对苯二甲酸-双(4-甲氧基苯酯)及其衍生物的结构与光谱

在密度泛函理论B3LYP/6-31 G*水平上计算研究了对苯二甲酸-双(4-甲氧基苯酯)及其OH和F腰接取代化合物的几何结构与红外振动光谱和电子光谱性质。研究发现这类化合物的酯基碳氧原子与苯环形成不同的离域大π键,空间位阻效应和共轭效应使三个苯环位于不同平面上,二面角在53°～59°范围。含时密度泛函理论计算第一激发态的电子垂直跃迁能,表明最大吸收光谱全部源于分子中HOMO→LUMO的π→π*跃迁,对应的最大吸收波长数值位于370～384nm之间,属于紫外区。腰接基对这类化合物的几何结构影响不大,仅由于空间位阻效应,使苯环(1)和苯环(2)之间的二面角增大3°～4°,但对其所在苯环的变形及其氢的振动有一定影响。同时,腰接羟基使HOMO→LUMO的能隙略有减小,最大吸收波长略有增大。腰接氟时因弱的共轭效应使得HOMO→LUMO的能隙减小0.1209eV,导致最大吸收波长红移14nm。     

Matlab编程的Hückel分子轨道法计算研究掺杂纳米碳管的化学反应性

使用Matlab自编简单Hückel分子轨道法（SHMO）计算程序,分析空位、Stone-Wales缺陷位、N和B原子掺杂的CNT（5,5）碳纳米管,计算π电子密度和前线分子轨道（HOMO和LUMO）为研究掺杂相对碳纳米管的化学反应性提供依据.具有不同电特性的掺杂相打破了碳纳米管的π电子、HOMO和LUMO的均衡分布.掺杂相和/或邻近的碳原子为HOMO或LUMO贡献了较其它原子更大的轨道系数,在不同的化学反应中表现出良好的亲核性或亲电性.此外,HOMO-LUMO能量差很好地反映了掺杂纳米碳管的导电性.计算结果与已报道的实验和理论结果吻合良好.     

苯乙烯化苯酚的密度泛函研究

以苯乙烯化苯酚(SP-2)为研究对象,采用密度泛函理论的M06-2X/6-311g(d,p)方法,进行了分子结构优化.在此基础上,对其分子轨道、能级、最高占据轨道(HOMO)和最低空轨道(LUMO)、红外光谱(IR)、核磁共振谱(NMR)、紫外-可见吸收光谱(UV-Vis)进行了模拟计算.根据能级和分子轨道计算结果,主要讨论了苯乙烯化苯酚的最高占据轨道(HOMO)和最低空轨道(LUMO)的特点;获得了红外光谱(IR)、核磁共振谱(NMR)、紫外-可见吸收光谱(UV-Vis)计算结果,并对谱图数据进行了分析讨论.     

TPD/PBD界面电致激基复合物几何结构和 电子结构的理论

利用第一性原理对由TPD⁺和PBD^-形成的电致激基复合物(TPD⁺PBD^-)进行基于密度泛函的能量、轨道等性质的计算。结果表明:界面处离子态的TPD⁺ 和 PBD^-更易形成处于更低能量状态的电致激基复合物。几何结构的数据分析表明:电致激基复合物(TPD⁺PBD^-)是电子从PBD^-转移至TPD⁺形成的电荷转移态;电致激基复合物的最低空轨道(LUMO)定域在电致激基复合物PBD^- 的一侧;它的最高占据轨道(HOMO)定域在电致激基复合物TPD⁺的一侧;且前线分子轨道无重叠。电致激基复合物的能隙为1.3 eV,与PBD 的LUMO到TPD的HOMO的能级差1.6 eV相近。在理论上说明了电致激基复合物的发光是从PBD的LUMO到TPD的HOMO的电子跃迁。     

Matlab编程的Hückel分子轨道法计算研究掺杂纳米碳管的化学反应性（英文）

使用Matlab自编简单Hückel分子轨道法(SHMO)计算程序,分析空位、Stone-Wales缺陷位、N和B原子掺杂的CNT(5,5)碳纳米管,计算π电子密度和前线分子轨道(HOMO和LUMO)为研究掺杂相对碳纳米管的化学反应性提供依据.具有不同电特性的掺杂相打破了碳纳米管的π电子、HOMO和LUMO的均衡分布.掺杂相和/或邻近的碳原子为HOMO或LUMO贡献了较其它原子更大的轨道系数,在不同的化学反应中表现出良好的亲核性或亲电性.此外,HOMO-LUMO能量差很好地反映了掺杂纳米碳管的导电性.计算结果与已报道的实验和理论结果吻合良好.     

