Vibrational Spectra and Density Functional Theory Calculations of Metallo-tetra-(tert-butyl)-tetra-azaporphyrines

The infrared absorption and 514.5 nm excited Raman spectra were measured for the metallo-tetra-(tert-butyl)-tetraazaporphyrin (MT(tBu)TAP, M=Cu, Co, Ni, Zn). The ground-state structures and vibrational spectra of MT(tBu)TAPs have been calculated at the B3LYP level of theory. The observed Raman and IR bands have been assigned based on the calculation results and by comparing with the normal metalloporphyrins. The relationship between the Raman/IR frequencies and the structures of TAP ring was investigated. The results show that the frequencies of C_βC_β′ stretch (A_g), asymmetric C_αN_m stretch (A_g), and symmetric C_αN_m stretch (B_g) modes increase linearly with the decrease of the core-sizes of TAP ring.Among the three modes, the later two are more sensitive to the core-size change.     

Density Functional Theory Investigation of Structures and Electronic Spectra of N-protonated Corroles

The geometries and electronic spectra of a series of N-protonated corroles, including unsub-stituted H₄Cor⁺ and meso-triaryl substituted H₄TPC⁺, H₄TpFPC⁺, and H₄TdCPC⁺, were theoretically studied with density functional theory (DFT). The results indicate that all these compounds have two conformers, one with C₂ symmetry (denoted as S1) is more stable than the other (denoted as S2, C₁ symmetry) by 15.8?18.5 kJ/mol. The corrole macrocycles of these compounds show significant out-of-plane deformation. The enantiomerizations of the chiral S1 conformers were found to be a multi-step process with the S2 conformers as the in-termediates. Electronic absorption spectra and electronic circular dichroism (ECD) of these compounds were calculated with time-dependent DFT. In comparison with H₄Cor⁺, the UV-Vis absorptions of meso-triaryl species are significantly red-shifted and their Q bands are enhanced due to the π-π conjugation between the aryl and corrole rings. Several neighboring electronic transitions were calculated with opposite signs in rotatory strengths, suggesting that ECD spectroscopy may be a useful tool in studying the electronic transitions of these compounds.     

弱氢键作用对硫脲水溶液拉曼光谱影响的密度泛函理论计算

将拉曼光谱和密度泛函理论(DFT)计算结合能够把拉曼谱峰和分子结构及分子间氢键作用之间的变化联系起来, 反映分子周围的结构信息. 本文通过理论计算水分子和硫脲形成复合物的拉曼光谱, 并结合实验报道的拉曼光谱, 探究硫脲基频对分子局域结构的依赖性. 通过轨道分析, 发现水分子的氢键作用可以引起硫脲的前线轨道对易, 这将影响到硫脲的拉曼光谱性质. 最后计算也表明在中性水溶液中由于大的正Gibbs 自由能变, 硫脲不易发生异构转变.     

弱氢键作用对硫脲水溶液拉曼光谱影响的密度泛函理论计算

将拉曼光谱和密度泛函理论(DFT)计算结合能够把拉曼谱峰和分子结构及分子间氢键作用之间的变化联系起来,反映分子周围的结构信息.本文通过理论计算水分子和硫脲形成复合物的拉曼光谱,并结合实验报道的拉曼光谱,探究硫脲基频对分子局域结构的依赖性.通过轨道分析,发现水分子的氢键作用可以引起硫脲的前线轨道对易,这将影响到硫脲的拉曼光谱性质.最后计算也表明在中性水溶液中由于大的正Gibbs自由能变,硫脲不易发生异构转变.     

I2-环己烯复合物的共振拉曼光谱和密度泛函理论计算研究

实验得到I2-环己烯电荷转移复合物的电子吸收光谱和共振拉曼光谱.用密度泛函方法计算了复合物的基态结构、振动频率和电子跃迁能.计算和吸收光谱实验结果表明,I2-烯烃复合物在约300nm处的强吸收带为pz(I17)→π*(C=C)跃迁,即由靠近C=C双键端的碘原子(I17)上的一个pz电子向C=C双键反键轨道跃迁引起的吸收.在约300nm共振拉曼光谱的强度模式表现为I—I伸缩振动模和C=C伸缩振动模的基频、泛频及其组合频,表明在该激发态上I2-环己烯复合物经历了显著的I—I和C=C的价键变化.     

