[Co(CO2)n]+团簇的红外解离光谱实验和理论研究

本文利用红外光解离光谱研究了一价钴阳离子与二氧化碳之间的相互作用. 通过密度泛函理论计算得到[Co(CO₂)_n]⁺团簇的几何结构,并且模拟了它们的振动光谱与实验数值进行比较. 研究结果表明,在[Co(CO₂)_n]⁺(n=2∽6)团簇中,钴阳离子通过电四极矩静电作用以端点结合的方式与二氧化碳中的氧原子结合在一起. 团簇的红外光谱都集中在二氧化碳反对称伸缩的波数附近,并且随着团簇尺寸的变化出现蓝移,最后把[Co(CO₂)_n]⁺的红外光解离光谱与稀有气体贴附的[Co(CO₂)_n]⁺-Ar的红外光解离光谱进行了比较.     

第三族金属氧化物离子对二氧化碳转化的红外光谱研究（英文）

木文利用红外光解离光谱研究了第三族金属氧化物离子对二氧化碳分子的转化机制.研究表明,对于[ScO(CO_2)_n]~+体系,在n≤4时,形成了溶剂化结构;在n=5时,形成了碳酸盐结构,实现了二氧化碳的转化.对于[YO(CO_2)_n]~+体系,需要4个二氧化碳分子就可以实现二氧化碳的转化.而在[YO(CO_2)_n]~+体系中,只发现了溶剂化结构,没有观察到碳酸盐结构.理论计算表明,[YO(CO_2)_n]~+体系拥有最小的溶剂化结构向碳酸盐结构转化能垒,[LaO(CO_2)_n]~+体系拥有最大的溶剂化结构向碳酸盐结构转化能垒.本文从分子水平揭示了不同金属氧化物离子对二氧化碳分子转化的影响规律.     

Ti+(CO2)2Ar和Ti+(CO2)n(n=3-7)络合物离子的红外光解离光谱 (cited: 1)

利用脉冲激光溅射-超声分子束载带方法制备了气相Ti⁺(CO₂)₂Ar和Ti⁺(CO₂)_n(n=3-7)络合物离子．采用红外光解离光谱研究了这些选定的质量离子的振动光谱． 对于每一种络合物离子, 在CO伸缩振动频率范围都观察到了振动峰,表明这些离子具有插入的OTi⁺CO(CO₂)_n-1结构． 对于n≦5的OTi⁺CO(CO₂)_n-1离子,其CO振动和CO₂的反对称伸缩振动频率都比自由的CO和CO₂的频率要高,表明CO和CO₂配体与中心金属离子之间主要是静电相互作用．实验结果还表明TiO⁺可以直接络合五个配体(1个CO和4个CO₂分子)．对于n=2络合物体系,除了插入的OTi⁺CO(CO₂)结构以外,还观察到了具有弯曲结构的OCO-Ti⁺-OCO异构体的存在     

二氧化碳对质子化甲醇的溶剂化作用 (cited: 1)

利用团簇模型研究了二氧化碳对质子化甲醇的溶剂化作用．H⁺(CH₃OH)(CO₂)_n⁺(n=1～7)的量子化学计算结果表明,需要3个或4个二氧化碳分子完成甲醇的羟基第一溶剂层．除了氢键,二氧化碳分子间的相互作用对大团簇的稳定性也起到了重要的作用．在这些溶剂化作用的早期阶段,不容易发生质子从甲醇到二氧化碳的转移过程．模拟的红外光谱揭示了自由O-H伸缩振动、氢键作用后的O-H伸缩振动、以及二氧化碳的O-C-O伸缩振动频率是研究质子化甲醇溶剂化过程的灵敏探针．     

