胺(或氨) - CHCl3系CT复合物密度泛函法研究

报道对氨(NH3母体)、甲胺(CH3NH2)、二甲胺[(CH3)2NH]、三甲胺[(CH3)3N]与三氯甲烷(CHCl3)形成的系列复合物的理论研究结果。把复合物看作一个超分子,在B3LYP/6-311G(d,p)的水平上进行密度泛函法计算,并运用完全均衡校正法进行基组超位误差校正(BSSE)。探讨该系列复合物的电子结构与相关性质,如稳定性、电荷转移及主要几何参数的变化规律等,结果表明,形成复合物的稳定性次序为NH3－CHCl3(Ⅰ)>CH3NH2-CHCl3(Ⅱ)>(CH3)2NH-CHCl3(Ⅲ)>(CH3)3N-CHCl3(Ⅳ)。形成复合物的过程包含着电荷转移。该系列复合物的稳定性与电荷转移量、前线轨道能量差△εL-H及广义H键距离良好的线性关系,与结合点的电荷布居也有密切的关系,复合物的稳定性是分子间共价作用和静电作用两方面因素综合的结果。计算结果能较好地解释有关的实验现象和规律。     

Water effect on the o-h dissociation enthalpy of para-substituted phenols: a DFT study

The effect of water on the O-H bond dissociation enthalpy (BDE) of para-substituted phenols has been investigated by means of DFT calculations. It is shown that the experimental BDE values are fairly well-reproduced by simple B3LYP/6-31G* calculations carried out on the phenol/phenoxyl-water complexes taking into account only hydrogen-bonding (HB) interactions of water molecules with molecular sites (HB model). On the contrary, the BDE values computed with the polarizable continuum model (PCM/B3LYP/6-31G*)8 are overestimated by about 3-4 kcal/mol. Discrepancy between theory and experiment increases using the PCM method in addition to the HB model. Calculations show that, in general, the HB interaction with water molecules decreases the BDE of phenols bearing electron-releasing groups while increasing the BDE of phenols bearing electron-withdrawing substituents. This opposite effect is explained by considering the resonance structures with charge separation both in phenols and in phenoxyl radicals. With electron donors, the phenoxyl radical is preferentially stabilized by the HB acceptor interaction with two water molecules, while with electron acceptors the phenol is preferentially stabilized by the HB donor interaction with one water molecule.     

胺(或氨)一CHCI3系CT复合物密度泛函法研究

报道对氨(NH3,母体)、甲胺(CH3NH2)、二甲胺[(CH3)2NH]、三甲胺[(CH3)3N]与三氯甲烷(CHCL3)形成的系列复合物的理论研究结果．把复合物看作一个超分子,在B3LYP/6-311G(d,p)的水平上进行密度泛函法计算,并运用完全均衡校正法进行基组超位误差校正(BSSE).探讨该系列复合物的电子结构与相关性质,如稳定性、电荷转移及主要几何参数的变化规律等.结果表明,形成复合物的稳定性次序为NH3-CHCl3(Ⅰ)>CH3NH2-CHCL3(Ⅱ)>(CH3)2NH-CHCl3(Ⅲ)>(CH3)3N-CHCl3(Ⅳ).形成复合物的过程包含着电荷转移.该系列复合物的稳定性与电荷转移量、前线轨道能量差ΔεL-H及广义H键距离有良好的线性关系,与结合点的电荷布居也有密切的关系.复合物的稳定性是分子间共价作用和静电作用两方面因素综合的结果.计算结果能较好地解释有关的实验现象和规律.     

Theoretical study of the inclusion processes of octopamine with β-cyclodextrin: PM6, ONIOM,and NBO analysis

The inclusion process involving β-cyclodextrin with octopamine (OA) was investigated by using PM6, HF/3-21G*, B3LYP/6-31G (d), WB97XD/6-31G (d) methods and several combination of ONIOM2 hybrid calculations. The obtained results clearly indicate the orientation in which the guest molecule penetrates into the hydrophobic cavity of β-CD with the aromatic ring is energetically preferred. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify donor–acceptor interactions between host and guest molecules. A study of these complexes in solution was carried out using the CPCM model to examine the influence of solvation on the stability of the octopamine/β-CD complex.     

