邻位甲基红水溶液的光谱性质随pH值的变化:含时密度泛函理论计算与实验研究（英文）

探明影响甲基红光谱性质的各种因素,有助于拓宽偶氮苯衍生物在有机光电器件中的应用。采用密度泛函理论和实验相结合的方法研究了溶液酸碱性和溶剂水对邻位甲基红水溶液光谱的影响。溶液pH从13.1逐渐降低至0.5,邻位甲基红水溶液的最大吸收波长从430 nm红移至520 nm。在不同酸碱条件下,主要有三种物种共存于甲基红水溶液中,它们分别是双质子化的甲基红o-H_2MR+(强酸性条件下),单质子化的甲基红oHMR(弱酸条件下)和碱性甲基红o-MR–(碱性条件下),通过密度泛函理论计算研究了三种不同形式的电子结构特征。采用含时密度泛函理论计算了甲基红偶极跃迁允许的最低激发能,分别采用连续介质模型和分子簇模型研究水溶剂对甲基红电子结构和光谱性质的影响。在酸性条件下,o-H_2MR+和o-HMR分子内氢键导致π共轭体系平面性增强,因而光谱红移。而在碱性条件下,溶剂对o-MR–的光谱有显著影响:极性o-HMR和o-MR–与水分子的偶极–偶极相互作用导致光谱进一步红移。     

BPh-2(mqp)的电子结构和光谱性质的含时密度泛函理论研究

采用abinitioHF和DFTB3LYP方法,对配合物BPh₂(mqp)基态结构进行优化,分析了前线分子轨道特征和能级分布.用abinitioCIS方法优化体系激发态结构.用含时密度泛函理论(TD-DFT)对BPh₂(mqp)的电子光谱进行了研究.结果发现,该物质是配体发光配合物,其发光源于mqp配体内π^*→π的电子跃迁.这表明在mqp配体上进行修饰,可有效地影响配合物前线分子轨道分布,达到调整发光波段的目的.     

靛族染料发色体电子光谱性质的含时密度泛函理论研究

采用密度泛函方法(DFT)在B3LYP／6—31 ^*水平上对一系列靛族染料发色体的几何构型进行优化计算；在获得基态稳定结构的基础上，应用含时密度泛函理论(TD—DFT)在相同水平下计算其电子吸收光谱．探讨了不同给电子基团和发色体的延伸对电子吸收光谱的影响，得到了与对应母体化合物一致的变化规律．结果表明，给电子基团给电子能力的增强和发色体的纵向延伸分别使光谱产生一定红移和轻微的蓝移．通过对前线轨道组成进行自然布居分析，揭示了靛族染料的发光均源自分子中HOMO—LUMO(π→π^*)电子跃迁．     

呋喃查尔酮结构与电子光谱的密度泛函理论研究

在密度泛函理论的PBE1PBE/6-31G(d)水平上对呋喃查尔酮及其衍生物的几何结构进行优化计算.在获得基态稳定结构的基础上,应用含时密度泛函理论计算其电子吸收光谱,探讨了取代基和溶剂对电子吸收光谱的影响,计算结果与实验结果吻合很好,平均绝对偏差仅为3.3nm(0.04eV).结果表明,取代基的引入和溶剂极性的增大均使光谱发生红移.通过前线轨道分析,揭示了该类化合物的主要吸收峰均源自分子中HOMO→LUMO电子跃迁.     

稠环芳烃菲电子激发态的含时密度泛函理论研究

用含时密度泛函理论TD-DFT及组态相关CIS、含时TD-HF方法对菲的UV光谱进行了理论研究,在几何构型优化的基础上,计算了其垂直电子激发能．计算表明,基函数的选择对激发能的计算影响较大,而不同的密度泛函交换一相关势对其影响较小,这和轨道能级的系统误差相互抵消有关．对菲的电子跃迁能的计算,与实验结果比较相一致,理论与实验的误差和不同的实验之间的误差在同一个数量级之内,显示TD-DFT方法比CIS,TD-HF方法更适合电子激发能的计算．     

