Vibrational phase relaxation of O–H stretch in bulk water: Role of large amplitude angular jumps and negative cross-correlations among the forces on the O–H bond

The ultrafast vibrational phase relaxation of O–H stretch in bulk water is investigated in molecular dynamics simulations. The dephasing time (T₂) of the O–H stretch in bulk water calculated from the frequency fluctuation time correlation function (C_ω(t)) is in the range of 70–80 femtosecond (fs), which is comparable to the characteristic timescale obtained from the vibrational echo peak shift measurements using infrared photon echo [W.P. de Boeij, M.S. Pshenichnikov, D.A. Wiersma, Ann. Rev. Phys. Chem. 49 (1998) 99]. The ultrafast decay of C_ω(t) is found to be responsible for the ultrashort T₂ in bulk water. Careful analysis reveals the following two interesting reasons for the ultrafast decay of C_ω(t). (A) The large amplitude angular jumps of water molecules (within 30–40 fs time duration) provide a large scale contribution to the mean square vibrational frequency fluctuation and gives rise to the rapid spectral diffusion on 100 fs time scale. (B) The projected force, due to all the atoms of the solvent molecules on the oxygen (F_O(t)) and hydrogen (F_H(t)) atom of the O–H bond exhibit a large negative cross-correlation (NCC). We further find that this NCC is partly responsible for a weak, non-Arrhenius temperature dependence of the dephasing rate.     

Comparison of the Electrochemical and Luminescence Properties of Two Carbazole‐Based Phosphine Oxide EuIII Complexes: Effect of Different Bipolar Ligand Structures

The photoluminescence (PL), electrochemical, and electroluminescence (EL) properties of Eu^III complexes, [Eu(cppo)₂(tta)₃] ( 1 ) and [Eu(cpo)₂(tta)₃] ( 2 ; TTA=2‐thenoyltrifluoroacetonate) with two carbazole‐based phosphine oxide ligands, 9‐[4‐(diphenylphosphinoyl)phenyl]‐9H‐carbazole (CPPO) and 9‐(diphenylphosphoryl)‐9H‐carbazole (CPO), which have different bipolar structures, donor–π‐spacer–acceptor (D–π–A) or donor–acceptor (D–A) systems respectively, are investigated. The CPPO with D–π–A architecture has improved PL properties, such as higher PL efficiency and more efficient intramolecular energy transfer, than CPO with the D–A architecture. Gaussian simulation proved the bipolar structures and the double‐carrier injection ability of the ligands. The carrier injection abilities of triphenylphosphine oxide, CPO, and CPPO are gradually improved. Notably, the Gaussian and electrochemical investigations indicate that before and after coordination, the carrier injection ability of the ligands show remarkable changes because of the particularity of the D‐π–A and D–A systems. The electrochemical studies demonstrate that coordination induces the electron cloud to migrate from electron‐rich carbazole to electron‐poor diphenylphosphine oxide, and consequently increases the electron‐cloud density on diphenylphosphine oxide, which weakens its ability for electron affinity and induces the elevation of LUMO energy levels of the complexes. Significantly, the π‐spacer in the D–π–A system exhibits a distinct buffer effect on the variation of the electron‐cloud density distribution of the ligand, which is absent in the D–A system. It is demonstrated that the adaptability of the D–π–A systems, especially for coordination, is stronger than that of D–A systems, which facilitates the modification of the complexes by designing multifunctional ligands purposefully. 1 seems favorable as the most efficient electroluminescent Eu^III complex with greater brightness, higher efficiencies, and more stable EL spectra than 2 . These investigations demonstrate that the phosphine oxide ligands with D–π–A architecture are more appropriate than those with D–A architecture to achieve multifunctional electroluminescent Eu^III complexes.     

辅酶NAD(P)H模型分子的研究进展

辅酶NAD(P)H在生物体内起着重要的调节作用, 已引起了有机化学工作者极大的兴趣, 尤其是在还原反应的立体选择性上, 人们已经开展了大量的研究工作. 讨论了NAD(P)H模型分子进行立体专一性还原反应的影响因素, 并对NAD(P)H模型分子的研究工作做了总结.     

制备方法对Ni2P/SiO2催化剂结构及萘加氢性能的影响

采用程序升温还原法和次磷酸盐歧化法制备了Ni_2P/SiO_2催化剂,结合现代仪器分析表征技术,研究了制备方法对Ni_2P/SiO_2催化剂结构和萘加氢性能的影响。结果表明,两种方法均可制备出仅含Ni_2P活性相的Ni_2P/SiO_2催化剂,在反应温度340℃、氢气压力4 MPa、空速为20.8 h~(-1)下,程序升温还原法制备的Ni_2P/SiO_2催化剂表现出更高的萘加氢活性,这主要是因为程序还原法制备的Ni_2P/SiO_2催化剂中有更多Ni_2P物种生成,提供了较多的活性位点(CO吸附量21.6μmol/g);且催化剂表面弱酸位点多,有利于芳烃吸附。当选用程序升温还原法制备Ni_2P/SiO_2催化剂时,在保证生成纯相Ni_2P的前提下,较低的Ni/P比更有利于合成高加氢活性的Ni_2P/SiO_2催化剂。     