化学计量的氧化钠团簇阳离子结构的离子迁移质谱法研究

本文通过离子迁移质谱法研究了氧化钠团簇阳离子(Na_nO_m⁺,n≤11)的稳定结构. 质谱结果表明化学计量组成Na(Na₂O)_(n-1)/2⁺ (n=3、5、7、9和11)系列是稳定的,并且NaO(Na₂O)_(n-1)/2⁺ (n=5、7、9和11)系列作为二级稳定系列. 为了获得这些团簇离子的结构,通过离子迁移率测量实验测定离子和氦缓冲气体之间的碰撞截面. 同时计算了这些组合物优化结构的理论碰撞截面. 结果表明,Na(Na₂O)_(n-1)/2⁺和NaO(Na₂O)_(n-1)/2⁺的结构除了n=9之外,其它具有相似结构框架. Na(Na₂O)_(n-1)/2⁺所有的化合键位于钠和氧之间. 另一方面,NaO(Na₂O)_(n-1)/2⁺中除了Na-O键之外,还存在一个O-O氧键,表明NaO(Na₂O)_(n-1)/2⁺具有过氧化物离子(O₂^2-)作为Na(Na₂O)_(n-1)/2⁺的氧化物离子(O^2-) 的替代物. Na(Na₂O)_(n-1)/2⁺和NaO(Na₂O)_(n-1)/2⁺两种稳定系列都是闭壳组合物. 这些闭壳特征对氧化钠簇阳离子的稳定性具有强烈影响.     

小尺寸VmOn+团簇的激光光解和密度泛函计算

通过激光溅射法产生了V₂O_n⁺ (n=1, 2), V₃O_n⁺ (n=1, 2, 3)和V₄O₃⁺等缺氧的钒氧团簇,并采用532和266 nm波长的激光对它们进行了光解研究. 利用密度泛函理论计算与激光光解实验相结合确定了这些团簇的几何结构和可能的光解通道. 激光光解实验表明V相似文献   

HC2nO+ (n=3-6) 正离子的红外光解离光谱以及理论计算研究

本文利用脉冲激光溅射-超声分子束载带离子源在气相中产生了HC_2nO⁺ (n=3-6)正离子. 通过对贴附CO的络合物离子的红外光解离光谱实验获得了HC_2nO⁺正离子在1600∽3500 cm^-1范围内的红外光谱. 通过比较实验光谱和理论模拟光谱确定了HC_2nO⁺正离子具有端接氢和氧的直线型碳链衍生物结构,基态为三重态,单重态比三重基态能量高10∽15 kcal/mol. 成键分析表明HC_2nO⁺中的碳链具有连烯的结构特征.     

OCS分子在128 nm附近的光解动力学研究：S(3PJ=2,1,0)、S(1D2)以及S(1S0)产物通道

本文利用时间切片离子成像技术对OCS分子进行了真空紫外波段的光解动力学研究. 在四个光解光波长(从129.32到126.08 nm)下测量了硫原子解离产物S(³P_J=2,1,0)、S(¹D₂)、S(¹S₀)的速度影像，并从中清晰地发现了四个主要的解离产物通道：S(³P_J=2,1,0)+CO(X¹Σ⁺)，S(³P_J=2,1,0)+CO(A³π)，S(¹D₂)+CO(X¹Σ⁺)和S(¹S₀)+CO(X¹Σ⁺). 在实验影像中，产物CO分子的部分振动态结构能够得到分辨. 实验还获取解离产物总平动能谱，产物分支比和角分布. 对实验结果进行分析显示除绝热解离通道S(³P_J=2,1,0)+CO(A³π)之外，在其他三个产物通道中非绝热效应都起到非常重要的作用.     

