H2CCC光谱性质的从头算研究

采用全活化空间自洽场方法(CASSCF)在C2v对称性和ANO-S基组水平下, 研究了H2CCC自由基及其阴阳离子的基态和低激发态性质. 为了进一步考虑动态电子相关效应, 采用多组态二级微扰理论(CASPT2)获得了更加精确的能量值. 计算得到X1A1 → 1A2, X1A1 → 1B1和X1A1 → 21A1在159.0, 216.5和476.4 kJ/mol处的激发可分别归因于π(b2)→π*(b1), n(a1)→π*(b1)和π(b1)→π*(b1)的跃迁, 理论波长与紫外吸收光谱得到的实验数据一致. 计算得到的电子亲和势与实验值也非常接近.     

氮化锇配合物离子[OsN(mnt)2]-的电子结构和光谱性质的理论研究

理论研究了离子型配合物[OsN(mnt)2]-[mnt=S2C2(CN)2)]的电子结构和光谱性质, 考察不同配体三价N、二硫氰烯S2C2(CN)2和金属Os的相互作用对光化学性质的影响. 分别在B3LYP/LANL2DZ和CIS/LANL2DZ水平上优化了配合物的基态和激发态结构. 与基态(1A1)相比, 激发态(3A2)的Os≡N 的键长缩短了0.0066 nm, 这与计算得到的频率增大一致, 使用TD-DFT方法计算得到了配合物的吸收和发射光谱. 计算得到的位于300 nm(f=0.1497)和262 nm(f=0.2890)的强吸收都来自1A1→1B1跃迁, 分别指认为SC→Os≡N+CN 和N+SC→Os≡N+CN的电子跃迁. 最低能量的吸收位于446 nm(f=0.0206) 处, 来自1A1→1B2的电子跃迁, 指认为N→Os和 N+SC→CN. 计算得到配合物在气态的磷光发射位于678 nm(A3A2→X1A1)处, 而在丙酮溶液中则蓝移到了625 nm处, 跃迁属性不变, 都是N→Os和S→Os的跃迁.     

[Au(PH3)]+修饰的芳香基炔基配合物发光机制的从头计算研究

用从头计算法研究H3PAuC≡CPh(a), H3PAu(C≡C-1,4-C6H4)Ph(b)和H3PAu(C≡C-1,4-C6H4)C≡CPh(c) 3种Au(Ⅰ)配合物的磷光发光性质, 使用MP2和CIS方法分别优化配合物的基态和激发态的几何结构. 计算结果表明, 激发态的电子跃迁减弱了Au与配体的成键作用. 由计算得出3种Au(Ⅰ)配合物的最低能量磷光发射光谱分别为530, 610和615 nm, 皆由A3A′→1A′产生, 属于Au(6p)→C(2p)的电荷转移(MLCT)修饰下的pπ*(C≡C, )→pπ(C≡C, )跃迁本质, 并伴有Au(6p)→Au(5d)的金属中心电荷转移(MCCT)性质. 随着分子增长, 其激发态轨道中Au的p轨道成分减少, 相应的最低能量磷光发射的波长红移.     

[Au(PH3)]+修饰下苯的激发态性质的理论研究

用MP2和CIS方法分别优化了H3PAuPh(a)、对位(H3PAu)2C6H4(b)和间位(H3PAu)3C6H3(c)的基态和激发态结构. 计算结果表明, [Au(PH3)]+的引入使Au(Ⅰ)配合物的苯环上的电子云密度降低, 削弱了苯基内C—C键的成键作用. 计算得到配合物a~c的最低能量磷光发射分别为443, 461和429 nm, 均属于苯基为π*→π跃迁本质, 并伴有Au(6p)→π(Ph)和Au(6p)→Au(5d)电荷转移性质. 与苯的最低能量磷光发射(413 nm)相比揭示了配合物a~c的发光过程是[Au(PH3)]+修饰的π*→π发光机制.     

