C2D2和C2H2分子键-键耦合研究

采用Morse根于描述C_2D_2分子中C－D键的伸缩振动，用谐振子描述C－C键伸缩振动，更新构造了C2D2分子的振动哈密顿，自行设计了非线性最小二乘拟合程序，并用它对C2D2分子的伸缩振动能级进行拟合，得到了基本的势能参数．理论计算与实验结果符合得很好，拟会的标准差为1.14cm－1；利用这些参数进一步计算了C2H2和C2D2的振动能级．     

De-Linker-Enabled Exceptional Volumetric Acetylene Storage Capacity and Benchmark C2H2/C2H4 and C2H2/CO2 Separations in Metal–Organic Frameworks

An ideal adsorbent for separation requires optimizing both storage capacity and selectivity, but maximizing both or achieving a desired balance remain challenging. Herein, a de-linker strategy is proposed to address this issue for metal–organic frameworks (MOFs). Broadly speaking, the de-linker idea targets a class of materials that may be viewed as being intermediate between zeolites and MOFs. Its feasibility is shown here by a series of ultra-microporous MOFs (SNNU-98-M, M=Mn, Co, Ni, Zn). SNNU-98 exhibit high volumetric C₂H₂ uptake capacity under low and ambient pressures (175.3 cm³ cm⁻³ @ 0.1 bar, 222.9 cm³ cm⁻³ @ 1 bar, 298 K), as well as extraordinary selectivity (2405.7 for C₂H₂/C₂H₄, 22.7 for C₂H₂/CO₂). Remarkably, SNNU-98-Mn can efficiently separate C₂H₂ from C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures with a benchmark C₂H₂/C₂H₄ (1/99) breakthrough time of 2325 min g⁻¹, and produce 99.9999 % C₂H₄ with a productivity up to 64.6 mmol g⁻¹, surpassing values of reported MOF adsorbents.     

B4C2,B2C4簇的从头算研究

用量子化学从头计算方法研究了Ｂ４Ｃ２，Ｂ２Ｃ４簇各种可能的几何构型，计算了相应的振动光谱。Ｂ４Ｃ２的稳定构型除直线，平面构型外还有三维模型，而Ｂ２Ｃ４的稳定构型均为直线、平面构型，因此，Ｂ４Ｃ２与Ｂ６接近，Ｂ２Ｃ４与Ｃ６接近。Ｂ－Ｃ和Ｃ－Ｃ多重键及强共轭效应是Ｂ４Ｃ２和Ｂ２Ｃ４簇稳定的重要因素。     

OH+C2H2与OH+C2H4加成反应的热力学和动力学

OH基与乙炔(乙烯)的反应是控制大气中OH基浓度的重要化学反应。对反应OH+C_2H_2,1975年Davis等用FP-RF技术测定了反应的速率常数。1977年,Perry又用同样方法对该反应作出了研究;结果表明,此反应的速率常数强烈地依赖于压力,与Davis等人的实验结果不符。对反应OH+C_2H_4,Atkinson等人的实验研究表明,压力在30.0kPa以下,反应的速率常数随压力而改变;而在30.0—88.4 kPa之间,与压力无关.这与前人的结果不同。两个反应的产物也因温度不同而异.此外,上述反应一般是在近101kPa下发生的,而实验结果大多是在低压下获得的。且目前尚无直接的理论计算结果。为此,我们在从头算水平上用统计热力学方法,对反应     

Fundamental vibrational frequency correlation—IV. C2υC2h in-plane trends

A simple symmetry model is advanced to explain the trends in the correlated in-plane fundamental vibrational frequencies (experimental and calculated) in various C_2υC_2h isomorphic pairs.     

Zinc-containing chainlike polymer {Cs_2[Zn(S_2C=C(CN)_2)_2]}_n,the second example of bridging [S_2C=C(CN)_2]

The title compound {Cs2[Zn(S2C=C(CN)2)2]}n(2),Catena-poly {dicesium [bis(l,l-dicyanoethene-2,2-dithiolato-S,S':N)-Zinc(Ⅱ)]},is the second example of bridging [S2C=C(CN)2] (hereafter referred to as i-mnt) for metal-containing polymer.It crystallizes in the non-centrosymmetric space group Ia (alt.Cc,No.9).There are two coordination modes of i-mnt in this compound:μ-η1-η1-i-mnt,bridging two Zn moieties with two S atoms and terminal i-mnt.A characteristic feature of the structure is the infinite-Zn(η2-i-mnt)(η1-η1-i-mnt)-Zn(η1-η1-i-mnt)(η2-i-mnt)-wave-like chain.Cs atoms are located between the chains to form three-dimensional network-like packing.An efficient second harmonic generation from the crystal has been observed on the irradiation with the 1064 nm output of a Nd:YAG laser.     

