从头算量子化学计算方法对高氯酸镁溶液中存在的离子缔合物种及缔合过程的研究

使用了量子化学计算方法在HF/6-31＋G*水平下对高氯酸镁溶液中的高氯酸根水合, 可能存在的离子缔合物种以及离子缔合过程进行了研究. 高氯酸根的第一水合层至少需要6个水分子才能填满, 在水合数6以下时, 每增加一个水分子可以造成v₁-频率1.7 cm^－1的蓝移. 高氯酸根与第一个无水镁离子结合可以造成较大的红移, 与第二个和第三个镁离子结合后, 可使v₁-频率连续的反向蓝移, 这种变化与镁离子的极化作用相关. 高氯酸根与水合镁离子可形成水合的缔合物种, 包括溶剂共享离子对、接触离子对、溶剂共享型三离子团簇和接触型三离子团簇, 其中溶剂共享型离子对和含有两个高氯酸根和一个镁离子的三离子团簇, 可对v₁-频率造成较小的蓝移, 与实验的拉曼光谱符合较好. 高氯酸镁在溶液浓度升高时发生的离子缔合过程被推测为: 自由水合离子→溶剂共享型离子对→含有两个高氯酸根的溶剂共享型三离子团簇→六水合高氯酸镁晶体, 这一过程与硫酸镁有较大不同而与硝酸镁接近.     

金属离子Na+ , Li+ , Mg2+与硫酸根离子形成的无水缔合物种的从头算量子化学研究

计算并讨论了Na+, Li+和Mg2+ 3种离子与SO42-离子形成离子缔合物的结构以及阳离子的结合对ν1-SO42-频率的影响. 结果表明, 在缔合物结构方面, 阳离子数目越少, 离子间斥力越小, 越容易形成阳离子与硫酸根间距离更短, 结合更紧密的双齿缔合结构; 而当阳离子数目增加时, 特别是当具有2个正电荷的Mg2+离子数目较多时, 离子间的斥力使多离子团簇不稳定, 易形成阳离子与硫酸根间距离更长的单齿缔合结构. 有2种阳离子作用可影响ν1-SO42-频率, 一种是极化作用, 可使ν1-SO42-频率红移; 另一种是成键作用, 可使ν1-SO42-频率蓝移. 当金属离子数目≤2时, 阳离子的极化作用占主导地位, 第一个阳离子能使ν1-SO42-频率发生红移, 而当阳离子数目增多时, 不同方向结合的其它阳离子可以削弱第一个阳离子的极化作用, 因此导致多离子团簇中ν1-SO42-频率红移的减小. 当阳离子数目≥3时, 极化作用影响减小, 成键作用占据主导地位, 导致ν1-SO42-频率更大蓝移的单齿缔合结构取代双齿结构, 并使多离子团簇中的ν1-SO42-频率继续发生蓝移.     

从头算量子化学计算方法对硝酸锂溶液中存在的离子缔合物种及缔合过程的研究

利用量子化学计算方法,在HF/6-31+G*水平下对硝酸锂溶液中可能存在的离子缔合物种,以及当浓度升高时溶液中发生的离子缔合过程进行了研究.硝酸根与水合锂离子可形成溶剂共享离子对、接触离子对、三离子及多离子团簇等离子缔合物种,在所有的缔合物种中,锂离子大都以形成四配位四面体结构为主,只有少数情况下存在能量较高的五配位结构.以上3种水合离子缔合物种中的v1(NO3-)频率与水合硝酸根中的参比值相比,分别发生1.4,-6.9以及大于2.8 cm-1的蓝移,考虑到实验光谱中v1(NO3-)带是持续蓝移的.推测的硝酸锂溶液在浓度升高时发生离子缔合的过程可简略表示为"自由水合离子→溶剂共享型离子对→阳-阴-阳型三离子团簇→链状多离子团簇→网状多离子团簇→晶体".这个过程与在硝酸镁和硝酸钠中的缔合过程是相似的.     