氰基铝(AlCN)及其阴阳离子低能激发态的理论研究

在C2v对称性下,采用全活化空间自洽场(CASSCF)和多组态二级微扰理论(CASPT2)方法研究氰基铝(AlCN)及其阴阳离子的基态和低能激发态.在ANO-L基组水平下,计算了AlCN及其阴阳离子低能电子态的几何,组态及其相互作用系数,谐振频率,绝热激发能,垂直激发能和振子强度.在CASSCF/CASPT2理论水平下,计算得到AlCN的11Π电子态的绝热激发能为352.4kJ·mol-1,与实验值344.0kJ·mol-1符合得很好.另外,预测AlCN的跃迁X1Σ+→21Π发生在673.1kJ·mol-1.激发能和振子强度的计算为研究AlCN的吸收光谱提供理论指导.     

卤代氰基卡宾自由基XCCN(X=F,Cl,Br)的理论研究

在C_s对称性和ANO-S基组下, 使用全活化空间自洽场方法(CASSCF), 研究了卤代氰基卡宾自由基及其阴离子的低能电子激发态性质. 为了进一步考虑电子的动态相关效应,采用多组态二级微扰理论(CASPT2)获得更加精确的能量值. 计算结果表明, XCCN的基态是三重态. 单重态和三重态的能隙差ΔE_S-T(kJ/mol): 7.4(FCCN)<13.4(ClCCN)<16.6(BrCCN). 计算得到, XCCN(X=F, Cl, Br)最低垂直激发能分别为408.3, 385.4和 345.2 kJ/mol, 这归因于π(a′) →n_xy 的电子跃迁; XCCN的电子亲和势分别为235.7, 233.0和 237.2 kJ/mol, 与HCCN相比, 其电子亲和势变大.     

[Os（PH3）2（CN）2（N^N）]配合物的溶剂化显色效应

采用HF/DFT的混合泛函PBE0和UPBE0优化了配合物[Os(PH3)2(CN)2(N^N)](其中N^N=2,2′-吡啶)的基态和激发态结构.在基态和激发态结构的基础上,利用含时密度泛函理论(TD-DFT)方法,结合极化连续介质(PCM)模型分别计算了它在二氯甲烷(1)、甲醇(2)、气态(3)和乙腈(4)溶液中的吸收和发射光谱.研究结果表明:优化得到的几何结构参数和相应的实验值符合得非常好.在极性较大的溶剂(2和4)中Os—P(1)和Os—C(1)键较长,Os—N(3)键较短,溶剂的极性会影响配合物的电子云分布.配合物在1-4溶剂中的最低能吸收和发射均来自分子轨道68→71的激发,该激发被指认为[d(Os)+π(CN)+π(N^N)→π*(N^N)]的跃迁具有混合的MLCT/LLCT特征.配合物在1-4溶剂中的最低能吸收和发射分别在471,410,488和445nm以及598,536,634和545nm,表明随着溶剂极性的逐渐增大(3<1<4<2),最低能吸收和发射发生明显的蓝移.这显示出通过改变溶剂极性可以调节配合物的发光颜色.     

姜黄素衍生物电子结构及光谱性质的理论研究

在B3LYP/6-31G**和TD B3LYP/6-31G**水平上对标题化合物电子结构和光谱性质进行了研究,为模拟真实条件,计算还考虑了甲醇溶液对电子结构和光谱性质的影响。研究结果表明:标题化合物存在A、B、C三类互变异构体,异构体稳定性为BAC。以ΔU、ΔH作为比较依据,则在气相和甲醇溶液中,A3、B3、C3分别为其异构体的能量最低构象,且B3为最稳定构型。以ΔG作为比较依据,气相中B3为最稳定构型;而甲醇溶液中B4为最稳定构型。异构体A的红外光谱在2503 cm-1处存在特征吸收峰,该吸收峰为其分子内缔合氢键的νO-H;异构体B的红外光谱在1627 cm-1处存在很强的特征吸收峰,该吸收峰为螯合羰基的νC=O。甲醇溶液使分子的ELUMO、EHOMO、ΔEgap均下降,电子光谱λmax发生红移。异构体A、B在气相和甲醇溶液中的λmax均都主要来源于H→L的π→π*跃迁;异构体C在气相中的λmax主要来源于H→L+1、H-1→L的π→π*跃迁,而在甲醇溶液中则主要来源于H-1→L的π→π*跃迁;以上跃迁存在分子内电荷转移现象。     

