2-(2’-羟基苯基)苯并咪唑的光谱特性

2-(2’-羟基苯基)苯并咪唑(简称HBI)是一类具有激发态质子转移效应的有机分子。观测了HBI分子在甲苯、甲苯与乙醇混合及乙醇三种溶液的吸收光谱,发现其吸收光谱相类似。用317 nm光激发,观测其荧光光谱,在甲苯溶液中只观测到一个荧光带,其峰值位于470 nm;在甲苯与乙醇的混合溶液及乙醇溶液的荧光光谱中,都观测到两个荧光带,其峰值分别位于370和450 nm。根据激发态质子转移理论可知,470 nm的荧光带是由激发态质子转移生成的互变异构体,即HBI酮式构型分子的发射,峰值位于370 nm的荧光带是HBI稀醇式构型分子的发射。由于乙醇具有较大的极性,可与HBI分子相互作用形成分子间氢键,即生成溶剂化物。当溶剂化物被激发,在激发态发生激发态质子转移生成两性离子,两性离子发射荧光回到基态。因此,在极性溶剂中HBI发射峰值位于450 nm的荧光带应归于两性离子的发射。当用532 nm强光激发HBI溶液时,发现HBI分子在非极性溶剂中无双光子效应,而在极性溶剂中却存在双光子效应,表明HBI的溶剂化物具有双光子效应。     

激发态下甘氨酸与水分子间氢键性质研究

在生物体中氨基酸通常以水作为溶剂,是形成细胞的重要成分.在该环境下,分子间氢键的产生会对氨基酸分子与水分子的结构和性质产生影响.为了研究其在基态和激发态下的性质,本文利用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对甘氨酸分子和H₂O分子在基态和激发态下的分子间氢键的静电势、键长、自然键轨道(NBO)电荷、分子中的原子理论(AIM)分析、Wiberg键级b、红外(IR)光谱、空穴-电子轨道和基态与激发态之间的电子转移进行了理论研究.结果表明：分子间氢键的形成会导致分子结构的改变和红外光谱振动频率的移动.在激发态下,分子间氢键有不同程度的增强或减弱.该计算结果为氢键的形成和激发态下分子间氢键的研究提供理论依据.     

聚酰胺66溶液弛豫行为的NMR研究

用1D和2D NMR技术归属了聚酰胺66的1H和13C的NMR共振信号,并通过聚酰胺66溶液温度和浓度改变对氢核弛豫时间的影响,得到了其分子运动信息.结果表明随着温度的升高,聚酰胺66链间氢键逐渐解离,大分子链间相互作用逐渐减弱.而解离出来的链段又与溶剂小分子可以形成新的氢键,使聚酰胺66链卷曲并包含着部分溶剂分子一起运动.随着溶液浓度的增大,由于分子链间距变小,使得分子间作用力增强,链缠结程度加大,使链运动受限.     

电子激发和溶剂效应对芴酮-甲醇分子间氢键增强现象的理论研究 (cited: 1)

理论研究了电子激发和溶剂效应导致的芴酮-甲醇复合体系中分子间氢键增强现象．通过基态和激发态性质的计算,不仅展示了分子间氢键键长的变化以及变化在振动光谱中的影响,而且揭示了导致氢键变化的内在物理机制：溶质分子的电子激发及溶剂化效应引起的电子重新分布,增大了溶质和溶剂分子的偶极矩,导致了它们之间的相互作用的增大,并最终加强了分子间氢键的强度．还分别对处于液相及气相中的复合体的基态和激发态的几何结构、红外谱、复合体及构成分子的偶极矩进行了理论计算,结果阐明了电子激发与溶剂化效应对氢键变化的贡献,同时还发现只有进一步引入溶剂化效应,复合体的基态、激发态的性质才能与实验达到精确一致．所有激发态均采用所开发的基于含时密度泛函理论解析计算一阶、二阶激发态能量导数的方法．     

