N4H4分子取代基效应的量子化学研究

本文计算了甲基(-CH3),羟基（-OH）对1-丁氮烯和2-丁氮烯的取代基效应。当1-丁氮烯引入取代基后,N=N双键的键长变短,而N-N单键的键长增长。异构体2-丁氮烯的键长变化较小。当引入甲基或羟基后,N原子的孤对电子会与相应的N-C(N-O)键之间发生相互作用,使整个分子的超共轭作用增强。随着取代基数目的增多,总能量和生成热就会降低,取代基数目与分子能量（生成热）之间具有很好的相关性。     

用分子子图法计算硝基呋咱化合物的生成热

用新的分子子图法计算硝基呋咱类化合物的生成热 ,将呋咱基团视为母体 ,即基子图项 ;硝基、叠氮基、甲基、氰基拆分为一个个原子 ,从原子的角度来分分子子图 ,将碳、氢、氧、氮原子视为取代基 ,即亚子图项 .同时考虑呋咱基团的个数 ,考虑 1位、2位、3位、4位上碳、氢、氧、氮原子及双键、叁键对生成热的影响 ,还考虑不饱和度、总硝基个数、环的个数 (除呋咱环 )、氮氮及氮氧双键的个数对生成热的影响 .用这种新的分子子图编码方法 ,对硝基呋咱化合物的生成热进行了拟合和预估 ,取得了满意的结果 ,其回归方程的相关系数达到了 0 .995 4 .     

3种黄酮醇类化合物核磁共振碳谱的理论研究

在B3LYP/6-31G水平下优化了3种黄酮醇类（山奈酚,槲皮素,杨梅素）化合物的几何构型. 在振动分析中,均未出现虚频率. 在B3LYP/6-31G的水平下计算了该类化合物的核磁共振碳谱. 研究结果表明：3种分子均有分子内氢键形成,且分子内氢键的键长为0.17~0.18 nm左右 . 本文讨论了羟基引入之后对邻近C的化学位移的影响. 从取代基对NMR的影响来看,随着取代基对苯环的供电子能力的加强,取代基邻近的一些C的化学位移有所改变.      

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.     

NH3分子在LiH（100）表面吸附的第一性原理研究

采用第一性原理方法研究了NH₃分子在LiH（100）晶面的表面吸附情况.通过研究LiH（100）/NH₃体系的吸附位置、吸附能和电子结构,发现NH₃分子在LiH（100）晶面主要是化学吸附,初始位置为NH₃分子中N-H键在Li顶住时失去一个H原子,并在LiH（100）面形成NH₂基,其吸附能为0.511 eV,属于强化学吸附,吸附作用最强.此时NH₂基与附近H原子和Li原子之间为离子键作用,NH₂基中N—H键为共价键;NH₃分子中另一个H原子与LiH表面的一个H原子形成一个H₂分子逸出表面.H₂分子中H-H键为明显的共价键.     

DITFB/4-OH-TEMPO体系中卤键作用的19F DNP研究

卤键与氢键相似,是实现分子与分子非共价键连接的作用之一,其广泛地应用于工程材料和生命化学等领域．有关卤键相互作用的动态核极化（DNP）研究还未见报道．本文利用连续波-电子顺磁共振（CW-EPR）谱仪及自主研制的DNP实验平台对存在卤键相互作用的体系——1,4-二碘四氟苯（DITFB）/4-羟基-2,2,6,6-四甲基吡啶-1-氧自由基（4-OH-TEMPO）进行¹⁹F DNP研究,并与无卤键作用对照组——六氟苯（PFB）/4-OH-TEMPO的¹⁹F DNP增强效果进行了比较．结果发现,DITFB/4-OH-TEMPO较PFB/4-OH-TEMPO具有更窄的EPR线宽和更大的¹⁹F DNP增强．这表明自由基与DITFB卤键作用削弱了自由基之间的电子自旋-自旋相互作用,从而使自由基横向弛豫时间（T_2e）增加、线宽变窄,导致DNP饱和因子和增强倍数变大．因此,可以通过卤键调控自由基电子自旋相互作用,以改善核的DNP增强效果．     

取代基位置对轮烯衍生物一阶超极化率影响的理论研究

以 [12]轮烯为母体,通过改变取代基的位置构造了一系列轮烯衍生物,运用密度泛函B3YLP方法在6-31G(d)基组水平上计算了分子一阶超极化率β和紫外吸收光谱,研究了分子结构和非线性光学性能的关系. 研究发现,二维电荷转移（2DCT）分子2-5均具有较大的β值,且分子3的紫外吸收光谱最大吸收峰和其余分子相比发生蓝移,这对解决“非线性效率-透光性矛盾”给予了很大启示. 分子2-5的一阶超极化率的大小和分子构型关系密切,随着键长交替(BLA)的增加,分子的β值不断减小.     