Specific hydration effects on oxo-thio triazepine derivatives

The specific hydration of 2,7-dimethyl-1,2,4-triazepine oxo-thio derivatives by one water molecule has been investigated at the B3LYP/6-311++G(3df,2p)//B3LYP/6-311+G(d,p) level of theory. The existence of different hydrogen bond (HB) donor and acceptor centers in these molecules led to different kinds of hydrogen bonds (CH-O, OH-S, NH-O, OH-N, and OH-O) and different kinds of complexes. Among them, the most stable structures correspond to complexes where the heteroatom X or Y at positions 3 and 5 behaves as HB acceptor and the hydrogen atom associated with the nitrogen atom at position 4 as HB donor. In accordance with previous studies, it has been shown that the thiocarbonyl group forms stronger HBs than the carbonyl group because the sulfur atom is a better HB acceptor than the oxygen one. With the help of the AIM (atoms in molecules) theory and ELF (electron localization function) analysis, it has been shown that, in the case of 3O5O, 3S5O, and 3S5S, the most basic site is the heteroatom at position 3, while in 3O5S species the most basic center is the sulfur atom.     

Computational study on the encapsulation of ethylparaben into β-cyclodextrin

Two models namely A and B were considered to investigate the inclusion process of ethylparaben into β-CD cavity by means PM3, HF/6-31G (d) and B3LYP/6-31G (d). The obtained results with PM3 method clearly indicate that the formed complexes are energetically favored with or without solvent; the B complex is found more favored than A complex. The calculated deformations energies show that the geometry of β-CD is deformed in the complexation process on the other hand the ethylparaben do not undergo deformation. Finally, From NBO analysis, the donor and acceptor interactions between ethylparaben and β-CD were analyzed and discussed.     

Theoretical study of novel porphyrins bearing electron donor–acceptor groups

This research project is focused on molecules that comprise a series of asymmetrically A₃B‐type meso‐substituted free‐base porphyrins and their related Zn‐metalloporphyrins. A and B were taken as electron‐donor and electron–acceptor groups. Full geometry optimizations without symmetry constrains were performed with B3LYP/6‐31G(d,P) methodology. Time‐dependent density functional theory calculations of the optimized structures indicate that there is a good agreement with the available experimental results. The highest occupied molecular orbital–lowest occupied molecular orbital (LUMO) gaps (ranging between 2.62 and 2.80 eV) are similar to those reported before for other porphyrins (2.29 eV). Also, the LUMO is situated close to the conduction band of titanium oxide, increasing the possibility of a charge transfer process. As porphyrins may act as electron transfer systems, the electron donor–acceptor capacity of these systems is characterized using two parameters; electrodonating (χ?) and electroaccepting (χ+) electronegativity. The main goal of this investigation is to analyze the electronic structure and the donor–acceptor properties of these porphyrins to see if these compounds could be useful for further applications related to the design of solar cells. © 2012 Wiley Periodicals, Inc.     

气相中O3与HSO自由基间的氢键复合物

气相中O3与HSO自由基之间的相互作用及其反应在大气化学中非常重要.在DFT-B3LYP/6-311++G**和MP2/6-311++G**水平上求得O3+HSO复合物势能面上的稳定构型,B3LYP方法得到了三种构型(复合物Ⅰ,Ⅱ和Ⅲ),而MP2方法只能得到一种构犁(复合物Ⅱ).在复合物Ⅰ和Ⅲ中,HSO单元中的1H原子作为质子供体.与O3分子中的端基O原子作为质子受体相互作用,形成红移氢键复合物;而在复合物Ⅱ中,虽与复合物Ⅰ和Ⅲ中具有相间的质子供体和质子受体,却形成了蓝移氢键复合物.B3LYP/6-311++G**水平上计算的单体间相互作用能的计算考虑了基组重甍误差(BSSE)和零点振动能(ZPVE)校正,其值在-3.37到-4.55 kJ·mol-1之间.采用自然键轨道理论(NBO)对单体间相互作用的本质进行了考查,并通过分子中原子理论(AIM)分析了三种复合物中氢键的电子密度拓扑性质.     

气相中O3与HSO自由基间的氢键复合物

气相中O3与HSO自由基之间的相互作用及其反应在大气化学中非常重要. 在DFT-B3LYP/6-311++G**和MP2/6-311++G**水平上求得O3+HSO复合物势能面上的稳定构型, B3LYP方法得到了三种构型(复合物I, II和III), 而MP2方法只能得到一种构型(复合物II). 在复合物I和III中, HSO单元中的1H原子作为质子供体, 与O3分子中的端基O原子作为质子受体相互作用, 形成红移氢键复合物; 而在复合物II中, 虽与复合物I和III中具有相同的质子供体和质子受体, 却形成了蓝移氢键复合物. B3LYP/6-311++G**水平上计算的单体间相互作用能的计算考虑了基组重叠误差(BSSE)和零点振动能(ZPVE)校正, 其值在-3.37到-4.55 kJ·mol-1之间. 采用自然键轨道理论(NBO)对单体间相互作用的本质进行了考查, 并通过分子中原子理论(AIM)分析了三种复合物中氢键的电子密度拓扑性质.     