Density Functional Theory Calculations on Ni-Ligand Bond Dissociation Enthalpies

The formation and breaking of Ni-L (L=N-heterocyclic carbene, tertiary phosphine etc.) bond is involved in many Ni-catalyzed/mediated reactions. The accurate prediction of Ni-L bond dissociation enthalpies (BDEs) is potentially important to understand these Ni-complex involving reactions. We assess the accuracy of diffierent DFT functionals (such as B3LYP, M06, MPWB1K, etc.) and diffierent basis sets, including both effective core potentials for Ni and the all electron basis sets for all other atoms in predicting the Ni-L BDE values reported recently by Nolan et al. [J. Am. Chem. Soc. 125, 10490 (2003) and Organometallics 27, 3181 (2008)]. It is found that the MPWB1K/LanL2DZ:6-31+G(d,p)//MPWB1K/LanL2DZ:6-31G(d) method gives the best correlations with the experimental results. Meanwhile, the solvent effect calculations (with CPCM, PCM, and SMD models) indicate that both CPCM and PCM perform well.     

Experimental and Density Functional Theory Calculation Studies on Raman and Infrared Spectra of 1,1'-Binaphthyl-2,2'-diamine

The IR absorption, visible excited normal Raman, and UV-excited near-resonant Raman (UVRR) spectra of 1,1'-binaphthyl-2,2'-diamine (BINAM) were measured and analyzed. Density functional theory calculations were carried out to investigate its vibrational frequencies, infrared absorption, normal Raman, and near-resonance Raman intensities. The observed Raman and IR bands of BINAM were assigned with respect to the local vibrations of substituted 2-naphthylamine. Several Raman bands of BINAM were found selectively enhanced in the UVRR in comparison with the normal Raman spectrum. Possible excited state geometry distortion was discussed based on the resonance Raman intensity analysis.     

丙酮酸分子结构与振动光谱的密度泛函理论研究

用密度泛函方法BLYP、B3LYP和从头算Hartree-Fock(HF)方法在6-31G*基组水平上对丙酮酸分子的几何结构（甲基的重叠式和交错式两种构象）和振动光谱分别进行了优化和计算,并给出了各种频率所对应的红外强度及拉曼活性,对光谱进行了指认。结果表明：在丙酮酸分子的两种构象中,重叠式比较稳定*B3LYP计算得到的构型参数与实验结果比较一致;在振动频率的计算中,BLYP未标度力场所计算的非CH3伸缩振动基频预测值和实验值的平均绝对偏差为10.4cm-1;而HF标度力场的平均绝对偏差为17.9cm-1。说明两者的结果与实验观测频率比较吻合,但B3LYP的频率计算值偏差（38.3cm-1）较大。根据振动频率的势能分布和红外光谱强度对此分子的振动基频进行了理论归属。     

6-硫代黄嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G**水平下,对14种气相和水相中可能存在的6-硫代黄嘌呤异构体进行了几何构型的全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能。Onsager反应场溶剂模型用于水相的计算.计算结果表明,6-硫代黄嘌呤在气相中和水相中主要以硫酮的形式存在.在气相和水相中,硫酮-N7(H)均比硫酮-N9(H)更稳定.计算结果同已有实验结果一致.6-硫代黄嘌呤异构化的熵效应小,对互变异构平衡几乎没有显著的影响,而焓变对互变异构产生了主要的影响.较详细地讨论了水溶剂化作用对异构体的能量、几何结构、电荷分布和偶极矩的影响.     

并五苯分子电荷注入导致自旋极化的密度泛函理论研究

用密度泛函理论研究了不带自旋的空穴注入并五苯后体系的自旋相关特性. 电荷注入后并五苯分子中存在自发自旋极化行为. 当注入电荷量达一定程度,分子磁矩随注入电荷量的增加呈线性增长,最大磁矩可达1μB. 注入电荷和并五苯分子的相互作用导致分子体系结构发生变化,同时电荷密度分布及自旋密度分布也发生了变化. 注入电荷先填充自旋劈裂的碳原子pz轨道.     

