依来铬蓝黑B的电还原

本文使用普通极谱、脉冲极谱、循环伏安法研究了依来铬蓝黑B的电还原。在pH=2-12间,依来铬蓝黑B可产生一个受扩散控制的不可逆还原波。随pH增加,在pH6附近电子数由2增到4(对数分析),E_1/2线性负移, ∂E_1/2/∂pH=-65mV。根据实验结果,提出一带有不稳定中间体的岐化反应的电还原机理。由此,解释了电子数随pH变化的原因。     

溴甲酚紫的极谱研究

溴甲酚紫是一应用广泛的有机式剂^[1-4]。关于羟基三苯甲烷类染料的极谱研究报导不多^[5]。Ghoneim^[6]曾报导溴甲酚紫在pH<7时产生一个2电子还原波,当pH大于10时,可产生两个1电子还原波。Goel^[7]只研究了第一波的还原机理。本文用普通极谱、脉冲极谱、循环伏安等方法较详细地研究了溴甲酚紫的电还原。提出一电还原机理,解释了半波电位随pH变化的特殊规律。     

CF-2沸石的表面酸性及催化性能

CF-2是一种新型的高硅沸石。1981年我们实验室首先在二乙醇胺-甘油-Na₂O-SiO₂-Al₂O₃-H₂O体系中制备成功^[1],以后才见到关于Theta-1^[2],ISI-1^[3],KZ-2^[4],NO-10^[5]和ZSM-22^[6]沸石的报道。     

利培酮的电化学行为及应用研究

采用循环伏安法、线性扫描伏安法、常规脉冲伏安法和恒电位电解法等电化学手段, 详细研究了利培酮在pH 7.07～10.32 B-R缓冲溶液和0.2 mol•L^－1 NaOH溶液中的电化学行为. 研究表明: 在pH 7.07～10.07 B-R缓冲溶液中, 利培酮产生的P₁波为催化氢波. 在pH＝10.32 B-R缓冲溶液中, 利培酮可以产生P₂和P₃两个波. 其中, P₂波为不可逆的单电子还原波, P₃波可以分裂成两个波P_3a和P_3b. P_3a波为P₂波的进一步单电子还原, 而P_3b波则属于催化氢波. 在0.2 mol•L^－1 NaOH溶液中, 利培酮产生的P₄波是一个两电子的不可逆还原波. 另外, 根据P₁波的一阶导数峰电流与利培酮浓度在1.6×10^－5～2.0×10^－6 mol•L^－1 (r＝0.9950)间的线性关系, 建立了利培酮片剂中利培酮含量的测定新方法. 新方法的检出限为1.0×10^－6 mol•L^－1, 回收率在105%～102%之间, 相对标准偏差为0.84%.     

开系下的极限环线

B-Z反应较早是用分光光度计观察颜色的周期性变化^[1]。Field采用电动势测定E～t或C～t图^[2]。最近大量工作证明上述二种方法仍然是很重要的。B-Z反应是属于非平衡态中存在自组织现象的一个实例,三分子模型^[3]和低浓度三分子模型^[4]至今尚未找到实例,因而Oregonator成了颇为重要的一个实际模型^[5]。原则上直接测到相平面上lg[Br^-]与lg[Ce⁴⁺]的变化。给验证理论提供了一种可靠性。     

静电纺丝法制备NiO纳米纤维及其表征

纳米级NiO因具有优良的催化和热敏等性能而被广泛用于催化剂^[1]、电池电极^[2,3]、光电转化材料^[4～6]、电化学电容器^[7～8]等诸多方面.迄今,已成功地制备出N iO的纳米颗粒^[9]、纳米线^[10]及纳米薄膜^[11],但是对于具有准一维结构的NiO纳米纤维的制备及性能研究尚未见报道.     

零电流示波电位滴定盐酸异丙嗪

盐酸异丙嗪是一种较重要的抗组胺药,现行的分析标准为非水滴定法^[1],此外尚有分光光度法^[2]、伏安法^[3]、电极法^[4]、液相色谱法^[5]和流动注射分析法^[6]等。本文将高鸿提出的零电流示波电位滴定法^[7]中的铂片电极修饰一层含四苯基硼酸-异丙嗪电活性物质的PVC膜,使电极对异丙嗪产生响应,可用于四苯基硼酸钠直接滴定异丙嗪的终点指示。     

