The Tolman length: is it positive or negative?

By means of a large-scale molecular dynamics simulation, we show that the Tolman length, although positive, is much smaller in magnitude than previously reported. We found that the range of interparticle interaction can significantly affect the magnitude of the Tolman length. When the range of interaction is longer than five molecular diameters, the Tolman length is on the order of a few hundredths of the molecular diameter, rather than a few tenths known previously.     

Concatenation of two molecular switches via a Fe(II)/Fe(III) couple

[reaction: see text] Modulation of the fluorescein fluorescence in the presence of spiropyran and ferric ion by light was observed. Such fluorescence modulation was due to the low oxidation potential of complex MC.Fe(2+), which made the electron transfer from MC.Fe(2+) to Flu(+)()(*)() thermodynamically favorable. As a result, the communication between two molecular switches based on fluorescein and spiropyan, respectively, was realized via the reversible Fe(III)/Fe(II) redox couple. The communicating behavior corresponds well to the function of an INHIBIT logic gate.     

An approach to comparative analysis of chromatographic fingerprints for assuring the quality of botanical drugs

The present study was focused on developing the chemometric methods for analysis of the chromatographic fingerprint to control the quality of botanical drugs, which has gained attention in Asia and other countries. We developed a novel approach to generate a set of fingerprint features, called Fisher components (FCs) that were extracted from the chromatographic fingerprint. The method greatly reduces the dimensionality of the fingerprint vector, and the resulting FCs still retain most discriminatory information of the original fingerprint. Choosing an example of relevance to contemporary botanical drugs, we applied the FCs to a set of Shenmai injection samples. We successfully identified the manufacturers of the samples using two classifiers, linear discriminant analysis (LDA) and k-Nearest Neighbor (k-NN) based on the FCs. We also applied a similarity assessment together with the visual analysis using the FCs to exam the products from different manufacturers. We found that the lot-to-lot consistency of products can be accurately determined using the FCs. Finally, we demonstrated that the application of chemometric methods for chromatographic fingerprinting offers reliability to detect suspected fraud samples. In summary, we demonstrated that the presented approaches could be useful to determine the identity, consistency, and authenticity of Shenmai injection through chromatographic fingerprinting. The methods are equally applicable to other botanical drugs.     

A reliable ab initio potential energy surface and vibrational states for the ground electronic state of HgH2(X1Sigma+g)

A three-dimensional global potential energy surface for the ground (X (1)Sigma(+)(g))electronic state of HgH(2) is constructed from more than 13,00 ab initio points. These points are generated using an internally contracted multireference configuration interaction method with the Davidson correction and a large basis set. Low-lying vibrational energy levels of HgH(2), HHgD, and HgD(2) calculated using the Lanczos algorithm are found to be in good agreement with the available experimental band origins. The majority of the vibrational energy levels up to 9000 cm(-1) are assigned with normal mode quantum numbers. Our results indicate a gradual transition for the stretching vibrations from the normal mode regime at low energies to the local mode regime near 9000 and 8000 cm(-1) for HgH(2) and HgD(2), respectively, as evidenced by a decreasing energy gap between the (0,0,n(3)) and (1,0,n(3)-1) vibrational states and bifurcation of the corresponding wave functions.     

Novel synthesis of 2-oxo-3-butynoates by copper-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride

A general and efficient Cu(I)-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride for the synthesis of 2-oxo-3-butynoates and 2-oxo-3-butynoamides was developed. Readily available starting materials, the mild reaction conditions, wide functional group tolerance, and the obviation of stoichiometric organolithium or magnesium reagents combine to highlight this reaction.     

A new serratane-type triterpene from Lycopodium phlegmaria

A new serratane-type triterpene, lycophlegmarin (1), has been isolated from Lycopodium phlegmaria L. Four known related triterpenoids were also found from the title plant. The structure of the new compound was elucidated on the basis of detailed spectroscopic analysis and chemical method. Lycophlegmarin exhibited modest growth-inhibitory activity in vitro against human hepatoma cells BEL 7402.     