采用密度泛函理论研究二甲基胺-二苯甲酮的分子内电荷转移激发态氢键

利用(含时)密度泛函理论研究了二甲基胺-二苯甲酮(DMABP)及其氢键二聚物DMABP-MeOH的光物理性质和弛豫动力学过程. 结果表明,在非极性和非质子性溶剂中,DMABP分子的第一和第二激发态跃迁同时具有局域激发和分子内电荷转移的特征;在极性质子性溶剂中,分子间氢键C=O…H-O的形成增加了这两个最低激发态之间的能量差,使DMABP-MeOH的第一激发态具有较强极性的分子内电荷转移特性. 通过计算DMABP和DMABP-MeOH分子的激发态构型弛豫势能曲线研究了激发态动力学弛豫过程. 结果表明,通过扭     

核黄素在不同极性溶剂中的光谱特性研究

实验测得核黄素在水、二甲基亚砜(DMSO)和三氯甲烷三种不同极性溶剂中的稳态吸收光谱、荧光光谱和时间分辨荧光光谱,研究了溶剂对核黄素光谱性质的影响。实验结果表明,在不同极性的溶剂中,核黄素的吸收峰位置几乎不变,而荧光光谱峰值随着溶剂极性的增大而出现红移。这是由于溶质分子的电子激发及溶剂化效应引起的电子重新分布导致它在极性溶剂中第一激发单重态能级的变化。在时间分辨荧光光谱实验中,核黄素在水溶液中荧光寿命也高于在其他两种溶剂中,荧光寿命的延长可归因于核黄素与氢键对体溶剂之间的分子间氢键相互作用。应用Gaussian09软件,采用密度泛函理论和含时密度泛函理论,结合基于密度的溶剂化模型,对不同极性溶剂中的核黄素分子进行基态和激发态优化和计算。通过前线分子轨道分析,核黄素的受激跃迁属于苯环和含氮杂环上的π电子向苯环及C N,C O共轭双键的反键轨道π*的跃迁。分子偶极矩的计算结果表明,核黄素分子的第一激发态偶极矩大于基态偶极矩,偶极矩的增大,导致溶质与溶剂分子之间的相互作用的增大。而溶剂分子与溶质分子基态和激发态的相互作用程度不同,使得吸收峰和荧光峰出现不同变化情况。极性越大的溶剂越有利于对激发态的稳定作用,使激发态能量降低,相应的发射波长发生红移。最后,通过分子表面静电势和弱相互作用分析,在水溶剂中考虑氢键作用对核黄素分子光谱的影响。多聚体结构的理论吸收和发射峰值更接近实验结果,说明多聚体结构合理。水分子二聚体与核黄素形成的环状结构,有利于提高核黄素分子的刚性,有利于荧光的发射,减少非辐射跃迁的几率,荧光寿命延长。     

可溶性钒氧酞菁在不同介质中的吸收光谱研究

研究了四丙基取代钒氧酞菁（Ｐｒ４ＶＯＰｃ）在不同介质中的吸收光谱。Ｐｒ４ＶＯＰｃ分子在不同介质中的吸收光谱差别很大：在稀溶液中以分子的单体吸收为主（λｍａｘ＝７０７ｎｍ），在浓溶液和ＰＭＭＡ薄膜中由于形成平行排列结构的二聚体而使分子单体的吸收峰发生蓝移（λｍａｘ＝６６０ｎｍ），在蒸发膜中则由于形成斜交结构的二聚体使得分子单体的吸收峰发生分裂形成红移和蓝移峰（λｍａｘ＝７２０ｎｍ，６６０ｎｍ），在溶液沉积的固态薄膜中由于形成结晶相Ｉ而表现出强烈的近红外吸收（λｍａｘ＝８２６．９ｎｍ）。造成这种差别的原因是四个丙基的引入加大了ＶＯＰｃ分子的空间位阻效应。通过热处理或溶剂蒸汽处理，可以使Ｐｒ４ＶＯＰｃ蒸发膜转变成具有强近红外吸收的结晶相Ｉ；而只有通过溶剂蒸汽处理才能使ＰＭＭＡ介质中的Ｐｒ４ＶＯＰｃ转变成结晶相ＩＩ。     