微波消解-微波等离子体炬原子发射光谱法测定无铅汽油中痕量铅的研究

四乙基铅作为一种良好的抗爆添加剂,曾广泛用于汽油生产中,但由于四乙基铅有很强的毒性,目前国际上已停止生产和使用车用含铅汽油,因此在生产车用无铅汽油时严格控制和准确测定铅的含量十分必要.迄今,测定汽油中铅含量的常用方法是铬酸盐容量法^[1]、一氯化碘法^[2]、X射线光谱法^[3]、分光光度法^[4,5]、原子吸收光谱法^[6]和等离子体光谱法^[7].这些方法或操作烦琐,测定时间较长^[4],或灵敏度低^[1～3],或测定误差较大,且在测试中需使用毒性较大的四乙基铅^[5],或所需的氯化甲基三辛基铵不易购买^[6],或处理过程繁琐,且仪器设备昂贵^[7].因此,建立一种简便、快速、灵敏、准确和无毒副作用的测定无铅汽油中痕量铅的方法已显得十分迫切.近年来发展的微波等离子体炬原子发射光谱法^[8]已有商品化仪器问世^[9].本文利用微波等离子体炬原子发射光谱仪研究了无铅汽油中痕量铅的测定方法,并提出用微波消解法预处理无铅汽油样品,将微波消解技术与微波等离子体炬原子发射光谱法相结合,建立了简便、快速、灵敏、准确和无污染的测定无铅汽油中痕量铅的新方法.     

二苯并噻吩及其氧化物与离子液体相互作用的理论研究

采用密度泛函理论方法比较了DBT/DBTO₂和[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-的相互作用。对最稳定的[BMIM]⁺[PF₆]^-、[BMIM]⁺[PF₆]^--DBT、[BMIM]⁺[PF₆]^--DBTO₂、[BMIM]⁺[BF₄]^-、[BMIM]⁺[BF₄]^--DBT、[BMIM]⁺[BF₄]^--DBTO₂进行了NBO和AIM分析。结果表明,DBT和[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-中的咪唑环彼此相互平行,NBO和AIM分析表明它们之间发生了π-π相互作用。H1'和H9'形成的F…H氢键有利于π-π堆积作用的形成。DBTO₂倾向于趋近C2-H2和甲基基团形成O…H相互作用;DBTO₂优先吸附在[BMIM]⁺[PF₆]^-/[BMIM]⁺[BF₄]^-。在模拟油中,[BMIM]⁺[PF₆]^-和[BMIM]⁺[BF₄]^-离子液体对DBTO₂的萃取能力大于DBT,其原因是可能是DBTO₂具有较大的极性和O…H与F…H的氢键作用。     

高等植物叶绿体中光诱导生成NO的ESR证据

NO分子在生物细胞体系中是一个十分重要的信使分子,它具有调节细胞凋亡、松弛平滑肌、抑制血小板聚集与黏附、抑制病原体和肿瘤生长等多种生理功能^[1,2],因而备受生物学家的关注.众所周知,动物细胞中NO主要来源于一氧化氮合酶(NOS)的表达^[3];然而,直到最近才有研究证明植物细胞中存在参与调节植物生长和激素信号转导的NOS基因^[4].一般认为植物细胞中NO主要来源于硝酸盐还原酶(NR)^[5].我们曾在高等植物光系统中研究发现了与电子传递相关的活性氧生成机制^[6～8],但其间是否也会通过光诱导电子传递产生NO尚不清楚.Kozlov等^[9]曾报道在小鼠线粒体内存在与亚硝酸盐还原酶功能类似的还原型烟酰胺腺嘌呤二核苷酸(NADH)诱导电子传递生成NO的反应,本文采用电子自旋共振(ESR)方法验证了高等植物叶绿体内光诱导电子传递可产生NO的设想.     