烷烃客体分子(C_nH_m,n≤6,m≤14)在5~(12)6~2和5~(12)6~4水笼中的稳定性与拉曼光谱的密度泛函理论计算

可燃冰矿藏中气体成分非常复杂,通过谱学分析对水合物样品成分进行指认具有重要意义.基于B97-D/6-311++G(2d,2p)的密度泛函理论(DFT)计算,我们系统地探索了构成水合物的两种标准水笼(51262和51264)包络十八种不同烷烃客体分子的稳定性.从计算结果可以看出,除了3-甲基戊烷和2,3-二甲基丁烷两个烷烃客体分子,其它16个烷烃客体分子都可以被容纳在51262笼中;但是与51262笼不同,十八种烷烃客体分子都可以被容纳在尺寸较大的51264笼中.同时,我们也模拟了五种直链烷烃和四种环状烷烃在51262和51264笼中相应的谱学特征,从拉曼谱图上可以看出,随着碳原子数量的增多,直链烷烃客体分子C―H键伸缩振动区的多数拉曼谱带向高波数移动,而环状烷烃客体分子C―H键伸缩振动区的拉曼谱带则向低波数移动.这些结果为实验上通过拉曼谱测量指认水合物矿藏的成分提供理论参考.     

2-硫代黄嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G**水平上,对14种气相和水相中可能存在的2-硫代黄嘌呤互变异构体进行了几何构型全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能.Onsager反应场溶剂模型用于水相的计算.计算结果表明,2-硫代黄嘌呤在气相和水相中主要以酮式结构形式存在,与已有实验结果一致.在气相和水相中,酮式结构—N(7)(H)均比酮式结构—N(9)(H)更稳定.2-硫代黄嘌呤互变异构的熵效应小,对互变异构平衡没有显著的影响,而焓变对互变异构却产生了主要的影响.水溶剂化自由能与异构体的气相偶极矩存在相关性.另外,较详细地考察了2-硫代黄嘌呤与6-硫代黄嘌呤的相对稳定性.     

石墨烯分子振动模式因子群分析与密度泛函计算

运用因子群分析法对石墨烯的分子振动模式进行了理论分析,得到石墨烯的分子振动模式,计算出各振动模式的光谱特性.对所建立的石墨烯晶体的布拉维单胞模型采用基于密度泛函理论的第一性原理进行分子振动频率与模式的计算,所得的振动模式数目以及各振动频率的光谱特性同因子群分析方法所得结论一致.结合上述计算结果,通过系统比较石墨与石墨烯之间的红外光谱和拉曼光谱的差别,从理论上解释了具有D6h对称的石墨烯的A2u、E1u红外活性特征振动模式没有在红外光谱中出现的原因.     

腺嘌呤和质子化腺嘌呤的结构和振动光谱

用密度泛函方法B3LYP/aug-cc-pVTZ分析了腺嘌呤和质子化腺嘌呤的低能稳定异构体的结构和振动光谱. 结果发现, 对于中性腺嘌呤分子, 腺嘌呤的异构体N9H比N7H的能量低32.76 kJ·mol-1(在极化连续模型下为6.28 kJ·mol-1). 基于标度量子力场方法所得到的势能分布, 对异构体N9H的部分振动基频重新进行了归属. 在极化连续模型下, 质子化腺嘌呤分子有5种低能稳定构型, 其中N1位质子化的9-位氢腺嘌呤最为稳定. 基于振动模式分析, 对这种最稳定构型的振动基频进行了归属, 并对腺嘌呤在pH=1的高氯酸溶液中的实验拉曼光谱进行了指认.     

菱形石墨炔薄膜He分离特性的密度泛函理论研究

氦气在科学和工业等领域中都具有不可替代的作用,其主要存在于天然气中。如何高效地从天然气中分离氦气显得至关重要。本文基于密度泛函理论(DFT)方法系统地探究了菱形石墨炔(rhombic-graphyne,R-GY)分离膜对He和其他天然气组分(Ne、Ar、CO_2、N_2和CH_4)的吸附、选择和渗透性能。结果表明,R-GY作为He分离膜可同时满足高选择性和高渗透率的要求。常温下,R-GY薄膜对He/Ne、He/CO_2、He/N_2、He/Ar和He/CH_4的选择性可分别达到2?10~7、3?10~(20)、9?10~(26)、7?10~(37)和5?10~(51),即使在600 K时仍可保持较高水平。此外,由于较低的扩散能垒,He穿透R-GY薄膜的渗透率在常温下可达到10~(-6) mol·m~(-2)·s~(-1)·Pa~(-1),高出工业标准近3个数量级;而其他气体组分在常温下的渗透率仅为10~(-58)-10~(-14) mol·m~(-2)·s~(-1)·Pa~(-1),气体无法渗透R-GY薄膜。     

