NH3R++NHR2(R=H,CH3)体系质子传递反应的从头算研究

用从头计算法在HF/6-31G^*基组水平上研究了NH₄⁺+NH₃→NH₃+NH₄⁺,NH₄⁺+NH₂CH₃→NH₃+NH₃CH₃⁺,NH₄⁺+NH(CH₃)₂→NH₃+NH₂(CH₃)₂⁺以及NH₃CH₃⁺+NH₂CH₃→NH₂CH₃+NH₃CH₃⁺等4个体系的质子传递反应的机理.结果表明:(1)上述质子传递反应均具有双阱型的势能面,质子沿N(1)、N(2)连线直接传递;(2)质子受体分子中的甲基对质子传递起促进作用,而质子给体离子中的甲基则阻碍质子的传递。     

Kinetic mass spectrometric determination of the absolute rate coefficient for the reaction NH3 (ν = 0) + NH3 → NH4 + NH2 at thermal kinetic energies

The absolute thermal rate coefficient for the reaction NH₃⁺ + NH₃ → NH₄⁺ + NH₂ has been determined experimentally for the first time for NH₃⁺ (ν = 0) reactant ions. An increase in E_vib results in a decrease in the rate coefficient for proton transfer.     

直径大于2nm的(15, 15)碳纳米管的仿生生物改性及其脱盐行为的分子模拟

模仿水通道蛋白结构在直径大于2 nm的(15, 15)的碳纳米管内壁添加不同数量的―NH₃⁺和―COO^-,并结合端口改性建立连续的碳纳米管膜模型,利用分子动力学模拟方法研究了水以及Na⁺和Cl^-在碳纳米管中的通量、密度分布和离子进入碳纳米管的平均力势。结果表明,在200 MPa压力下,对碳纳米管进行内壁和端口改性可以在保持较高水通量基础上显著提高碳纳米管的截盐作用。当在(15, 15)碳纳米管内壁添加5对―COO^-和―NH₃⁺基团或内壁添加4对―COO^-和―NH₃⁺且端口添加1对时, Cl^-截盐率可达到100%, Na⁺的截盐率达到88%。改性(15, 15)碳纳米管的最小水通量仍是未改性(8, 8)碳纳米管的4.6倍。     

Ion chromatography of organic-rich natural waters from peatlands II. Na, NH4, K, Mg and Ca

Organic rich natural waters from peat bogs in continental (Switzerland) and maritime (Shetland Islands, Scotland) environments were analysed for Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ using ion chromatography. These cations were determined simultaneously in surface and pore water samples from the continental bogs using a 250-μl injection loop in an isocratic separation. Using this loop, detection limits of the order of 1 ng/g were achieved. An organics-removal cartridge (Dionex OnGuard P) was used to remove humic materials. Analyses of deionized water filtered through these cartridges showed acceptably low blank values (e.g., ca. 5 ng/g) and appeared to have no significant effect on the measured cation concentration. For the maritime bog waters, the low concentrations of NH₄⁺ (ca. 1 μg/g) compared with Na⁺ (ca. 100 μg/g) required improved peak separation. This was accomplished using a gradient separation beginning with 40 mM HCl—1 mM , -2,3-diaminopropionic acid monochloride (DAP) and switching to 40 mM HCl-12 mM DAP after 2 min. Using a 25 μl injection loop, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ were determined simultaneously in less than 25 min. In this instance, even with Na⁺/NH₄⁺ > 100, there was no interference from Na⁺ in the determination of NH₄⁺ (baseline separated).     

Vibrational dependence of the NH3 (v2)+NO and NO(v)+NH3 charge transfer cross sections

A tandem quadrupole mass spectrometer is used to study the charge transfer reactions NH₃⁺ + NO and NO⁺ + NH₃ over a collision energy range 1.5–13 eV. The vibrational state of the reagent ions is selected by resonance-enhanced multiphoton ionization. For the 0.9 eV exothermic process NH₃⁺ + NO → NH₃ + NO⁺ excitation of the v₂ umbrella bending mode (v₂ = 0–12) causes no marked change in the charge transfer cross section, while in the reverse process NO⁺ + NH₃ → NO + NH₃⁺ excitation of the NO⁺ vibration (v = 0–6) strongly enhanced the charge transfer cross section.     

