C砷异噁唑环衍生物的结构、电子光谱和非线性光学性质的研究

应用半经验AM1量子化学方法研究了8种C60异噁唑环衍生物的结构，以AMl优化几何构型为基础，用ZINDO／CIS方法计算了目标分子的电子光谱．结果表明，异噁唑环的引入导致HOMO与LUMO间的能级差减小，C60母体与加成基团之间存在分子内电荷转移．计算所得电子光谱值与实验结果较吻合，几种化合物在400nm以上均产生非C60特征吸收峰，这些峰是电荷从加成基团向C60部分转移产生的．用FF／AM1方法计算了分子非线性光学系数α、β、γ值，在所得计算结果上推测了影响体系非线性光学系数效应的因素．     

C72O3的结构和光谱的理论研究

采用AM 1方法理论研究了C70 五元环酸酐衍生物C72 O3 的 8种可能异构体的结构和稳定性 ;以各异构体稳定构型为基础 ,分别用AM 1和ZINDO/CI方法计算了它们的振动光谱和电子光谱。结果表明 ,酸酐基团—C2 O3 主要加成在CⅠ CⅡ(异构体A)和CⅢ CⅢ(异构体B)键上形成闭环结构 ,异构体B的稳定性与实验已证实存在的异构体A十分相近 ;异构体A的振动光谱理论计算值与实验值符合较好 ,B的振动光谱理论计算值与A相似 ;对C72 O3 各异构体的电子跃迁进行了理论指认 ,讨论了其电子光谱的红移现象 ;其他异构体的振动和电子光谱属于理论预测。     

DFT研究给/吸电子取代基对D-π-A型苯并噻唑衍生物光电性质及非线性光学性质的影响

采用密度泛函理论(DFT)B3LYP方法计算了苯并噻唑及其三种D-π-A型衍生物的电子结构、电子光谱及重组能,同时结合有限场(FF)方法计算了它们的二阶非线性光学系数βtol值,从而探索取代基与分子的电荷分布、电子光谱及非线性光学性质的关系.计算结果显示,在母体分子的2,5位同时引入给/吸电子基团,2位碳原子的电荷布居发生较大变化,且分子的HOMO能级升高,LUMO能级降低,能隙减小,吸收和发射光谱发生显著的红移,增大了二阶非线性光学系数βtol.随着取代基吸电子能力的增强,分子的电子重组能逐渐变大,而空穴重组能的变化却不大,同时分子的偶极矩有所增加,有利于产生二阶非线性光学活性.     

DFT研究给/吸电子取代基对D-π-A型苯并噻唑衍生物光电性质及非线性光学性质的影响

采用密度泛函理论(DFT) B3LYP方法计算了苯并噻唑及其三种D-π-A型衍生物的电子结构、电子光谱及重组能,同时结合有限场(FF)方法计算了它们的二阶非线性光学系数βtol值,从而探索取代基与分子的电荷分布、电子光谱及非线性光学性质的关系。计算结果显示,在母体分子的2,5位同时引入给/吸电子基团,2位碳原子的电荷布居发生较大变化,且分子的HOMO能级升高,LUMO能级降低,能隙减小,吸收和发射光谱发生显著的红移,增大了二阶非线性光学系数βtol。随着取代基吸电子能力的增强,分子的电子重组能逐渐变大,而空穴重组能的变化却不大,同时分子的偶极矩有所增加,有利于产生二阶非线性光学活性。     

Y型均三嗪类衍生物三阶非线性光学性质研究

采用密度泛函理论B3LYP/6-31+G*方法对含Y型均三嗪类衍生物的6个分子(Y1-Y6)进行几何构型优化,对其最优构型采用TD-DFT (TDB3 LYP/6-31+G*)计算电子吸收光谱,用有限场FF方法及自编程序计算三阶非线性光学(NLO)性质.结果表明,6个含Y型均三嗪类有机分子的三阶非线性光学系数γ值为1010数量级个原子单位(10-30 esu),显示出良好的三阶非线性光学性能.在其三支链的末端引入不同的推、拉电子基团(Y2→Y6),对其电子光谱和三阶非线性光学响应具有明显的影响.引入强供电子基团,γ增大幅度较大,有利于改善体系的三阶非线性光学性质,从而可获得良好的非线性光学材料.     

1,3-取代方酸衍生物非线性光学性质的从头算和半经验方法的比较研究

利用从头算HF方法在6 31G 基组水平下,全优化计算了1,3 取代方酸衍生物体系Sq1～Sq12的分子 几何和优化构型下的电子结构.以优化后的构型为基础,应用CIS/6 31G 方法计算了电子光谱.同时应用从头算 CPHF/6 31G 方法和半经验FF/AM1、FF/PM3、FF/MNDO有限场方法计算了分子的二阶非线性光学系数,并对 这四种计算方法的结果进行了系统的比较.结果表明,1,3 取代方酸衍生物的二阶非线性光学系数(β0)受五员 杂环的影响较大,引入吡咯、噻唑和口恶唑五员杂环能提高其β0,含两个杂原子的五员环与方酸碳四员环相连的位 置对β0也有很大的影响.     