Theoretical binding affinities and spectra of complexes formed by a cyclic β-peptoid with amino acids

Binding affinities of a cyclic β-peptoid to amino acids were studied using the density functional theory (DFT) at the B3LYP/6-311G(d,p) level after the basis set superior error (BSSE). The host molecule possesses binding ability to amino acids since the binding energies of the complexes formed are negative. The complexes were stabilized via hydrogen bonds between the host and the guest molecules. Based on the B3LYP/6-31G(d) optimized geometries, electronic spectra of the complexes were calculated using the INDO/CIS method. ¹³C NMR spectra and nucleus-independent chemical shift (NICS) values of the complexes were computed at the B3LYP/6-31G(d) level. Carbon atoms in the carboxyl groups of the complexes are shifted downfield relative to those of the host. Some complexes exhibit aromaticity although the host shows anti-aromaticity. Formation of hydrogen bonds leads to cyclic current formation in these complexes.     

Cyclic vinyl p-tolyl sulfilimines as chiral dienophiles: theoretical study on the stereoselectivity, Lewis acid catalysis, and solvent effects in their Diels-Alder reactions

The theoretical study reported in the present work deals with chiral cyclic vinyl sulfilimines and their reactivity as dienophiles in [4 + 2] cycloaddition reactions, using B3LYP/6-31G(d)//AM1 and B3LYP/6-31G(d)//B3LYP/6-31G(d) model chemistries. Consideration of Lewis acid catalysis, illustrated by BF(3), decreases the activation energies of the cycloaddition process while the charge transfer from the diene to the sulfilimine is augmented. The [4 + 2] cycloaddition reactions of sulfilimines with both furan and cyclopentadiene occur in the gas phase with endo stereoselectivity, which is more pronounced with the latter diene. Endo-exo energy differences in the gas phase with the B3LYP/6-31+G(d)//B3LYP/6-31+G(d), B3LYP/6-31G(d)//B3LYP/6-31G(d), and B3LYP/6-31G(d)//AM1 model chemistries are almost the same. Solvent effects are responsible for the inversion of the stereoselectivity in the reactions of sulfilimines with furan because of the great difference in the dipole moments in endo and exo approaches.     

CH3SH…HOO开壳型氢键复合物的结构及其电子密度拓扑性质

在DFT-B3LYP/6-311++G**水平下求得CH3SH…HOO复合物势能面上的稳定构型. 计算结果表明, 在HOO以其O8—H7作为质子供体与CH3SH分子中的S5原子为质子受体形成的氢键复合物1和2中, O8—H7明显被“拉长”, 且其伸缩振动频率发生显著的红移, 红移值分别为330.1和320.4 cm-1; 在CH3SH分子以其S5—H6作为质子供体与HOO的端基O9原子为质子受体形成的氢键复合物3和4中, 也存在类似的情况, 但S5—H6伸缩振动频率红移不大. 经MP2/6-311++G**水平计算的4种复合物含BSSE校正的相互作用能分别为-20.81, -20.10, -4.46和-4.52 kJ/mol. 自然键轨道理论(NBO)分析表明, 在CH3SH…HOO复合物1和2中, 引起H7—O8键长增加的因素包括两种电荷转移, 即孤对电子n1(S5)→σ*(H7—O8)和孤对电子n2(S5)→σ*(H7—O8), 其中后者为主要作用. 在复合物3和4中也有相似的电荷转移情况, 但轨道间的相互作用要弱一些. AIM理论分析结果表明, 4个复合物中的S5…H7间和O9…H6间都存在键鞍点, 且其Laplacian量▽2ρ(r)都是很小的正值, 说明这种相互作用介于共价键和离子键之间, 偏静电作用为主.     

