High-pressure structural trends of Group 15 elements: simple packed structures versus complex host-guest arrangements

The Group 15 elements P, As, Sb, and Bi all have layered structures consisting of six-membered rings under ambient conditions and attain the body-centered cubic (bcc) structure at the highest pressures applied. In the intermediate pressure region, however, phosphorus and its heavier congeners behave profoundly differently. In this region P first attains the open packed simple cubic (sc) structure for a wide range of pressures and then transforms into the rarely observed simple hexagonal (sh) structure. For the heavier congeners complex, incommensurately modulated host-guest structures emerge as intermediate pressure structures. We investigated the high-pressure behavior of P and As by ab initio density functional calculations in which pseudopotentials and a plane wave basis set were employed. The incommensurately modulated high-pressure structure of As was approximated by a supercell. Our calculations reproduced the experimentally established pressure stability ranges of the sc and sh structures for P and the host-guest structure for As very well. We found that the sc and especially the sh structure are decisively stabilized by the admixture of d states in the occupied levels of the electronic structure. This admixture releases s-s antibonding states above the Fermi level (s-d mixing). With pressure, s-d mixing increases rapidly for P, whereas it remains at a low level for As. As a consequence, the band energy contribution to the total energy determines the structural stability for P in the intermediate pressure region, giving rise to simple packed structures. On the other hand, in the intermediate pressure region of the heavier Group 15 elements, a delicate interplay between the electrostatic Madelung energy and the band energy leads to the formation of complex structures.     

A new class of low-molecular-weight amphiphilic gelators

A new powerful class of low-molecular-weight amphiphilic compounds has been synthesized and their structure-property relationships with respect to their gelation ability of organic solvents have been investigated. These compounds are able to gel organic solvents over a broad range of polarity. Especially polar solvents such as valeronitrile and gamma-butyrolactone can be gelled even at concentrations far below 1 wt %. It was found that the gelation ability of these asymmetrically substituted p-phenylendiamines depends on a well-balanced relation of the terminal head group, the units involved in hydrogen bonding (amide or urea groups), and on the length of the alkyl chain. With this class of new gelators it is possible to tailor thermal and mechanical properties in different organic solvents and open various application possibilities.     

Synthesis and Characterization of Novel Monoazo N‐Ester‐1,8‐Naphthalimide Disperse Dyestuffs

Five novel monoazo disperse dyestuffs based on N‐ester‐1,8‐naphthalimide were synthesized. Acenaphthene was nitrated, then oxidized to 4‐nitro‐1,8‐naphthalic anhydride. 4‐Nitro‐1,8‐naphthalic anhydride was reacted with methyl and ethyl glycinate in alcoholic media, followed with reduction. 4‐Amino‐N‐methyl and ethyl glycinate‐1,8‐naphthalimide were obtained. These products were diazotized and coupled with appropriate aromatic amines to give bluish‐red or violet dyestuffs. All intermediates and dyestuffs were purified and characterized by ¹H‐NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Dispersion of dyestuffs was prepared in water and applied to polyester fabrics. The dyed fabrics showed that four of the synthesized dyestuffs were suitable for coloring polyester fibers, producing deep bluish red with very good build up properties.     

含松香骨架的新型手性季铵盐相转移催化剂的合成及其在不对称环氧化反应中的应用

以天然松香为原料合成了4个新型手性季铵盐类相转移催化剂, 并用于催化不对称查尔酮环氧化反应, 发现这类手性相转移催化剂可以有效地催化查尔酮的不对称环氧化, 环氧化产物ee最高达20%.     

Conformational Transformation Exhibited by the Peptide Extracted from Crystalline Region of Bombyx mori Silk Fibroin in Solid and Solution States

The conformational transformation of a 30-residue peptide H（Ala-Gly-Ser-Gly-AIa-Gly）5OH, i.e., （AGSGAG）5, extracted from highly crystalline region of Bombyx mori （B. mori） silk fibroin was described by using the high resolution solid state 13^C NMR, and CD spectroscopies. Based on the conformation-dependent 13^C NMR chemical shifts of the Ala, Gly and Ser residues and the line-shape analysis of the conformation sensitive Ala Cβ resonance, the peptide revealed a strong preference for silk Ⅱ structural form, i,e,, an antiparallel fl-sheet structure （φ= - 140±20°and ψ= 135±20°） in solid state. On the contrary, the CD spectra of this peptide in the two non-native hexafluorinated fibre spinning solvents, hexafluoroisopropanol （HFIP） and hexafluoroacetone （HFA）, exhibited the existence of an unusual tightly-folded conformation resembling 310-helix （φ=- 60±20° and ψ=-30±20°）, as judged from the R ratio of [θ]222/[θ]203 in HFIP solution, whereas a dynamically averaged unordered structure in HFA, Taken together, the information inclined to hypothesis that the primary structure of the highly crystalline regions of B. mori silk fibroin may be easily accessible to the large conformational changes, which in turn may be critical for facilitating the structural transformation from unprocessed silk fibroin （silk I form） to processed silk fiber （silk Ⅱform）.     