反夹心化合物[E-C{5-n}H{5-n}Nn-E]+和[E-C{5-n}H{5-n}Pn-E]+(n=1，2，3; E=Al，Ga，In，Tl)的理论研究

研究了含有低价族元素的反夹心化合物[E-C_{5-n}H_{5-n}N_n-E]⁺和[E-C_{5-n}H_{5-n}P_n-E]⁺(n=1,2,3; E=Al,Ga,In,Tl)．(η5, η5) 配位的反夹心构型[E-C_{5-n}H_{5-n}N_n-E]⁺ 在能量上不稳定或不存在．而(η5,η5)配位的反夹心构型[E-C_{5-n}H_{5-n}P_n-E]⁺不但在能量上稳定, 在解离过程中也具有稳定性． 对于含有相同的E元素来说,[E-C_{5-n}H_{5-n}P_n-E]⁺的解离稳定性随着n的增加而降低;而对于确定的n来说, 含有不同E的化合物的解离能是类似的．其中[E-C₄H₄P-E]⁺的解离稳定性与已知的[E-C₅H₅-E]⁺非常相似．C_{5-n}H_{5-n}P_n与E之间的相互作用主要是离子性的． 由于在(η5,η5)配位的[E-C_{5-n}H_{5-n}N_n-E]⁺中,E和P原子上都具有孤对电子,因此该反夹心化合物可以作为多电子供体．     

甲胺水合离子团簇的结构模型及红外光谱研究

本文利用量子化学计算方法，研究了甲胺和水复合离子团簇[(CH₃NH₂)(H₂O)_n]⁺的几何结构、能量和红外光谱，揭示了结构生长模型、氢键作用机制和质子转移机理. 研究结果表明，在[(CH₃NH₂)(H₂O)_n]⁺团簇中，甲胺甲基上的一个氢原子转移到氨基上，形成分子内质子转移的CH₂NH₃⁺离子核心结构模型，水分子作为氢键受体，与质子化氨基NH₃⁺形成氢键. CH₃NH₂⁺离子核心结构模型没有CH₂NH₃⁺离子核心结构模型稳定. 在团簇的红外光谱中，CH振动、自由NH振动、氢键结合的NH振动和OH振动模式在CH₃NH₂⁺和CH₂NH₃⁺两种离子核心结构模型的理论计算红外光谱中明显不同，因此可用于鉴别甲胺水合离子团簇的结构模型，有助于理解甲胺和水复合团簇的氢键网络结构.     

Computational investigation of the performance of ZIF-8 with encapsulated ionic liquids towards CO2 capture*

The effect of Ionic Liquid (IL) encapsulation in Metal Organic Frameworks (MOFs) is extensively studied towards the enhancement of the MOFs as CO₂-selective materials. The influence of the IL anion-cation pair type is investigated through the combination of two different cations, namely 1-butyl-3-methylimidazolium [bmim⁺] and 1-octyl-3-methylimidazolium [omim⁺] and three distinct anions, namely bis-trifluoromethylsulfonyl-imide [Tf₂N^?], tricyanomethanide [TCM^?], and tertracyanoborate [B(CN)₄^?], that can be encapsulated in ZIF-8, resulting in a series of ZIF hybrids (IL@ZIF-8). The study investigates the impact of the anion and the cation on the separation of CO₂ from mixtures with CH₄ and N₂. Monte Carlo simulations of adsorption of the three gases in both the pristine ZIF-8 and in ILs@ZIF-8 reveal that CO₂ capacity increases dramatically for the case of ILs@ZIF-8. Moreover, analysis of the simulations and additional density functional theory calculations show that CO₂/CH₄ (related to natural gas purification) and CO₂/N₂ (related to post-combustion CO₂ capture) mixture selectivity is affected by the distribution, composition and type of the IL pair. Moreover, the sorbent selection parameter, S, and the regenerability factor, R, are used to evaluate the performance of all IL@ZIF-8 analogues along with other known CO₂-selective materials.     

Effect of oxygen content and charge on the structure,stability and optoelectronic properties of yttrium oxide clusters

The electronic and geometrical structures of neutral and charged YOn (n=2–12) clusters have been investigated using density functional theory (DFT) with generalized gradient approximation. The oxygen atom in YOn has been found to be in oxo, peroxo and in superoxo forms. The geometrical structures and topologies of small size anionic clusters resemble that of neutral clusters. Yttrium showed higher coordination number than scandium. Computed results reveal the existence of YO₁₀ cluster to have a penta-peroxo oxygen with a homoleptic Y(η² –O₂)₅ geometrical configuration. The HOMO–LUMO gaps decrease with increasing n due to the increase in 2p orbital population of oxygen atoms. It has been shown that in these clusters bonding are predominantly ionic in nature and anions are thermodynamically more stable, due to the charge delocalization between the metal atom and oxygen ligands. YO₁₀⁺ and YO₁₂⁺ were found to be highly exothermic to release one and two oxygen molecules, while YO₁₁⁺ dissociates though the ozonide dissociation channel. Computed absorption spectra of small clusters are mainly contributed by yttrium metal d and s valence orbitals. The absorbance spectra, shifts towards lower energy with cluster size increase, while charge has no substantial effect on the absorption spectrum.     

