态定(线性响应)-极化连续模型/含时密度泛函方法研究一种有机发光材料的吸收和发射光谱

3-(二氰亚甲基)-5,5-二甲基-1-(3-[9-(2-乙基-己基)-咔唑基]-乙烯基)环己烷(DCDHCC)是一种用于光电器件中的有机染料,它具有良好的发光特性.我们使用含时密度泛函方法(TD-PBE0,TD-BMK和TD-M06)以及极化连续模型(PCM)计算了该材料在溶剂中的吸收和发射特性.计算中使用了线性响应(LR)、态定(SS)两种溶剂模型和6-31G(d)、6-31+G(d,p)两种基组.计算了DCDHCC在苯、四氢呋喃和丙酮溶剂中的吸收和发射光谱,并与实验观测进行了比较.结果表明:对于吸收光谱的计算,杂化函数的影响大于基组和溶剂模型,在三种函数中BMK更适于研究DCDHCC的吸收光谱;而对于发射光谱,基组的影响最大,基组通过影响激发态构型从而影响发射光谱,对于激发态构型的优化需要使用6-31+G(d,p)基组.我们希望这些研究能对今后设计类似的发光分子有帮助.     

Solvation effects on reaction profiles by the polarizable continuum model coupled with the Gaussian density functional method

An efficient version of the polarizable continuum model for solvation has been implemented in the Gaussian density-functional-based code called deMon. Solvation free energies of representative compounds have been calculated as a preliminary test. The hydration effects on the reaction profile of the Cl⁻+CH₃Cl→ClCH₃+Cl⁻ reaction and the thermodynamics of the Menschutkin reaction have also been investigated. Finally, the conformational behavior of the 1,2-diazene cis–trans isomerization process in water was examined. Comparisons between the results obtained and the available experimental data and previous theoretical computations have been made. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 290–299, 1998     

The ORP basis set designed for optical rotation calculations

Details of generation of the optical rotation prediction (ORP) basis set developed for accurate optical rotation (OR) calculations are presented. Specific rotation calculations carried out at the density functional theory (DFT) level for model chiral methane molecule, fluorooxirane, methyloxirane, and dimethylmethylenecyclopropane reveal that the ORP set outperforms larger basis sets, among them the aug‐cc‐pVTZ basis set of Dunning (J. Chem. Phys. 1989, 90, 1007) and the aug‐pc‐2 basis set of Jensen (J. Chem. Phys. 2002, 117, 9234; J. Chem. Theory Comput. 2008, 4, 719). It is shown to be an attractive choice also in the case of larger systems, namely norbornanone, β‐pinene, trans‐pinane, and nopinone. The ORP basis set is further used in OR calculations for 24 other systems, and the results are compared to the aug‐cc‐pVDZ values. Whenever large discrepancies of results are observed, the ORP values are in an excellent agreement with the aug‐cc‐pVTZ results. The ORP basis set enables accurate specific rotation calculations at a reduced cost and thus can be recommended for routine DFT OR calculations, also for large and conformationally flexible molecules. © 2013 Wiley Periodicals, Inc.     

Thermodynamic Estimate of pKa Values of the Carboxylic Acids in Aqueous Solution with the Density Functional Theory

The 96 pK_a values of 85 carboxylic acids in aqueous solution were calculated with the density functional theory method at the level of B3LYP/6‐31+G(d,p) and the polarizable continuum model (PCM) was used to describe the solvent. In the calculations of pK_a values, the dissociation Gibbs free energies were directly calculated using carboxylic acid dissociation reactions in aqueous solution, i. e., no thermodynamic cycle was employed, which is different from the previous literatures. A highly significant correlation of R²=0.95 with a standard deviation (SD) of 0.36 between the experimental pK_a values and the calculated dissociation Gibbs free energies [ΔG(calc.)] was found. The slope of pK_a vs. (G(calc.)/(20303RT) is only 47.6% of the theoretically expected value, which implies that the ΔG(calc.) value from the theoretical calculation is larger than the actual one for all 85 carboxylic acids studied. Thus, by adding the 0.476 scaling‐factor into the slope, we can derive a reliably procedure that can reproduce the experimental pK_a values of carboxylic acids. The pK_a values furnished by this procedure are in good agreement with the experimental results for carboxylic acids in aqueous solution.     

