三种常见农药荧光光谱的量子化学研究

扑海因、啶虫脒和西维因是几种较为常用的农药分子。文章对此三种化合物分子的荧光光谱进行了理论研究。在B3LYP/6-31G水平下优化了这三种化合物的几何构型。在振动分析中,均未出现虚频率。基于此,在B3LYP/6-31+G的水平下计算了该类化合物的荧光光谱,所有计算结果与实验值基本吻合。此外,作者还发现扑海因分子中形成了分子内氢键,但是不太稳定,其键长为0.234 8 nm左右。     

20,20-二氯-1,10-二甲氧基三环[5,4,0,012,19]十一碳 -1,5,6-三烯结构和性质的理论研究

在RHF/6-31G、B3LYP/6-31G和MP2/6-31G水平下优化了标题化合物的平均几何构型,用B3LYP/6-31G方法计算了该化合物的红外光谱.并用GIAO分别在B3LYP/6-31G、B3LYP/6-311G和B3LYP/6-311++G水平对该化合物的核磁共振谱进行了研究.计算结果与实验结果吻合很好.同时对在合成过程中发现的两个中间产物进行了理论计算,研究证实了合成标题化合物时中间产物的存在.     

新型含氧亚甲基和亚胺桥键液晶化合物分子结构与光谱的密度泛函理论研究

采用密度泛函理论方法在B3LYP/6-31G*水平上对6个新型含氧亚甲基和亚胺桥键液晶化合物分子的几何结构进行优化计算,讨论了取代基H,CH3,CH3O,C2H5O,NO2,Cl对分子电荷、前线轨道能量和电子吸收光谱等性质的影响.在此基础上使用含时密度泛函理论方法计算了分子第一激发态的电子垂直跃迁能,得到最大吸收波长λmax.计算表明,取代基的引入导致最大吸收波长红移.     

取代基对8-羟基喹啉金属配合物电子光谱和二阶非线性光学性质的影响

在B3LYP/LANL2DZ/6-31G^*水平上优化目标化合物分子的几何结构,并分别在TD- B3LYP/LANL2DZ/6-31++G^**和B3LYP/LANL2DZ/6-31++G^**水平计算目标化合物分子的电子吸收光谱和二阶非线性光学性质.计算结果表明,引入共轭给电子基使配合物分子的最大吸收波长红移,强共轭吸电子基的引入使配合物的最大吸收波长蓝移,取代基的引入使IrQ₃型配合物的二阶非线性光学性质明显增大.对AgQ型配合物,电子跃迁属于配体内部的电荷转移（LLCT）.对PtQ₂和IrQ₃型配合物,电子跃迁属于LLCT和部分金属向配体的电荷转移.取代基对AgQ,PtQ₂,IrQ₃型配合物分子的跃迁性质几乎无影响. 关键词： 8-羟基喹啉金属配合物 电子光谱 二阶非线性光学性质 密度泛函理论     

甘氨酸和丙氨酸二肽、三肽中N-H…O=C分子内氢键键能的理论研究

提出一种计算多肽中N-H…O=C分子内氢键键能的新方法.并将新方法应用于计算甘氨酸和丙氨酸二肽、三肽中N-H…O=C分子内氢键键能.利用密度泛函理论B3LYP/6-31G(d)方法优化几何构型和计算频率.对全部结构计算MP2/6-311 G(3df,2p)水平上的单点能量.结果表明:在甘氨酸二肽中氢键键能为-6.38 kcal/mol,在丙氨酸二肽中氢键键能为-7.09-、6.25 kcal/mol;在甘氨酸三肽中氢键键能为-5.62 kcal/mol,在丙氨酸三肽中氢键键能为-5.37,-5.74 kcal/mol.     