7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子的光谱和激发态的密度泛函理论研究

采用密度泛函理论(DFT)对7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子做理论研究。用B3LYP/6-31G(d,p)对其几何结构进行优化,得到其最稳定构型及能量。在优化结构的基础上,对其进行频率分析得到了分子的红外光谱和拉曼光谱,并对谱线中的各峰值做了具体指认,同时也得到了分子的最高占据轨道(HOMO)和最低空轨道(LUMO)能隙为2.150eV。利用含时密度泛函理论(TDDFT)对该分子的激发态进行计算,得到最低十个跃迁允许的单激发态。对前线分子轨道最高占据轨道和最低空轨道分析得到,C-C原子之间形成了离域π键。研究结果表明:7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素是一种良好的有机半导体材料,并具有很好的发光性能。     

扑尔敏分子的密度泛函理论研究

马来酸氯苯那敏（chlorpheniramine maleate,CPM）,化学名为2-[对-氯-α-（二甲氨基）乙基丁苯基], 又名扑尔敏,分子式C20H23ClN2O4,本文采用密度泛函理论（density functional theory,DFT）,在M06-2X/6-311+g(d,p)水平上对扑尔敏分子的两种可能的结构进行了优化,优化结果显示分子基态结构具有C1对称性,分子由50个原子组成,共有144个简正自由度,所有的简正振动模式均具有拉曼活性。计算结果表明,吡啶环和苯环所在平面的二面角是92.1°,丁烯二酸和苯环所在平面的二面角是-174.5°。O40-H41和H41-N25键长分别为0.103nm、0.162nm,O40-H41-N25键角为175.29°,采用多功能波函数Multiwfn软件处理结果表明用于表征氢键强度的CVB指数（CVB指数越负,通常氢键越强。）为-0.2268,结果表明O40-H41-N25原子之间存在氢键,马来酸通过羧基上的氢原子和氯苯那敏吡啶环上的N原子通过氢键作用相结合;通过频率计算,获得了扑尔敏分子的拉曼光谱,并利用势能函数分布（PED）对拉曼光谱进行了指认,对谱图信息比较丰富的200-1800cm-1波段进行了分析归属;此外分析并讨论了扑尔敏分子的前线轨道,扑尔敏分子的最高占据轨道HOMO和最低未占据分子轨道LUMO轨道能量分别为-7.95ev、-1.05ev,能级差为6.90ev。为扑尔敏分子的光谱测定和电子结构分析提供了理论基础。     

不同电子取代基卟啉化合物的光谱和DFT研究

采用实验与密度泛函理论计算(DFT)相结合,研究了不同电子取代基修饰的5-邻羟基苯基-10,15,20-三苯基卟啉(TPPOH)和5-邻羟基苯基-10,15,20-三(对甲氧基)苯基卟啉[(p-OCH₃)TPPOH]化合物的吸收光谱及其电化学性质。结果表明,相对于TPPOH,由于对位甲氧基(-OCH₃)给电子能力强致使(p-OCH₃)TPPOH的卟啉环电子云密度增加,从而引起吸收光谱红移(3 nm)、氧化还原电位发生明显的负移,最高占据分子轨道(HOMO)和最低空轨道(LUMO)能级差降低0.06 eV。DFT理论分析分子前线轨道电子分布结果显示(p-OCH₃)TPPOH的HOMO和LUMO轨道能量均增加,而能级差却比TPPOH能级差小0.05 eV。理论结果与电化学和光谱实验结论一致,并进一步阐明了光谱和电化学性质变化机理,为揭示不同取代基卟啉化合物的设计与应用提供重要依据。     

2-巯基-5-硝基苯并咪唑振动光谱的密度泛函理论研究

选用密度泛函理论中的B3LYP杂化泛函,在B3LYP/6-31++g(d,p)（C,H,N,S）水平下,优化了2-巯基-5-硝基苯并咪唑分子（MNBMZ）的结构,优化结果表明,2-巯基-5-硝基苯并咪唑分子是一个近平面结构。通过频率计算,获得了2-巯基-5-硝基苯并咪唑分子（MNBMZ）的拉曼光谱,并和实验获得的拉曼光谱图进行了对比,200～800 cm-1波数段实验获得的拉曼谱带波数和理论计算波数相比,有一定程度的蓝移,800～1 800 cm-1波数段实验获得的拉曼谱带波数和理论计算波数相比,发生了一定的红移。对实验和理论计算光谱主要振动峰进行线性回归拟合,相关系数r=0.998,标准偏差14.98。实验和理论计算获得的拉曼光谱图基本上是一致的,表明本文选取的DFT理论计算方法是可靠的。结合VEDA4软件对2-巯基-5-硝基苯并咪唑分子的拉曼谱带简正振动模式进行了指认。此外,分析并讨论了2-巯基-5-硝基苯并咪唑分子（MNBMZ）前线轨道及HOMO,LUMO轨道的组成,HOMO和LUMO轨道能级差为3.31 eV,电子有从HOMO跃迁到LUMO的趋势。HOMO轨道中S原子的贡献是52.53%,LUMO轨道中硝基N和O原子的贡献分别为23.03%,19.97%和19.36%。采用含时密度泛函理论（time dependent density functional theory,TDDFT）对2-巯基-5-硝基苯并咪唑分子（MNBMZ）的激发态进行了计算分析,计算结果表明甲醇溶剂中2-巯基-5-硝基苯并咪唑分子（MNBMZ）理论计算的吸收波长为213,281和437 nm;实验获得的吸收波长223,272和353 nm。对研究2-巯基-5-硝基苯并咪唑分子的性质,提供了理论基础。     