2-(2-巯苯基)苯并噁唑分子内质子转移的理论研究

在B3LYP/6-31G(d,p)水平上研究了2-(2-巯苯基)苯并噁唑气态中五种异构体(E1, E2, E3, E4和K)在气态中的稳定性及其在基态下的质子转移, 同时结合极化连续介质模型(PCM)研究了水、二甲亚砜、乙腈、乙醇、苯胺和环己烷等对2-(2-巯苯基)苯并噁唑溶剂化作用的影响. 研究结果表明, 醇式异构体E1为2-(2-巯苯基)苯并噁唑的优势构型; 在E1向K(酮式异构体)转变过程中, 存在一个较小的能垒; 当考虑零点振动能(ZPVE)后, 逆向能垒消失. 在溶液中, 随着溶剂极性的增强, 醇式异构体E1与K之间的反应平衡向K方向移动, 在非极性溶剂环己烷中, E1为优势构型, 而在强极性水溶液中, K为优势构型.     

Dissociation constants of 2‐azidoethanamines in aqueous solution

Aqueous‐phase dissociation constants (K_a) for the conjugate acids of a series of 2‐azidoethanamine bases: R¹N(R²)CH₂CH₂N₃ ( 1 , R¹ = CH₃, R² = H; 2 , R¹ = CH₃, R² = CH₃; 3 , R¹ = CH₂CH₃, R² = CH₂CH₃; 4 , R¹/R² =  CH₂CH₂CH₂CH₂ ; 5 , R¹/R² =  CH₂CH₂OCH₂CH₂ ; 6 , R¹ = CH₂CH₃, R² = CH₂CH₂N₃) were measured and found to fall between those for analogous unfunctionalized and cyano‐functionalized ethanamines. To explore the possibility of a relationship existing between the constants and molecular geometry, a theoretically based study was conducted. In it, the Gibbs free energies of aqueous‐phase (equilibrium) conformers of the bases and their conjugate acids were determined via a density functional theory/polarizable continuum model method. The results indicate that an attractive interaction between the amine and azide groups that underlies the lowest‐energy gas‐phase conformer of 2 is negated in an aqueous environment by solvent–solute interactions. The magnitudes of the free energy changes of solvation and −TS (entropic) energies of the conformers of the 2‐azidoethanamines and their conjugate acids are observed to correlate with the magnitude of the separation between the conformers' amine and azide groups. However, those correlations are not by themselves sufficient to predict the relative free energies of a molecule's conformers in an aqueous environment. That insufficiency is due to the influence of the correlations being mitigated by three other parameters that arise within the thermodynamic framework employed to compute the observable. The nature of those parameters is discussed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis（thiocyanato）（2,2^1-bipyridyl）platinum（ll）

This paper presents a Density Functional or Time Dependent Density Functional （DFT/TDDFT） study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers： bis（isothiocyanato-S）（2,2^1-bipyridyl） platinum（II） （[Pt（SCN）2（bpy）]）, （isothiocyanato-S）（thiocyanato-N）-（2,2^1-bipy- ridyl） platinum（II） （[Pt（SCN）（NCS）（bpy）]）, and bis（thiocyanato-N）（2,2^1）-bipyridyl）platinum（II） （[Pt（NCS）2（bpy）]）, in which different coordination ligands based on the N- and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries Were compared to the experimentally observed structures. TDDFT calculation was carded out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model （PCM） to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agree- ment with the experimental determinations. The first two absorptions were found to originate from mixed plati- num-SCN （or NSC） to bipyridyl-n＊ transitions rather than pure metal-to-ligand-charge-transfer （MLCT） transitions, whereas the higher-energy bands arose from intraligand n→π＊ transitions. The stretching frequencies of C≡N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper.     