乙二醇分子间氢键结构与溶剂效应

采用密度泛函理论在B3LYP/6-311++G** (范德华校正)水平上研究乙二醇在气相中分别与乙腈、丙酮、四氢呋喃、水、乙二醇形成氢键二聚体的结构性质,根据PCM 极化统一场模型讨论氢键溶剂效应。结果表明,五种氢键二聚体分子中的氢键属于红移氢键,溶剂使氢键二聚体分子的偶极矩变大,并对OH振动频率的影响不大。     

乙二醇分子间氢键结构与溶剂效应

采用密度泛函理论在B3LYP/6-311++G~(**)水平上研究乙二醇在气相中分别与乙腈、丙酮、四氢呋喃、水、乙二醇形成氢键二聚体的结构性质,根据PCM(polarized continuum model)极化统一场模型讨论氢键溶剂效应.结果表明,五种氢键二聚体分子中的氢键属于红移氢键,溶剂使氢键二聚体分子的偶极矩变大,并对OH振动频率的影响不大.     

溶剂对香豆素343染料光谱性质和最低激发态偶极矩的影响

通过对香豆素343(C343)在不同溶剂中的稳态吸收光谱、稳态荧光光谱和时间分辨荧光光谱的分析,研究了溶剂对C343的光谱性质的影响,并获得了光谱特性与溶剂极性之间的依赖关系. 吸收光谱峰值的红移随着溶剂极性的增加而发生较小的变化. 然而,荧光光谱的峰值对溶剂的极性却很敏感,并随着溶剂极性参数f(ε,n)的增加呈线性增长. 这是由于C343激发态电荷分布的变化导致了它在极性溶剂中第一激发单重态能级的变化. 用溶剂效应测量法和量子化学计算方法确定了C343最低激发态的偶极矩,这两方法所得的结果一致. C343在不同溶剂中的时间分辨荧光光谱研究表明荧光寿命随着溶剂极性的增加而增加,即从甲苯溶液的3.09 ns线性地增加到水溶液中4.45 ns;荧光寿命延长的根源可归因于C343与氢键给体溶剂之间的分子间氢键相互作用.     

Time-resolved study of intramolecular charge transfer fluorescence in 1,2,3,4-tetrachloro-11H-isoindolo-[2, 1-a]-benzimidazol-11-one

Fluorescent properties of 1,2,3,4-tetrachloro-11H-isoindolo-[2,1-a]-benzimidazol-11-one (TCIB) in various organic solutions are described. Detailed investigation of the fluorescence from the solutions revealed that it was ascribable to the electronic transition from the lowest singlet excited state of an isolated molecule to its ground state, though the fluorescence spectrum was broad and structureless and the Stokes’ shift was about 1 eV. The absorption peak of TCIB was relatively insensitive to change in solvent polarity, whereas its fluorescence peak shifted to the red with an increase in the polarity. This finding suggests that the dipole moment of the molecule in the ground state is almost zero, and that the excited state has a non-zero dipole moment, which coincides with the predicted semiempirical molecular orbital calculation. Fluorescence quantum efficiency decreased with increase of solvent polarity. The efficiency was reduced by a factor of 39 in going from n-hexane solution to acetonitrile solution. The radiative rate constant also decreased with increase of solvent polarity. However, its reduction was very moderate; the reduction factor was only 2.5 for acetonitrile solution as compared with n-hexane solution. This finding indicates that the emitting state of the title compound is influenced by a solvent-dependent non-radiative mechanism, for which solvent-sensitive intersystem-crossing deactivation is tentatively proposed.     

双丙酮丙烯酰胺的紫外光谱研究

双丙酮丙烯酰胺（DAAM）是一种应用广泛的聚合物单体,可与其他乙烯基单体共聚得到性能各异的聚合物材料,而对DAAM的光谱研究报道较少。文章主要研究了DAAM在水、乙腈、甲醇和环己烷四种溶剂中的紫外光谱。结果发现,在这四种溶剂中,DAAM溶液的紫外光谱主要在200 nm左右及226 nm左右有2个强吸收峰。200 nm左右的吸收峰对溶剂的极性及溶液的浓度非常敏感。在极性溶剂中200 nm吸收峰发生蓝移,在极性较大的乙腈及水中,蓝移更大;在各种溶剂中,200 nm吸收峰都随溶液浓度增大而发生红移。而226 nm左右的吸收峰在各种极性不同的溶剂中吸收峰的位置变化不明显,对溶液浓度也不敏感。因此,DAAM在226 nm吸收峰可以用于DAAM的定量分析,而200 nm吸收峰可用于研究DAAM与其他分子的相互作用。另外,溶剂极性对2个吸收峰强度的影响也不相同。     

