聚并苯的链间作用对其导电能力的影响

采用量子化学晶体轨道ＣＮＤＯ／ ２ 方法,在考虑聚并苯链间作用的基础上对聚并苯双链模型的电子结构进行计算和讨论．结果表明：聚并苯链处于不同相对位置的链间作用对聚并苯的电荷分布规律及能带结构均有一定影响,位置不同,影响不同．从聚并苯的能带结构可以得出：聚并苯是有较小能隙、良好本征导电性能的半导体材料,考虑链间作用,对能带结构特征未有大的改变,能隙等值略有修正,导电能力有所加强．利用此模型讨论,更接近于晶体的真实结构,对进行聚并苯导电材料的性能改进将有一定帮助．     

羟基代聚并苯的氢键作用对其导电能力的影响

采用量子化学晶体轨道ＣＮＤＯ／ ２ 方法，在考虑了羟基代聚并苯氢键作用的基础上对其双链模型的电子结构进行系列的计算和讨论．结果表明羟基代聚并苯链位于不同位置时，氢键的作用有明显的不同，能带结构差别很大     

含氮杂环并苯类高聚物结构与能带规律的从头算和半经验量子化学研究

采用从头算ＨＦ和半经验量子化学方法,对含氮杂环并苯类高聚物体系进行几何结构优化．比较不同方法下它们的电子性质的差异,揭示聚并苯、聚并吡啶、聚并吡嗪的能带分布特征和规律．为深入研究导电、发光等功能材料及能带匹配器件的分子设计提供依据．     

聚并苯和聚并吡啶类化合物非线性光学性质及其分子材料设计

选取聚并苯、聚并吡啶和聚并吡嗪的 3种共振结构为基体 ,计算不同共轭单体齐聚物的结构及被取代后的聚合物二阶和三阶非线性光学系数 .结果表明 ,聚合物的二阶非线性光学系数与其单体相比有显著增大 ,被—NH2 和 NO2 取代后的聚并苯、聚并吡啶和聚并吡嗪的非线性光学系数又在聚合物的基础上进一步大幅度增加 ,有的增加 2～ 3个数量级 .在非取代的聚合物中 ,聚吡啶各种结构的二阶非线性光学系数均较大 ;取代聚合物中 ,单—NH2 和—NO2 取代的聚并苯 ,尤其是反式共振结构聚并苯的二位— NH2 和五位—NO2 取代结构的聚合物二阶非线性光学系数高达 3 .2 7× 1 0 - 2 7esu,说明这种— NH2 和 -NO2 取代后的聚并苯是一种很好的非线性光学材料 .     

聚并苯同系分子稳定性及电子极化率规律的研究

引入外电场微扰的量子化学ＣＮＤＯ／２方法，计算了聚并苯同系分子（Ｃ４ｎ＋２Ｈ２ｎ＋４）的能量和电子极化率，结果表明：全价电子极化率和π电子极化率均随并苯数目的增加而增大，但增率逐渐降低，当ｎ值足够大时，增率趋于一常数；极化率沿分子链增长方向的增率远远大于其它方向；π电子极化率的增率高于全价电子，聚并苯同系分子的稳定性规律为：顺反型相当，二者强于均键长型，分子链每增加一个单元（Ｃ４Ｈ２）体系能量降低     

硫化聚并苯导电材料结构的理论化学研究

采用量子化学从头算方法和AM1半经验方法,探讨了聚并苯导电聚合物硫掺杂前后结构和电子性质的变化,提出了硫化聚并苯导电材料的“双层夹心”分子结构模型.研究表明,硫化后的聚并苯材料,S原子位于两层聚并苯分子平面中间,并与两个聚并苯分子平面中相应的两个C原子相键合,形成C—S—C“桥式”共价单键;并解释了硫化聚并苯导电材料比本征态聚并苯材料作电极时可逆容量增大的原因.     

氯代聚并苯同系物稳定性和电子极化率规律研究

采用引入外电场微扰的量子化学ＣＮＤＯ／２方法，计算了不同构型氯代聚并苯同系物的电子极化率，并采用ＡＭ１方法得到了它们的能量，比较了它们的稳定性、能量和电子极化率随结构单元增加的变化规律。     

聚噻吩取代效应的理论研究

用自洽场晶体轨道法（ＳＣＦ ＣＮＤＯ／２－ＣＯ）对聚噻吩的一些一取代物和二取代物的电子结构进行了研究，计算的取代基包括－ＣＨ３，－Ｃ２Ｈ５，－ＯＣＨ３和－ＣＮ。计算结果表明，这些取代基基本没有影响聚噻吩主链的平面结构，除聚－３，４－二甲基噻吩的主链发生了４０°的扭转外，其它衍生物的主链仍处于同一平面。根据各取代高分子的电子特性我们得到结论：给电子基团和吸电子基团的取代教师将使能隙（Ｅｇ）减小，价带     

聚噻吩与取代聚噻吩的能带结构的计算

聚噻吩与取代聚噻吩的能带结构的计算曹阳，陈良进（苏州大学化学系苏州２１５００６）关键词取代，聚噻吩，能带结构，导电性在五元杂环的高聚物中，３－取代聚噻吩已引起了人们广泛的兴趣，已有人对其能带结构和导电性能［１－２］尤其是其温度与导电性能的关系［３－５...     