A new extension of the polarizable continuum model: Toward a quantum chemical description of chemical reactions at extreme high pressure

A quantum chemical method for studying potential energy surfaces of reactive molecular systems at extreme high pressures is presented. The method is an extension of the standard Polarizable Continuum Model that is usually used for Quantum Chemical study of chemical reactions at a standard condition of pressure. The physical basis of the method and the corresponding computational protocol are described in necessary detail, and an application of the method to the dimerization of cyclopentadiene (up to 20 GPa) is reported. © 2015 Wiley Periodicals, Inc.     

The Role of Computational Chemistry in the Experimental Determination of the Dipole Moment of Molecules in Solution

The methods for the experimental determination of electric dipole moment of molecules in solution from measurements of dielectric permittivity and refractive index are traditionally based on the classical Onsager model. In this model the molecular solute is approximated as a simple polarizable point dipole inside a spherical or ellipsoidal cavity of a dielectric medium representing the solvent. However, the inadequacies of the model resulting from the assumption of a simple shape of the cavity, for the evaluation of the cavity field effect, and from the uncertainty of the polarizability of the molecular solute influences the results and hampers the comparison with the electric dipole moments computed from quantum chemical solvation models. In this article we propose a new method for the experimental determination of the electric dipole moment in solution in which information from the Polarizable Continuum Model calculations are used in place of the Onsager model. The new method overcomes the limitations of this latter model regarding both the cavity field effect and the polarizability of the molecular solutes, and thus allows a coherent comparison between experimental and computed dipole moments of solvated molecules. © 2019 Wiley Periodicals, Inc.     

Chiral discrimination in hydrogen‐bonded complexes of 2‐methylol oxirane with hydrogen peroxide

A systematic quantum chemical study reveals the effects of chirality on the intermolecular interactions between two chiral molecules bound by hydrogen bonds. The methods used are second‐order Møller–Plesset perturbation theory (MP2) with the 6‐311++g(d,p) basis set. Complexes via the O? H···O hydrogen bond formed between the chiral 2‐methylol oxirane (S) and chiral HOOH (P and M) molecules have been investigated, which lead to four diastereomeric complexes. The nomenclature of the complexes used in this article is enantiomeric configuration sign corresponding to English letters. Such as: sm, sp. The relative positions of the methylol group and the hydrogen peroxide are designated as syn (same side) and anti (opposite side). The largest chirodiastaltic energy was ΔE_chir = ?1.329 kcal mol^?1 [9% of the counterpoise correct average binding energy D_e(corr)] between the sm‐syn and sp‐anti in favor of sm‐syn. The largest diastereofacial energy was ?1.428 kcal mol^?1 between sm‐syn and sm‐anti in favor of sm‐syn. To take into account solvents effect, the polarizable continuum model (PCM) method has been used to evaluate the chirodiastaltic energies, and diastereofacial energies of the 2‐methylol oxirane···HOOH complexes. The chiral 2,3‐dimethylol oxirane (S, S) is C₂ symmetry which offers two identical faces. Hence, the chirodiastaltic energy is identical to the diastereomeric energy, and is ΔE_chir = 0.563 kcal mol^?1 or 5.3% of the D_e(corr) in favor of s,s‐p. The optimized structures, interaction energies, and chirodiastaltic energies for various isomers were estimated. The harmonic frequencies, IR intensities, rotational constants, and dipole moments were also reported. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Substituent and solvent effects on the structural bioactivity and anticancer characteristic of catechin as a bioactive constituent of green tea

In this study, quantum chemical calculations using density functional theory and 6‐311G (d) basis set have been applied to analyze the substituent effect on the electronic structural properties including thermochemical parameters as well as anticancer characteristics of catechin as a bioactive constituent of green tea. It has been found out that different substituents with two kinds of electron donating and electron withdrawing groups including ? NO₂, ? NH₂, ? Cl, ? OCH₃, and ? CH₃ leaded to different structural stabilities. The catechin with chloro substituents has been referred to the most stable catechin derivatives based on the minimum energy of investigated compounds. In this study, the calculated values have been compared in gas phase and different solvent media with a wide range of solvent dielectrics using the self‐consistent reaction field method with polarizable continuum model. Relative interaction energies between solute and solvent as well as dipole moment values have been analyzed. The results of solvent effect study revealed that the formation of hydrogen bonds accounts for the stabilization of catechin. These calculated data were found to be a logical way in predicting the relative stability of catechin derivatives and can be useful for drug design of anticancer drugs and would open a new door for the researchers who are interested in natural products. The results presented in this article will be helpful to improve existing model and will open up a whole new arena of study to understand the anticancer characteristic of these antioxidant drugs derived from natural products against the photosensitizing DNA damage induce by catechin extracts and enable a much clearer understanding of how anticancer drugs mediate their effects on the specific spot. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Density functional theory study on the reactions of X− with CH3SY (X,Y = F,Cl, Br,I)