The structure of liquid methylamine and solutions of lithium in methylamine

The technique of hydrogen/deuterium isotopic substitution in neutron diffraction has been used to measure the intra- and intermolecular correlations in liquid methylamine, and 2 and 8 MPM (mole percent metal) lithium methylamine solutions. We find that pure methylamine forms only one strong hydrogen bond per molecule, with evidence for weaker orientations towards the methyl group. As one introduces lithium metal, the intramolecular structure of the solvent is unaltered. However, intermolecular hydrogen bonding is progressively disrupted as the concentration of (solvated) cations and excess electrons increases. Comparison of the total structure factors for 0, 2, 8 and 20 MPM lithium methylamine solutions shows that the greatest shift in the position of the principal peak occurs between 8 and 20 MPM. This can be correlated to the electron delocalization associated with the non-metal-metal transition.     

Electronic structure and spectral fluorescence properties of umbelliferone and herniarin

We have studied the characteristic features of the spectral fluorescence properties of natural compounds (umbelliferone and herniarin) in aprotic and proton-donor solvents of different polarities. Based on quantum chemical analysis by the AM1 semiempirical method of the changes in the electronic charge and bond orders in the ground state and the first excited state, we have interpreted the anomalously high Stokes shifts and mirror symmetry of the absorption and fluorescence bands of these compounds in aprotic solvents. We have established that the fluorescence spectra of umbelliferone in water, ethanol, alkaline and acidic solutions differ considerably from the analogous spectra of herniarin. This is connected with detachment and transfer of a proton in the neutral form of umbelliferone upon photoexcitation, with possible formation (depending on the pH of the medium) of an anion, cation, or tautomer. Good agreement was achieved between the calculated and experimental values of the maxima for the electronic bands of these forms. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 569–576, September–October, 2007.     

有/无金属离子Cu2+或Zn2+参与时中药有效成分伞形花内酯与生物大分子BSA的相互作用

运用荧光光谱(FS)及紫外光谱(UV)研究了有/无金属离子Cu2 或Zn2 参与时中药有效成分伞形花内酯与生物大分子牛血清白蛋白(BSA)的相互作用。实验结果表明:有/无金属离子参与时,伞形花内酯均与BSA形成基态复合物从而猝灭BSA的内源性荧光,猝灭原因主要为静态猝灭和非辐射能量转移;金属离子参与使得KA增大,n仍维持在2左右;伞形花内酯分子能够扦插入BSA分子内部,温度以及金属离子参与对伞形花内酯与BSA分子中荧光性氨基酸残基间的空间距离r影响不大。有/无金属离子参与时伞形花内酯与BSA的作用过程均是一个熵增加和Gibbs自由能降低的自发超分子作用过程。伞形花内酯与BSA之间以静电相互作用为主,金属离子参与使伞形花内酯与BSA分子间静电相互作用增强,故ΔH对ΔG的贡献增大。     