量子反应散射的动力学李代数方法

用动力学李代数方法描述了量子反应散射问题 .对共线交换反应A BC→AB C ,得到了含有主要动力学参数的反应跃迁几率的解析表达式 .计算了共线反应散射过程H H2 (n =0 )→H2 (n′ =0 ) H的反应跃迁几率 .结果表明 ,动力学李代数方法对计算反应几率是非常有效的 .     

多组态二级微扰理论计算CH3O2激发光谱以及CH3O2→CH3＋O2解离反应

在C_s对称性和aug-cc-pVTZ基组水平下, 采用全活化空间自洽场方法(CASSCF)研究了CH₃O₂自由基基态及其阴阳离子的12个低激发态. 为了进一步考虑动态电子相关效应, 采用二级多组态微扰理论(CASPT2)获得更加精确的能量值. 所有计算得到的电子态都是价电子态, 而且所得绝热激发能和电子亲和势与实验值非常接近.在CASPT2//CASSCF理论水平下计算了CH₃O₂从²A"和²A'电子态的CH₃O₂→CH₃＋O₂的解离反应的势能曲线(PECs). 优化得到的裂解产物的几何结构和能量与分别优化CH₃和O₂得到的结果进行比较, 从而确定裂解产物的电子态. 结果表明, 从²A"和²A'电子态的解离反应分别对应产物CH₃(²A")＋O₂(³A")和CH₃(²A")＋O₂(¹A").     

铁原子与氮分子间的相互作用——单侧双配位构型

用密度泛函理论的B3LYP/6-311+G(d)方法对单侧双配位FeN2体系(简记为S-FeN2)不同自旋多重度的稳定态、范德华力作用态和过渡态的多个电子态的几何结构、电子结构、能量和振动频率进行了计算比较研究. 结果表明, S-FeN2体系三种自旋态间, Fe—N 距离R1和N—N 距离R2值均比较接近; 能量最低的是15B2态, 相近态有15B1、13B1和13B2, 彼此能差约25 kJ·mol-1. 三重态电子结构复杂, 单重态能量普遍偏高; 基组态Fe原子与N2间存在强的σ-π电子对排斥而无有效轨道重叠和电子转移, 其它组态4s13d7、4s13d64p1和3d74p1, Fe 和N2间发生σ(sd)-π和π-π*轨道重叠作用, 有少量电子转移, 体系呈现一定的离子性特征, 活化N2键长基本不超过120 pm. Fe 原子的电子单或双重被激发到由N2反键轨道为主要成分的分子轨道上时, 能使N2活化到单键程度甚至解离.     