2,4,6-三甲氧基苯-1-O-D葡萄糖苷的核磁共振谱的理论研究

应用规范不变原子轨道GIAO法,分别在HF/6-311+G(2d,p)//B3LYP/6-31G(d)和HF/6-311+G(2d,p)//B3LYP/6-31G(d,p)水平上,计算了从卫茅科南蛇藤属植物苦皮藤中分离鉴定出的2,4,6-三甲氧基苯-1-O-D葡萄糖苷(化合物1)的α和β分子构型的1HNMR和13CNMR的化学位移值,并对理论计算值与实验值的误差进行了统计分析,其中β分子构型的计算值与实验值较为接近,结合α和β分子构型的总能量计算值,预测化合物1分子应择型于β构型,即为2,4,6-三甲氧基苯-1-O-β-D葡萄糖苷,这与根据糖的端基质子化学位移和耦合常数实验值(δH=4.81,J=7.3Hz)推断的结论相吻合,进一步说明理论计算的合理性.     

Theoretical Study of the C-Cl Bond Dissociation Enthalpy and Electronic Structure of Substituted Chlorobenzene Compounds

利用密度泛函(DFT)三种交换/相关函数(B3LYP, B3PW91,B3P86)结合6-31G**和6-311G**基组,计算了13个取代氯苯化合物的键离解能. 结果表明B3P86/6-311G**方法是计算取代氯苯化合物键离解能的可信方法,研究发现C-Cl键的键离解能与所使用的基组和计算方法密切相关,取代基对C-Cl键的键离解能的影响不明显. 研究了目标化合物的前线轨道能级差,并对取代氯苯化合物的热稳定性做了评估.     

苯硫酚分子内质子转移取代基效应的理论研究

在B3LYP/6-311+G(d, p)水平上研究了2-(1H-咪唑)苯硫酚(1d)、2-(噁唑)苯硫酚(2d) 、2-(噻唑)苯硫酚(3d)及其衍生物的基态质子转移过程, 探讨取代基电子效应对质子转移的影响. 结果表明: 吸电子引入后分子平面电子密度减小, N2-H1间距减小, 分子内氢键增强, 醇式到酮式质子转移能垒减小; 供电子基引入后分子平面电子密度增大, N2-H1间距增大, 分子内氢键减弱, 质子转移能垒增大. Localized orbital locator(LOL)分析表明: 取代基的引入对N1原子成键性质产生影响明显. 三者质子转移能垒大小为1d<3d<2d, 取代基引后能垒相对大小不变.     

苯硫酚分子内质子转移取代基效应的理论研究

在B3LYP/6-311+G(d,p)水平上研究了2-(1H-咪唑)苯硫酚(1d)、2-(噁唑)苯硫酚(2d)、2-(噻唑)苯硫酚(3d)及其衍生物的基态质子转移过程,探讨取代基电子效应对质子转移的影响.结果表明:吸电子引入后分子平面电子密度减小,N2-H1间距减小,分子内氢键增强,醇式到酮式质子转移能垒减小;供电子基引入后分子平面电子密度增大,N2-H1间距增大,分子内氢键减弱,质子转移能垒增大.Localized orbital locator(LOL)分析表明:取代基的引入对N1原子成键性质产生影响明显.三者质子转移能垒大小为1d3d2d,取代基引后能垒相对大小不变.     

寡聚(亚硅基二炔基蒽)电子结构和光谱性质的密度泛函理论研究

聚(亚硅基二炔基蒽)(PSDEA)经实验测定具有空穴传输的能力. 为了模拟此高聚物的性质, 设计了一系列亚硅基二炔基蒽(SDEA)的寡聚物,利用密度泛函理论方法在B3LYP/6-31G(d)水平上对其构型进行优化. 寡聚物的能隙随着链长的增加而减少,同时蒽环上吸电基团的存在也使能隙减少. 在B3LYP/6-31G水平上计算寡聚物的¹³C化学位移以及蒽环中心位置的核独立化学位移. 寡聚物中与硝基相连的碳原子的化学位移与未连硝基的寡聚物中相同碳原子的化学位移相比向高场移动. 蒽环中心的芳香性在吸电子基团存在时减弱,但随着亚硅基数目的增加而增强. 用于核独立化学位移计算的最敏感区域是蒽环上方0.1 nm处.     