A systematic density functional and wavefunction-based study on dicarboxyl dianions −O2C–R–CO2 − with R = C2, C2X2, C2X4, and C6X4 (X = H, F)

The possible existence of the gas phase cis- and trans-maleate, i.e. completely deprotonated maleic acid (O₂C–CΗ=CΗ–CO₂)^2–, is investigated by density functional (B3LYP) and ab-initio quantum chemical methods (MP2, CCSD(T)) using large basis sets. The calculations reveal that only the trans-isomer is Coulomb stable with respect to electron loss. The results are compared to other previously investigated dicarboxylate dianions of the general form ^?O₂C–R–CO₂ ^? with R = C₂, C₂X₂, C₂X₄, and C₆X₄ (X = H, F). Fluorine substitution on the carbon framework helps to stabilize these doubly charged systems, and we predict that all of the aromatic fluorine substituted dicarboxylate dianions are Coulomb stable in the gas phase. Only the highest levels of theory reveal the slight stabilization of both the succinate dianion and the ortho-isomer of the phthalic acid dianion in unprecedented agreement with experiments.     

C2v对称性簇Ru2N2的理论计算

采用密度泛函(B3LYP)方法计算了Ru2的部分低能电子组态，得到Ru2基态的电子谱项为7Δu，平衡核间距re=0.228 nm，振动频率ωe=338 cm－1，离解能De=1.92 eV. 同时计算了具有C2v对称性的Ru2N2簇中氮的活化情况，得到了各个优化几何构型下的键参数和体系能量.计算结果表明，氮氮键的活化程度由Ru2对氮起反馈作用的轨道数目决定.一般来说，氮氮键活化越强，体系能量越高，在相同的活化程度下，自旋多重度高的体系较稳定.     

镍催化还原偶联反应构筑C(sp~2)—C(sp~2)/C(sp~2)—C(sp~3)键的研究进展

亲电试剂的还原偶联反应避免了有机金属试剂的制备与使用,对各类官能团拥有极好的兼容性,为C—C键的构筑提供了一类重要的方法.近些年来,该反应的研究取得了突破性进展,实现了一系列C(sp2)—X与C(sp3)—X亲电试剂参与的交叉偶联反应.主要针对镍催化亲电试剂交叉偶联反应构筑C(sp2)—C(sp2)和C(sp2)—C(sp3)键的研究展开综述,详细介绍了各种偶联反应及其反应机制.     

CeO2对CuCl/活性炭吸附剂C2H4/C2H6吸附分离性能促进作用

通过等体积浸渍方法制备了添加CeO₂助剂的用于C₂H₄/C₂H₆吸附分离的CuCl/活性炭(AC)吸附剂,使用氮气吸附-脱附曲线、X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、能量分散X射线光谱(EDX)等分析方法对吸附剂进行了表征.结果表明,吸附剂表面Cu(II)在氮气气氛焙烧过程中被部分还原成Cu(I).重点研究了Ce元素的添加对于吸附剂的C₂H₄/C₂H₆吸附分离性能的影响,等温吸附曲线结果表明添加了CeO₂的吸附剂通过降低乙烷的吸附容量从而显著提高了吸附分离性能. XRD及XPS结果表明,和未添加助剂样品相比,其表面晶体团簇较小,分散性更好, Cu(II)还原程度更高.添加CeO₂的吸附剂样品5Ce50Cu(CeO₂和CuCl2的质量分数(w)分别为5%和50%)获得了最好的吸附分离效果,相对于未添加CeO₂的样品50Cu,其在660 kPa下的吸附选择性由4.2提升到8.7.     

[Cu2(C2O4)(C12H8N2)2(C3H7NO)2](ClO4)2配合物的合成及其热分解

以邻菲罗啉、2,5二羟基-1,4-二噻烷和Cu(ClO4)2.6H2O为原料,合成了中心对称的双核配合物[Cu2(C2O4)(C12H,N2)2(C3 H7NO)2](ClO4)2(1).通过红外光谱、元素分析等分析测试手段对其进行了表征;借助TG-DTG技术在氮气气氛下研究了配合物的热分解情况,并根据热分析结果确定了...     