Y型均三嗪类衍生物三阶非线性光学性质研究

采用密度泛函理论B3LYP/6-31+G*方法对含Y型均三嗪类衍生物的6个分子(Y1-Y6)进行几何构型优化,对其最优构型采用TD-DFT(TDB3LYP/6-31+G*)计算电子吸收光谱,用有限场FF方法及自编程序计算三阶非线性光学（NLO）性质。结果表明,6个含Y型均三嗪类有机分子的三阶非线性光学系数g值为1010数量级个原子单位(10-30 esu),显示出良好的三阶非线性光学性能。在其三支链的末端引入不同的推、拉电子基团（Y2→Y6）,对其电子光谱和三阶非线性光学响应具有明显的影响。引入强供电子基团,g增大幅度较大,有利于改善体系的三阶非线性光学性质,从而可获得良好的非线性光学材料。     

电子传输材料1,3,4-恶二唑衍生物和1,2,4-三唑衍生物的DFT研究

采用密度泛函理论B3LYP方法,对1,3,4噁二唑衍生物和1,2,4三唑衍生物两类电子传输材料在中性、阴离子态和阳离子态下分别进行几何结构优化计算.结果表明,1,3,4噁二唑衍生物的电子传输过程主要是分子内噁二唑上的N→O电子转移,1,2,4三唑衍生物的电子传输过程主要是分子内三唑上N(双键)→N(单键)以及三唑环向与N相连的苯环电子转移.当其苯环上3位被拉电子基团取代后,其电子传输性能提高;而被给电子基团取代后,电子传输性能降低.     

使用CNDO/S型近似方法计算NaNO_2晶体的倍频系数

本文使用CNDO/S型近似方法,计算(NO_2)~(-1)的单电子分子轨道,然后按基团理论的通用计算程序计算NaNO_2晶体的倍频系数,计算值和实验值符合得较好,计算结果明确指出:NaNO_2晶体倍频系数各向异性的原因来自基团的共轭π轨道,另外,本文的计算表明,有可能对非线性光学新材料探索提供计算机的预测。 本文还就非线性光学效应的双能级模型作了讨论,并指出了它的局限性。     

使用CNDO/S型近似方法计算NaNO2晶体的倍频系数

本文使用CNDO/S型近似方法,计算(NO₂)^-1的单电子分子轨道,然后按基团理论的通用计算程序计算NaNO₂晶体的倍频系数,计算值和实验值符合得较好,计算结果明确指出:NaNO₂晶体倍频系数各向异性的原因来自基团的共轭π轨道,另外,本文的计算表明,有可能对非线性光学新材料探索提供计算机的预测。本文还就非线性光学效应的双能级模型作了讨论,并指出了它的局限性。 关键词：     

运用分子模拟计算和NMR研究确定化合物3-(3,5-二甲基-2-吡咯亚甲基)-5-溴-吲哚酮的绝对构型

用MM2和半经验AM1方法对化合物进行计算,获得化合物两种构型的原子间距离参数,依据¹H NMR产生NOE效应所需条件预报分子中可能存在的NOE.通过与实验测得的核磁共振NOE效应结果对比,确定化合物构型.     

Dependence of the Electronic Spectra of the Chlorin Molecule on the Degree of Alternation of the Macrocycle Bond Lengths

The geometric structure of the chlorin molecule (H₂Ch) has been calculated by the restricted and unrestricted Hartree-Fock (RHF and UHF) methods with an AM1 Hamiltonian. Transformations of this molecule into excited electronic states have been calculated by the CNDO/S method. The RHF method without symmetry restrictions gives a plane structure for the chlorin macrocycle with an alternation of the lengths of the bonds along the 18-member azacyclopolyene and a C_1h symmetry for the molecule as a whole. The level of the first excited state Q₁ of this structure is substantially shifted (δ ≅ +4000 cm⁻¹) relative to the Q_x level of porphin (H₂P) toward shorter waves, which is in contradiction with the experimental data, according to which this shift is long-wave and is equal to δ = −400 to −550 cm⁻¹. The optimization of the geometry of H₂Ch by the UHF method has shown that it has a structure with an 18-member azacyclopolyene with bonds of equal lengths and a D_2h symmetry. For this geometry of H₂Ch the calculated shift of the Q_x level, equal to δ = −70 cm⁻¹, is bathochromic and the position of the Q_y level is practically exactly coincident with the experimental one. For the geometry calculated by the RHF method with restrictions on the D_2h symmetry of the 18-member azacyclopolyene δ = +180 cm⁻¹, and for the geometry calculated with restrictions on the highest C_2v symmetry of the H₂Ch molecule δ = +620 cm⁻¹. The latter result shows that the “natural” requirement for the C_2v symmetry of the H₂Ch macrocycle, which is frequently used in various calculations, is inadequate to achieve a quantitative agreement between the calculation and experimental data and, in this case, the lengths of the bonds along the 18-member azacyclopolyene are not equal. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 339–347, May–June, 2005.     