3（或）4—取代苯甲亚氨酸酯中取代基效应的^13C—NMR研究

本文测定了三个3(或4)-取代苯甲亚氨酸乙酯(1)和八个N-氰甲基-3(或4)-取代苯甲亚氨酸乙酯(2)的~(13)C-NMR谱。归属了1 和2和各碳化学位移。求得了的取代基化学位移(substituent Chemical Shift,SCS)。碳-13化学位移与单取代苯的取代基化学位移(SCS)的相关分析表明:4-取代苯甲亚氨酸酯1 b～g和2b～e中,除C_(2,6)外,其他各芳碳的化学位移值与加和规则基本相符;3-取代苯甲亚氨酸酯1h～j和2f～h中,除C_1外,其他各芳碳的化学位移值与加和规则基本相符。另外,本文还进行了碳-13化学位移与σ_(I)/σ_(R)~O和F/M的双参数相关分析。     

Substituent Effects in the Carbon NMR of Aliphatic bis(Amidinohydrazones) ['Bis(Guanylhydrazones)']. Construction of a set of Quantitative Empirical Rules. Unambiguous Assignment of Several Previously Unassigned Carbon Resonances

The effects of substituents on the ¹³C chemical shifts of the various carbons of aliphatic 1,2-bis(amidinohydrazones) have been systematically studied using previously published experimental data as the basis. Mathematical formulae have been constructed that describe the effects of various structural features of the molecules on the chemical shifts of the carbons and that also make possible an accurate prediction of the spectra of compounds belonging to this class. It is also shown that the effects of side chains on the chemical shifts of the two carbons of the glyoxal moiety are strictly additive. A mathematical model has been constructed that makes possible a very accurate prediction of the chemical shift of each one of the glyoxal carbons of symmetrical as well as unsymmetrical bis(amidinohydrazones). In the case of ethylmethylglyoxal bis(amidinohydrazone) free base dissolved in dimethyl sulfoxide, the theory predicts that the glyoxal carbons resonate at 157.45 ppm (the one connected to the ethyl group) and 151.21 ppm, while the experimental values are 157.30 and 151.29 ppm. This has, for the first time, made possible the unambiguous individual assignment of the resonances of the glyoxal carbons of unsymmetrical dialkylglyoxal bis(amidinohydrazones). The results also indicate that in all such compounds so far studied, that one of the glyoxal carbons that bears the longer alkyl side chain resonates more downfield than does the other one. This result is in total agreement with conclusions derived from relaxation time measurements.     

2,4—二氨基—6—(取代苄基)—5—甲基吡啶(2,3d)并嘧啶类化合物的~(13)C NMR研究

2,4-二氨基-6-(取代苄基)-5-甲基吡啶(2,3d)并嘧啶类化合物是一类很有前途的抗癌新药。本文研究了24种7位氯代和氧代的该类化合物的碳谱,归属了母核及取代苄基上各碳的化学位移,并对两种取代对母核碳上的化学位移的影响规律进行了探讨,文中所有数据迄今未见文献报道。     

2D-NMR Studies on Bis(Amidinohydrazones). I. A Proton-Carbon Heteronuclear Shift Correlation Study on the Enzyme Inhibitors Methylpropylglyoxal Bis(Amidinohydrazone) and Butylmethylglyoxal Bis(Amidinohydrazone)

The first 2D-NMR study on bis(amidinohydrazones) [‘(guanylhydrazones)’] is reported. Heteronuclear shift correlation (HETCOR) experiments were performed on the enzyme inhibitors methylpropylglyoxal bis(amidinohydrazone) (MPGBG) and butylmethylglyoxal bis(amidinohydrazone) (BMGBG). The results obtained made possible the unambiguous assignment of the previously unassigned resonances of the side-chain carbon atoms of MPGBG. The results indicate that the chemical shifts of the protons of the propyl side chain of MPGBG are positively correlated to the ¹³C chemical shifts of the corresponding carbon atoms. The chemical shifts of the carbon atoms of the propyl side chain decrease as a function of the position of the atom in the side chain, the terminal methyl group having the lowest shift value. These results are in full agreement with previous results on the analogous compound dipropylglyoxal bis(amidinohydra- zone), whose side-chain carbon resonances were assigned using totally different techniques. In the case of BMGBG, however, HETCOR contour plots clearly indicate that there is no correlation between the chemical shifts of the protons of the butyl side chain and the 13C chemical shifts of the corresponding carbons. Because the 200 MHz proton spectrum of BMGBG is not fist-order, only the 1 3 resonance～ of the methyl substituent and the resonances of carbons 1 and 4 (but not those of carbons 2 and 3) of the butyl side chain could be assigned on the basis of the HETCOR study. Yet, the results gave a rough estimate of the previously unknown chemical shifts of the protons bound to butyl carbon atoms 2 and 3.     