CH3和CN取代8-羟基喹啉电子光谱性质的含时密度泛函理论研究

对8－羟基喹啉QH及其代衍生物MQH和CNQH用密度泛函方法（DFT）在B3LYP／6－31G＊水平上进行理论计算，探讨了供电子取代基（－CH3）和吸电子取代基（－CN）对分子电子结构，前线分子轨道能和光谱性质等的影响规律，在此基础上采用含时密度泛涵方法（TD－DFT）计算了电子光谱，计算结果表明，MQH，QH和CNQH的最低激发单重态都是A，激发能分别为3．58，3．72和3．74eV，在高激发态，无论是供电子基团（－CH3）还是拉电子基团（－CN），都导致取代衍生物的电子光谱红移。     

8-羟基喹啉锰配合物电子结构和光谱性质的含时密度泛函研究

采用密度泛函理论(DFT)B3LYP方法, 对8-羟基喹啉锰配合物进行结构优化, 探讨了配合物的结构、分子轨道能级和组成、电荷分布和转移等; 采用含时密度泛函理论(TDDFT)B3LYP/6-31G(d,p)方法对配合物的电子结构进行计算, 获得其吸收光谱. 结果表明, Mn(Ⅲ)与8-羟基喹啉中的N原子和O原子形成不对称六配位的稳定配合物, 金属锰对前线轨道的贡献很大, 在HOMO轨道中占28.53%, 在LUMO轨道中占68.30%; 中心金属锰(Ⅲ)强烈地参与发光, 电子在基态与激发态之间的跃迁, 主要是中心金属锰及8-羟基喹啉配体间的电荷转移, 在可见光区存在2个强度较大的吸收峰, 分别位于756.8 nm和532.7 nm处. 通过对双分子体系的研究发现, 相邻2个分子之间能够进行微量电荷的转移, 分子间的相互作用对前线轨道组成有明显的影响.     

8-巯基喹啉阴离子的锌配合物及其衍生物的电子光谱性质的含时密度泛函理论研究

采用从头算(ab initio)和密度泛函理论(DFT B3LYP)方法, 对配合物8-巯基喹啉锌Zn(tq)₂及其5种衍生物基态结构进行优化, 用含时密度泛函理论(TD-DFT/B3LYP)及6-31＋G(d)基组计算吸收光谱; 同时用ab initio HF 单激发组态相互作用(CIS)法在6-31G(d)基组上优化其最低激发单重态几何结构, 用含时密度泛函理论计算发射光谱. 结果表明, 电子在基态与激发态间的跃迁, 主要是在配体8-巯基喹啉(tq)环内的电荷转移, 电子从含S的苯硫酚环转移至含N的吡啶环上; 吸收光谱和发射光谱的计算值与实验值基本符合. 该类配合物都是优良的电子传输材料, 改变金属离子和取代基均可以调控发光材料的光谱波段.     

双核镉配聚物及其衍生物荧光光谱的密度泛函理论研究

采用DFT-B3LYP/6-31+G(d)方法,对配聚物[Cd2Cl4(Hbm)2]及其6种衍生物([M2-Cl4(HbmL)2],M=Zn2+,Hg2+;L=-CH3;-NH2;-CN)基态结构进行优化,用TD-DFT/B3LYP/6-31+G(d)方法计算其吸收光谱;同时用HF-CIS/6-31G(d)方法优化其最低激发单重态的几何结构,用含时密度泛函理论计算发射光谱.结果表明:电子在基态与激发态间的跃迁,主要是在卤素配体Cl到金属离子M的电荷转移(LMCL);发射光谱峰的计算最大值与实验值基本符合.改变中心金属离子M和咪唑环上的5位取代基可以精细地调控发光材料的光谱波段.     