碳掺杂硼氮纳米管电子场发射的第一性原理研究

对闭口硼氮纳米管（BNNT）顶层掺碳体系,运用第一性原理研究了电子场发射性能.结果表明,掺碳的BNNT体系电子结构变化显著;外电场愈强,体系态密度向低能端移动幅度愈大,且最高占据分子轨道（HOMO）/最低未占据分子轨道（LUMO）能隙愈小.体系态密度和局域态密度,HOMO和LUMO及其能隙分析一致表明,各种碳掺杂体系中C_eqBNNT的场发射性能最佳. 关键词： 硼氮纳米管 碳掺杂 第一性原理     

Contact electrification of polymers due to electron transfer among mechano anions,mechano cations and mechano radicals

Many studies have been reported for contact electrification based on the electron transfer from donors to acceptors. However, the chemical structures of donors and acceptors have not been identified. Here we calculated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of model structures of mechano anions, mechano cations and mechano radicals which were produced by the heterogeneous and homogeneous scissions of covalent bonds comprising polymer main chain in vacuum at 77 K. We identified the donors are mechano anions(HOMO) and mechano radicals(HOMO), and the acceptors are mechano cations(LUMO) and mechano radicals(LUMO). The contact electrification is due to the electron transfer from the donors to the acceptors during contacting on the friction surface, and produces mosaic nano-scopic domains with opposite sign. The sign of the net charge of polymer was deduced from the number of paths of electron acceptance reaction. The relative sign of charge and position on the triboelectric series were deduced from their chemical structure.     

Electronic structure of the molecular switch tetra-<Emphasis Type="Italic">tert</Emphasis>-butyl-azobenzene adsorbed on Ag(111)

Occupied and unoccupied electronic states in tetra-tert-butyl-azobenzene (TBA) absorbed on Ag(111) have been investigated by one-photon and two-photon photoemission spectroscopy. These measurements allow the quantitative determination of energetic positions of the highest occupied (HOMO) and the lowest unoccupied molecular orbital (LUMO) as well as the n=1 image potential state. The assignment of the electronic states are supported by quantum chemical calculations. Experimentally a HOMO–LUMO gap of 2.85 eV is observed, whereas the gap obtained from the calculated molecular orbital energies is 0.92 eV larger. This discrepancy can be explained by image charge screening. Furthermore, two unoccupied final states located 0.18 and 0.43 eV above the vacuum level, respectively, have been identified. PACS 73.20.-r; 74.25.Jb; 79.60.-i; 79.60.Dp; 68.43.Vx     

Photoelectron spectra of some aromatic mono- and di-ketones

The photoelectron spectra of benzophenone, 4-OH benzophenone, benzil, 4-OH benzil, dibenzoylmethane, 2,2-dibenzoylpropane, 1,2-dibenzoylethane and 2-(p-methoxy-benzoyl)-2-benzoylpropane have been determined and ionization potentials lying below 15 eV have been assigned. These assignments lead to the result that for compounds containing substituents on the phenyl ring, an aromatic π orbital is the highest occupied. For the enolizable ketone, di-benzoylmethane, an enol π is the HOMO, whereas for all other compounds investigated an n orbital is the highest occupied.     

外电场下GaN的特性研究

以6-311G(3df,3pd)为基组,采用B3PW91方法优化得到GaN基态分子的几何结构,并探究了电场对GaN分子基态能量、电荷布居数、键长、偶极矩、振动频率、红外光谱强度、HOMO、LUMO能级影响.研究表明:无电场时,谐振频率值为576.2218 cm~(-1),与实验值484.9 cm~(-1)很接近.有电场时,键长、偶极矩、能隙Eg、电荷布居数、红外谱强度、HOMO和LUMO能级随电场的增大而减小;谐振频率和分子总能量随电场的增加而增加.谐振频率和红外谱强度对电场有着明显的依赖关系,这对材料的光学特性研究有提供理论参考.     