Gas‐phase anionic reactions X^? + CH₃SY (X, Y = F, Cl, Br, I) have been investigated at the level of B3LYP/6‐311+G (2df,p). Results show that the potential energy surface (PES) of gas‐phase reactions X^? + CH₃SY (X, Y = Cl, Br, I) has a quadruple‐well structure, indicating an addition–elimination (A–E) pathway. The fluorine behaves differently in many respects from the other halogens and the reactions F^? + CH₃SY (Y = F, Cl, Br, I) correspond to deprotonation instead of substitution. The gas‐phase reactions X^? + CH₃SF (X = Cl, Br, I), however, follow an A–E pathway other than the last two out going steps (COM2 and PR) that proceeds via a deprotonation. The polarizable continuum model (PCM) has been used to evaluate the solvent effects on the energetics of the reactions X^? + CH₃SY (X, Y = Cl, Br, I). The PES is predicted to be unimodal in the solvents of high polarity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Model studies of the optical rotation,and theoretical determination of its sign for β‐pinene and trans‐pinane

We have carried out extensive studies on the basis set dependence of the calculated specific optical rotation (OR) in molecules at the level of the time–dependent Hartree–Fock and density functional approximations. To reach the limits of the basis set saturation, we have devised an artificial model, the asymmetrically deformed (chiral) methane (CM) molecule. This small system permits to use basis sets which are prohibitively large for real chiral molecules and yet shows all the important features of the basis set dependence of the OR values. The convergence of the OR has been studied with n‐aug‐cc‐pVXZ basis sets of Dunning up to the 6–ζ. In a parallel series of calculations, we have used the recently developed large polarized (LPolX) basis sets. The relatively small LPolX sets have been shown to be competitive to very large n‐aug‐cc‐pVXZ basis sets. The conclusions reached in calculations of OR in CM concerning the usefulness of LPolX basis sets have been further tested on (S)‐methyloxirane and (S)‐fluoro‐oxirane. The smallest set of the LPolX family (LPol–ds) has been found to yield OR values of similar quality as those obtained with much larger Dunning's aug‐cc‐pVQZ basis set. These results have encouraged us to carry out the OR calculations with LPol–ds basis sets for systems as large as β‐pinene and trans‐pinane. In both cases, our calculations have lead to the correct sign of the OR value in these molecules. This makes the relatively small LPol–ds basis sets likely to be useful in OR calculations for large molecules. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

[EPy][BF4]和[EPy][PF6]离子对的气相及液相阴阳离子相互作用研究

采用从头算HF/6-31G和密度泛函理论B3LYP/6-31+G(d,p)方法, 对乙基吡啶四氟硼酸盐([EPy][BF4])和乙基吡啶六氟磷酸盐([EPy][PF6])的离子对进行了结构优化和频率分析, 并利用自洽反应场(SCRF)的导体极化连续模型(CPCM)考察了离子对液态下的结构及相互作用, 得到了两种离子对的红外光谱及气相、液相下最稳定结构. 由两种离子对的几何参数可知, 阴阳离子通过氢键相互作用, 两种离子液体的红外光谱特征值与实验值比较吻合. 应用自然键轨道(NBO)理论分析了吡啶阳离子及离子对中的原子电荷分布和电荷转移情况, 结果表明两种离子对中阴阳离子间存在静电相互作用和氢键作用. 通过几何参数、相互作用能及NBO分析研究发现, 液相下由于周围电荷的中和作用, 离子对中阴阳离子的相互作用明显降低.     