苯并咪唑羧酸及其碱土金属配合物电子光谱性质的含时密度泛函及其概念密度泛函研究

用密度泛函理论(DFT)以及B3 LYlP泛函在6-311++G**水平上,对苯并咪唑羧酸(L)及其3种碱土金属配合物ML(M=Mg,Ca,Ba)的基态(S0)结构进行优化,用含时密度泛函理论(TD-DFT)在6-311++G**水平下计算其吸收光谱.用单激发组态相互作用(CIS)法在HF/6-31+G*上优化其最低激发单重态(S1)的几何结构,用ID-DFT B3IYP/6-311++G**计算其发射光谱.结果表明,配体L与M(Ⅱ)结合成ML后,随原子序数的增大(Mg相似文献   

2(1H)-pyridinone (2-pyridone): self-association and association with water. Spectral and structural characteristics: infrared study and ab initio calculations

DFT calculations of 2(1H)-pyridinone (2-pyridone NHP), the centrosymmetric dimer (NHP)2 and the closed complexes (NHP, H2O) and (NHP, 2H2O), with their deuterated homologues NDP, (NDP)2, (NDP, D2O) and (NDP, 2D2O), are compared with vibrational spectra of NHP and NDP in ternary mixtures CH3CN, NHP, H2O. Experimental data are also obtained for NHP or NDP in various solvents. The protic solvent effects demonstrate that mechanical couplings are different in the 1500-1700 cm(-1) range for the nuC=O and nu8b (valence of the ring) modes in NHP and NDP (or (NHP, H2O) and (NDP, D2O)). For the first time, data are obtained for NDP in the dimer (NHP, NDP). Comparison of data for pyridone, monomer, dimer or complexed with water, shows that in the complexes, water is a weaker proton acceptor and a stronger proton donor than a second pyridone molecule in the centrosymmetric dimer.     

Extraction of Uranium from Aqueous Solutions by Using Ionic Liquid and Supercritical Carbon Dioxide in Conjunction

Super powers! Uranium(VI) ions can be extracted from aqueous solutions into supercritical CO₂ (sc‐CO₂) via an ionic liquid phase that contained tri‐n‐butyl phosphate (TBP) as a complexing agent (see figure). This process has potential applications in the nuclear industry for removing actinides from nuclear waste.

     

利用瞬态吸收光谱技术研究水体中苯与亚硝酸的交叉反应机理

利用瞬态吸收光谱技术进行了有氧、无氧条件下苯与亚硝酸水溶液复相体系的交叉反应机理研究 ,初步考察了这些瞬态物种的生长与衰减等行为 ;并对其光解产物进行了GC/MS分析 .研究表明 ,HNO2 在 3 5 5nm紫外光的照射下可产生·OH和NO+ ,·OH自由基和苯反应生成C6H6 OHadduct ,反应速率常数为 8 9× 10 9L·mol-1·s-1,在有氧条件下C6H6 OHadduct进一步氧化为C6H6 OHO2 ,反应速率常数 3 3× 10 8L·mol-1·s-1;NO+ 自由基和苯作用形成C6H6 NO+ πcomplex ,然后进一步分解     

Conformations of Carnosine in Aqueous Solutions by All-Atom Molecular Dynamics Simulations and 2D-NOSEY Spectrum

All-atom molecular simulations and two-dimensional nuclear overhauser effect spectrum have been used to study the conformations of carnosine in aqueous solution. Intramolecular distances, root-mean-square deviation, radius of gyration, and solvent-accessible surface are used to characterize the properties of the carnosine. Carnosine can shift between extended and folded states, but exists mostly in extended state in water. Its preference for extension in pure water has been proven by the 2D nuclear magnetic resonance (NMR) experiment. The NMR experimental results are consistent with the molecular dynamics simulations.     

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene (band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hy-drogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethyl.amine to the excited naphthalene on the rel.ative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hy-drogen-bonding interaction quantitatively.     

用荧光光谱跟踪钙-海藻酸水溶液的Sol-gel转变

为了克服传统方法在测定凝胶化点的同时, 作用力对物理交联点的破坏和对大分子链运动的干扰, 探索和建立不施加应力的凝胶化点测定方法, 采用荧光光谱跟踪了异硫氰酸荧光黄(FITC)标记海藻酸与钙离子在水溶液中螯合的物理凝胶化. 随着凝胶化的进行, 荧光相对强度和各向异性比在凝胶化时间曲线的80 min时出现了明显的转折点, 与Winter方法得到的凝胶化点(80 min)完全一致. 因此可以利用FITC标记的荧光发射相对强度及各向异性比来决定钙-海藻酸体系凝胶化点.     