2-硫代嘧啶酮和2-硫代吡啶酮在B-吸收带中的动态结构

采用共振拉曼光谱学结合量子化学计算研究了2-硫代嘧啶酮(2TPM)和2-硫代吡啶酮(2TP)在B-带吸收时的动态结构. 在气相时, 2-巯基嘧啶(2MPM, 硫醇式)比2TPM(硫代酮式)更稳定, 能量差约为15.1 kJ·mol^-1, 而在水和乙腈溶液中, 2TPM比2MPM更稳定, 能量差分别为29.3和28.0 kJ·mol^-1. 气相及基电子态时,由B3LYP/6-311++G(d,p)计算水平获得的2TPM和2MPM之间发生质子转移异构化反应的过渡态能垒约为130 kJ·mol^-1. 2TPM三个吸收带分别被指认为π_H→π_L^*, π_H→π_L+1^*和π_H-1→π_L^*跃迁. 基于对2TPM在固体和溶液相傅里叶变换-拉曼(FT-Raman)和傅里叶变换-红外(FT-IR)光谱测量, 以及B3LYP/6-311++G(d,p)计算, 开展了2TPM在水和乙腈溶液中的B-带共振拉曼光谱的振动指认, 由此获得了2TPM的动态结构, 并与2TP的动态结构进行了比较. 2TPM和2TP动态结构的差异反映了ππ^*/πσ^*锥形交叉点结构的差异, 因此, 可被用于洞察光诱导的氢原子脱离-复合机制.     

Electronic structure and absorption spectra of supramolecular complexes of a fullerene crown ether with a π-extended TTF derivative

The present work is a theoretical investigation on supramolecular complexes of a fullerene crown ether (A and B isomers) with a derivative of π-extended tetrathiafulvalene (T). The geometry and the electronic structure of seven different conformers of the complex of dibenzo-18-crown-6 ether of fullero-N-methylpyrrolidine with a N-benzyl-N-(4-{[9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracen-2-yl]ethynyl}benzyl)ammonium cation were determined. We calculated the complexation energies and the absorption spectra, i.e., the lowest 50 excited electronic states of the complexes have been determined at the ground state optimum geometry. All calculations were carried out employing the density functional theory (DFT) and the time-dependent DFT, using the B3LYP, CAM-B3LYP, ωB97X-D, and M06-2X functionals in conjunction with the 6-31G(d,p) basis set. Various types of van der Waals interactions are observed in the complexes. Conformer complexation energies (CE) range from 2.54 to 2.14 eV in the gas phase and from 1.75 to 1.34 eV in CHCl(3) solvent at the ωB97X-D/6-31G(d,p)//M06-2X/6-31G(d,p) level of theory. There are three major features at about 390, 330, and 290 nm in the calculated absorption spectra of all the conformers. The major peaks correspond to T→T, T→T/F (electron density in both T and the fullerene F of B) and to T→F transitions, depending on the particular conformer. Other charge transfer T→F transitions are observed close to the T→T transition, indicating the possibility of photoinduced electron transfer in all these complexes.     

CuCl2催化（2-甲基辛烷-2，3-二烯-4-基）磷酸乙酯氯代环化反应机理理论研究

采用密度泛函理论（DFT）中的B3LYP方法对CuCl2催化的（2-甲基辛烷-2,3-二烯-4-基）磷酸乙酯氯代环化反应机理进行了理论研究．在6-31＋G（d）基组水平上对反应机理中所有反应物、过渡态、中间体和产物进行了优化,通过能量和振动频率分析以及IRC计算证实了中间体和过渡态的合理性．在相同基组水平上应用自然键轨道（NBO）理论和分子中的原子（AIM）理论分析了复合物的成键特征和轨道间相互作用．反应物R和催化剂CuCl2可通过IA和IB两条可行反应通道生成中间体IM9,控制步骤活化能分别是129．61和142．10kJ／m01．中间体IM9到产物P也有两条反应路径PA和PB,控制步骤活化能分别是179．55和9．83kJ／m01．整个反应机理中IA—PB和IB—PB反应通道可能同时发生,反应控制步骤活化能最低反应通道为IA→PB．     

Influence of the protein and DFT method on the broken‐symmetry and spin states in nitrogenase