氧化石墨阳离子交换容量测定过程中结构的变化

氧化石墨(GO)结构层上的碳羟基(―C―OH)和边缘羧基(―COOH)在水介质中发生质子化反应解离出的H+具有阳离子可交换性。实验采用甲醛缩合法测量了GO的阳离子交换容量(CEC),用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和X射线光电子能谱(XPS)分析测试手段对GO阳离子交换过程中间产物的结构变化进行了分析。结果表明,GO的CEC高达541.48 mmol/100 g。NH_4~+和Ca~(2+)交换后的GO,保持稳定的层状结构,c轴方向层间距分别增大了0.1499和0.2905 nm。NH_4+和Ca~(2+)主要以层间可交换阳离子形式存在于层间域中,并与水分子形成可交换水化阳离子层,部分以[NH_4(H_2O)_6]+和[Ca(H_2O)_6]_2+的形式存在于结构层的边缘附近,共同平衡结构层水解产生的负电荷。     

Molecular recognition of sulfonatocalixarene with organic cations at the self-assembled interface: a thermodynamic investigation

A microcalorimetric study on molecular recognition of p-sulfonatocalix[4]arene derivatives at selfassembled interface in comparison with in bulk water was performed,inspired by the dramatic change in physicochemical characteristics from bulk water to interface.A total of six cationic molecules were screened as model guests,including ammonium(NH_4~+),guanidinium(Gdm~+).N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane(DMDABCO~(2+)),tropylium(Tpm~+),N-methyl pyridinium(N-mPY*) and methyl viologen(MV~(2+)).The complexation with NH_4~+.Gdm~+ and DMDABCO2* is pronouncedly enhanced when the recognition process moved from bulk water to interface,whereas the complexation stabilities with Tpm~+,N-mPY~+ and MV2* increase slightly or even decrease to some extent.A more interesting phenomenon arises from the NH_4~+/Gdm~+ pair that the thermodynamic origin at interface differs definitely from each other although with similar association constants.The results were discussed in terms of differential driving forces,electrostatic,hydrogen bond as well as π-stacking interactions,originating from the unique physicochemical features of interfaces,mainly the polarity and dielectric constant.     

8-羟基喹啉合十钒酸盐的研究(Ⅲ)——锂、钾、铵盐的合成、鉴定与性质

在合成与研究钠盐的基础上^[1,2],我们又合成了锂、钾和铵盐,通过元素分析、分子量测定、质谱分析、X射线衍射、紫外和红外吸收光谱分析和热重分析确定了新化合物的组成与化学式并推测了化合物的结构式。     

SO_4~(2-)功能化处理对Fe_2O_3催化剂上氨选择性催化还原NO_x性能的促进机理研究

采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。     

A Fourier-transform ion-cyclotron-resonance study of the reactions of polycyclic aromatic hydrocarbon cations with molecules of interstellar interest

The reactivity of naphthalene and pyrene radical cations and their derivatives (C₁₀H_n⁺, n=6,7,8,9), C₁₆H_n (n=9,10,11) has been studied with molecules of interstellar interest in an ion cyclotron resonance apparatus. The radical cations C₁₀H₈⁺ and C₁₆H₁₀⁺ are unreactive with H₂,CO,H₂O and NH₃. Adduct formation is the only channel for almost all reactions of C₁₀H₇⁺ with these molecules. The implications of these results for the stability of polycyclic aromatic hydrocarbon (PAH) cations in the interstellar medium are briefly discussed. Exploratory studies of the ion chemistry of a larger PAH, coronene, have also been done.     

Ion-exchange properties of hypercrosslinked polystyrene impregnated with methyl orange

A novel bipolar stationary phase (HCPS–MO) was prepared by impregnation of hypercrosslinked polystyrene (HCPS) with methyl orange (MO; 4-dimethylamino-4′-sulfoazobenzene) and its ion-exchange properties were studied. Simultaneous separation of cations and anions on HCPS–MO is possible, although it behaves preferentially as a cation-exchanger. Unusual selectivity of HCPS-MO for alkali and alkaline-earth metal cations: Na⁺+K⁺+4⁺+ and Mg²⁺2+2+2+ was observed. The effect of temperature on retention of alkali and alkaline-earth metal cations was studied. Separation of Na⁺, K⁺, Rb⁺, NH₄⁺, Cs⁺, Mg²⁺ and Ca²⁺ on HCPS–MO with diluted cerium(III) nitrate solution as an eluent in single run is presented.     