Valence-delocalization of the mixed-valence oxo-centered trinuclear iron propionates [Fe 2 III FeIIO(C2H5CO2)6(py)3]npy;n=0, 1.5

Mixed-valence trinuclear iron propionates [Fe ₂ ^III Fe^IIO(C₂H₅CO₂)₆(py)₃]npy, wheren=0, 1.5, were synthesized and the structure of the pyridine-solvated complex was determined by single-crystal X-ray diffraction. Mössbauer spectra of the solvated propionate complex showed a temperature-dependent mixed-valence state related to phase transitions, reaching an almost delocalized valence state at room temperature. On the other hand, the non-solvated propionate showed a remarkable change of the spectral shape related to a phase transition, remaining in a localized valence state at higher temperatures up to room temperature.     

Interaction of Li ions with ethylene carbonate (EC): Density functional theory calculations

Electronic structures of Li⁺ ion-ethylene carbonate (EC) complexes were studied by density functional theory. The structural, electronic and dynamical properties of Li⁺-EC complexes were studied for both an isolated EC molecule and clusters including Li⁺ ion. Our structural analysis showed only one type of Li⁺ coordination with EC through Li⁺?OC which was supported by the vibration spectral analysis for interaction between Li⁺ ion and a solvent (EC) molecule. It was analyzed that the solvation energy and Mulliken charge of Li+ ion solvated by EC molecule decrease with increase in number of EC molecule. However, electron affinity shows the opposite change. This analysis with solvation energy, electron affinity and Mulliken charge supported the stabilization of 4-coordinated solvation shell among [Li⁺(EC)_n]_n=1-5 complexes.     

Solubility of highly charged anionic polyelectrolytes in presence of multivalent cations: Specific interaction effect

Studies performed on strong polyelectrolytes and on a weak polyelectrolyte, sodium poly(acrylate), show that their stability in presence of multivalent cations depends on the chemical nature of the charged side groups of the polymer. For sulfonate groups (SO₃ ^-) or sulfate groups (OSO₃ ^-) phase separation generally occurs in presence of inorganic cations of valency 3 (as La³⁺) or larger and a resolubilization takes place at high salt concentration. The interactions of the polyelectrolyte with multivalent cations are of electrostatic origin and the phase diagrams are weakly dependent on the chemical nature of the polymer backbone and on the specificity of the counterions. For acrylate groups, (COO^-), the phase separation was observed with inorganic cations of valency 2 (as Ca²⁺) or larger without resolubilization at high salt concentration. The phase separation is due to a chemical association between cations and acrylate groups of two neighboring monomers of the same chain. This chemical association creates a hydrophobic complex by dehydrating both monomer and cation. With organic trivalent cation, as spermidine ⁺H₃N(CH₂)₄NH₂ ⁺(CH₂)₃NH₃ ⁺, where no chemical association occurs with the charged side groups COO^- or SO₃ ^- of the polyelectrolyte, similar phase diagrams were observed whatever was the polyelectrolyte with a resolubilization at high trivalent cation concentration. Received 3 March 1999 and Received in final form 2 September 1999     