Theoretical investigation on the oligothienoacenes under the influence of external electric field

Theoretical investigation on a series of oligothienoacenes has been carried out at the B3LYP/6-31G* level by considering the influence of the external electric field. With the electric field increasing, the carbon-carbon single bonds become shorter and the carbon-carbon double bonds become longer, resulting in a better conjugation. Due to the different electron density, the charge mobility of the sulfur is more obvious than that of the carbon. The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap decreases with the EF intensity increasing. The applied EF also changes the spatial distribution of the molecular orbits: LUMO and several higher orbitals shift to the high potential side, whereas HOMO and several lower ones shift to the low potential side. All these features behave more pronounced with increasing conjugated chain length.     

Charge-transfer at silver/phthalocyanines interfaces

Valence band photoemission spectroscopy (VB-PES) and inverse photoemission spectroscopy (IPES) were employed to determine the occupied and unoccupied density of states upon silver deposition onto layers of two phthalocyanines (H₂Pc and CuPc). The two different Pc molecules give rise to very distinct behaviour already during the initial stage of silver deposition. While in the CuPc case no shift occurs in the energy levels, the H₂Pc highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are shifting simultaneously by 0.3 eV, i.e., the HOMO shifts away from the Fermi level while LUMO shifts towards the Fermi level. As the silver quantity increases the HOMO levels of both Pcs are shifting towards the Fermi level. When the Fermi level is resolved in the VB spectra, the characteristic features of H₂Pc and CuPc are smeared out to some extent. Shifts in HOMO and LUMO energy positions as well as changes in line shapes are discussed in terms of charge-transfer and chemical reactions at the interfaces.     

Tuning HOMO–LUMO levels: trends leading to the design of 9‐fluorenone scaffolds with predictable electronic and optoelectronic properties

Highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) tuning is an important consideration in the development of organic‐based semiconducting materials. A study of the specific effects and overall trends for the HOMO–LUMO tuning of a diverse series of 9‐fluorenones by means of extended conjugation and substituent effects is described. Trends were explored in a range of compounds, beginning with structures having highly electron‐withdrawing substituents and progressing to structures having highly electron‐donating substituents. Compounds with an incremental increase in conjugation were also examined. Electrochemical and optical measurements were used to calculate the HOMO–LUMO levels and HOMO–LUMO bandgap (HLG) for each structure. Results from both methods were compared and correlated with the differences in molecular structure. Increasing the electron‐donating character of the substituents was observed to decrease the HLG and increase the energy levels of the HOMO and the LUMO, whereas an increase in the electron‐withdrawing character produced the opposite results. Increasing conjugation decreased the HLG, increased the HOMO energy level, but decreased the LUMO energy level. Spectroscopic evidence of substituent influence on the carbonyl suggests that substituents directly impact the HLG by influencing the availability of nonbonding electrons within the carbonyl, which impacts the probability of an nπ* transition. The data presented not only elaborate on the HOMO–LUMO tuning of 9‐fluorenone systems but also enable the consideration of 9‐fluorenones as analogous models for HOMO–LUMO tuning in other more complex polyaromatic systems such as bifluorenylidenes. These trends may provide insight into developing materials with specifically tuned HLGs and HOMO–LUMO levels for a variety of applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Ab initio study for structure, electric properties and light emission of linear-trans-quinacridone

The structure, electric properties and emission rate of linear-trans-quinacridone are investigated within the density functional theory (DFT) calculations. We find the structure of the molecule to be planar with an energy gap of 3.06 eV. The emission lifetime from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) of this material is found to be 24 ns, which is in good agreement with experimental results.     

Dynamics of self-localized excitations in a polyacene chain

Dynamical formation processes of self-localized excitations induced by charge injection or photoexcitations in a polyacene chain are investigated by a nonadiabatic dynamic method. The polyacene chain is treated as two alternatively coupled polyacetylene chains. The initial lattice configuration is taken as the pristine polyacene chain. It contains an interchain-coupled neutral soliton as a consequence of odd-number sites in each of the two chains. The nonadiabatic dynamical processes are carefully investigated in the following physical cases: (1) electron injection; (2) electron transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO); (3) electron transition from HOMO to the localized soliton level, and (4) electron-hole pair excited at the continuum absorbtion edge for light polarized parallel to the chain. It is interestingly found that the centers of the electron and the hole excited by light polarized parallel to the chain are separated. Therefore, the photogenerated charge carriers should be favorable in polyacene, which is remarkably different from those found in a single polyacetylene chain.