新型Lewis固体酸Ce~(3+)-Ti~(4+)-SO_4~(2-)/MWCNTs制备及催化酯化反应合成生物柴油性能研究

采用高温浸渍法,通过Ce~(3+)、Ti~(4+)和浓硫酸磺化反应对多壁纳米碳管进行了改性处理,制备了Lewis酸型固体酸催化剂Ce~(3+)-Ti~(4+)-SO_4~(2-)/MWCNTs,并采用透射电镜、拉曼光谱、X射线光电子能谱、吡啶吸附红外光谱、X射线荧光光谱、X射线衍射光谱和NH_3程序升温脱附等多种测试技术对催化剂的物理化学特性和结构特征进行了表征。以Ce~(3+)-Ti~(4+)-SO_4~(2-)/MWCNTs为油酸与甲醇经酯化反应合成生物柴油的催化剂,对其催化性能进行了研究。结果表明,当醇油物质的量比为12∶1,催化剂与反应物质量比为1%,反应温度为65℃,反应5 h,油酸转化率为93.4%。催化剂Ce~(3+)-Ti~(4+)-SO_4~(2-)/MWCNTs在重复使用八次后,油酸的转化率仍为80.8%,由此表明其具有较高的催化活性和稳定性。高催化活性和稳定性是因为,纳米碳管的C 1s结合能较一般炭材料低,使得电子在其管状结构中的流动和逃逸非常容易,从而有助于负载于纳米碳管之上的活性组分之间发生强烈的相互作用,最终促使Ce~(3+)和Ti~(4+)分别与SO_4~(2-)形成稳定的配位键,增大催化剂的晶化程度,并使SO_4~(2-)与纳米碳管结合的更加牢固,增强了催化剂的稳定性,减少了催化剂中活性组分的流失。最后,由于SO_4~(2-)与Ce~(3+)的强相互作用,在不增加纳米碳管表面缺陷的情况下,改变了Ti~(4+)-SO_4~(2-)中表面原子的化学状态,使得S~(6+)离子和Ti~(4+)离子的吸电子能力增加,使催化剂以Lewis酸性活性位为主,避免了SO_4~(2-)/MWCNTs因为以Brnsted酸位为主,而在富含水的反应介质中,由于水合反应而降低其催化活性的现象发生。     

X-ray diffraction, Raman study and electrical properties of the new mixed compound [Rb0.44(NH4)0.56]2HgCl4 · H2O

Differential scanning calorimetry of [Rb_0.44(NH₄)_0.56]₂HgCl₄ · H₂O material showed three anomalies at 340, 355 and 424 K, respectively. The room temperature phase has space group Pcma (a=8.433(1) Å, b=9.1817(9) Å and c=11.954(1)). Phase II (T=350 K) is disordered and exhibits orthorhombic symmetry (a=8.456(13), b=9.202(9) and c=12.011(10) Å). Hydrogen bonding, the nature and the degree of structure (dis)order and the mechanisms of the transitions are discussed. The dielectric constant ^′ at different frequencies and temperature revealed a phase transition at T=340 K related to NH₄⁺ reorientation and H⁺ diffusion, and a characteristic increase above 355 K, which might be due to loss of water of crystallization. Transport properties in this compound appear to be due to an Rb⁺/NH₄⁺ and H⁺ ions hopping mechanism.     

Voltammetric determination of glucose based on reduction of copper(II)–glucose complex at lanthanum hydroxide nanowire modified carbon paste electrodes

A novel voltammetric method for the determination of β-d-glucose (GO) is proposed based on the reduction of Cu(II) ion in Cu(II)(NH₃)₄²⁺–GO complex at lanthanum(III) hydroxide nanowires (LNWs) modified carbon paste electrode (LNWs/CPE). In 0.1 mol L⁻¹ NH₃·H₂O–NH₄Cl (pH 9.8) buffer containing 5.0 × 10⁻⁵ mol L⁻¹ Cu(II) ion, the sensitive reduction peak of Cu(II)(NH₃)₄²⁺–GO complex was observed at −0.17 V (versus, SCE), which was mainly ascribed to both the increase of efficient electrode surface and the selective coordination of La(III) in LNW to GO. The increment of peak current obtained by deducting the reduction peak current of the Cu(II) ion from that of the Cu(II)(NH₃)₄²⁺–GO complex was rectilinear with GO concentration in the range of 8.0 × 10⁻⁷ to 2.0 × 10⁻⁵ mol L⁻¹, with a detection limit of 3.5 × 10⁻⁷ mol L⁻¹. A 500-fold of sucrose and amylam, 100-fold of ascorbic acid, 120-fold of uric acid as well as gluconic acid did not interfere with 1.0 × 10⁻⁵ mol L⁻¹ GO determination.     

阳离子交换型聚合物AQ薄膜修饰碳纤维电极及伏安行为

本文成功地制备了Eastman-AQ-55D聚合物修饰碳纤维电极,用循环伏安法探讨了一些实验参数的影响,并对Ru(NH₃)₆³⁺、甲基紫精进行了分析,结果表明,AQ-55D修饰的微电极稳定性好,修饰方法简单,灵敏度和选择性都有一定的提高,Ru(NH₃)₆³⁺、甲基紫精的峰电流与浓度在1.2×10^-6～1.2×10^-5mol/L、1.7×10^-6～1.4×10^-5mol/L范围内呈线性关系,其相关系数分别为0.999、0.998.利用此电极测定了几种离子在膜中的扩散系数.     