Calculations on the octupolar molecules with enhanced two-photon absorption cross sections based on the Zn (II) and Cu (I) as centers

The equilibrium geometries, electronic structures, as well as one- and two-photon absorption cross sections of a series of octupolar chromophores with Zn(2+) or Cu(+) as coordinate centers and 4,4'-bis(dibutylaminostyryl)-[2,2']-bis(bipyridyl) as ligands have been determined by using B3LYP/6-31G and ZINDO methods. These molecules are designed by controlled combination of two or three bipyridyl ligands with the metal centers. The results show that Zn(2+) is an effective template for the design of octupolar structures which enable it to form tetrahedral and octahedral coordinated complexes; while Cu(+) only exists in a tetrahedral coordinated complex, comparing the tetrahedral complex with Zn(2+) as the center with that of Cu(+) as the center, it is found that the complex with the Cu(+) center is a better two-photon absorption material than the former as far as the transparency/nonlinearity is concerned. Furthermore, for the same metal center of Zn(2+), both one- and two-photon absorptions of the tetrahedral complex are redshifted relative to those of the octahedral complex, is attributed to the spiroconjugation effect in the tetrahedral complex. Our theoretical findings are consistent with recent experimental observations and provide an important foundation for the design of improved transparency-nonlinearity two-photon absorption materials.     

The Chemical Constituents of the Wood of Pinus Luchuensis Mayer

From the hexane extractive of the wood of Pinus luchuensis Mayer, α-pinene, β-pinene, camphene, camphor, 4-terpineol, α-terpineol, carvacrol, tetracosanol, hexacosanol, octacosanol, β-sitosterol, stigmasterol, methyl dehydroabietate, pinosylvin monomethylether, pimaric acid, dehydroabietic acid and straight chain hydrocarbons C₂₃-C₃₅ were isolated.     

Synthesis, spectroscopic characterization and reactivities of linear and butterfly chromium/selenium complexes containing substituted cyclopentadienyl ligands: crystal structures of [{η-MeC5H4Cr(CO)2}2Se] and [{η-EtO2CC5H4Cr(CO)2}2Se2]

The Cr-Cr singly-bonded dimers [{η⁵-RC₅H₄Cr(CO)₃}₂] (1, R=Me; 2, R=CO₂Et) reacted with an equivalent of elemental selenium in THF at room temperature to give the linear Cr₂Se complexes [{η⁵-RC₅H₄Cr(CO)₂}₂Se] (3, R=Me; 4, R=CO₂Et), whereas the linear Cr₂Se complex (5, R=MeCO) reacted with excess NaBH₄, Ph₃PCHPh or 2,4-dinitrophenylhydrazine under respective conditions to afford the linear Cr₂Se derivatives [{η⁵-RC₅H₄Cr(CO)₂}₂Se] (6, R=MeCH(OH); 7, R=PhCHCMe; 8, R=2,4-(NO₂)₂C₆H₃NHNCMe). Similarly, while the butterfly Cr₂Se₂ complexes [{η⁵-RC₅H₄Cr(CO)₂}₂Se₂] (9, R=Me; 10, R=CO₂Et) could be produced either by reaction of dimers 1 and 2 with an excess amount of elemental selenium, or by reaction of the linear complexes 3 and 4 with an equivalent of elemental selenium, the butterfly Cr₂Se₂ derivatives [{η⁵-RC₅H₄Cr(CO)₂}₂Se₂] (12, R=MeCH(OH); 13, R=PhCHCMe; 14, R=2,4-(NO₂)₂C₆H₃NHNCMe) were yielded by reaction of the butterfly Cr₂Se₂ complex (11, R=MeCO) with an excess quantity of NaBH₄, Ph₃PCHPh and 2,4-dinitrophenylhyazine. Both the linear complexes 3, 4, 6-8 and the butterfly complexes 9, 10, 12-14 are new, which have been fully characterized by elemental analysis, spectroscopy and X-ray crystallography.