Inclusion complexes of ortho-anisidine and β-cyclodextrin: A quantum mechanical calculation

The structural aspects for the complexation of ortho-anisidine (O-AN)/β-cyclodextrin were explored by using PM6, density function theory B3LYP/6-31G*, M05-2X/6-31G*, B3PW91/6-31G*, MPW1PW91/6-31G*, HF/6-31G* methods and several combinations of ONIOM2 hybrid calculations. Calculations were performed upon the inclusion complexation of β-cyclodextrin (β-CD) with neutral (O-AN1) and cationic (O-AN2) species of ortho-anisidine. The obtained results with PM6 method clearly indicate that the formed complexes are energetically favored, the complex of O-AN2/β-CD in B orientation is significantly more favorable than the others energetically. The structures show the presence of several intermolecular hydrogen bond interactions that were studied on the basis of natural bonding orbital (NBO) analysis, employed to quantify the donor–acceptor interactions between ortho-anisidine and β-CD.     

六烷氧基取代的苯并菲和六氮杂苯并菲盘状液晶中的电荷转移

用电子转移的半经典模型在量子化学B3LYP/6-31G(d)水平(对单体)和B3LYP/STO-3G水平(对二聚物)对六烷氧基取代的苯并菲和六烷氧基取代的六氮杂苯并菲组成的盘状晶体系的电荷转移性质进行了研究,发现在用量子化学方法研究电荷转移反应时,不能简单地用氢氧基代替长链烷氧取代基。由于在电荷转移反应中,要考虑参与反应的分子之间前线轨道的细微差别,所以将长链取代基用氢氧基取代,可能得不到定性正确的结果。     

Density functional studies on the effects of hydrogen bonding on the formation of a charge-transfer complex between p-benzoquinone and 2,6-dimethoxyphenol

The ability to form a ground-state charge-transfer (CT) complex between an electron acceptor, p-benzoquinone (BQ) and an electron donor, 2,6-dimethoxyphenol (DMOPh) was found to be enhanced by H-bonding of BQ to a hydrogen-bond donor, trifluoroacetic acid (TFA) and H-bonding DMOPh to a hydrogen-bond acceptor, 4-(N,N-dimethylamino)pyridine (DMAPy) [Chem. Phys. Lett. 2005, 401, 200]. Here is reported density functional theory (DFT) calculations to study the effect of H-bonding to electron donor and electron acceptor moieties on the ground-state CT complex formation ability between the aforementioned electron donor/acceptor pair. DFT calculations using B3LYP with the 6-311G(d,p) basis set show that the HOMO and LUMO energies of BQ drop on H-bonding to TFA through its C=O groups and the HOMO and LUMO energies of DMOPh increase on H-bonding to DMAPy via its O-H group. BQ molecules hydrogen-bonded as 1:1 and 1:2 complexes to TFA act as stronger acceptors than the bare molecule, while 1:1 complexes of DMOPh and DMAPy act as better donors. Vertical excitation energies for electronic transitions from the ground state to the first few excited states of BQ, DMOPh, DMAPy, and their different complexes have been investigated in the framework of time-dependent density functional theory (TD-DFT) to simulate and interpret experimental ultraviolet absorption spectra. Good agreement between experimental and calculated spectra is established. The enhancement of the CT complex formation ability between the BQ and DMOPh pair is favored by the strong H-bonding interaction of BQ with TFA as well as by the H-bonding interaction of DMOPh with DMAPy.     

NMR spectra, GIAO and charge density calculations of five-membered aromatic heterocycles

The B3LYP/6-31+G(d) molecular geometry optimized structures of 17 five-membered heterocycles were employed together with the gauge including atomic orbitals (GIAO) density functional theory (DFT) method at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p) and B3LYP/6-311+G(2d,p) levels of theory for the calculation of proton and carbon chemicals shifts and coupling constants. The method of geometry optimization for pyrrole (1), N-methylpyrrole (2) and thiophene (7) using the larger 6-311++G(d,p) basis sets at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p), B3LYP/6-31+G(2d,p) and B3LYP/cc-pVTZ levels of theory gave little difference between calculated and experimental values of coupling constants. In general, the (1)H and 13C chemical shifts for all compounds are in good agreement with theoretical calculations using the smaller 6-31 basis set. The values of nJHH(n=3, 4, 5) and rmnJ(CH)(n=1, 2, 3, 4) were predicted well using the larger 6-31+G(d,p) and 6-311++G(d,p) basis sets and at the B3LYP/6-31+G(d,p), B3LYP/6-311++G(d,p), B3LYP/6-31+G(2d,2p) levels of theory. The computed atomic charges [Mülliken; Natural Bond Orbital Analysis (NBO); Merz-Kollman (MK); CHELP and CHELPG] for the B3LYP/6-311++G(d,p) geometry optimized structures of 1-17 were used to explore correlations with the experimental proton and carbon chemical shifts.     