[EPy]Cl和[EPy]Br离子对的气相和液相结构及阴阳离子间的相互作用

采用密度泛函理论B3LYP/6-31+G(d,p)方法对氯化乙基吡啶([EPy]Cl)、溴化乙基吡啶([EPy]Br)的离子对进行了结构优化和频率分析, 并利用自洽反应场(SCRF)的导体极化连续模型(CPCM)考察了离子液体液相下的结构及相互作用. 得到了两种离子液体的离子对在气相、液相下最稳定结构及气相红外光谱特征值, 两种离子液体的离子对结构存在相似性, 红外光谱特征值与文献值比较吻合. 应用自然键轨道(NBO)理论分析了离子对中原子电荷分布及电荷转移情况, 结果证明两种离子液体中阴阳离子间除了静电相互作用外还存在着氢键作用. 通过对比气相及液相下的几何参数、相互作用能及NBO分析结果, 发现液相下阴阳离子的相互作用明显降低. 液相环境抵消了大部分阴阳离子间的静电作用, 导致液相下阴阳离子间相互作用的减小.     

N,N-二（对氟苄基）-N′-（2′,3′-二脱氧-3′-硫代胞苷）甲脒水解反应的理论研究

采用密度泛函理论方法B3LYP/6-31 G(d,p)//B3LYP/6-31G(d,p)和导体极化连续模型B3LYP/CPCM/6-31 G(d,p)方法对苯环对位上有F取代的N,N-二(对氟苄基)-N′-(2′,3′-二脱氧-3′-硫代胞苷)甲脒(FBFA-3TC)水解反应机理和溶剂效应进行了研究.考虑两条可能反应途径:水分子首先进攻CN双键的途径(PathA)和先进攻C—N单键的途径(PathB).计算结果表明,气相和水中两条途径的第一步都是速率控制步骤,PathA比PathB更有利.对优势途径PathA的第二步反应的进一步研究发现,中间体的羟基H原子转移到双键N比单键N更容易,从而形成2′,3′-二脱氧-3′-硫代胞苷(3TC)的最终水解产物.     

富勒烯和富勒烯衍生物中的Stone-Wales旋转

Stone-Wales旋转是富勒烯异构化的基本方式,了解其特征和规律对于理解富勒烯和富勒烯衍生物的形成至关重要.本文采用密度泛函理论方法系统研究了富勒烯和富勒烯衍生物的Stone-Wales旋转.结果显示,富勒烯异构体趋向于从高B55键(两个五元环共用的边)结构向低B55结构转化,满足独立五元环原则的结构或具有低B55键数的异构体在热力学上更为有利.相反,对于富勒烯衍生物,具有更多B55的异构体不仅在热力学上更有利,而且从动力学角度讲,从满足独立五元环原则的结构向不满足的结构的转变比相反过程更容易.这些结果可以解释目前的相关实验事实,暗示了富勒烯衍生物可能是先衍生化后异构化而形成.     

A Density Functional Theory Study of Optical Rotation in Some Aziridine and Oxirane Derivatives

We present time-dependent density functional theory (TDDFT) calculations of the electronic optical rotation (ORP) for seven oxirane and two aziridine derivatives in the gas phase and in solution and compare the results with the available experimental values. For seven of the studied molecules it is the first time that their optical rotation was studied theoretically and we have therefore investigated the influence of several settings in the TDDFT calculations on the results. This includes the choice of the one-electron basis set, the exchange-correlation functional or the particular polarizable continuum model (PCM). We can confirm that polarized quadruple zeta basis sets augmented with diffuse functions are necessary for converged results and find that the aug-pc-3 basis set is a viable alternative to the frequently employed aug-cc-pVQZ basis set. Based on our study, we cannot recommend the generalized gradient functional KT3 for calculations of the ORP in these compounds, whereas the hybrid functional PBE0 gives results quite similar to the long-range correct CAM−B3LYP functional. Finally, we observe large differences in the solvent effects predicted by the integral equation formalism of PCM and the SMD variant of PCM. For the majority of solute/solvent combinations in this study, we find that the SMD model in combination with the PBE0 functional and the aug-pc-3 basis set gives the best agreement with the experimental values.