Photoinduced Intramolecular Charge Transfer in Donor-acceptor Dyad and Donor-bridge-acceptor Triad

在fullerene-PBTDP-TPA三体体系中的光诱导的分子内电荷转移的实验基础上,分别利用密度泛函理论和含时密度泛函理论以及结合二维、三维实空分析方法对fullerene、PBTDP-TPA二体以及fullerene-PBTDP-TPA三体的基态和激发态的性质进行了理论研究．二维定点表象揭示了激发情况下电子和空穴的相干情况．三维跃迁矩阵展示了跃迁偶极矩的方向和强度,而且三维电荷差密度给出了光诱导的分子内电荷转移的方向和结果．同时,用二维和三维表象的方法对fullerene-PBTDP-TPA三体中光诱导的分子内电荷转移过程进行了验证,揭示了在给予者-桥-接收者三体分子体系中分子内激发时电荷转移的机制．除此之外,还发现直接从给予者到接收者超交换的分子内电荷转移极大地促进了给予者-桥-接收者三体分子体系内的电荷转移．     

三体关联与次近邻两体关联下的渗流

本文用实空间重正群(RSRG)方法对二维三角格子的淬火体系,处理其在三体关联及最近邻与次近邻关联下的渗流问题。对于格点多体关联函数采用叠加近似,对于格点-空位多体关联是由几率守恒求出的。结果表明,引入三体关联或次近邻关联后,都并不改变临界现象的普适律。 关键词：     

LiAl5O8高压相变研究

 运用金刚石压砧同步辐射X射线衍射,对尖晶石结构的LiAl₅O₈进行了高压原位研究。实验发现：在高压下,一组LiAl₅O₈的新相衍射峰出现,随着压力的增加,其新相衍射峰逐渐增强,当压力增加到45.0 GPa时,LiAl₅O₈的低压相衍射峰全部消失,而形成了一组高压新相衍射峰。采用指标化程序对衍射数据进行处理和分析,确定这一高压新相为正交晶系结构,其晶胞参数为a=0.995 9 nm,b=0.644 7 nm,c=0.333 4 nm ,空间群为Pmm2。     

纳米晶复合Pr2Fe14B/α-Fe永磁材料磁性的研究

采用熔体快淬的方法制备Pr₂Fe₁₄B/α-Fe纳米晶复合永磁材料.使用振动样品磁强计(VSM)测量样品的室温磁性能.实验合金成分为(Pr_xFe_94.3-xB_5.7)_0.99Zr₁(其中x＝8.2，8.6，9.0，9.4，9.8，10.2，10.6，11.0，11.4(原子分数，%)).系统地研究了辊速及合金成分对快淬带磁性能的影响，当Pr原子分数由8. 关键词： 纳米复合永磁材料 熔体快淬 2Fe₁₄B/α-Fe')" href="#">Pr₂Fe₁₄B/α-Fe 磁性     

基于动态混沌映射的三维加密正交频分复用无源光网络

提出了一种基于混沌映射的三维加密正交频分复用无源光网络保密通信系统.该系统通过相关性检测锁定收发端混沌系统参数,实现收发双方混沌系统同步;并利用同步混沌系统生成密钥,实现符号扰动以及二重子载波加密.该加密方案的密钥空间超过10~(86),能够有效对抗穷举攻击.实验实现了13.3 Gb/s基于64进制正交幅度调制的加密正交频分复用信号在25 km标准单模光纤中的传输,并完成了信息的有效解密.     

Synthesis of chiral β-amino acid derivatives by asymmetric hydrosilylation with an imidazole derived organocatalyst

The organocatalysed asymmetric hydrosilylation of a number of N-aryl and alkyl β-substituted enamino esters proceeds in generally good yield and enantioselectivity. Crucial to obtaining high yield and selectivity was the addition of benzoic acid as an additive and under these conditions, both N-alkyl and N-aryl substituents were well tolerated. β-Aryl and alkyl substituents were evaluated and a model proposed to account for the experimental observations based upon enamine tautomerisation and conformational preferences of the reactive ketimine intermediate.     

DNA-directed formation of peptide bond: a model study toward DNA-programmed peptide ligation

A model study of DNA-directed peptide ligation has been developed by transferring fluorescent reporting group from small molecule thioester to a DNA strand (template DNA) in the presence of a thiol-functionalized DNA strand (auxiliary DNA), mimicking the Native Chemical Ligation (NCL) reaction. This DNA-directed transfer shows dependence on the sequence complementarity of the two DNA strands, with in situ generated 4-thiolphenylmethyl functionalized oligonucleotide as the auxiliary DNA strand, under mild basic condition (pH=8.5), and with tris(2-carboxyethyl) phosphine hydrochloride (TCEP) as a reducing agent. Reactions with different amino acid α-thioesters resulted in varied transfer efficiencies from glycine to α-substituted amino acids. This study has provided the basic foundation to use DNA-programmed chemistry toward the chemical synthesis or unnatural modification of protein molecules.     

Facile synthesis of sulfenyl-substituted isocoumarins,heterocycle-fused pyrones and 3-(inden-1-ylidene)isobenzofuranones by FeCl3-promoted regioselective annulation of o-(1-alkynyl)benzoates and o-(1-alkynyl)heterocyclic carboxylates with disulfides

Reported herein is the FeCl₃-promoted intermolecular sulfoesterification of o-(1-alkynyl)benzoates with disulfides, which provides a convenient and efficient method for synthesis of 4-sulfenylisocoumarins. Various functional groups such as methoxy, halides, ester, cyano and silicon groups in the substrates are tolerated, and heterocycle-fused chalcogenylpyrones are also successfully achieved directly from the corresponding heterocyclic precursors under the same reaction conditions. In addition, starting from diynylbenzoate, this reaction sequence can be combined with a bicyclization step leading to the tetracyclic (E)-3-(2-phenyl-3-phenylchalcogenylinden-1-ylidene)isobenzofuranone frameworks with high regiospecificity and exclusive trans stereoselectivity.     

Immobilized palladium on surface-modified Fe3O4/SiO2 nanoparticles: as a magnetically separable and stable recyclable high-performance catalyst for Suzuki and Heck cross-coupling reactions

A palladium-based catalyst (Fe₃O₄/SiO₂/HPG–OPPh₂–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe₃O₄/SiO₂ with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe₃O₄/SiO₂/HPG–OPPh₂–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity.     

An efficient synthesis of δ-glyconolactams by intramolecular Schmidt–Boyer reaction under microwave radiation

δ-Glyconolactams were first synthesized by the intramolecular Schmidt–Boyer reaction using corresponding δ-azidosugars as starting material. The reaction could be efficiently performed in good yields of 61–69% under microwave radiation in acid condition, providing an alternative protocol to iminosugar δ-lactam.