Design of donor–acceptor–donor (D–A–D) type small molecule donor materials with efficient photovoltaic parameters

Four Donor–Acceptor–Donor (D–A–D) type of donor molecules (M1‐M4) with triphenylamine (TPA) as donor moiety, thiophene as bridge, and thiazolothiazole as acceptor unit were designed and its photovoltaic parameters were equated with reference molecule “R.” DFT functional CAM‐B3LYP/6‐31G (d,p) was found best for geometry optimization and TD‐CAM‐B3LYP/6‐31G (d,p) was found suitable for excited state calculations. Among designed donor molecules, M4 manifests suitable lowest band gap of 4.73 eV, frontier molecular orbital energy levels as well as distinctive broad absorption of 455.3 nm due to the stronger electron withdrawing group. The electron‐withdrawing substituents contribute to red shifts of absorption spectra and better stabilities for designed molecules. The theoretically determined reorganization energies of designed donor molecules suggested excellent charge mobility property. The lower λ_e values in comparison with λ_h illustrated that these four donor materials would be ideal for electron transfer and M4 would be best amongst the investigated molecules with lowest λ_e of 0.0177. Furthermore, the calculated Voc of M4 is 2.04 V with respect to PC₆₀BM (phenyl‐C61‐butyric acid methyl ester). This study revealed that the designed donor materials are suitable and recommended for high performance organic solar cell devices.     

Quantum chemical calculations based on ONIOM and the DFT methods in the inclusion complex: doxycycline/2-O-Me-β-cyclodextrin

A computational study of inclusion complexes of 2-methyl-βCD with Doxycycline tautomeric (enol and keto form) has been performed with several combinations of ONIOM hybrid calculations. The reliability of the ONIOM2 calculations at the integrated level, ONIOM2 (M05-2X/6-31G(d): M05-2X/3-21G*), ONIOM2 (M05-2X/6-31G(d):HF/3-21G*), ONIOM2 (B3LYP/6-31G(d):HF/3-21G*), ONIOM2 (B3LYP/6-31G(d):B3LYP/3-21G*) and ONIOM2 (B3PW91/6-31G(d):B3PW91/3-21G*) was examined. Their complexation, binding, deformation and stabilization energies, and geometrical data were compared with those of the target geometry structure optimized at the M05-2X/6-31G(d) level of theory. Mixed combinations ONIOM2 (M05-2X 6-31G(d):HF 3-21G*) and ONIOM2 (B3LYP 6-31G(d):HF 3-21G*) reproduces nearly the target geometry structure and provides realistic energetic results at a relatively low computational cost.     

EC-backward-E electrochemistry supported by an alkoxyphenyl group

EC-backward-E electrochemistry through electrocatalytic formal [2+2] cycloaddition reaction between anodically activated aliphatic enol ethers and unactivated olefins possessing an alkoxyphenyl group was clearly described by using cyclic voltammetric studies and spin density observation with B3LYP/6-31G(d) calculations. The alkoxyphenyl group was found to regulate the electron transfer, which operates as an electron donor during the formation of the cyclobutane ring and as an electron acceptor from the anode to give the final product (EC-backward-E).     

Gas-phase ion/molecule reactions between dimethoxyphosphonium ions and aromatic hydrocarbons

Ion/molecule reactions between O=P(OCH(3))(2)(+) phosphonium ions and six aromatic hydrocarbons (benzene, toluene, 1,2,4-trimethylbenzene, naphthalene, acenaphthylene and fluorene) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH(3))(2)(+) phosphonium ions, formed by electron impact from neutral trimethyl phosphite, were found to react with aromatic hydrocarbons (ArHs) to give (i) an adduct [ArH, O=P(OCH(3))(2)](+) and (ii) for ArHs which have an ionization energy below or equal to 8.14 eV, a radical cation ArH(+ *) by charge transfer reaction. Collision-induced dissociation experiments, which produce fragment ions other than the O=P(OCH(3))(2)(+) ions, indicate that the adduct ions are covalent species. Isotope-labeled ArHs were used to elucidate fragmentation mechanisms. The charge transfer reactions were investigated using density functional theory at the B3LYP/6-311 + G(3df,2p)//B3LYP/6-31G(d,p) level of theory. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH(3))(2)(+) and benzene is described.