环庚烷的高压拉曼光谱研究

 利用金刚石对顶砧（DAC）装置产生高压,在室温下对环庚烷进行了高压原位拉曼光谱研究。实验的最高压力是17.00 GPa。研究结果表明,在实验的压力范围内,室温常压下为液态的环庚烷在0.53 GPa发生了液-固相变;在3.45~5.58 GPa压力区间,环庚烷的拉曼频移随压力变化的曲线和拉曼峰的半高宽随压力的变化曲线都出现了拐点,由此判断,环庚烷可能发生了固-固相变。     

Prediction of Superhard BN_2 with High Energy Density

Considering that pressure-induced formation of short,strong covalent bonds in light-element compounds can produce superhard materials,we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN₂,which are stable relative to alpha-B and alpha-N₂ at ambient pressure.At ambient pressure,the most stable phase has a layered structure(h-BN₂) containing hexagonal BN layers between which there are intercalated N₂ molecules.At 25 GPa,a three-dimensional P4₂/mmc structure with single N-N bonds becomes the most stable.Dynamical,thermal,and mechanical stability calculations reveal that this structure can be recovered under ambient conditions.Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of ~43 GPa.This structure has a potentially high energy density of ~4.19 kJ/g.     

Metal-Element-Incorporation Induced Superconducting Hydrogen Clathrate Structure at High Pressure

The recent observation of high critical temperature T_c in lanthanum and Yttrium hydrides confirms the key role of hydrogen cage(H-cage)in determining high superconductivity.Here,we present a new class of metastable H₁₂ clathrate structures based on the icosahedral cI 24-Na that can be stabilized by incorporation of metal elements.Analysis shows that the charge transfer from metal atoms to H atoms contributes to forming the H₁₂ clathrate.Nine dynamically stable structures are identified to exhibit superconductivity,and a maximum T_c of 28K is found in voids-doped Mo₆H₂₄.Calculations reveal that the low T_c is attributed to the weak interaction between H atoms in each cage due to the long H–H distance.The current results provide a possible route to design H-cage containing superconductors.     

含氟咪唑啉型有机催化剂在不对称Aldol反应中的研究

手性1,2-二醇骨架是天然产物或生物活性分子构建过程中的重要骨架,而α-羟基酮参与的不对称Aldol缩合反应是实现手性1,2-二醇骨架的重要手段.设计并合成了含三氟甲基的咪唑啉型化合物,并将其应用于羟基丙酮和醛的不对称Aodol缩合反应.研究结果表明,当采用含氟咪唑啉(2R,4S)-4-苄基-1,2-二甲基-2-三氟甲基咪唑啉(1a)作为不对称Aldol反应的催化剂时,能够以产率高达96%、最高ee值达到99%及dr值达到15∶1的效率高效构建一系列顺式1,2-二醇产物.同时,我们也初步探讨了氟-氢键在不对称催化反应中的作用.