新型蓝紫光荧光分子N2-烷基-1,2,3-三氮唑的光谱性质

采用对甲苯磺酸催化合成N¹-烷基-1,2,3-三氮唑和N²-烷基-1,2,3-三氮唑。两种产物均有紫外吸收,但只有N²-烷基-1,2,3-三氮唑有荧光。研究了在N²位和C⁴位引入不同取代基后化合物的紫外可见吸收光谱和荧光激发发射光谱。结果表明,N²位是甲苯基或C⁴位是吸电子取代基的荧光强度最高,荧光量子产率高达79%,调节C⁴位取代基可以更好地提升荧光性能（荧光发射波长300~440 nm,Stokes位移49~70 nm）。N²-烷基-1,2,3-三氮唑良好的蓝紫光荧光性能使其具有潜在应用价值。     

六硝基六氮杂三环十四烷对二呋咱（HHTTD）的合成

杂环硝胺是重要的含能化合物，研究表明：用羰基取代环胺中的次甲基，可以提高炸药的结晶密度，进而提高爆速，比如硝基甘脲及我国20世纪70年代就已合成的六硝基六氮杂三环十二烷二酮。如果将呋咱基引入到氮杂稠环类化合物分子结构中，以取代结构中的羰基，则又有可能创造一类密度及能量都非常高的炸药。基于该思想，文中利用两种化合物DAF和1，4-甲酰基-2，3，5，6-四羟基哌嗪（DFTHP），合成了目标炸药分子：六硝基六氮杂三环十四烷对二呋咱（HHTTD）及前体化合物六氮杂三环十四烷对二呋咱（HTTD）。文中给出了HTTD的合成方法及HTTD的硝化反应，提出了一种新化合物HHTTD的合成方法并对羟胺缩合反应进行了较详细的研究，HTTD及HHTTD的结构见图1。     

Theoretical investigation of a series of bis(1H-tetrazol-5-yl)furazan and bis(1H-tetrazol) derivatives as high-energy-density materials

Using density functional theory (DFT), a series of bis(1H-tetrazol-5-yl)furazan and bis(1H-tetrazol) derivatives with different linkages and substituents are investigated theoretically as potential high-energy-density materials (HEDMs). The heat of formation (HOF), detonation properties, natural bond orbital (NBO) and thermal stabilities are calculated and reported. The introduction of a furazan ring, an –N=N– bridge group and an –N₃ substituent is beneficial to increase the HOF of the title compounds. NBO analysis shows that there are electronic delocalisation effects among the bridge groups, furazan and tetrazole rings, and substituted groups. The conjugation effects and electronic transitions are influenced by the different linkages and substituents. The estimated detonation velocities and pressures indicate that the –ONO₂ and –NO₂ groups and the –N=N– linkage play important roles in enhancing the detonation properties. The bond dissociation energy (BDE) calculations reveal that the –NO₂ group is the substituent group which causes the least thermal stability. The bond between the substituent group and the tetrazole ring is the weakest bond in the title molecules. Considering the detonation performance and the thermal stability, 17 compounds may be promising candidates for HEDMs with good performance. Eight of them (A3, A4, C3, C4, D3, F3, G1 and G3) have better detonation properties than HMX.     