MgH^+,Mg2H^+量子化学从头计算的研究

用量子化学自洽场分子轨道从头计算方法,采用STO-3G基组计算了MgH~+,Mg_2H~+离子的位能曲线与位能面;给出电子波函数与电子集居数;得到MgH~+的平衡构型键长γ_(Mg-H)1.60A.Mg_2H~+的平衡构型有C_(∞v)与D_(∞h)两类,前者为[Mg—Mg—H]~+,键长γ_(Mg-Mg)2.41,γ_(Mg-H)1.63A;后者为[Mg—H—Mg]~+,γ_(Mg-H)1.73A.前者的总能量比后者低50kcal/mol.还讨论了它们的稳定性.MgH~+的键长计算结果和实测值较吻合,Mg_2H~+的平衡构型计算结果支持了Porter从热力学研究提出的假设.     

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。     

Ab initio Investigation on Unhydrated Ion-associated Species Between Na+, Li+, Mg2+ and SO2-4 Ions

计算并讨论了Na+,Li+和Mg2+3种离子与SO2-4离子形成离子缔合物的结构以及阳离子的结合对v1-SO2-4频率的影响.结果表明,在缔合物结构方面,阳离子数目越少,离子间斥力越小,越容易形成阳离子与硫酸根间距离更短、结合更紧密的双齿缔合结构;而当阳离子数目增加时,特别是当具有2个正电荷的Mg2+离子数目较多时,离子间的斥力使多离子团簇不稳定,易形成阳离子与硫酸根间距离更长的单齿缔合结构.有2种阳离子作用可影响v1 -SO2-4频率,一种是极化作用,可使v1-SO2-4频率红移;另一种是成键作用,可使v1 -SO2-4频率蓝移.当金属离子数目≤2时,阳离子的极化作用占主导地位,第一个阳离子能使v1-SO2-4频率发生红移,而当阳离子数目增多时,不同方向结合的其它阳离子可以削弱第一个阳离子的极化作用,因此导致多离子团簇中v1-SO2-4频率红移的减小.当阳离子数目≥3时,极化作用影响减小,成键作用占据主导地位,导致v1 -SO2-4频率更大蓝移的单齿缔合结构取代双齿结构,并使多离子团簇中的v1-SO2-4频率继续发生蓝移.     

4-甲醛-1-甲基-1-苯基环己硅烷的从头算研究

运用从头计算法，在HF／6－31G水平上，求得4-甲醛-1-甲基-1-苯基环己硅烷的全优化几何构型和电子结构。将从头算结果与经典电子理论以及AM1和PM3半经验计算结果进行了比较和评估。     

离子色谱法测定啤酒中的F^-、C1^-、SO4^2-、NO3^-和PO4^3-

建立了以AS11—HC型阴离子交换柱分离、NaOH溶液为淋洗液、甲醇为有机改进剂、化学抑制电导检测测定啤酒中的F^-、C1^-、SO4^2-、NO3^-和PO4^3-?A的离子色谱方法。各被测离子的线性关系良好，相关系数为0．9778～0．9991．测定结果的相对标准偏差为0．02％～3．60％，样品回收率为97．88％～103．80％。     

铕缔合物(C34H54N2O10)［Eu(NO3)5］的合成和晶体结构

在乙腈溶液中合成了标题化合物,（C(34)H(54)N2O10）[Eu（NO3）5]（C(34)H(52)H2O(10)＝1,2-二（2,3-苯并-10－氮杂-15-冠-5－N-乙氧基）乙烷）并用X射线衍射分析测定了它的结构。该晶体属单斜晶系,P21／c空间群,晶胞参数：a＝1．1801（2）nm,b＝2．3560（5）nm,c＝1．7025（3）nm,β=99．67（3）°。V＝4．6662（16）nm',Z＝4,Dc=1．581g·cm(－3)。Eu(3 )与5个NO3的10个O配位。大环化合物上无论是O还是N都未与Eu(3 )成键。     