深共熔溶剂-高效液相色谱联用提取测定环境水样中的3种药品和个人护理品

建立了深共熔溶剂-高效液相色谱联用提取测定环境水样中3种药品和个人护理品(PPCPs)的方法。通过优化前处理条件,3种PPCPs(氯霉素、氯苯甘醚和萘普生)利用氯化胆碱-乙二醇深共熔溶剂为提取剂,经超声功率120 W下超声波提取5 min,离心转速9000 r/min下离心10 min富集提取。采用外标法定量分析,在5.0~200.0 mg/L范围内线性关系良好,相关系数r≥0.9998。3种环境水样中PPCPs的回收率为81.4%~94.8%,相对标准偏差分别为1.5%,0.4%和0.3%。氯霉素、氯苯甘醚和萘普生的方法检出限(LODs)分别为0.9,3.3,1.6 mg/L,定量限(LOQs)分别为3.1,12.2,5.0 mg/L。方法能够满足环境水样中3种PPCPs的检测需求。     

深共融溶剂中合成2,4-二取代喹啉衍生物

在氯化胆碱和氯化锌组成的深共融溶剂中,以2-氨基苯乙酮和芳香炔烃为原料,通过环化偶联反应,合成了一系列2,4-二取代喹啉衍生物;当n(氯化胆碱)∶n(氯化锌)=1∶2,反应温度为80℃时,反应3 h即获得高达98%的产率.该方法无需额外添加催化剂,而且反应条件温和、操作简单、底物范围较广泛.     

细胞色素P450酶催化的烷烃选择性羟化

碳氢键选择氧化是合成化学领域的重要课题,其中烷烃选择性羟化反应更是面临着化学选择性、区域选择性和立体选择性等多重挑战.细胞色素P450酶广泛分布于动植物和微生物体内,是公认的多功能生物氧化催化剂. P450酶对惰性C—H键的选择性氧化具有独特优势,在催化烷烃选择性羟化反应方面拥有巨大潜力.本综述简述了P450单加氧酶及其催化烷烃选择性羟化的反应机理,梳理了来自CYP153家族、CYP52家族和其他家族的天然P450酶催化各类烷烃底物的氧化反应和选择性,讨论了理性设计和定向进化策略在开发烷烃羟化P450突变酶过程中的经典案例,介绍了底物工程、诱饵分子、双功能小分子协同催化等几种化学活化P450酶的策略及其在烷烃羟化上的应用,探讨了P450酶在烷烃选择性羟化方面所面临的挑战和解决途径,并展望了其应用前景.     

In vitro anticancer activity and biologically relevant metabolization of organometallic ruthenium complexes with carbohydrate-based ligands

The synthesis and in vitro anticancer activity of dihalogenido(eta6-p-cymene)(3,5,6-bicyclophosphite-alpha-D-glucofuranoside)ruthenium(II) complexes are described. The compounds were characterized by NMR spectroscopy and ESI mass spectrometry, and the molecular structures of dichlorido-, dibromido- and diiodido(eta6-p-cymene)(3,5,6-bicyclophosphite-1,2-O-isopropylidene-alpha-D-glucofuranoside)ruthenium(II) were determined by X-ray diffraction analysis. The complexes were shown to undergo aquation of the first halido ligand in aqueous solution, followed by hydrolysis of a P--O bond of the phosphite ligand, and finally formation of dinuclear species. The hydrolysis mechanism was confirmed by DFT calculations. The aquation of the complexes was markedly suppressed in 100 mM NaCl solution, and notably only very slow hydrolysis of the P--O bond was observed. The complexes showed affinity towards albumin and transferrin and monoadduct formation with 9-ethylguanine. In vitro studies revealed that the 3,5,6-bicyclophosphite-1,2-O-cyclohexylidene-alpha-D-glucofuranoside complex is the most cytotoxic compound in human cancer cell lines (IC50 values from 30 to 300 microM depending on the cell line).     

Mechanisms and Kinetics of Reactions of the O（^1D,^3P） ＋ CF3Cl System

In the stratosphere,CF3Cl(CFC13)can either photodecompose or react directly with atomic oxygen to generate ozone-depleting agents such as Cl and ClO in the gas phase[1—3].Since the1970s,attention has been focused on the effects of these compounds on the …     

Metal-free and base-free decarboxylation of substituted cinnamic acids in a deep eutectic solvent

Abstract

A metal-free and base-free strategy was developed in DES to synthesize styrenes for the first time by decarboxylation of cinnamic acid derivatives, which provided a renewable and cost efficiently protocol to access various styrenes including those with functional groups such as 4-vinylphenol and 1-chloro-4-vinylbenzene.