硫化反式聚异戊二烯电子性质的理论化学研究

应用量子化学计算方法,对反式聚异戊二烯本征态和硫化态结构的能量及电子性质等进行了计算.结果表明,当聚异戊二烯掺杂硫后,相邻两链之间的距离a⊥变窄,体系的总能量降低,从而使整个掺杂体系更加稳定.另外,在硫化聚异戊二烯分子中,S原子位于两个相邻聚异戊二烯链之间,并偏向于其中一个分子链的C C双键的一侧,即与相邻两链中相对应的两个C C双键形成π-p-π共轭体系,增加了电子在两个聚异戊二烯链间的流动性,从而使硫化的反式聚异戊二烯更加稳定.另外,根据固体能带理论,采用量子化学EHMO方法,对反式聚异戊二烯本征态和硫掺杂态的能带结构进行了计算,根据硫化前后能隙和带宽的变化,解释了反式聚异戊二烯掺杂后呈现电导率各向异性的原因.     

14顶点闭合型碳硼烷异构体的结构和稳定性的密度泛函理论研究

采用密度泛函理论(DFT) B3LYP/6-31G(d)方法对14顶点闭合型碳硼烷异构体的几何结构进行优化, 分析了它们的稳定性、电荷分布以及前线分子轨道能级. 结果表明, C₂B₁₂H₁₄碳硼烷的9个异构体都有对应的稳定构型, 并基本保持了B₁₄H₁₄^2－的骨架构型; 除两个C原子取代轴顶点位置B原子的1,14-C₂B₁₂H₁₄外, 其稳定性均随着两个C原子之间距离的增大而增加, 但C原子取代高配位数的B原子不利于其构型的稳定性. 各异构体的负电荷主要分布在C原子上, 同时处于轴向位置的B原子也有部分负电荷, 它们可能成为反应的亲核活性中心. 异构体的HOMO能级的高低与其稳定性相对应, HOMO能级低的异构体稳定性好.     

Structure and properties of tetrakis[3(4)-chlorophthalocyaninato]copper(II) protonated forms in the isolated state and in the sulfuric acid solutions

Results of the quantum-chemical PM3 and experimental spectrophotometric studies of the stepwise protonation of tetrakis[3(4)-chlorophthalocyaninato]copper(II) are presented. The number, structure, and energy characteristics of consecutively protonated isolated molecules of the substituted complexes have been determined; the stability and electron absorption spectra of the complexes protonated forms in concentrated sulfuric acid solution have been studied. The special effect of substitution with halogen on the electronic structure of the exocyclic nitrogen atoms of (phthalocyaninato)copper(II) has been examined.     

Photoacoustic and luminescence spectra study on the effects of chlorine substituent on the energy transfer of Eu(III)-chlorobenzoic acid

The photoacoustic (PA) amplitude spectra of three complexes of Eu(III) combined with chlorobenzoic acid (Eu(o-ClC6H4CO2)3.H2O, Eu(m-ClC6H4CO2)3.H2O and Eu(p-ClC6H4CO2)3.H2O) have been measured, and the PA phase of the different complexes have been calculated. Both the PA amplitude spectra and the luminescence spectra reflect the variation of the luminescent properties, and the PA phase is directly relative to the relaxation time. Since the relaxation is the process of the intramolecular energy transfer between the ligands and the central ion, the molecular structure of ligand is the important factor to decide the energy gap between the lowest triplet state of ligand and the resonance level of central ion. The effects of chlorine substituent on the molecular structure and energy gap of the complexes have been studied by PA phase and luminescence spectra.     

Theoretical studies on the structures, heats of formation, energetic properties and pyrolysis mechanisms of nitrogen-rich difurazano[3,4-b:3′,4′-e]piperazine derivatives and their analogues

The molecular structure, heats of formation, energetic properties, strain energy and thermal stability for a series of substituted difurazano[3,4-b:3′,4′-e]piperazines and their analogues were studied using density functional theory. The results show that it is a useful way to increase the heat of formation values of energetic compounds by incorporating a five- or six-membered aromatic heterocycle to construct a fused ring system. The calculated detonation properties reveal that introducing one heterocycle to construct a fused ring structure greatly enhances their detonation properties. The substitution of the –NF₂, –NO₂ or –NHNO₂ group is very useful for enhancing the detonation performance for the substituted derivatives. According to molecular structure and natural bond orbital analysis, the introduction of the –NO₂, –NF₂ or –NHNO₂ group decreases the stability of the substituted derivative. There is a weak N–NO₂ bond conjugation in the NO₂-substituted derivatives. An analysis of the bond dissociation energies for several relatively weak bonds suggests that all the unsubstituted derivatives have good thermal stability, but the substitution of –NO₂ or –NF₂ remarkably decreases their stability. Considering the detonation performance and thermal stability, eight compounds may be considered as the potential candidates of high-energy density materials with less sensitivity.     