Transition state analysis of acid-catalyzed dAMP hydrolysis

Multiple kinetic isotope effects (KIEs) on deoxyadenosine monophosphate (dAMP) hydrolysis in 0.1 M HCl were used to determine the transition state (TS) structure and probe its intrinsic reactivity. The experimental KIEs revealed a stepwise (SN1) mechanism, with a discrete oxacarbenium ion intermediate. This is the first direct evidence for the deoxyribosyl oxacarbenium ion in solution. In 50% methanol/0.1 M HCl the products were deoxyribose 5-phosphate (dRMP) and alpha- and beta-methyl dRMP. The alpha-Me-dRMP/beta-Me-dRMP ratio was 8.5:1. Assuming that a free oxacarbenium ion is equally susceptible to nucleophilic attack on either face, this indicated that approximately 20% proceeded through a solvent-separated ion pair complex, or free oxacarbenium ion, a DN+AN mechanism, while approximately 80% of the reaction proceeded through a contact ion pair complex. The oxacarbenium ion lifetime was estimated at 10(-11)-10(-10) s. Computational transition states were found for ANDN, DN*AN, DN*AN, and DN+AN mechanisms using hybrid density functional theory calculations. After taking into account 20% of DN+AN, there was an excellent match of calculated to experimental KIEs for 80% of the reaction having a DN*AN mechanism. That is, C-N bond cleavage is reversible, with dAMP and the {oxacarbenium ion*adenine} complex in equilibrium. The first irreversible step is water attack on the oxacarbenium ion. The calculated 1'-14C KIE for a stepwise mechanism with irreversible C-N bond cleavage (DN*AN) was 1.052, in the range previously associated only with ANDN transition states, and close to the calculated ANDN value, 1.059. The 1'-14C KIE was strongly dependent on the adenine protonation state.     

XAFS study of the complex of an acetylacetonate-based ligand and copper ion

An X-ray absorption fine structure (XAFS) study has been conducted to reveal the local structure and chemical state of the copper in the complex of an acetylacetonate-based ligand (L1) and copper ion in acetonitrile solution. The copper ion in the complex was found to be divalent from the Cu K-edge X-ray absorption near-edge structure (XANES) spectrum. The FEFF (ab initio multiple scattering calculations of XAFS) were performed with the model compounds, whose structures were optimized by using MOPAC program with AM1 Hamiltonian. The comparative study of the experimental XAFS spectra and theoretical calculations from FEFF gave the perspectives for clarifying the coordination structure of the complex of L1 and copper ion.     

Electronic structure and normal vibrations of the 1-ethyl-3-methylimidazolium ethyl sulfate ion pair

Electronic and structural properties of the ion pair 1-ethyl-3-methylimidazolium ethyl sulfate are studied using density functional methods. Three locally stable conformers of the ion pair complex are considered to analyze molecular interactions between its cation and anion. Manifestations of these interactions in the vibrational spectra are discussed and compared with experimental IR and Raman spectroscopy data. NBO analysis and difference electron density coupled with molecular electron density topography are used to interpret the frequency shifts of the normal vibrations of the ion pair, compared to the free anion and cation. Excitation energies of low-lying singlet excited states of the conformers are also studied. The density functional theory results are found to be in a reasonable agreement with experimental UV/vis absorption spectra.     

Synthesis and characterization of a metal complex containing naringin and Cu, and its antioxidant, antimicrobial, antiinflammatory and tumor cell cytotoxicity

The antioxidant activity of flavonoids is believed to increase when they are coordinated with transition metal ions. However, the literature on this subject is contradictory and the outcome seems to largely depend on the experimental conditions. In order to understand the contribution of the metal coordination and the type of interaction between a flavonoid and the metal ion, in this study a new metal complex of Cu (II) with naringin was synthesized and characterized by FT-IR, UV-VIS, mass spectrometry (ESI-MS/MS), elemental analysis and 1H-NMR. The results of these analyses indicate that the complex has a Cu (II) ion coordinated via positions 4 and 5 of the flavonoid. The antioxidant, anti-inflammatory and antimicrobial activities of this complex were studied and compared with the activity of free naringin. The Naringin-Cu (II) complex 1 showed higher antioxidant, anti-inflammatory and tumor cell cytotoxicity activities than free naringin without reducing cell viability.     

Absorption spectra of caffeic acid, caffeate and their 1:1 complex with Al(III): density functional theory and time-dependent density functional theory investigations

The UV-visible absorption spectra of caffeic acid, caffeate and of the predominant complex obtained in the presence of aluminum ion (1:1 stoichiometry) have been simulated by using the time-dependent density functional theory (TD-DFT) technique, taking into account solvent effects. Whereas the use of the B3LYP hybrid XC functional with the 6-31+G(d,p) basis set allows us to reproduce fairly well the essential features of the experimental spectra of caffeic acid and caffeate, it is necessary to introduce an effective core potential to properly describe the aluminum ion and its environment and to obtain a good agreement between theoretical and experimental spectra of the 1:1 complex. The ligand presents two potential complexing sites in competition. The results of our calculations show that the aluminum ion coordinates preferentially at the level of the catecholate group, and the [Al(H(2)O)(4)(CA)], [Al(H(2)O)(3)(OH)(CA)](-) and [Al(H(2)O)(4)(HCA)](+) complexed forms could coexist in aqueous solution at pH = 5.     