催化裂解C2H2制备空心碳球

在高岭土负载的镍催化剂上,于850 ℃催化裂解乙炔制备了直径约500 nm 的空心碳球.用XRD、TEM、SEM和显微激光Raman光谱对所得的碳球及催化剂进行了表征,并初步探讨了反应机理.     

C02+OH2/C03+OH2电子转移反应性的理论研究

提出了研究Co2+OH2/Co3+OH2反应体系电子转移反应性的接触距离依赖关系的分析方案和ab initio计算的应用方法,并讨论验证了此方案及其相应模型的可行性,分析了有关动力学量的接触距离依赖关系.详细的结果表明,用精确PES法得出的活化能与用非谐振子势得出的活化能吻合较好,它们明显优于谐势模型.对分布函数随接触距离从1.20～0.35 nm改变而从10-2变到10-5.偶合矩阵元随接触距离的增加呈指数性降低.有效电子偶合要求接触距离＜0.75 nm.在0.50～0.75 nm范围内,相应的电子发射系数值在1.0～10-6之间.电子因子使得定域ET速率也指数性的随接触距离的增加而降低,而对分布函数对总电子转移速率的贡献与电子因子的贡献则相反.球平均ET速率随接触距离的变化呈抛物线变化,并在接触距离为0.5 nm时有最大值.此最大值与总观测ET速率非常接近.对于此偶合体系,气态时ET速率是106 L@mol-1@s-1.进一步来说,实验上难于确定此类水合体系尤其是未饱和中间组分的电子结构和PES,abinitio算法在讨论其ET反应性方面能起到一个有效的辅助作用.     

BH+2与C2H2反应势能面的量子化学研究

用B3LYP/6-311G(d,p) 密度泛函方法和高级电子相关的CCSD(T)/6-311G(2df,p)偶合簇法研究BH+2与C2H2反应势能面. 结果表明 该势能面上存在(a) H2B+*C2H2, (b) HBCHCH2+, (c) H2BCCH+2和(d) H2*BHCCH+四种异构体, 其中(b)能量最低且在动力学上最稳定, (a), (c)和(d)在动力学上均不稳定; BH+2通过对C2H2的分步亲电加成以及随后的氢迁移和H2消除等反应形成离解产物HBCCH++H2, 该反应不需要活化能且大量放热. 计算结果有助于深入了解BH+2等缺电子硼氢正离子的反应行为.     

ZnWO4 : Ni2+晶体中Oh C2v C2群链分解的能级分裂计算

An analytic approximation wave function of free ion Ni~(2+) is obtained from Watson′s SCF-3d orbit. Crystal field energy levels in the ZnWO_4 : Ni~(2+) crystal are then calculated with this wave function using ligand theory. The calculation are based on real C_2 symmetry of the crystal and according to the descending symmetry devided in two steps. O_h C_(2v) and C_(2v) C_2. Sometimes it is difficult to determine the numerous parameters from spectral data in case of lower symmetry crystal. We try to overcome this difficulty. The theoretical calculations are in good agreement with the experimental results.     

Single Atom Bi Decorated Copper Alloy Enables C−C Coupling for Electrocatalytic Reduction of CO2 into C2+ Products**

Single atom alloy (SAA) catalysts have been recently explored for promotion of various heterogeneous catalysis, but it remains unexplored for selective electrocatalytic reduction of carbon dioxide (CO₂) into multi-carbon (C₂₊) products involving C−C coupling. Herein we report a single-atomic Bi decorated Cu alloy (denoted as BiCu-SAA) electrocatalyst that could effectively modulate selectivity of CO₂ reduction into C₂₊ products instead of previous C₁ ones. The BiCu-SAA catalyst exhibits remarkably superior selectivity of C₂₊ products with optimal Faradaic efficiency (FE) of 73.4 % compared to the pure copper nanoparticle or Bi nanoparticles-decorated Cu nanocomposites, and its structure and performance can be well maintained at current density of 400 mA cm⁻² under the flow cell system. Based on our in situ characterizations and density functional theory calculations, the BiCu-SAA is found to favor the activation of CO₂ and subsequent C−C coupling during the electrocatalytic reaction, as should be responsible for its extraordinary C₂₊ selectivity.