Nd^3＋离子的晶场劈裂与基质晶体的化学键

利用研究复杂晶体化学键的理论方法，计算了一组ＡＢＯ４型基质晶体的结构参数和化学键参数，发现Ｎｄ＾３＋离子的总晶场劈裂能△Ｅ与晶体的平均共价性有线性关系。     

LaX_3(X=F、Cl、Br、OH)晶体中的化学键参数计算

稀土化合物中稀土离子和配位体的成键性质一直是人们注意研究的课题之一,一般认为属于离子键,但具有少量的共价性,然而,具体的数量级尚不清楚。本文利用Phillips,VanVechten和Levine理论,对LaX_3(X=F、Cl、Br、OH)晶体的键性和有关参数进行了具体计算,定量指出了镧离子和配体成键的离子性和共价性程度,比较了各晶体中有关的键参数,发现了和宏观物理现象相关的规律。1 理论公式     

LaX(X=N,P,As,Sb)晶体的能带结构和化学键性质研究

用LMTO-ASA能带程序计算了LaX(X=N,P,As,Sb)晶体的能带结构,得到的晶体能隙分别为LaN_2.30eV,LaP_2.05eV,LaAs_1.66eV,LaSb_1.34eV,与实验结果基本相符.利用价电子总数在阴阳离子上的分配数之比,给出计算晶体化学键性质的经验关系式,根据该式计算晶体化学键的共价性与文献结果非常吻合,说明了该关系式的合理性.     

Tb3+离子4f75d组态能级的电子云扩大效应

研究了电子云扩大效应对Tb3+离子5d能级的影响. 利用光谱理论, 将电子云扩大效应比率β同Tb3+离子4f75d组态的自旋允许和禁阻跃迁能级的能级差联系起来, 通过复杂晶体化学键理论确定了化学键的共价性、 相应键体积极化率以及配体离子的有效电荷与β的线性关系, 同时得到了对β有影响并与Tb3+离子自身相关的因子.     

ANB8-N晶体晶格能与德拜温度的关系

研究发现Ⅰ-Ⅶ,Ⅱ-Ⅵ,Ⅲ-Ⅴ三族晶体的晶格能与德拜温度均呈线性关系,线性随着共价性的增加而降低.通过分析这些关系发现了德拜理论模型不恰当之处,预测A和B电荷均为1,2或3的AB(1∶1)型离子晶体最小晶格能值分别为546,2 481及2 969 kJ/ mol ,其中546 kJ/ mol是离子晶体晶格能的最小可能值.     

不同化学环境对Er^3＋离子的配位场能级结构的影响

首次在C3v点群对称汤中，运用双层点电荷配位场（DSCPCF）模型计算了CS3Y2I9晶体中Er^3 离子的59个配位场能级，与实验得到的能级比较，其均方根偏差为24．89cm^-1，而用点电荷配位场（PCF）模型计算的均方根偏差为29．08cm^-1，这说明双层点电荷配位场模型能更好地符合实验结果。同时，详细地分析CsLu2,Cs3Lu2Br9,Cs3Y2I9晶体中Er^3 离子能级结构的变化，由于Er^3 -X^-键共价性的增强，使Er^3 离子的能级重心发生红移，Cl→Br→I的配位场能级的分裂程序减小。     

合成氨装置101D堵塞物中晶体定性分析

基于Boentgen、Laue与Ewald、W.H.Bragg及W.L.Bragg、Friedrich和Knipping等前辈X射线及其晶体学的研究与发现,X射线晶体结构分析已成为研究原子或离子在晶体点阵中结合、鉴定晶体化合物空间结构的可靠方法.Debye-Scherrer粉晶X射线衍射法(XRPD)在合成氨装置101D工况技术分析中,比较有意义的实际应用是解决由不同单质或化合物组成的复杂混合堵塞物中晶体的鉴定问题.采用XRPD定性分析了合成氨装置101D堵塞物样品中的主要晶体成分.实验结果表明:本法对合成氨装置101D工况技术分析具有重要的意义.     

镧系元素f-f跃迁光谱计算

运用不可约张量算符方法,建立了f-f超灵敏跃迁光谱的计算模型,编制了计算f离子^2s+1L~J能级、约化矩阵元、晶体场Stark能级、晶体场态-态跃迁振子强度及模拟吸收光谱的计算机程序.其中,自由f离子能级计算采用包括双电子与叁电子组态相互作用的二三参数模型,晶体场Stark分裂计算采用单电子轨道近似,用Newman角叠加模型计算晶体场参数.f-f跃迁振子强度计算包括静电诱导偶极跃、配体极化偶极跃、振动诱导电偶极跃迁及磁偶极跃迁的贡献.     

三维周期性超分子有机框架:水相和微晶相离子海绵

<正>Nature Commun.2014,5,5574周期性是晶体、金属有机框架及共价有机框架结构的最重要特征之一,而拥有空穴是金属有机框架和共价有机框架展示各种材料性质的关键.但在溶液相通过自组装技术产生周期性的框架结构,是超分子化学的一个挑战,主要是因为,在溶液相分子和离子都存在固有的发生布朗运动及扩散运动的倾向性.复旦     

二元化合物离子性的经验计算

以电负性和原子共价半径为基础,提出了一个计算二元化合物离子性的经验公式。应用本文结果,不仅可对典型的离子化合物和共价化合物进行分类,对氧化物的酸碱性也可较好地解释。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.