分子体系的高压化学反应

在高压(一万到百万大气压)下物质的组成、结构、化学反应都可以发生前所未知的巨大变化。运用高压合成目标产物,表征高压下的物质结构与反应过程是高压化学研究的主要问题。一般而言,高压下不饱和化合物倾向于聚合形成高密度饱和共价键体系;反应中分子与原子扩散严重受限,常形成亚稳态化合物;反应物的空间晶体结构、官能团性质、反应体系的温度、静水压效果都对反应有显著影响。对高压下分子化学反应的研究需要综合运用晶体学、谱学、化学等实验手段和热力学、动力学等方面的理论计算相互验证,进而建立理论,深入极端条件化学的星辰大海。     

聚氧化乙烯/高岭石聚合物电解质的制备与表征

通过尿素对高岭石的插层及随后的超声脱除处理,制备了一种片层剥离的高岭石粉体,并将这种剥离高岭石与聚氧化乙烯/高氯酸锂(PEO/LiClO_4)体系复合,制备出PEO/高岭石复合物.采用X射线衍射仪、红外光谱仪、扫描电子显微镜、透射电子显微镜、扫描量热仪、电化学工作站和万能材料试验机进行结构表征和性能测试.结果表明,尿素在高岭石层间的插层和脱除引起了高岭石片层的剥离,片层厚度小于50 nm.剥离高岭石在PEO/LiClO_4体系中与PEO形成了强烈的氢键作用,促进了PEO结晶度的降低,进而提高复合物的离子电导率.含有20 wt%剥离高岭石填料的PEO/高岭石复合物的离子电导率达到6.0×10~(-5) S/cm,与未复合的PEO/LiClO_4相比,提高了一个数量级.复合物制备过程中的烘干温度对PEO的结晶度会产生一定的影响,95°C下的烘干处理能得到结晶度较低,离子电导率较高的复合物.此外,剥离高岭石的添加显著提高了聚合物的杨氏模量和拉伸强度,与未复合的PEO/LiClO_4相比,杨氏模量和拉伸强度最大提高了256%和121%.     

Recent advances of transformable nanoparticles for theranostics

We summary recent advances of transformable NPs for nanomedicine. In this review, the transformation of NPs is divided into three groups including changes in size, surface charge and morphology, which is induced by internal stimuli, such as pH, enzyme, receptor or external stimuli, such as light, temperature.     

Aqueous polymerization of acrylamide initiated by cerium (IV)–ethylenediamine tetraacetic acid redox system

Ethylenediamine tetraacetic acid (EDTA) terminated polyacrylamide was obtained by using the EDTA–cerium(IV) ammonium nitrate [Ce(IV)] redox initiator in the aqueous polymerization of acrylamide. The polymerization behaviors as a function of the concentration of Ce(IV), EDTA, and acrylamide as well as temperature were studied. The consumption rate of cerium(IV) depends a first-order reaction on the ceric ion concentration ([Ce(IV)]). The complex formation constant (K) and disproportionation constant (k_d) of Ce(IV)–EDTA chelated complex are 1.67 × 10⁴ and 3.77 × 10^?3, respectively. The rate dependences of polymerization on monomer concentration and EDTA concentration both follow a second-order reaction in the run of initial monomer concentration ([M]_i) equal to 0.2 mol dm^?3. The number average molecular weight increases linearly with the ratio of [M]_i/[Ce(IV)]_i. The mechanism and kinetics for the polymerization was proposed. The kinetic parameters involved were determined. © 1992 John Wiley & Sons, Inc.     

Synthesis,Structures, and Physical Properties of Benzo[k]fluoranthene‐Based Linear Acenes

This work describes the syntheses, crystal structures, photophysical properties, and electro‐chemical analyses of benzo[k]fluoranthene‐based linear acenes, together with ab initio density functional theory computations on them. The molecules were prepared in generally moderate to good yields through Pd‐catalyzed cycloadditions between 1,8‐diethynylnaphthalene derivatives and aryl iodides. This protocol is simpler and more efficient than conventional methods. The scope and limitations of this reaction were examined. The structures of compounds 4 hb , 15 ac , 17 ab , 19 ac , and 24 je were determined by X‐ray analysis; they are either bent or twisted, rather than planar. The photophysical and electrochemical properties of these cycloadducts were also investigated and compared with computational predictions based on density functional theory.     

