PuH2气态分子热力学稳定性的理论研究

用密度泛函B3LYP方法计算了PuH2分子的微观性质、不同温度下气态PuH2分子的能量（E）、熵（S）及气态PuH2分子生成反应的标准焓变ΔH、标准熵变ΔS和标准自由能变ΔG.计算结果表明,气态PuH2分子不具有热力学稳定性.     

ChemInform Abstract: Theoretical Study on the Assembly and Stabilization of a Magic Cluster Al4N‐

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

AlmN(m=2～9)团簇结构与稳定性的DFT研究

用密度泛涵理论(DFT)的B3LYP方法在6-31G*水平上对AlmN(m =2～9)团簇的几何构型、电子结构、振动频率等性质进行了理论研究.给出了以Alm团簇作为设计AlmN类结构的母体,考虑在不同位置上结合N原子的结构,可以较快找到AlmN类团簇基态结构的一种方法.通过对基态结构的几何参数分析发现, m＜4的结构只存在Al－N键; m≥4的结构, Al－N键和Al－Al键共存.对基态结构的绝热电离能讨论结果表明,只存在Al－N键的Al2N和Al3N团簇较稳定.     

First Principles Study of Neutral and Anionic (Medium‐Size) Aluminum Nitride Clusters: AlnNn,n = 7—16.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

ChemInform Abstract: Ab initio Study of the Electronic Structure and Bonding of Aluminum Nitride.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

羰基硼化合物B2n(CO)n (n＝1～6)的理论研究

运用密度泛函理论(DFT)的B3LYP/6-31G*方法, 对羰基硼化合物B_2n(CO)_n (n＝1～6)各种可能的结构进行了优化,对它们的几何构型、电子态、振动频率、核独立化学位移(NICS)和B₂CO的分子轨道进行了理论研究, 得到了B_2n(CO)_n (n＝1～6)结构的稳定性信息. 在它们的基态结构中, 羰基的配位方式是端配位(μ₁-CO), B_2n(CO)_n (n＝1～5)的基态构型是线形或平面结构, B₁₂(CO)₆的基态构型则较为复杂. B_2n(CO)_n (n＝1～3)的基态是三重态, B_2n(CO)_n (n＝4～6)的基态是单重态. 振动频率和轨道的研究为实验提供了重要的理论依据.     

N8H8链状异构体结构与稳定性的理论研究

采用密度泛函理论(DFT), 在B3LYP/6-311＋＋G(d,p)基组上计算得到了21种N₈H₈链状异构体, 并研究了这些异构体间可能的互变异构情况. 为了得到更为精确的能量信息, 计算了QCISD(T)/6-311G(d,p)基组水平上各物质的能量. 所得的21种异构体分为4类(4种类型链状化合物): A为直链, B有一个支链, C有2个支链, D有3个支链; D类只有一种, A类稳定构型2种, B类稳定构型12种, C类稳定构型6种; 相对稳定的分别为: B2-1构型, B2-3构型和C23-2构型. 我们研究发现N₈H₈链状异构体中含有明显N＝N双键特征有利于化合物稳定性的提高.     

DFT calculations on the structural stability and infrared spectroscopy of endohedral metallofullerenes

Endohedral metallofullerenes M@C₂₄ (M = Li^0/+, Na^0/+, K^0/+, Be^0/2+, Mg^0/2+ and Ca^0/2+) with different spin configurations have been systematically investigated using the hybrid DFT-B3PW91 functional in conjunction with 6-31G(d) basis sets. Our theoretical studies show that Li@C₂₄, Be@C₂₄, Be²⁺@C₂₄, and Mg²⁺@C₂₄ are energetically favorable. In these endohedral metallofullerenes, only the encapsulated Be and Ca atoms can donate the electrons to the cage. With exception of Be²⁺@C₂₄, the energy gaps of other charged compounds are larger than that of corresponding neutral compounds. We also find that some endohedral metallofullerenes have high energy gaps, but they are unlikely to show high thermodynamic stability. Additionally, the vibrational frequencies and active infrared intensities are also used as evidence to identify these endohedral metallofullerenes.     