Dehydrotropylium-Co2(CO)6 ion: generation, reactivity and evaluation of cation stability

The dehydrotropylium–Co₂(CO)₆ ion was generated by the action of HBF₄ or BF₃ ? OEt₂ on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The reaction of the cycloheptadienynol complex via the dehydrotropylium–Co₂(CO)₆ ion with several nucleophiles results in substitution reactions with reactive nucleophiles (N>1) under normal conditions, and a radical dimerisation reaction in the presence of less reactive nucleophiles. Competitive reactions of the cycloheptadienynol complex with an acyclic trienynol complex show no preference for generation of the dehydrotropylium–Co₂(CO)₆ ion over an acyclic cation. DFT studies on the dehydrotropylium–Co₂(CO)₆ ion, specifically evaluation of its harmonic oscillator model of aromaticity (HOMA) value (+0.95), its homodesmotic‐reaction‐based stabilisation energy (≈2.8 kcal mol^?1) and its NICS(1) value (?2.9), taken together with the experimental studies suggest that the dehydrotropylium–Co₂(CO)₆ ion is weakly aromatic.     

ATP与Mg2+、Ca2+生成配合物反应的热力学研究

The formation constant (K) and thermodynamic parameters (ΔC.ΔH.ΔS) in reactions in which complexes of adenosine triphosphate with magnesium ion and calcium ion are formed have been obtained by a microcalorimetric method. All experimentes were made at 30 ℃, pH=8.0 and at ionic strength μ=0.2 mol L~(-1). Measured experimental values indicate that complex formation reactions are driven by the entropic factor.     

镉试剂与银显色反应体系中乙醇的超分子作用及其应用

金属离子、有机溶剂与偶氮类试剂之间存在一定的超分子作用,有机溶剂及缓冲介质的浓度对显色反应的灵敏度有很大的影响。据此建立了乙醇存在下的镉试剂与银的显色反应新体系。在pH9.5的硼砂-NaOH缓冲介质中,表面活性剂吐温-80的存在下,镉试剂与银反应生成2:1稳定配合物。络合物的λmax=518nm,摩尔吸光系数7.01×104L.mol-1.cm-1,银质量浓度0～1.0μg/mL范围内符合比尔定律。方法用于环境水样中银的测定,取得满意效果。     

Magnetic Properties of a Terbium–[1]Ferrocenophane Complex: Analogies between Lanthanide–Ferrocenophane and Lanthanide–Bis‐phthalocyanine Complexes

A rare example of an organometallic terbium single‐ion magnet is reported. A Tb³⁺–[1]ferrocenophane complex displays a larger barrier to magnetization reversal than its isostructural Dy³⁺ analogue, which is reminiscent of trends observed for lanthanide–bis‐phthalocyanine complexes. Detailed ab initio calculations support the experimental observations and suggest a significantly larger ground‐state stabilization for the non‐Kramers ion Tb³⁺ in the Tb complex than for the Kramers‐ion Dy³⁺ in the Dy complex.     

Ion chemistry of anti-o,o dibenzene

The ion chemistry of anti-o,o'-dibenzene (1) was examined in the gaseous and the condensed phase. From a series of comparative ion cyclotron resonance (ICR) mass spectrometry experiments which involved the interaction of Cu+ with 1, benzene, or mixtures of both, it was demonstrated that 1 can be brought into the gas phase as an intact molecule under the experimental conditions employed. The molecular ions, formally 1*+ and 1*- , were investigated with a four-sector mass spectrometer in metastable-ion decay, collisional activation, charge reversal, and neutralization-reionization experiments. Surprisingly, the expected retrocyclization to yield two benzene molecules was not dominant for the long-lived molecular ions; however, other fragmentations, such as methyl and hydrogen losses, prevailed. In contrast, matrix ionization of 1 in freon (77 K) by gamma-radiation or in argon (12 K) by X-irradiation leads to quantitative retrocyclization to the cationic dimer of benzene, 2*+. Theoretical modeling of the potential-energy surface for the retrocyclization shows that only a small, if any, activation barrier is to be expected for this process. In another series of experiments, metal complexes of 1 were investigated. 1/Cr+ was formed in the ion source and examined by metastable ion decay and collisional activation experiments, which revealed predominant losses of neutral benzene. Nevertheless, comparison with the bis-ligated [(C6H6)2Cr]+ complex provided evidence for the existence of an intact 1/Cr+ under these experimental conditions. No evidence for the existence of 1/Fe+ was obtained, which suggests that iron mediates the rapid retrocyclization of 1/Fe+ into the bis-ligated benzene complex [(C6H6)2Fe]+.