碘杂环类化合物的13C NMR谱研究

合成了一系列含不同杂原子的3,6二硝基二苯并六元碘杂环类化合物,应用¹³C-¹H COSY谱对它们的¹³C NMR谱峰进行了归属,讨论了杂原子及碘离子对谱峰的影响情况.     

2,4-二氨基-6-(取代苄基)-5-甲基吡啶(2,3d)并嘧啶类化合物的13C NMR研究

2,4-二氨基-6-(取代苄基)-5-甲基吡啶(2,3d)并嘧啶类化合物是一类很有前途的抗癌新药。本文研究了24种7位氯代和氧代的该类化合物的碳谱,归属了母核及取代苄基上各碳的化学位移,并对两种取代对母核碳上的化学位移的影响规律进行了探讨,文中所有数据迄今未见文献报道。     

2D NMR技术在多季碳二萜结构确定中的应用

应用二维核磁共振技术（2D NMR：¹H-¹H COSY、HMQC、HMBC）, 尤其是HMBC谱准确归属了多季碳二萜伊丽莎白素B（Elisabatin B）的¹H,¹³C信号,并经与已报道的数据比较,进一步明确指定了11个季碳的化学位移. 以伊丽莎白素B为例,较系统阐明了几种二 维核磁共振技术在天然产物结构确定中的作用和方法.     

Knight shift tensors and π-spin densities in the organic metals αt-(BEDT-TTF)2I3 and (BEDT-TTF)2Cu(NCS)2

¹³C-MASS spectra of pure BEDT-TTF and of the organic metals α_t-(BEDT-TTF)₂I₃ and (BEDT-TTF)₂Cu(NCS)₂ were recorded atν _L = 68 MHz. Isotropic shifts and the principal components of the shift tensors were determined, respectively, from the center and spinning side bands. For pure BEDT-TTF which is a diamagnetic insolator, the measured shifts arechemical shifts while for the organic metals they are the sum of chemical and Knight shifts. In each of the compounds the shifts are assigned ingroups to theinner, middle andouter carbons of the BEDT-TTF molecule. For the organic metals the separation of the experimental shifts into chemical and Knight shifts is discussed. From the anisotropic part of the Knight shift tensors the π-spin densities at the carbon and sulphur positions of the BEDT-TTF molecule are inferred. The result is that the π-spin density of the unpaired hole is concentrated on the center part of the BEDT-TTF molecule, i.e., on the inner and middle carbons, and on the inner sulphurs. It is argued that the current density is concentrated on this part of the BEDT-TTF molecule as well.     

Separation of aromatic-carbon 13C NMR signals from di-oxygenated alkyl bands by a chemical-shift-anisotropy filter

Selection of alkyl-carbon and suppression of aromatic-carbon 13C nuclear magnetic resonance (NMR) signals has been achieved by exploiting the symmetry-based, systematic difference in their 13C chemical-shift anisotropies (CSAs). Simple three- or five-pulse CSA-recoupling sequences with "gamma-integral" cleanly suppress the signals of all sp2- and sp-hybridized carbons. The chemical-shift-anisotropy-based dephasing is particularly useful for distinguishing the signals of di-oxygenated alkyl (O-C-O) carbons, found for instance as anomeric carbons in carbohydrates, from bands of aromatic carbons with similar 13C isotropic chemical shifts. The alkyl signals are detected with an efficiency of > 60%, with little differential dephasing. Combined with C-H dipolar dephasing, the CSA filter can identify ketal (unprotonated O-C-O) carbons unambiguously for the first time. Conversely, after short cross polarization and the CSA filter, O-CH-O (acetal) carbon signals are observed selectively. The methods are demonstrated on various model compounds and applied to a humic acid.