Novel iodoammonium cations: Synthesis and characterization of o-C6H4(NH2)2IX (X = I, AsF6, AlI4)

The new iodoammonium salts o-C₆H₄(NH₂)₂I⁺I⁻ (1) and o-C₆H₄(NH₂)₂I⁺ AsF₆⁻ (2) were prepared by reaction of o-phenylene diamine with I₂ or I₃⁺AsF₆⁻, respectively. Compound 1 reacts with AlI₃ yielding quantitatively the corresponding tetraiodoaluminate o-C₆H₄(NH₂)₂I⁺AlI₄⁻ (3). The species were characterized by chemical analysis, vibrational (IR and Raman) and temperature-dependent ¹H NMR spectropscopy. Direct evidence for a N---I bond was found in the Raman spectra of 1, 2 and 3 (ν(NI) = 599–600 cm⁻¹).     

气相中CrO2+和H2反应的理论研究

用密度泛函UB3LYP/6-311++G(3df, 3pdpd)//6-311G(2dd, p)方法计算研究了在二重态和四重态两个势能面上的气相反应：CrO₂⁺ + H₂→CrO⁺+ H₂O. 对影响反应机理和反应速率的势能面交叉进行了讨论, 并运用Hammond 假设和Yoshizawa 等的内禀反应坐标(IRC)单点垂直激发计算的方法找出了势能面交叉点(crossing point (CP)). 运用碎片分子轨道(fragment molecular orbital(FMO))理论, 对初始复合物2IM1和4IM1的轨道相关进行了分析, 解释了CrO₂⁺活化H—H σ键及H₂迁移的机理.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

Simultaneous determination of anions and cations by ion-exclusion chromatography–cation-exchange chromatography with tartaric acid/18-crown-6 as eluent

Ion-exclusion chromatography–cation-exchange chromatography was developed for the simultaneous separation of common inorganic anions and cations (Cl⁻, NO₃⁻ and SO₄²⁻; Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺) on a weakly acidic cation-exchange column by elution with weak acid. Generally, the resolution among these monovalent cations was only moderate, thereby hindering the determination of these analytes in natural-water samples. Therefore, 18-crown-6 was added to the eluent to improve the resolution. A good separation of these anions and cations on a weakly acidic cation-exchange column was achieved in 30 min by elution with 5 mM tartaric acid/6 mM 18-crown-6/methanol–water (7.5:92.5). The ion-exclusion chromatography–cation-exchange chromatography method developed here was successfully applied to the separation of major anions and cations in an environmental water sample.     

拉曼光谱法研究Na+, Mg2+//SO42-, Cl-, H2O四元体系中SO42-离子缔合结构特征及其变化规律

复杂水盐体系存在稳态和介稳固液相平衡以及复杂的成盐规律。为了解固液平衡状态下液相的结构特征,本文采用拉曼光谱技术并结合高斯-洛伦兹去卷积分峰拟合程序对Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系及其二元和三元子体系中ν₁-SO₄^2-的离子缔合结构特征进行了分析。研究结果表明:SO₄^2-在Na₂SO₄-H₂O体系存在自由态SO₄^2-和SO₄^2-离子簇两种结构,在MgSO₄-H₂O, MgSO₄-MgCl₂-H₂O及Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O等含镁体系中,还有Mg²⁺-H₂O-SO₄^2-和Mg²⁺-OSO₃^2-两种缔合结构。在二元和三元体系中ν₁-SO₄^2-的离子缔合结构以自由态SO₄^2-为主,随着SO₄^2-离子总浓度的变化,上述四种结构所占比例会发生规律性变化。Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系在NaCl减少及等温蒸发过程中,自由态SO₄^2-结构比例逐步降低, Mg²⁺和SO₄^2-相结合形成Mg²⁺-H₂O-SO₄^2-或Mg²⁺-OSO₃^2-结构的机会增多,在复盐区还会形成SO₄^2-离子簇结构。由此判断溶液结构的适应性变化是导致介稳现象的重要原因。进一步的相关分析表明:SO₄^2-的浓度和耶涅克指数J与ν₁-SO₄^2-峰的峰强度和峰面积存在正相关关系, Mg²⁺浓度是影响ν₁-SO₄^2-峰中四种缔合结构的比例发生变化的主要因素。