氧化物体系中Eu2+的价态稳定和转换

采用光谱方法研究了氧化物体系中Eu2 的价态稳定和转换问题．研究表明体系中Eu2 的价态稳定与取代离子的半径、电荷及基质晶相等密切相关．运用晶格能理论和晶体结构变化对实验结果进行了计算和讨论．     

An ab initio study of substituent effects on the excited states of purine derivatives

Several excited singlet electronic states of purine nucleobases and related derivatives have been calculated using high-level multireference perturbation theory methods. Purine derivatives with one or two amino or carbonyl groups substituted at positions C(2) and/or C(6) of the purine ring have been included in the study. The effect of the substituents on excited-state energies and wave functions is examined. Some trends have been observed, such as the fact that substitution at the C(2) position decreases the energy of the first pi --> pi* state considerably. Although basic qualitative features of the effects can be explained with the simple frontier molecular orbital theory, ab initio calculations are required to describe the effects quantitatively.     

Octafluoro-4,4′-bipyridine and its derivatives: Synthesis, molecular and crystal structure

The structure and chemical properties of perfluoro-4,4′-bipyridine have been studied. It was found that octafluoro-4,4′-bipyridine is a quite electron deficient system stable to the action of alkylating agents and sensitive to nucleophilic substitution of fluorine atoms. Depending on the reaction conditions and reagents used products could be obtained in which two and six fluorine atoms are substituted by nucleophiles. For all isolated compounds X-ray structure determination has been performed and the main peculiarities of the molecular and crystal structure of fluorine-containing bipyridines have been determined.     

A simple rule for classification of polychlorinated dibenzo-p-dioxin congeners on the basis of IR frequency patterns

The IR spectra of 76 dioxin congeners with zero to eight chlorines have been calculated by the DFT (B3LYP) method. Close inspection of the calculated spectra provides a simple rule for IR spectral analysis in polychlorinated dibenzo-p-dioxins (PCDDs). All congeners with a common structural motif of chlorine substitution in either of two benzene rings share the same main IR frequency, and the chlorination of one ring has little influence on the vibrational frequencies of the other ring. As a result, the main ring vibrational frequencies of all dioxin congeners could be classified into 10 groups according to the chlorine substitution pattern. This simplifies the complex IR spectral analysis of PCDDs to identifying two main peaks in essence, each of which corresponds to either of two chlorinated benzene rings. The systematic trend originates from the mass effect of the substituted chlorines. The C-H bending (in plane) character in the ring skeleton vibration mode is affected in quite different ways, depending on whether the chlorine is substituted on longitudinal or lateral positions. In particular, when all the lateral positions (2, 3, 7, 8) are chlorinated in PCDDs, the vibrational frequency of a b(1u) mode (or its analogues in other symmetry) gives a characteristic IR peak around 1392 cm(-1). This peak is unique to all toxic congeners and could be used as an indicator for them.     

Structural, electronic, and bonding properties of zeolite Sn-beta: a periodic density functional theory study

The structural, electronic, and the bonding properties of the zeolite Sn-beta (Sn-BEA) have been investigated by using the periodic density functional theory. Each of the nine different T-sites in BEA were substituted by Sn atoms and all the nine geometries were completely optimized by using the plane-wave basis set in conjunction with the ultra-soft pseudopotential. On the basis of the structural and the electronic properties, it has been demonstrated that the substitution of Sn atoms in the BEA framework is an endothermic process and hence the incorporation of Sn in the BEA is limited. The lowest unoccupied molecular orbitals (LUMO) energies have been used to characterize the Lewis acidity of each T-site. On the basis of the relative cohesive energy and the LUMO energy, the T2 site is shown to be the most favorable site for the substitution Sn atoms in the BEA framework.     

Interaction between ions and substituted buckybowls: A comprehensive computational study

Complexes formed by substituted buckybowls derived from corannulene and sumanene with sodium cation or chloride anion have been computationally studied by using a variety of methods. Best results have been obtained with the SCS‐MP2 method extrapolated to basis set limit, which reproduces the highest‐level values obtained with the MP2.X method. All bowls form stable complexes with chloride anion, with stabilities ranging from ?6 kcal/mol in the methylated corannulene derivative to ?45 kcal/mol in the CN‐substituted sumanene. The opposite trend is observed in sodium complexes, going from deeply attractive complexes with the methylated derivatives (?36 kcal/mol with sumanene derivative) to slightly repulsive ones in the CN‐substituted bowls (2 kcal/mol in the corannulene derivative). Anion complexes are stabilized by large electrostatic interactions combined with smaller though significant dispersion and induction contributions. Conversely, cation complexes are stabilized by large induction contributions capable of holding together the bowl and the cation even in cases where the electrostatic interaction is repulsive. The effect of substitution is mainly reflected on changes in the molecular electrostatic potential of the bowl and, thus, in the electrostatic contribution to the interaction. Therefore, the variations in the stability of the complexes on substitution could be roughly predicted just considering the changes in the electrostatic interaction. However, other contributions also register changes mainly as a consequence of displacements on the position of the ion at the minimum, so the accurate prediction of the stability of this kind of complexes requires going further than the electrostatic approach. © 2014 Wiley Periodicals, Inc.