Theoretical study of the electronic ground states and low-lying singlet excited states of thiophene-based spirofluorenes

The electronic structures and optical properties of oligothiophene substituted spirofluorenes are investigated theoretically with semi-empirical quantum chemical calculations. A theoretical investigation of the interaction between two perpendicular π-systems of various oligothiophene substituted spirofluorenes is conducted. The results demonstrate that the interaction between two perpendicular branches is reduced by oligothiophene substitutions. Photoexcitation induced relaxation is mainly located on one of...     

溴代作用对竹红菌乙素分子性质影响的量子化学研究

用半经验量子化学方法ＡＭ１和ＰＭ３对竹红菌乙素及其溴代物进行了对比计算,考究了溴代作用对竹红菌乙素分子性质的影响,两种方法所得结果的均表明,溴代作用使分子的生成热、前线轨道能级及偶极矩等参数都有所降低,溴代作用也影响了竹红菌乙素分子内氢健的性质,并能使其对光的吸收产生红移。『     

Characterization of a Solvatochromic Fluorophore: 1-(2,2-Dicyanovinyo)-2,5-Dimethoxybenzene (DCN-2,5-DMOB)

Absorption spectra and steady-state fluorescence emission spectra for l-(2,2-dicyanovinyl)-2,5-dimethoxybenzene in five solvents were determined. Although the absorption spectra demonstrate little solvatochromism, emission peaks show a red shift of roughly 90 nm between cyclohexane and methanol or acetonitrile, which appears to indicate charge transfer associated with a relaxed, as opposed to a vertical, excited state. Semiempirical gas phase AM1 calculations on this compound and the related unsubstituted 2,2-dicyanovinyl benzene indicate a dihedral twist of roughly 35° between the phenyl and the dicyanovinyl planes for both molecules in their ground states, as well as substantial polarity associated with the ground states of these compounds.     

运用分子模拟计算和NMR研究确定化合物3-(3,5-二甲基-2-吡咯亚甲基)-5-溴-吲哚酮的绝对构型

用MM2和半经验AM1方法对化合物进行计算,获得化合物两种构型的原子间距离参数,依据¹H NMR产生NOE效应所需条件预报分子中可能存在的NOE.通过与实验测得的核磁共振NOE效应结果对比,确定化合物构型.     

Raman Spectrum Study on the Doping Effect in LiNbO3: MgO Crystals

Raman spectra of LiNbO₃: MgO crystals have been obtained and compared with Raman spectra of pure LiNbO₃ crystals. For both of the two kinds of Raman active modes (4A₁+9E), no changes of the numbers, frequency-shifts, and relative intensities of the Raman spectral lines are found. However, it is observed that some modes coupled to each other at room temperature. The observed modes coupling phenomena, disappeared at low temperature. It is shown from these results that the Raman spectral lines of A₁ (TO) and E (TO) vibrational modes are mainly determined by the (NbO₆) oxygen octahedra characteristic groups of LiNbO₃ crystals.     

Vibrational Analysis and Geometry Optimization of a Local Anesthetic by Means of the Am1 Semiempirical Method

The semiempirical method AM1 was used to optimize the geometric parameters: bond lengths, bond angles and torsional angles in the local anesthetic benzocaine hydrochloride. The frequencies and intensities of the normal modes were computed. These results were compared with the infrared and Raman spectroscopic data. A theoretical spectrum using several scale coefficients was plotted. Electron density maps in two and three dimensions were drawn. Several calculated thermodynamic parameters are discussed.     

双噻吩基四硫富瓦烯富勒烯C60几何构型与电子结构的理论研究

利用半经验AM1法研究双噻吩基四硫富瓦烯富勒烯 C60 (BTTTF C60 )和四硫富瓦烯 C60 (TTF C60 )的几何构型、电子结构和前线轨道 .计算结果显示 ,两化合物的TTF面发生弯曲 ,形成独特的空间构型 ,电子结构的分析表明其原因是由C60与TTF或BTTTF的相互作用引起的 .C60的LUMO能与BTTTF的HOMO能接近 ,易发生D A反应 ,形成BTTTF C60 .BTTTF C60和TTF C60的LUMO能仍较低 .LUMO分布集中在C60部分 ,表明BTTTF C60的C60母体仍可接受电子 .另外对两分子的电荷分布、HOMO及LUMO的分析比较 ,表明所设计的BTTTF C60分子可能产生与TTF C60分子类似的电荷分离态     

pH自旋探针分子的ESR波谱性质和量子化学研究─pH自旋探针应用研究之二

系统研究了咪唑类氮氧自由基作为pH自旋探针的ESR波谱特性．用量子化学方法AM1研究了pH自旋探针分子的几何结构、电子结构及电子自旋密度分布．aN理论值与实验结果基本一致．得到了pka值与电子密度关系曲线．指出了它们在生命科学中的应用前景．