Computational Investigation of Neutral and Anionic AlnCom Clusters by Density-functional Theory

Structural and electronic properties of bimetallic clusters AlnCom with n=1～7 and m=1～2 have been investigated using the B3LYP-DFT method.Structural optimization and frequency analysis were performed at the CEP-121G level.The charge-induced structural changes in these anions were discussed.In addition,the corresponding total energies,binding energies,adiabatic electron affinities and vertical electron affinity were also presented and discussed.Our predicted vertical ionization potentials are in reasonable agreement with the experimental ionization potentials.Among different AlnCom and AlnCom-anions (n=1～7,m=1～2),Al4Co,Al6Co,Al4Co-,Al6Co-and Al4Co2-are predicted to be species with high stabilities.     

Size effect of fullerene cages and encaged clusters in M<Subscript>3</Subscript>N@C<Subscript>2<Emphasis Type="Italic">n</Emphasis></Subscript>

Based on the calculated findings that the sizes of encaged clusters determine the structures and the stability of C₈₀-based trimetallic nitride fullerenes (TNFs), more extensive density functional theory calculations were performed on M₃N@C₆₈, M₃N@C₇₈ and M₃N@C₈₀ (M=Sc, Y and La). The calculated results demonstrated that the structures and stability undergo a transition with the increasing of the sizes of the cages and clusters. Sc₃N is planar inside the three considered cages, Y₃N is slightly pyramidal inside C₆₈-6140 and C₇₈-5 and planar inside I_h C₈₀-7, however, La₃N is pyramidal inside all the three cages. Those cages with pyramidal clusters inside deformed considerably, compared with their parent cages. In these cases, the bonding of metallic atoms toward the cages does not play an important role, and the encaged cluster tends to be located inside the cages with the largest M-M and M-C distances so that the strain energy can be released mostly. These calculations revealed the size effect of fullerene cages and encaged clusters, and can explain the position priority of M3N inside fullerene cages and the differences in yield of M₃N@C_2n . Supported by the Southwest University, China (Grant No. SWNUB2005002)     

高能密度材料H2N5MN5H2 (M=Be,Mg,Ca,Zn,和Cd)的密度泛函理论研究

借助密度泛函理论,用B3LYP和BP86方法,对一系列潜在的新型高能密度材料分子H2N5MN5H2(M=Be,Mg,Ca,Zn,和Cd)进行了理论预测研究.结果表明,这些材料分子都非常稳定,不容易分解,其中H2N5BeN5H2最稳定.金属离子的配位作用对化合物的稳定起了重要作用.配体H2N5也因从金属M获得一个电子变成H2N5-离子而变得更稳定.     

N5H5异构体的结构与稳定性的理论研究

采用密度泛函理论的B3LYP方法在6-311++G**基组水平上对N5H5氮氢化合物异构体可能存在的构型进行了几何优化, 得到23种稳定异构体, 并研究了这些异构体间可能的互变异构情况. 为了讨论N5H5异构体作为含能材料候选物质的可能性, 还采用了G3B3方法计算了能量, 并且计算了异构体的生成热(⊿Hf,298).结果表明, 在23种异构体中链状异构体最稳定, 四元环四氮烷异构体最不稳定, 存在一个N=N双键的异构体较同类异构体能量低, 较为稳定; N5H5氮氢化合物的生成热均为正, 其中异构体E1生成热最高. 估算了N5H5的摩尔体积, 由密度公式ρ=MT/Vmol,得到E1 的密度最大.     

Addition Reactions of Me3SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O,S, and N Ligands

The reaction of one equivalent of LAlH₂ ( 1 ; L=HC(CMeNAr)₂, Ar=2,6‐iPr₂C₆H₃, β‐diketiminate ligand) with two equivalents of 2‐mercapto‐4,6‐dimethylpyrimidine hydrate resulted in LAl[(μ‐S)(m‐C₄N₂H)(CH₂)₂]₂ ( 2 ) in good yield. Similarly, when N‐2‐pyridylsalicylideneamine, N‐(2,6‐diisopropylphenyl)salicylaldimine, and ethyl 3‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐2‐carboxylate were used as starting materials, the corresponding products LAl[(μ‐O)(o‐C₆H₄)CN(C₅NH₄)]₂ ( 3 ), LAlH[(μ‐O)(o‐C₄H₄)CN(2,6‐iPr₂C₆H₃)] ( 4 ), and LAl[(μ‐NH)(o‐C₈SH₈)(COOC₂H₅)]₂ ( 5 ) were isolated. Compounds 2 – 5 were characterized by ¹H and ¹³C NMR spectroscopy as well as by single‐crystal X‐ray structural analysis. Surprisingly, compounds 2 – 5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN).