H_2O与NO,CN,OH自由基及负离子相互作用的CP研究

采用量子化学从头算方法在均衡（CounterPolse）校正和非校正势能面上研究 了珑O与NO，NO~-，CN，CNoH~-之间的相互作用比较了CP-梯度优化和非校正梯度优 化以及基组的选择对超分子结构和能量的影响．研究311++g**基组对于这些体系的 研究有很高的效率．这些自由基和负离子均能与H_2O形成强弱不同的氢强弱次序依 次为OH~-，CN，NO~_，OH，CN，NO，由相互作用能．△E~(CP)，成键临界点电荷密 E（2）分析均得到同样结果CF梯度优化和非校正梯度优化所得能量及正BSSE相差不 大。     

甲醛与乙腈相互作用的理论研究

在HF/6-311G(d,p)、 MP2/6-311G(d,p)和B3LYP/6-311G(d,p)水平上,对H2CO和CH3CN以及设计的4种结构H2CO…CH3CN复合物等进行几何全优化和振动频率计算,排除振动频率为负值的非局域极小点结构,并对稳定的环状构型复合物结合能进行基组重叠误差校正和零点振动能校正.分子间相互作用的能量分解分析显示,静电能在H2CO...CH3CN相互作用能量中占主导地位,电荷转移能居第二位.     

(CH2)2O, (CH2)2S与双卤分子间卤键的理论研究

运用量子化学密度泛函B3LYP方法, 采用6-311＋＋G(d,p)及aug-cc-pVDZ基组, 通过CP校正的几何梯度优化对(CH2)2O和(CH2)2S与双卤分子XY (XY＝Cl2, Br2, ClF, BrF, BrCl)形成的卤键复合物的几何构型、振动频率和相互作用能等进行了研究. 利用电子密度拓扑分析理论方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, (CH2)2O和(CH2)2S与双卤分子间的卤键介于共价键与离子键之间, 偏于静电作用成分为主. 形成卤键后, 双卤分子的键长增加, 振动频率减小, 原子积分性质发生改变. 卤键键长的变化、键能的强弱、键鞍点处的电子密度值与双卤分子的电负性有关.     

复合物C2H6·(H2O)2中分子间相互作用的理论研究

在B3LYP/6-311 G**水平上得到C2H6.(H2O)2复合物势能面上四种稳定构型。在相同基组下经MP2电子相关能和基组叠加误差(BSSE)进行单点能量校正,求得单体间相互作用能的大小。结果发现:四种稳定构型都通过CH…O氢键而形成,相应σ(CH)键都出现了较小的收缩,导致伸缩振动发生蓝移,在最稳定的复合物Comp lex2和Comp lex3中,H2O(A)分子的一个H原子与C2H6的两个H原子相对距离较短,并且具有最大的总相互作用能和两个单体AC分子间相互作用能,这说明三个氢原子间存在着较强的相互作用,并对分子的稳定性起着重要作用.     

NO_2,OH和OH~-对环四甲撑四硝胺初始热解的影响

在密度泛函理论的(DFT)B3LYP/6-31g(d)水平上,优化得到了环四甲撑四硝胺(β-HMX)及其与高氯酸铵(AP)裂解产物NO2、OH及OH-分别形成复合物的各种稳定构型,计算了β-HMX及各复合物中最弱的N—NO2键解离能.结果发现:β-HMX与NO2、OH结合后构型变化不是很大,但对称性降低;β-HMX与OH-结合后,HMX构型发生较大变化,原有的对称性明显遭到破坏.计算表明:NO2易与HMX骨架环上亚甲基(—CH2—)中的H作用,"置换"出H而引发HMX的热解,从而改变了HMX的初始分解通道;OH对HMX的N—NO2键解离影响不大,而OH-与β-HMX结合后其N—NO2键解离能比β-HMX降低近200kJ.mol-1,表明OH-对其裂解有明显的促进作用.NO2、OH-的存在可使HMX的分解温度大大降低.     

NO2, OH和OH-对环四甲撑四硝胺初始热解的影响

在密度泛函理论的(DFT)B3LYP/6-31g(d)水平上, 优化得到了环四甲撑四硝胺(β-HMX)及其与高氯酸铵(AP)裂解产物NO2、OH及OH-分别形成复合物的各种稳定构型, 计算了β-HMX及各复合物中最弱的N—NO2键解离能. 结果发现: β-HMX与NO2、OH结合后构型变化不是很大, 但对称性降低; β-HMX与OH-结合后, HMX构型发生较大变化, 原有的对称性明显遭到破坏. 计算表明: NO2易与HMX骨架环上亚甲基(—CH2—)中的H作用,“置换”出H而引发HMX的热解, 从而改变了HMX的初始分解通道; OH对HMX的N—NO2键解离影响不大, 而OH-与β-HMX结合后其N—NO2键解离能比β-HMX降低近200 kJ·mol-1, 表明OH-对其裂解有明显的促进作用. NO2、OH-的存在可使HMX的分解温度大大降低.     

HCN(HNC)与NH3, H2O和HF分子间相互作用的理论研究

在MP2/aug-cc-pVTZ水平上, 对HCN(HNC)与NH3, H2O和HF分子间可能存在的氢键型复合物进行了全自由度能量梯度优化, 通过在相同水平上的频率验证分析发现了稳定的分子间相互作用形式是HCN(HNC)作为质子供体或作为质子受体形成的复合物. 基组重叠误差对总相互作用能的影响均小于3.34 kJ/mol. 通过自然键轨道(NBO)分析, 研究了单体和复合物中的原子电荷和电荷转移对分子间相互作用的影响. 对称性匹配微扰理论(SAPT, Symmetry Adapted Perturbation Theory)能量分解结果表明, 在分子间相互作用中, 静电作用与诱导作用占主导地位, 而诱导作用与复合物的电荷转移之间具有良好的正相关性.     

H2CO与双卤分子间卤键的电子密度分析

运用B3LYP和MP2方法在6-311++G(d,p)基组水平上, 对H2CO-XY(XY=F2、Cl2、Br2、ClF、BrF、BrCl)卤键体系进行构型全优化, 得到了O…X—Y型卤键复合物. 结果表明, MP2/6-311++G(d,p)计算结果与实验值较吻合. 并在MP2水平下计算了分子间的相互作用能, 用完全均衡校正CP(counterpoise procedure)方法对基函数重叠误差(BSSE)进行了校正. 利用电子密度拓扑分析方法对卤键复合物的电子密度拓扑性质进行了分析研究.     

吡咯-HCN体系在气相及溶液中相互作用的理论研究

用量子化学B3LYP方法在6-311G(d, p)水平上优化了吡咯-HCN氢键复合物，通过振动频率分析确定了两个吡咯-HCN体系稳定构型.为了得到更加精确的氢键作用能，采用相关一致基组aug-cc-pVDZ以及Boys 和Bernardi的CP(counterpoise)校正方法消除基组重叠误差后得到C－H…π和N－H…N型复合物的氢键相互作用能.为了确定B3LYP方法计算的相互作用能的可靠性，在MP2/aug-cc-pVDZ水平计算了复合物的氢键相互作用能，结果分别为－25.10和－19.30 kJ·mol－1.采用自然键轨道(NBO)分析考察了吡咯与HCN分子间轨道相互作用.以自洽场理论(SCRF)中的Onsager模型研究了不同极性溶剂对吡咯-氰化氢体系N－H…N型氢键几何构型，频率位移，电荷分布以及相对能量的影响.研究发现，当溶液的介电常数在1.5～30.0范围时，溶液作用十分显著，而当介电常数超过30.0以后，溶液作用已经达到了极限.     

DNA甲基化-非甲基化碱基间堆积作用的理论研究

运用二级Mфller-Plesset(MP2)理论方法和cc-pVDZ基组优化了6-甲基鸟嘌呤(O6-MethylG),4-甲基胸腺嘧啶(O4-MethylT)以及5-甲基胞嘧啶(C5-MethylC)与DNA碱基鸟嘌呤(G),腺嘌呤(A),胞嘧啶(C),胸腺嘧啶(T)之间的堆积构型.在MP2/aug-cc-pVXZ//MP2/cc-pVDZ(X=D,T)水平上,采用完全基组外推方法校正了堆积碱基对间的相互作用能,并用完全均衡校正法(CP)校正了基组重叠误差(BSSE).MP2计算结果表明,DNA碱基甲基化使得嘧啶-嘧啶、嘧啶-嘌呤堆积碱基间的平行旋转角发生明显改变,并使堆积碱基间的相互作用能增大.在MP2/cc-pVDZ计算级别上得到了各堆积碱基对的全电子波函数,并用分子中的原子理论(AIM)分析了堆积碱基对间的弱相互作用.AIM分析结果显示,甲基化增强了堆积碱基间的π-π作用,且甲基氢与相邻碱基间形成H2CH…X(X=O,N,CH3,NH2)等类型的氢键.甲基化损伤使碱基间重叠程度增大、π-π作用增强以及堆积碱基间形成多个氢键,是堆积作用能增加的主要原因.     

Organogermyl,Organostannyl, and Organoplumbyl Phosphines,Arsines, Stibines,and Bismuthines

The preparation, properties, and reactions of the compounds named in the title are described, with particular reference to the possible participation of (p→d)_π components in the bonding between the group IVB and the group VB elements.     

Pyrenes,Peropyrenes, and Teropyrenes: Synthesis,Structures, and Photophysical Properties

The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems.     

Pyrenes,Peropyrenes, and Teropyrenes: Synthesis,Structures, and Photophysical Properties

The design of a relatively simple and efficient method to extend the π‐conjugation of readily available aromatics in one‐dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl–aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X‐ray crystallography. As expected, photophysical characterization clearly shows increasing red‐shifts as a function of extended conjugation within the fused ring systems.     

Borinium, borenium, and boronium ions: synthesis, reactivity, and applications

Boron cations are elusive and highly electrophilic species that play a key role in the chemistry of boron. Despite early interest in the chemistry of boron cations, until recently they have largely remained chemical curiosities. However, hints at harnessing their potential as potent electrophiles have begun to appear and developments in weakly coordinating anion technology suggest that this is an area of research that is ripe for exploration. It has been nearly 20 years since the last major review on boron cations; herein we summarize the progress in the area since that time.     

Structural, magnetic, and spectroscopic studies of YAgSn, TmAgSn, and LuAgSn

The rare earth-silver-stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P6₃mc, Z=2, a=468.3(1), pm, wR₂=0.0343, 353 F² values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), , wR₂=0.0399, 659 F² values, 15 variables for TmAgSn, and a=723.8(2), , wR₂=0.0674, 364 F² values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with , in order to clarify the silver-tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag-Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag-Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie-Weiss paramagnet with an experimental magnetic moment of 7.2 μ_B/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by ¹¹⁹Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental ¹¹⁹Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag-Sn bonds and also significant Ag-Ag bonding in LuAgSn.     

Pi bonding and negative hyperconjugation in mono-, di-, and triaminoborane, -alane, -gallane, and -indane

A systematic quantum chemical investigation of mono-, di-, and triaminoborane, -alane, -gallane, and -indane is carried out to determine quantitatively the effects of pi bonding and negative hyperconjugation on structures, energetics, and rotational barriers in these systems. Pi bonding plays a significant role in the aminoborane compounds, but becomes rapidly less significant in the aminoalanes, -gallanes, and -indanes. For each main-group metal X investigated, X-N rotational barriers are found to be essentially equal depending only on the number of remaining in-plane amino groups. The contribution of negative hyperconjugation to reducing rotational barriers, as assessed from natural bond orbital (NBO) delocalization energies, is independent of the pyramidalization of the out-of-plane amino group, and is also dependent only on the number of rotated groups. Optimized tris[bis(trimethylsilyl)amino]-substituted structures of boron, aluminum, gallium, and indium are found to compare quite well with available experimental structural data, and exhibit X-N torsion angles that are independent of the central metal atom.     

Transition-metal-free O-, S-, and N-arylation of alcohols, thiols, amides, amines, and related heterocycles

A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained.     

Metal-Directed Formation of Tetra-, Hexa-, Octa-, and Nonanuclear Complexes of Magnesium,Calcium, Manganese,Copper, and Cadmium

Efficacious metal control of self-assembly of dialkylketipinate dianions leads to completely different supramolecular assemblies. The structures of grid 1 , double-decker 2 , triple-decker 3 , and metalla-spherand 4 were characterized by X-ray crystallographic analyses or by NMR spectroscopy.     

Synthesis of yttrium,lanthanum, neodymium,praseodymium, and lutetium alkoxides and acetylacetonates

A convenient and practical method is proposed for the synthesis of lanthanide and yttrium alkoxides. The method involves dissolving the metals or their hydrides in a solution of dry HCl in the corresponding alcohol, with subsequent dehalogenation of the LnCl₃ solution by an equivalent amount of alkali metal (Na, Li), The rareearth alkoxides are easily converted into acetylacetonates Ln(acac)₃ by the action of acetylacetone.A. N. Nesmeyanov Institute of Elementoorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2490–2493, November, 1992.