1-乙基-3-甲基咪唑四氟硼酸盐离子液体的量子化学研究

The results of the quantum chemistry study of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM+BF4-) were reported. The ab initio method and density functional theory (B3LYP method) was used to optimize the stable structure of the gas phase ion pair at the level of 6-311++G** basis set, respectively. An IR spectra for EMIM+BF4- were obtained through the vibrational analysis. The changes of atomic charge assignments have been investigated using the Natural Bond Orbital method. The computational results show that there exist hydrogen bonds and other weak interactions between the cation and the anion. Using counterpoise correction method to estimate the basis set superposition error, the interaction energy between the cation and anion is 346.78 kJ/mol.     

NO2-对乳酸-丙酮-BrO3--Mn2+-H2SO4化学振荡反应的影响

研究NO₂^-对乳酸-丙酮-BrO₃^--Mn²⁺-H₂SO₄化学振荡反应的影响时发现,NO₂^-对振荡反应的诱导期t_in、周期t_p有显著的影响。NO₂^-的浓度C_NO2^-与诱导期倒数的对数ln(1/t_in)、NO₂^-浓度的对数lnC_NO2^-与周期的对数lnt_p均有良好的线性关系,线性范围为7.46×10^-5～2.99×10^-3mol·L^-1。在此浓度范围内,NO₃^-无影响,是一重现性好,灵敏度高,操作简单的NO₂^-动力学分析测试体系。获得诱导期、周期的表观活化参数E_in、E_p分别为56.82kJ·mol^-1、64.51kJ·mol^-1。结合被动采样法,测得室外大气中NO₂日平均浓度值为1.59×10^-9mol·L^-1,最后对NO₂^-共存时的振荡反应诱导期机理进行了初步探讨。     

Ab initio MO calculations on the stable conformations and their binding energies of the ion-molecule complexes: Ion = H+, Li+, Na+, K+ Be2+, and molecule = CO and N2

The most stable conformation of ion-molecule complexes involving a CO molecule were surveyed by the use of Hartree-Fock (HF) MO and third-order Moller-Plesset perturbation (MP3) methods with a 6–31G* basis set ion = H⁺, Li⁺, Na⁺, K⁺, Bc²⁺, Mg²⁺, and Ca²⁺. The MP3 level of theory reveals the ion-CO conformation in which the ion bonds to a carbon atom of CO to be the most stable; these MP3 results are contrary to the HF ones. Binding energies of ion-molecule complexes involving CO and N₂ were computed; MP3 energies are in good agreement with the experimental ones. The computed binding energies of cation-N₂ are about one-third of cation-NH₃ due to the absence of dipole moment and the smaller polarizability of N₂. The decrease in binding energy in cation-CO and -N₂ complexes, with increasing cation size, is mainly caused by the decrease of the electrostatic and polarization stabilizations.     

Molecular structure and character of bonding of mono and divalent metal cations (Li+, Na+, K+, Mg2+, Ca2+, Zn2+, and Cu+) with guanosine: AIM and NBO analysis

The B3LYP/6-311++G (d,p) density functional approach was used to study the gas-phase metal affinities of Guanosine (ribonucleoside) for the Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Cu⁺ cations. In this study we determine coordination geometries, binding strength, absolute metal ion affinities, and free energies for the most stable products. We have also compared the results for Guanosine, with our previously reported results for 2′-Deoxyguanosine. Based on the results, it is obvious that MIA is strongly dependent on the charge-to-size ratio of the cation. Guanosine interacts more strongly with Zn²⁺ than do with Mg²⁺, Ca²⁺, and Cu⁺ and therefore stronger interactions lead to higher MIA. In both free molecules and their complexes, the Syn orientation of the base is stabilized by an intramolecular O5′–H···N3 hydrogen bond and the anti orientation of the base is stabilized by an intramolecular C–H···O hydrogen bond formed between the (C8-H8) and the O5′ atom of the sugar moiety. It is also interesting to mention that linear correlation between calculated MIA values and the atomic numbers (Z) of the metal ions of Li⁺, Na⁺, and K⁺ were found. Furthermore, the influences of metal cationization on the strength of the N-glycosidic bond, torsion angles, angle of pseudorotation (P), and intramolecular C–H···O and O–H···O hydrogen bonds have been studied. Natural bond orbital (NBO) analysis was performed to calculate the charge transfer and natural population analysis of the complexes. Quantum theory of atoms in molecules (QTAIM) was also applied to determine the nature of interactions.     

K~+、Na~+、Ca~(2+)、Mg~(2+)对胜利褐煤平衡复吸水的影响

以胜利褐煤为研究对象,利用FT-IR等手段,用灰分、不同湿度下的平衡复吸水含量等,系统研究了不同相对湿度下K+、Na+、Ca2+、Mg2+的水合作用对胜利褐煤平衡复吸水含量的影响。结果表明,相同浓度不同类型的金属离子与煤样的交换能力的趋势为Ca2+Na+K+Mg2+。金属离子对胜利褐煤平衡复吸水含量影响力的顺序为Mg2+Ca2+Na+≈K+。相对湿度高时,平衡复吸水含量的主要控制因素为游离水分子之间的分子作用力;相对湿度中等时,平衡复吸水含量的主要控制因素为金属水簇与毛细管之间的毛细管作用力;相对湿度低时,平衡复吸水含量的主要控制因素为金属离子的水合作用。     

三元体系Li+, K+(Mg2+)/SO2-4-H2O 25 ℃相关系和溶液性质的研究

研究了两个三元体系Li~+，K~+/SO_4~(-2)-H_2O(1)和Li~+，Mg~(2+)/SO_4~(2-)-H_2O(2)在25 ℃时的相关系和溶液密度、粘度、折光率、电导、pH等物化性质．体系(1)25 ℃等温图由三条溶解度线构成，分别对应于K_2SO_4、复盐LiKSO_4和Li_2SO_4·H_2O相区．复盐LiKSO_4 25 ℃时为不相称溶解化合物，其转变温度为45.5～46 ℃，高于此温度时变为相称溶解．复盐与LiSO_4无固溶体形成．体系(2)为简单共饱型，两段溶解度线对应于体系的两种原始组分Li_2SO_4·H_2O和MgSO_4·7H_2O的结晶区，无复盐或固溶体形成，亦未发生脱水作用．用Pitzer模型检验测得的两个体系25 ℃的溶解度，并用经验或半经验公式描述物化性质随浓度的变化规律，其结果令人满意．     

Complexing ability of pesticides and related compounds. Formation and stability in aqueous solution of H+ , Li+, Na+, K+, Mg2+ and Ca2+ phenoxyacetate complexes at different temperatures and ionic strengths

The formation constants of Li⁺, N⁺, K⁺, Mg²⁺ and Ca²⁺ phenoxyacetate complexes were determined potentiometrically using an (H⁺)-glass electrode at 10, 25, 37 and 45°C, at several ionic strengths, in the range 0.04?I? 0.9 mol 1^?1. Simple empirical equations for the dependence of the formation constants on ionic strength were derived. From the temperature coefficients, estimates of ΔH^o and ΔS^o were obtained.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Fluorescence Quantum Efficiency Enhancement in CaWO4:Eu3+,Na+ Nanocrystals by Tridoping with F- Ions

We demonstrated that tridoping with F- ions is an effective way to improve the fluorescence quantum efficiency of CaWO4:Eu3+,Na+ nanocrystals. F--tridoped samples with different F- concentrations were synthesized by a hydrothermal process. The fluorescence spectra and decay curves were measured at room temperature. The fluorescence intensity of F--tridoped samples is about 3 times that for the non F--doped sample. The fluorescence quantum efficiency can be enhanced by 21% when the atomic ratio of F to W was 0.7.