Comparative studies on CH⋯F− hydrogen bond formation in benzene and exocyclically substituted pentafulvene derivatives

Optimization of CH?F^? complexes of exo‐substituted pentafulvene and meta‐substituted and para‐substituted benzene (substituents: NMe₂, NHMe, NH₂, NHOH, OH, OMe, Br, Cl, F, Me, CCH, CF₃, CONH₂, COMe, CHO, NO₂, NO, and CN) have been performed at the density functional theory level by using Becke hybrid B3LYP functional with 6‐311++G(d,p) basis set. The acidity of the ring CH bond in benzene and fulvene are of similar magnitude, whereas the acidity of the fulvene exocyclic CH₂ group is significantly higher. Various properties based on the H?F^? hydrogen bond (bond length, electron density at BCP, and bond dissociation energy), and the whole molecule (HOMA, sEDA, pEDA, substituent active region, and substituent effect stabilization energy) were analyzed and compared between the fulvene and benzene systems. Sensitivity of the ring CH?F^? hydrogen bond and other substituent dependent properties to substituent effect is substantially greater in fulvene than that of benzene derivatives. In fulvene, the 3‐position is more sensitive than the 4‐position. The sEDA and pEDA parameters used to measure sigma‐electron and pi‐electron excess/deficiency of the ring are mutually correlated for the studied systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Computational studies of the effects of ortho‐ring and para‐ring activation on the kinetics of SNAr reactions of 1‐chloro‐2‐nitrobenzene and 1‐phenoxy‐2‐nitrobenzene with aniline

Computational studies are reported for reactions of 4‐substituted‐1‐chloro‐2,6‐dinitrobenzenes 1 , 6‐substituted‐1‐chloro‐2,4‐dinitrobenzenes 2 and some of the corresponding 1‐phenoxy derivatives 3 and 4 with aniline in the gas phase. The effects of substituent groups in the calculated energy values for reactants 1–4 , transition states structures, intermediates and products formed in the reactions between the compounds and anilines have been compared. Calculated bonds length and angles from optimized structures of the reactants were comparable with values reported for some of compounds 1–4 obtained by X‐ray crystal structures analysis. Generally, the decomposition of the Meisenheimer intermediate to the products requires more energy compared with the reactants except for when R = H. The order of stabilization of the intermediate was found to reflect the relative order of activation by substituents in the substrates. The 4‐substituted‐1‐chloro‐2,6‐dinitrobenzenes 1 and the phenoxy derivatives 3 were found to be more stable than their corresponding 6‐substituted analogues. This is an indication that the rate of nucleophilic attack at 1‐position will increase with increasing ring activation but may be reduced by steric repulsion at the reaction centre that increases in the order Cl < OPh. However, the steric hindrance to the steps involved in nucleophilic substitution by aniline is significantly increased when the substrates contain two ortho‐substituents. In most cases, the rate determining step is the decomposition of the σ‐adduct intermediate except with 1‐chloro‐2,6‐dinitrobenzenes 1 and 6‐substituted‐1‐chloro‐2,4‐dinitrobenzenes 2 , either because of reduction in ring activation or the presence of bulky ortho‐substituents in the chloro compounds 1 and 2 . Copyright © 2014 John Wiley & Sons, Ltd.     

Electronic effects of heterocyclic ring systems as evaluated with the aid of 13C and 15N NMR chemical shifts and NBO analysis

The electronic effects of the 5‐ and 6‐membered heterocyclic rings on the C?N? N unit of five different hydrazone derivatives of pyridine‐2‐, ‐3‐ and ‐4‐carbaldehydes, pyrrole‐2‐carbaldehyde, furan‐2‐ and ‐3‐carbaldehydes and thiophene‐2‐ and ‐3‐carbaldehydes have been studied with the aid of ¹³C and ¹⁵N NMR measurements together with the natural bond orbital (NBO) analysis. As model compounds are used the corresponding substituted benzaldehyde derivatives. The polarization of the C?N unit of the hydrazone functionality of the heteroaryl derivatives occurs in an analogous manner with that of phenyl derivatives. The electron‐withdrawing heteroaryl groups destabilize and the electron‐donating groups stabilize the positive charge development at the C?N carbon while the effect on the negative charge development is opposite. The ¹⁵N NMR chemical shift of the C?N and C?N? N nitrogens and the NBO charges at C?N? N unit can be correlated with the replacement substituent constants σ of the heteroaryl groups. ¹³C NMR shifts of the C?N carbon of N,N‐dialkylhydrazones of the heteroarenecarbaldehydes can be correlated with a dual parameter equation possessing the polar substituent constant σ* of the heteroaryl group and the electronegativity of the heteroatom as variables. Copyright © 2008 John Wiley & Sons, Ltd.     