Cucurbit[n]urils/CdS-MoS2的表征及可见光催化性能

为了降低CdS光生电子-空穴的复合对其光催化性能的影响,利用窄带隙半导体MoS₂和有机大分子瓜环(cucurbit[n]uril,Q[n])对CdS进行改性研究. 本文采用水热法合成了Q[n]/CdS-MoS₂\\(n=6,7,8)复合光催化剂. 利用FT-IR、XRD、XPS、SEM、UV-Vis和PL等手段对产物结构、形貌和光学等性质进行表征,并考察Q[n]/CdS-MoS₂复合催化剂对次甲基蓝、罗丹明B和结晶紫溶液的催化降解性能. 结果表明,瓜环对CdS-MoS₂颗粒生长结晶起到了调控作用,Q[n]/CdS-MoS₂(n=6,7,8)形成了具有花瓣状叶片的花团,催化剂表面积增大,活性位点增加,禁帯宽度减小,电子-空穴对得到了更好的分离和迁移. Q[6]/CdS-MoS₂和Q[7]/CdS-MoS₂对亚甲基蓝具有良好的光催化活性,催化过程为羟基自由基原理.     

Study of alkyl chain length dependent characteristics of imidazolium based ionic liquids [CnMIM]+[TFSA]− by Brillouin and dielectric loss spectroscopy

This study examined the acoustic phonon mode of ionic liquids consisting of 1-alkyl-3-methyl-imidazolium family (C_nMIM) cations with n values ranging from 2 to 10 and bis(trifluoromethylsulfonyl)amide (TFSA) anion in the temperature range from 300 K to 100 K. [C_nMIM]⁺[TFSA]^? showed depolarized (VH) components of Brillouin peaks at temperatures below the glass transition temperature when n is larger than 4. On the other hand, in the case of ionic liquids with different anions, such as [C₄MIM]⁺[BF₄]^?, [C₄MIM]⁺[PF₆]^? and [C₈MIM]⁺[BF₄]^?, the VH component of Brillouin peaks was not observed in the temperature range investigated. The dielectric loss spectra showed that the temperature dependence of alkyl chain domain relaxation of all ionic liquids followed the Arrhenius law and showed an increase in activation energy at the temperature where the VH component of Brillouin peak appeared. These results suggest that the observed depolarized component of Brillouin peak might originate from uniquely induced polarization in the 2nd domain composed of head groups of cations and anions.     

Electrochemical properties of Li[CnF2n+1BF3] as electrolyte salts for lithium-ion cells

The fundamental electrochemical properties of lithium perfluoroalkyltrifluoroborates Li[C_nF_2n+1BF₃] (n = 1∼4) were evaluated as electrolyte salts for lithium-ion battery in comparison with LiBF₄ and LiPF₆. Li[C_nF_2n+1BF₃] showed higher electrolytic conductivities than LiBF₄ in aprotic solvents. In these series, the conductivities decreased with the perfluoroalkyl group being longer, and Li[C₂F₅BF₃] exhibited a comparable conductivity to LiPF₆. The relationship between the conductivity and the anion size showed that the anion with a moderate size is in favor of obtaining high conductivities. The limiting oxidation potentials determined by linear sweep voltammetry demonstrated that Li[C_nF_2n+1BF₃] were less resistant against oxidation than LiBF₄. The HOMO energies and ionization energies of [C_nF_2n+1BF₃]⁻ calculated by ab initio molecular orbital (MO) theory and density functional theory (DFT) supported this observation, however, there was no accuracy to explain the effect of the chain length of perfluoroalkyl groups on the limiting oxidation potentials. The cell performances of a LiC₆/Li_0.5CoO₂ cell using Li[C₂F₅BF₃] were comparable to those using LiPF₆ at room temperature, however, it deteriorated at elevated temperature due to the reaction on the cathode.     

Preparation of LSGM powders for low temperature sintering

La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 powders were prepared by carbonate coprecipitation and the tuning of the cation composition by a solid state reaction. The relative compositions of La, Sr, Ga, and Mg were dependent upon the supersaturation ratio (R = [(NH₄)₂CO₃]/([La³⁺] + [Sr²⁺] + [Ga³⁺] + [Mg²⁺])) during the coprecipitation. The coprecipitation of a Sr-deficient source solution and the subsequent replenishment of SrO and MgO by ball milling were effective for accomplishing a phase-pure La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 specimen by low-temperature sintering.