Synthesis and characterization of aromatic polyamides containing alkylphthalimido pendent groups

A series of polyisophthalamides containing pendent phthalimido groups and flexible side spacers were prepared from four novel diacids and three commercial aromatic diamines. These polyamides were prepared in high yields and with high molecular weights by direct polycondensation with triphenyl phosphite and pyridine as condensing agents. The weight‐average and number‐average molecular weights, measured by gel permeation chromatography, were 70,000–137,000 and 47,000–86,000 g/mol, respectively. The novel polyamides were amorphous and readily soluble and showed glass‐transition temperatures of 150–240 °C, as measured by differential scanning calorimetry. Thermogravimetric analysis showed that the 10% weight‐loss temperatures in nitrogen were 355–430 °C, a significant improvement in thermal stability having been observed with the increase in the side‐chain length. A theoretical quantum mechanical study was successfully carried out to explain these results. Flexible and tough films, cast from polymer solutions, showed tensile strengths of 50–125 MPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3711–3724, 2002     

Superoxes,high temperature universal phases in (GC)2

Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ～50° to ～300°. High MW Superox-4 has a MAOT about 20° higher than the lower MW Superox-0.1. Several applications illustrating the versatility of Superox phases in (GC)² are presented.     

Mathematical Correction for Polyatomic Isobaric Spectral Interferences in Determination of Lanthanides by Inductively Coupled Plasma Mass Spectrometry

The determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP‐MS) is complicated by several spectral overlaps from M⁺, MO⁺ or MOH⁺ ions formed in the ICP. Especially, it is essential to avoid the spectral interferences from lighter lanthanide and Ba polyatomic ions on middle or heavier lanthanides. To tackle this problem, we have developed a mathematical correction method, which reduces all the spectral overlaps from oxide species of Pr, Nd, Ce and Sm over Gd, Tb, Dy and Ho, and Gd, Tb over Yb and Lu. It can also successfully correct the oxide and hydroxide interference of Ba over Eu. The effectiveness of the proposed the mathematical correction scheme is demonstrated for the USGS Standard Rock samples AGV‐1 and G‐2. The results show that the experimental data obtained by applying the mathematical correction scheme for lanthanides is in good agreement with the reported values, using pneumatic and ultrasonic nebulisation methods, for their ICP‐MS analysis.     

基于课程标准的教学——以常见阴、阳离子的检验为例

以常见的阴、阳离子的检验为例，研究了如何实施基于标准的教学。校本教材的开发为标准、教材、教学、评价的一致性提供保障；以学生应知的和能做的驱动课堂活动；根据达成标准应有怎样的质量表现，试卷编制先于教学设计。课堂上，“教”“学”双方都明确学习目标，教师提供多种策略来满足学生多样的学习需要，如提供工具，搭建脚手架，并以“微”研究性学习的方式展开教学，给学生提供了充分的进步空间。     

Theoretical study of the reaction of alkynes with furan catalyzed by AuCl3 and AuCl

A general scheme for the endo‐ and exo‐cyclization of furan reactivity with [L ‐Au^{III, I}Cl_x] with (x = 3, 1 and L ‐acetylene and vinylidene) complexes is investigated using density functional theory (DFT) code. Two conceivable mechanisms via a [4 + 2] Diels–Alder process or carbene complex are analyzed. According to the activation energy values of the gold (III and I) catalyst, the first mechanism, which implies the Diels–Alder reaction of Au^III, is thermodynamically favored and gives more evidence of the intramolecular addition of the furan with the alkynes. The second mechanism, presumably assisted by the spontaneous formation of the exo‐vinylidene complexes and intermediates of gold (III, I) by forming the carbene complex, is kinetically favored. Additionally, we compare our results with other structures with intramolecular additions that exhibit the quasi‐similarity of gold analogue structures. Differences in activation energies are observed, according to the functional used. Finally, we probe the solvent effects, which decrease the energy barrier in the path. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007