (1β,3β,8β,10β)‐3‐(angeloyloxy)‐1,10‐epoxy‐8‐hydroxyeremophil‐7(11)‐en‐8,12α‐olide ( 4 ). Their structures were elucidated by spectroscopic methods, including 2D‐NMR techniques and chemical transformations.     

A preliminary study on fabrication of nanoscale fibrous chitosan membranes in situ by biospecific degradation

A new approach for in situ fabrication of nanoscale fibrous chitosan membrane by biospecific degradation under physiological situation was studied. The chitosan binary blend membranes were fabricated by solvent casting of chitosan solution containing highly deacetylated chitosan (HDC) and moderately deacetylated chitosan (MDC) with different ratio. The biodegradation process was performed in PBS (pH 7.4) containing lysozyme at the temperature of 37 °C. Experimental results from weight loss, reducing sugar in surrounding media, FT-IR, X-ray diffraction, gel permeation chromatography (GPC) and SEM throughout the study showed that the biospecific degradation by lysozyme had removed MDC component selectively. When the ratio of MDC in the binary blend membranes amounted to 0.5, nanoscale domains of HDC and MDC were obtained, and thus a nanoscale fibrous structure was fabricated after biospecific degradation of MDC. This nanofibrous structure and the biospecific degradation of chitosan membranes can have potential advantages and interesting implications in tissue engineering and drug delivery.     

Additive Pummerer reaction of heteroaromatic sulfilimines with carbon nucleophiles

The additive Pummerer reaction of several heteroaromatic sulfilimines has been investigated. The overall process involves the reaction of the sulfilimine with TFAA to produce a transient N-tosyl-N-trifluoroacetyl sulfonium ion. Nucleophilic attack at the adjacent vinyl carbon results in the ejection of the sulfonamide group and the resulting thionium ion loses a proton to give the observed product.     

An efficient synthesis of novel spiro[[8H]indeno[2,1-b]-thiophene-8,9′-fluorene] building block for blue light-emitting materials

We have developed efficient synthetic routes to obtain a novel building block spiro[[8H]indeno[2,1-b]thiophene-8,9′-fluorene] (SITF), a monothiophene-containing spirobifluorene analogue, and constructed blue light-emitting materials, including 2′,7′-bis([1,1′-biphenyl]-4-yl)-spiro[indeno[2,1-b]thiophene-8,9′-fluorene] (BBP-SITF) and 2′,7′-bis(9,9′-spirobifluoren-2-yl)spiro[[8H]indeno[2,1-b]-thiophene-8,9′-fluorene] (BSBF-SITF). BSBF-SITF has shown to be a stable blue light-emitting material with high PL quantum efficiency (89%) and unique regioselective feature at the C2 of thiophene, which indicate that BSBF-SITF will be useful for constructing complicated optoelectronic systems.     

[{Cu(phen)2}(μ‐malato){Cu(phen)(NO3)}](NO3)·4H2O: malate acting as a tetra­dentate and dibridging ligand in a dinuclear copper complex

The crystal structure of the title compound, μ‐2‐hydroxy­butane­dioato‐1κ²O⁴,O^4′:2κ³O¹,O²,O⁴‐nitrato‐2κO‐tris­(1,10‐phen­anthroline)‐1κ⁴N,N′;2κ²N,N′‐dicopper(II) nitrate tetra­hydrate, [Cu₂(C₄H₃O₅)(NO₃)(C₁₂H₈N₂)₃](NO₃)·4H₂O, contains an unsymmetrical dinuclear copper complex with Cu(phen)₂ and Cu(phen)(NO₃) moieties (phen is 1,10‐phenanthroline) bridged by a malate (2‐hydroxy­butane­dioate) ligand, which acts as a double‐bridging and tetra­dentate ligand. As a result of this double‐bridging action, especially the direct coordination of the O atom of one carboxyl­ate group of malate to the two Cu atoms, the Cu⋯Cu distance is only 4.199 (1) Å and the two phen planes are roughly parallel [the shortest inter­planar distance is 3.28 (1) Å], exhibiting an obvious intra­molecular π–π stacking inter­action.