尼古丁分子的能级结构和光谱计算

研究尼古丁分子的能级结构与光谱特征,对更好地了解尼古丁分子的毒性和药性有理论指导作用.基于密度泛函理论(DFT),本文利用Gaussian 09软件在B3LYP/6-311G(d,p)基组水平上对尼古丁分子进行结构优化,再采用含时密度泛函理论(TD-DFT)在乙醇溶剂中计算尼古丁分子的15个激发态.使用Multiwfn波谱分析软件对分子前线轨道进行计算,并绘制出分子的红外谱图和紫外谱图.通过前线轨道分析可知,尼古丁分子的亲核位点是吡啶环上的C3和N6、亲电位点是吡咯环上的N22.吡啶环上的C-H、N-H键面内伸缩振动峰主要集中在3049～3079 cm~(-1),吡咯环上的甲基、亚甲基的伸缩振动峰主要集中在2796～3005 cm~(-1),其中在2816 cm~(-1)处甲基上C-H键振动峰最为明显,占比43.3%;吡咯环与吡啶环的摆动峰主要集中在1027～1455 cm~(-1),吡啶环的面内振动峰主要集中在1008～1027 cm~(-1),在800 cm~(-1)以下吸收峰都为吡啶环的面外摆动峰.紫外光谱的最大吸收峰位于173.46571 nm处,主要是由基态S0跃迁到激发态S5、S6、S10、S11、S12、S13、S14形成的,其中基态S0跃迁到激发态S11的贡献最大,其余激发态跃迁振子强度小于0.03,为禁阻跃迁.     

Design considerations for SERS detection in colloidal solution: reduce spectral intensity fluctuation

The intensity fluctuation of surface‐enhanced Raman scattering (SERS) has seriously hampered its practical applications. The previous studies that involved SERS intensity fluctuation mostly focus on the assembled substrates or single molecule and single nanoparticle but have few attention on colloidal solutions containing numerous molecules and/or nanoparticles. Here, we studied the time‐elapsed SERS spectra of three different analytes in colloidal solution. Their peak intensities fluctuated simultaneously and uniformly throughout the acquisition process and had no correlation with their wavenumber wandering. Gravity‐induced inhomogeneous distributions of Ag nanocubes in solution led to the spatial and temporal variations of peak intensities, which could be reduced by altering the integration time, particle concentration, and solvent viscosity and density. Furthermore, the dissimilar interactions between analytes and Ag nanocubes showed non‐detectable influence over their intensity fluctuations. This investigation gives out the significant guidance for SERS detection in colloidal solution. Copyright © 2015 John Wiley & Sons, Ltd.     

Three- and four-nucleon systems from chiral effective field theory

Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading order (NLO), that describe NN phase shifts up to about 100 MeV fairly well, have been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been solved rigorously. The resulting 3N and 4N binding energies are in the same range as found using standard NN potentials. In addition, low-energy 3N scattering observables are very well reproduced as for standard NN forces. The long-standing A(y) puzzle is absent at NLO. The cutoff dependence of the scattering observables is rather weak.     

Vibrational relaxation study in 4-chloroacetophenone

Vibrational relaxation process has been emerged as a useful tool in probing the nature of solute solvent interactions in liquid phase. The Laser Raman techniques have been used to study the vibrational and rotational frequencies of molecules, which provide detailed information about the dynamic processes involved in liquids. Raman spectra of C=O stretching mode of 4-chloroacetophenone dissolved in acetonitrile and chlorobenzene have been recorded as a function of solvent concentration ranging from 10% to 90% concentration at room temperature. The 4-chloroacetophenone is a molecule having wide application in manufacture of drugs, perfumes and cosmetics. This study may provide useful information about the vibrational relaxation mechanisms in liquid solutions at molecular level. The Laser Raman components were determined and the spectra were analyzed at different solvent concentrations. The theoretical models have been tested and compare with the experimental results.     

Effects of alcohols on multi-bubble sonoluminescence spectra

Spectra of multi-bubble sonoluminescence (MBSL) were measured in argon-saturated water and ethanol solutions in the concentration range 2-100 mM at the frequencies of 116 kHz and 1.0 MHz. The spectral peaks from OH-radical emission near 310 nm were observed at relatively low ultrasonic power at both frequencies. The sub-peaks at 290 and 340 nm were also observed, which are attributed to OH-radical vibronic transition. The MBSL spectra from ethanol solutions indicated that the quenching of OH-radical emission was more efficient than that of underlying continuous spectrum. The continuous spectrum suggested the decrease in temperature with increasing ethanol concentration. The concentration dependence of spectrum quenching showed no frequency dependence. A new peak was observed at 385 nm only at small ethanol concentrations and at the frequency of 1.0 MHz, which attributed to CH or CN molecule emission.