C-13 and H-1 NMR Study of Alkyl and Aryl-Substituted 1-(4′-Dimethylaminobenzylideneamino)pyridinium Perchlorates

C-13 and H-1 NMR spectra of some 1-(4′-dimethylaminobenzylideneamino)pyridinium perchlorates show that the angle of twist of the pyridine ring in unsubstituted, 1, and 2-alkyl substituted compounds 2–5 is comparable. However, it is considerably increased in 2,6-dialkyl derivatives. As seen from the spectral data, pyridine and phenyl rings in 2,6-diphenyl derivative 15 are not coplanar. The effect of 4-alkyl substituent is of hyperconjugative chacter. In general, the amount of the positive charge at C-4 in 2,6-dialkyl substituted salts is higher as compared to 2-monosubstituted compounds.     

An Investigation of 13C-NMR Spectra of Some Intramolecular Hydrogen Bonded and Non-Bonded Azo Dyes

The ¹³C-NMR spectra of the azo dyes which were synthesized by reacting substituted benzenediazonium chloride with derivatives of some phenol have been measured. The spectral data of these compounds were described considering intramolecular hydrogen bond and not. The chemical shift assignments were made regarding substituent effects.     

DFT and ab initio study on non-linear optical (NLO) properties of some organic complexes with different conjugate linker and substituent groups

A series of Schiff-bases chromophores containing imine or double C=C bond linkers between the donor and acceptor have been studied by first-principles calculations. The molecular structures, electronic properties and second order nonlinearities were investigated by DFT and ab initio methods. The optimized structural parameters of these Schiff-base derivates showed that these compounds are stable. The results of TD-DFT calculations indicate that the derivatives with the heterocyclic and imine linker have a red shift absorption compared to derivatives with the double C=C or N=N bonds. The analysis of the frontier molecular orbitals indicates that the CN group and the heterocycle linked by the CN or imine group has contribution to the LUMO orbital while the groups N(CH₃)₂ and the benzene ring linked by the double C=C or N=N bond have contribution to the HOMO orbital. The CN and the heterocyclic acceptors enable the derivatives to have a larger first static hyperpolarizability. However, the compounds 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-pyridin-1-yl}-propanel-1-sulfonoperoxoic acid and 3-{4-[(4-Dimethylamino-phenylimino)-methyl]-quinolin-1-yl}propanel-1-sulfonoperoxoic acid with a substituent also have large first static hyperpolarizabilities due to the overwhelming contributions of electron density of the group to the HOMO orbital, that is, the HOMO orbital were constituted by the SO ₃ ^? group only. In order to understand the influence of the energy gap (??E) between the HOMO and the LUMO orbitals on the first static hyperpolarizability, we calculated the energy gap (??E) of all Schiff-base compounds. The results show that the smaller the HOMO-LUMO energy gap the larger the first static hyperpolarizability. The present study demonstrated that these compounds which have pure C=N double bond and heterocyclic substitution groups may have potential applications in the development of NLO materials.     

The substituent effect on the UV energy of 4,4′‐disubstituted benzylideneanilines

In this paper, 72 samples of disubstituted benzylideneanilines were all synthesized, and their UV data were measured in anhydrous ethanol. In the study on the UV energy of the titled compounds with single substituent changed, for the effect of the aniline substituent Y on the UV wavenumbers, its UV data can be correlated with a dual‐parameter equation; for the effect of benzylidene substituent X on the UV data, its UV energy can be correlated with a single‐parameter equation (Y is an electron‐withdrawing group and H) or a dual‐parameter equation (Y is an electron‐donating group). In the study on the UV energy of model compounds with double substituents changed, a correlation equation between the UV absorption wavenumbers and substituent constants and σ_p, was obtained. For 72 samples of 4,4′‐disubstituted benzylideneanilines, the correlation coefficient was 0.9876, and the standard deviation s was only 358.46 cm^–1. The equation can be used to predict well the UV energy of BA derivatives. It was found that Δσ² is a better parameter than σ_XY to scale the substituent cross‐interaction effect on the UV wavenumbers of benzylideneanilines molecules. The results implied that the law of substituent effect on the UV energy of titled compounds is different from that of substituted stilbenes, and it is helpful to understand the effect of substituent effects on the chemical and physical properties of conjugated compounds with an imine bridging group (C = N) or a nonplanar parent. Copyright © 2011 John Wiley & Sons, Ltd.