Analysis of magnolol and honokiol in biological fluids by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) method was used for analysis of magnolol and honokiol. Under the optimized condition, CZE with UV absorption detection provided that the limit of detection was at microM level. To enhance detection sensitivity of magnolol and honokiol, CZE separation system was coupled with a laser-induced fluorescence (LIF) detector for the first time. The limits of detection of magnolol and honokiol were 12 nM (3.20 ng ml(-1)) and 18 nM (4.79 ng ml(-1)), respectively, showing that the CZE-LIF system provides greater than 100-fold sensitivity improvements than does the CZE-UV system. The developed method was applied to analyze magnolol and honokiol in spiked human plasma samples, microsome incubation samples as a preliminary demonstration of its potential in pharmacokinetic studies.     

Intramolecular cyclization of ruthenium vinylidene complexes with a tethering vinyl group: facile cleavage and reconstruction of the C-C double bond

Protonation of ruthenium acetylide complexes [M]-*C*CCPh2CH2CH=CH2 (2a, [M] = (eta5-C5H5)(P(OPh)3)(PPh3)Ru; 2a', [M] = (eta5-C5H5)(dppp)Ru; *C = 13C-labeled carbon atom) with HBF4 in ether produces [[M]=*C=CHCH2CPh2*CH=CH2][BF4] (4, 4') exclusively via a metathesis process of the terminal vinyl group with the *C=*C of the resulting vinylidene group. For 4 in methanol, bond reconstruction of the two labeled *C atoms readily takes place via a retro-metathesis process followed by a cyclization of the resulting vinylidene ligand giving the cyclic carbene complex 5, which is fully characterized by single-crystal X-ray diffraction analysis. The protonation of 2a in MeOH is followed by a cyclization, also giving 5. Deuterium-labeling study indicates that the C-C bond formation of this cyclization proceeds simultaneously with the formation of 4 consistent with facile cleavage and reconstruction of C=C bonds. For comparison, complex 4 in alcohol yields, besides 5, the corresponding alkoxycyclohexene 6. Formation of 6 from 4 also involves a skeletal rearrangement with reconstruction of the C=C bond. Interestingly, [[Ru']=*C=C(Me)CH2CPh2*CH=CH2][BF4] (8') originally from a complex with two connected labeled carbon atoms also undergoes reestablishment of the *C=*C bond yielding the cyclic allenyl complex 9'. 13C-labeling studies clearly reveal the reestablishment of two C=C double bonds in the transformation of both 4 to 5 and 8' to 9'. The proposed mechanism implicates a cyclobutylidene intermediate formed either via a regiospecific [2+2] cycloaddition of two double bonds in the ruthenium vinylidene 4 or via a cyclization of 4 giving a nonclassical ion intermediate followed by a 1,2-alkyl shift.     

Peripheral aryl-substituted pyrrole fluorophores for glassy blue-light-emitting diodes

In this work, a series of aryl-substituted pyrrole analogues were synthesized. These pyrrole analogues emit violet to blue light. Fluorescence and amorphous glassy properties of these pyrrole analogues were induced by manipulating the peripheral aryl groups. These crowded peripheral aryl groups would effectively prevent the fluorophores from aggregation, resulting in higher quantum efficiency and a stable emission spectrum in the solid state. One of the aryl-substituted pyrrole analogues, namely NPANPy can be used as hole-transporting material or hole-transporting/emitting material. The devices would emit blue light when the fluorophore NPANPy acts as the hole-transporting/emitting material. Their CIE coordinate is around (0.16, 0.14), whereas the maximum brightness can reach 4300-5000 cd m⁻². Apart from that, when the fluorophore was used only as the hole-transporting material, better device performances, especially in low current density, were found, as compared with the standard device.     

Compatibility between methanol and water in the three-dimensional cage formation of large-sized protonated methanol-water mixed clusters

Infrared spectra of large-sized protonated methanol-water mixed clusters, H(+)(MeOH)(m)(H(2)O)(n) (m=1-4, n=4-22), were measured in the OH stretch region. The free OH stretch bands of the water moiety converged to a single peak due to the three-coordinated sites at the sizes of m+n=21, which is the magic number of the protonated water cluster. This is a spectroscopic signature for the formation of the three-dimensional cage structure in the mixed cluster, and it demonstrates the compatibility of a small number of methanol molecules with water in the hydrogen-bonded cage formation. Density functional theory calculations were carried out to examine the relative stability and structures of selected isomers of the mixed clusters. The calculation results supported the microscopic compatibility of methanol and water in the hydrogen-bonded cage development. The authors also found that in the magic number clusters, the surface protonated sites are energetically favored over their internal counterparts and the excess proton prefers to take the form of H(3)O(+) despite the fact that the proton affinity of methanol is greater than that of water.