取代基电性效应对碳硅还原消除区域选择性调控的理论研究

有机反应区域选择性的调控是有机化学的重要研究内容之一,而电性效应则是其重要调控因素.运用密度泛函理论计算,以钯催化2-碘联苯化合物与硅杂环丁烷的环化反应为模板,研究了取代基电性效应在还原消除过程中对区域选择性的影响,并给出了该反应的详细反应机理.计算结果表明,该反应经历了Pd—I键氧化加成、协同金属去质子、Pd—Si键氧化加成、还原消除过程得到硅杂八元环产物,且C—Si键还原消除是反应的速率决定步骤.对Pd(IV)还原消除过渡态中电子效应的研究证明,当使用不对称2-碘联苯作为反应底物时,芳环电子密度是区域选择性的主要控制因素,电子密度更高的基团更容易发生还原消除,与该基元反应电子流向一致.     

Nonlocal Andreev reflection and spin current in a three-terminal Aharonov--Bohm interferometer

This paper theoretically reports the nonlocal Andreev reflection and spin current in a normal metal-ferromagnetic metal-superconducting Aharonov--Bohm interferometer. It is found that the electronic current and spin current are sensitive to systematic parameters, such as the gate voltage of quantum dots and the external magnetic flux. The electronic current in the normal metal lead results from two competing processes: quasiparticle transmission and nonlocal Andreev reflection. The appearance of zero spin-up electronic current (or spin-down electronic current) signals the existence of nonlocal Andreev reflection, and the presence of zero electronic current results in the appearance of pure spin current.     

Phase coherence of the electron and hole in a ferromagnetic film in proximity with a superconductor

The scattering matrix approach between the clean and dirty limits is developed for the study of tunneling spectra in a ferromagnetic film in proximity to a superconductor. The minigap and the damped oscillation from ``0" to ``π" state in tunneling conductance are attributed to the phase coherence of the electrons and the corresponding Andreev-reflected holes in the ferromagnetic film. The calculated results provide a reasonable explanation for the behavior observed in recent experiments.     

Coexistence of ferromagnetism and superconductivity in normal mental/superconductor/ferromagnet structures

<正>We extend the Blonder,Tinkham and Klapwijk theory to the study of the inverse proximity effects in the normal mental/superconductor/ferromagnet structures.In the superconducting film,there are the gapless superconductivity and the spin-dependent density of states both within and without the energy gap.It indicates an appearance of the inverse-proximity-effect-induced ferromagnetism and a coexistence of ferromagnetism and superconductivity near the interface.The influence of exchange energy in the ferromagnet and barrier strength at the superconductor/ferromagnet interface on the inverse proximity effects is discussed.     

铑催化去对称氢酰化机制理论研究

本文运用密度泛函理论(DFT)计算,研究了手性双膦络合Rh(I)催化去对称性烯烃氢酰基化反应机理.计算确定了该反应最优反应路径包括醛基C–H键活化、第一个烯基插入Rh–H键、β-H消除、第二个烯基插入Rh–H键以及还原消除.计算结果表明,第一个烯基插入Rh–H键是立体选择性决定步,还原消除反应是整个反应的决速步.我们还通过理论计算研究了可能的烯烃碳酰基化副反应机理.计算预测反应主产物是S构型——季碳环戊酮,与实验报道一致.我们通过非共价弱相互作用分析研究配体对反应化学选择性的影响,结果表明,当使用位阻大的双膦配体(R)-DTBM-MeOBIPHEP时,由于配体与底物的排斥较大,不利于碳酰化反应发生,反应优势产物是烯烃氢酰化产物;而当用空间位阻小的双膦配体BzDPPB时,碳酰化反应变得更加有利,反应主产物为碳酰化产物双环[2.2.1]庚酮.因此,配体的空间位阻决定了Rh(I)催化烯烃酰基化反应的化学选择性.     

Nonlocal Andreev reflection with Rashba spin-orbital interaction in a triple-quantum-dot ring

We theoretically studied the nonlocal Andreev reflection with Rashba spin-orbital interaction in a triple-quantumdot(QD) ring,which is introduced as Rashba spin-orbital interaction to act locally on one component quantum dot.It is found that the electronic current and spin current are sensitive to the systematic parameters.The interdot spin-flip term does not play a leading role in causing electronic and spin currents.Otherwise the spin precessing term leads to shift of the peaks of the the spin-up and spin-down electronic currents in different directions and results in the spin current.Moreover,the spin-orbital interaction suppresses the nonlocal Andreev reflection,so we cannot obtain the pure spin current.     

含磺酰胺结构的1,3,4-噁二唑砜类化合物的设计、合成及抗菌活性研究

为了寻找新型抗菌剂,采用活性亚结构拼接,设计合成了23个含磺酰胺结构的1,3,4-噁二唑砜类化合物,并对其抗菌活性进行了测试.在100μg/m L浓度下,大多数化合物对水稻细菌性条斑病菌(Xanthomonas oryzae pv.oryzicola)和水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae)表现出优异的离体抗菌活性.除N-((5-(丙基磺酰基)-1,3,4-噁二唑-2-基)甲基)-4-(三氟甲基)苯磺酰胺(18)外,所有化合物对水稻细菌性条斑病菌的半数有效浓度(EC₅₀)值为1.3～22.5μg/mL所有化合物对水稻白叶枯病菌的EC₅₀为1.1～32.7μg/m L,均优于对照药剂叶枯唑(84.1和71.4μg/mL)和噻菌酮(122.1和84.0μg/m L).此外,4-氟-N-((5-(甲基磺酰基)-1,3,4-噁二唑-2-基)甲基)苯磺酰胺(4)可以通过抑制胞外多糖(EPS)的产生、生物膜的形成以及改变细胞膜的通透性和细胞表面形态,从而抑制水稻细菌性条斑病菌和水稻白叶枯病菌的正常生长.