The enzyme nitrogenase contains a complicated MoFe₇CS₉ cofactor with 35 possible broken‐symmetry (BS) states. We have studied how the energies of these states depend on the geometry, the surrounding protein, the DFT functional and the basis set, studying the resting state, a one‐electron reduced state and a protonated state. We find that the effect of the basis set is small, up to 11 kJ/mol. Likewise, the effect of the surrounding protein is restricted, up to 10 and 7 kJ/mol for the electrostatic and van der Waals energy terms. Single‐point energies calculated on a single geometry give a good correlation (R² = 0.92‐0.98) to energies calculated after geometry optimization, but some BS states may be disfavored by up to 37 kJ/mol. A change from the pure TPSS functional to the hybrid B3LYP functional may change the relative energies by up to 58 kJ/mol and the correlation between the two results is only 0.57‐0.72. Both functionals agree that BS7 is the most stable BS state and that the ground spin state is the quartet for the resting state and the quintet for the reduced state. With the TPSS functional, the BS6 state is the second most stable state, always at least 21 kJ/mol less stable than the BS7 state. However, with the B3LYP functional, BS10 is the second most stable state and for the protonated state it comes close in energy. Based on these results, we suggest a procedure how to consider the 35 BS states in future investigations of the nitrogenase reaction mechanism.     

F Cl_2→ClF Cl和Cl′F Cl→Cl′ ClF的反应机理

用密度泛函理论(DFT)B3LYP方法,取6-311G基组,计算研究了F＋Cl2→ClF＋Cl的反应机理.求得1个线形和2个三角形过渡态,反应能垒分别为1.24、46.37和105.09kJ·mol－1;同时发现F以∠FClCl为10～20°（或120～160°）进攻Cl2时,反应无能垒.此外,求得对称反应Cl′F＋Cl→Cl′＋ClF的能垒为40.57kJ·mol－1的1个过渡态.     

Effect of histidine on the sensitized generation of singlet oxygen in the complexes with chlorophyll

The energies of the intermolecular interactions of an O₂ molecule in the ground and excited states with the electron-excited and non-excited model complexes of chlorophyll were calculated using the DFT, CASSCF, SA-CASSCF, MCQDPT2, and XMCQDPT2 methods. The activation energies of formation and dissociation of the oxygen complexes were estimated. The radiative electric dipole moments of (0 → 0) spin-allowed S → S, T → T, and spin-forbidden S → T transitions were calculated taking into account the spin-orbit coupling, and rate constants of nonradiative transitions that determine the generation and deactivation of the O₂ molecule (¹Δ_g) were evaluated. The effect of histidine on the probability of singlet oxygen generation sensitized by the model chlorophyll complex was considered in detail.     

The electronic spectrum and photodissociation of dinitrogen tetroxide (N(2)O(4)): Multireference configuration interaction studies

Multireference configuration interaction (MRCI) calculations were performed for vertical excitation energies and potential curves of N(2)O(4) in D(2h) symmetry using the TZVPP basis set with diffuse functions on the nitrogens. The strong absorption of N(2)O(4) around 185 nm is assigned to the transition from the ground state to 1?(1)B(1u) (σ(O)→σ(?) (N-N)) rather than 1?(1)B(2u) (π(O)→π(?) (NO(2) ),n→σ(?) (N-N)), as previously assumed. (N(2)O(4) is placed in the yz-plane, with N-N along z.) Transition to 1?(1)B(1u) is calculated to have an oscillator strength f=0.71 and is z-polarized, in agreement with the experimental observations. Another state, 2?(1)B(2u), lies close by, however, at a much lower f-value. The weak absorption around 340 nm is assigned to 1?(1)B(3u). Excitation to 1?(1)B(2u) is calculated at 227 nm. There is no clear assignment of a state for the observed shoulder around 260 nm. TD-DFT (time-dependent density functional theory) vertical excitation energies are close to MRCI values. MRCI singlet and triplet potential curves for the dissociation N(2)O(4)→2NO(2), combined with a table of NO(2) states correlating with those of N(2)O(4), indicate possible products of photodissociation at various wavelengths. The extensive literature on the photodissociation of N(2)O(4) is reviewed. DFT geometry optimizations have been performed on low-lying singlet and triplet states.