Modeling Photovoltaic Performances of BTBPD-PC61BM System via Density Functional Theory Calculations

Designing and fabricating high-performance photovoltaic devices have remained a major challenge in organic solar cell technologies.In this work,the photovoltaic performances of BTBPD-PC₆₁BM system were theoretically investigated by means of density functional theory calculations coupled with the Marcus charge transfer model in order to seek novel photovoltaic systems.Moreover,the hole-transfer properties of BTBPD thin-film were also studied by an amorphous cell with 100 BTBPD molecules.Results revealed that the BTBPDPC₆₁BM system possessed a middle-sized open-circuit voltage of 0.70 V,large short-circuit current density of 16.874 mA/cm²,large fill factor of 0.846,and high power conversion efficiency of 10%.With the Marcus model,the charge-dissociation rate constant was predicted to be as fast as 3.079×10¹³ s^-1 in the BTBPD-PC₆₁BM interface,which was as 3-5 orders of magnitude large as the decay (radiative and non-radiative) rate constant (10⁸-10¹⁰ s^-1),indicating very high charge-dissociation efficiency (～100%) in the BTBPD-PC₆₁BM system.Furthermore,by the molecular dynamics simulation,the hole mobility for BTBPD thin-film was predicted to be as high as 3.970×10^-3 cm²V^-1s^-1,which can be attributed to its tight packing in solid state.     

三卤化硼Lewis酸性的密度泛函理论研究

用密度泛函理论的DFT-LDA/NL方法研究BX₃(X=F,Cl,Br)分子的Lewis酸性.计算BX₃分子的硬度时,采用一个可供选择的方法.该法是密度泛函理论的Janak定理的推广.结果表明,分子硬度是BX₃Lewis酸性的最好表征.应用Pearson的软硬酸碱(HSAB)原理可以合理地解释BX₃酸性的变化规律     

酚氧桥联铜钴异双核配合物的密度泛函研究

用密度泛函方法,在ROB3LYP/SDD//ROB3LYP/LanL2MB水平上,对酚氧桥联CuⅡ-CoⅡ异双核配合物CuCo(TS)(H2O),进行了理论计算.优化得到了它的单、三重态的平衡几何构型,计算了它们的谐振动频率.结果表明,该配合物分子的三重态比单重态稳定;电子自旋布居高度集中在Co(6)及其周围的配体原子上,而Cu（1）则没有发现电子自旋布居; 体系中存在较强的自旋离域效应.体系的前线分子轨道主要由Co(6)的d轨道和配体原子的p轨道组成,这有利于配体原子与Co(6)之间的电子转移.计算结果与实验符合得很好.     

Density Functional Theory Study of Solvent Effects on the Structure and Vibrational Frequencies of Tetranitrotetraazabicyclooctane “bicyclo‐HMX”

Density Functional Theory (DFT) calculations have been performed on the high explosive compound tetranitrotetraazabicyclooctane (bicyclo‐HMX) in gas phase employing the self‐consistent field (SCF) theory and in different solvents, i.e. cyclohexane, dichloroethane, ethylalcohol, acetonitrile, and water, utilizing the self‐consistent reaction field (SCRF) theory at a B3LYP/6–31 1G** level of theory. Reasonable agreement has been found between the computed and the available experimental data. The effects of different solvents on the geometry, electronic structure, and vibrational frequencies are discussed. Various solvents under consideration are found to have similar effects on the above properties. But some properties change regularly with the increasing polarity of the solvents, and the stronger the solvent polarity is, the larger the change is. In addition, based on the vibrational analysis, standard thermodynamic properties of bicyclo‐HMX in gas phase are also computed by using the statistical thermodynamic principle.