Time-dependent Density Functional Theory Study on the Electronically Excited States of N-Methylformamide in Aqueous Solution

Excited-state hydrogen-bonding dynamics of N-methylformamide (NMF) in water has been investigated by time-dependent density functional theory (TDDFT) method. The ground-state geometry optimizations were calculated by density functional theory (DFT) method, while the electronic transition energies and corresponding oscillation strengths of the low-lying electronically excited states of isolated NMF, water monomers and the hydrogen-bonded NMF-H 2 O were calculated by TDDFT method. According to Zhao's rule on the excited-state hydrogen bonding dynamics, our results demonstrate that the intermolecular hydrogen bond C=O···O-H is strengthened and weakened in different electronically excited states. The hydrogen bond strengthening and weakening in the electronically excited state plays an important role in the photophysics of NMF in solutions.     

葡萄糖水溶液氢键结构和动力分析

利用分子动力学模拟方法研究了不同浓度下葡萄糖水溶液的氢键结构和氢键生存周期. 分析了参与i个氢键(分子内、分子间、所有类型)的葡萄糖分子和水分子的百分比分布. 研究发现存在一个特征数N, 参与N个氢键的分子的比例最高, 当iN时, 参与i个氢键的分子的比例随着浓度的增加而减小. 还分析了不同类型氢键(葡萄糖分子内、葡萄糖分子间、水分子间、葡萄糖分子与水分子间、所有类型)的连续和截断自相关函数, 并计算了对应的氢键生存周期.     

Solvent‐Modulated Influence of Intramolecular Hydrogen‐Bonding on the Conformational Properties of the Hydroxymethyl Group in Glucose and Galactose: A Molecular Dynamics Simulation Study

Intramolecular hydrogen‐bonding (H‐bonding) is commonly regarded as a major determinant of the conformation of (bio)molecules. However, in an aqueous environment, solvent‐exposed H‐bonds are likely to represent only a marginal (possibly adverse) conformational driving as well as steering force. For example, the hydroxymethyl rotamers of glucose and galactose permitting the formation of an intramolecular H‐bond with the adjacent hydroxyl group are not favored in water but, in the opposite, least populated. This is because the solvent‐exposed H‐bond is dielectrically screened as well as subject to intense H‐bonding competition by the water molecules. In the present study, the effect of a decrease in the solvent polarity on this rotameric equilibrium is probed using molecular dynamics simulation. This is done by considering six physical solvents (H₂O, DMSO , MeOH , CHC l₃, CC l₄, and vacuum), along with 19 artificial water‐like solvent models for which the dielectric permittivity and H‐bonding capacity can be modulated independently via a scaling of the O–H distance and of the atomic partial charges. In the high polarity solvents, the intramolecular H‐bond is observed, but arises as an opportunistic consequence of the proximity of the H‐bonding partners in a given rotameric state. Only when the polarity of the solvent is decreased does the intramolecular H‐bond start to induce a conformational pressure on the rotameric equilibrium. The artificial solvent series also reveals that the effects of the solvent permittivity and of its H‐bonding capacity mutually enhance each other, with a slightly larger influence of the permittivity. The hydroxymethyl conformation in hexopyranoses appears to be particularly sensitive to solvent‐polarity effects because the H‐bond involving the hydroxymethyl group is only one out of up to five H‐bonds capable of forming a network around the ring.     

Identification of Triplet States in Carotenoids by Intracavity Absorption Spectroscopy and Measurements of Delayed Fluorescence

Owing to the low quantum yield of phosphorescence , triplet states of carotenoids have been very difficult to identify. These states can be characterized by intracavity absorption spectroscopy, which allows the direct measurement of the spin-forbidden singlet–triplet transitions in low concentrated solutions, and by delayed fluorescence measurements.