基于溶剂化效应的BDE-15分子振动光谱增强特征振动研究

利用密度泛函与自洽反应场理论在B3LYP/6-31+G(d)水平下分别计算气态及24种不同极性溶剂中4,4’-二溴二苯醚(4,4’-dibrominated diphenyl ethers, BDE-15)的分子振动光谱(红外光谱、拉曼光谱),以气态分子振动光谱为基准,筛选出对溶剂极性敏感的特征振动作为指标构建溶剂对BDE-15振动光谱溶剂化效应指标体系,探究溶剂对BDE-15分子振动频率、红外/拉曼峰强溶剂化效应及综合效应,并寻求显著增强BDE-15分子特征振动频移/强度的溶剂。研究表明：从分子振动频率角度,溶剂极性敏感的(频移>1 cm-1)分子特征振动均为伸缩振和面外弯曲振,但24种溶剂对BDE-15分子振动频率溶剂化效应并不显著;从分子振动峰强角度,24种溶剂对BDE-15分子振动光谱峰强的增强效应主要发生在红外光谱的中低频区及拉曼光谱的高频区,其中起显著增强(红外/拉曼效应指标值分别大于6与5)的溶剂为醇类、乙腈、二甲亚砜、硝基苯;不同极性溶剂对BDE-15拉曼峰强溶剂化效应及综合效应指标值均表现出随溶剂介电常数增长由线性到对数的增长趋势,而红外峰强只保留低介电常数溶剂时的线性关系。利用上述BDE-15分子振动光谱峰强增强方法对BDE-153,BDE-154和BDE-209进行验证,醇类、乙腈、二甲亚砜、硝基苯对三者的振动光谱红外/拉曼峰强的效应指标值分别大于6与5,且最大峰强增倍数皆大于33,说明所建BDE-15分子振动光谱增强特征振动方法有助于进一步开展基于分子振动光谱的PBDEs同系物间辨识研究。     

Characterization of polycyclic aromatic hydrocarbons using Raman and surface‐enhanced Raman spectroscopy

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous atmospheric pollutants and food contaminants, which exhibit potent carcinogenicity, mutagenicity, and teratogenicity. Vibrational spectroscopy techniques, especially Raman spectroscopy and surface‐enhanced Raman spectroscopy (SERS), can be potentially used as an alternative technique to liquid and gas chromatography in PAH analysis. However, there is limited information on the intrinsic Raman and SERS fingerprints of PAHs. In this study, we have acquired the Raman and SERS spectra of seven PAH compounds and compared their experimental spectra with theoretical Raman spectra calculated by density function theory (DFT). The vibrational modes corresponding to the Raman peaks have also been assigned using DFT. Characteristic Raman and SERS peaks have been identified for five PAH compounds, and the limits of detection were estimated. Such information could be useful for developing SERS assays for simple and rapid PAH identification. Copyright © 2014 John Wiley & Sons, Ltd.     

Vibronic spectra of matrix-isolated lead sulfide

Vibronic spectra are reported for lead sulfide in argon, krypton and SF₆ matrices at low temperatures. Emission stimulated by laser line irradiation of PbS is observed from the v′ = 0 level of three electronic states lying at about 14 500, 18 500 and 21 500 cm^?1 above the ground state. Emission is also observed from an excited state of Pb₂S₂ at about 17 000 cm^?1. In addition, the laser radiation gives rise to the vibrational Raman spectrum of PbS in argon at 423.2 cm^?1 and to a very weak Raman band at 297 ± 2 cm^?1 which we attribute to Pb₂S₂.The effects of temperature on the matrix spectra, of matrix material on the band origins, and of matrix concentration on the vibrational relaxation process, and the apparent degrees of coupling among the electronic states have all been examined. The electronic absorption spectrum of PbS in Ar is reported and the matrix data are compared with available information on gaseous PbS.     

Infrared and Raman Study of the Local Anesthetic Procaine

The infrared and Laser Raman spectra of procaine with free basis in the solid state were obtained. The characteristic vibrational frequencies of their different modes were identified and assigned from isotope shifts and theoretical calculations. An infrared study in the liquid phase was also carried out. The corresponding rotation and inversion barriers in p-amino group were computed by means of different optimization procedures.     

Laser excitation spectra and lifetimes of CBrCl and CBr2 in solid Ar

The CBr₂ and CBrCl emissions in solid Ar have lifetimes of 5.6 and 14.5 μsec, respectively. Laser excitation spectra of the fluorescence provide information about the upper state vibrations structure of these species. Mode-to-mode vibrational energy transfer in CBrCl appears to be inefficient.     

Changes in spectral features with varying mole fractions of anisaldehyde in binary mixtures

Raman and IR spectra of neat anisaldehyde (4‐methoxybenzaldehyde (4MeOBz)) and its binary mixtures (in polar and nonpolar solvents) with varying mole fraction of 4MeOBz were investigated. The concentration dependence of the wavenumber position and line width (full width at half maximum, FWHM) was analyzed to study the interaction of the solute vibrational modes with the microscopic solvent environment. The wavenumbers of Raman modes of 4MeOBz, namely, the carbonyl stretching, aldehydic δ (C H) and ring‐breathing modes, showed a linear variation in the peak position for varying concentrations of 4MeOBz in the different solvents. The dependence of Raman line width with concentration of 4MeOBz of these modes was also taken into account. The solute–solvent interaction is stronger in 2‐propanol and acetonitrile because of the formation of hydrogen bonds between them, whereas in benzene the interaction is too weak to affect the Raman modes. The modes, ν (CO) in 2‐propanol and aldehydic δ (C H) in acetonitrile, gave a Gaussian‐type line width variation, which was explained by the concentration fluctuation model, and the linear variation of the line widths was also interpreted by solute–solvent interactions. IR spectra were taken for these binary mixtures, which also give further support to these data. Copyright © 2006 John Wiley & Sons, Ltd.     

激光拉曼光谱分析中药复方制剂中青蒿素含量的研究

从中药材黄花蒿中提取的青蒿素,是一种含有过氧基团的倍半萜内酯药物,目前已成为世界卫生组织推荐的抗疟疾药物。含有青蒿素的复方制剂具有抗疟、抑菌和调节免疫功能等作用,然而含青蒿素的复方制剂没有可量化的统一质量标准,因此难以控制和评价这些复方制剂的质量。目前对于青蒿素复方制剂的研究主要集中在定性分析其有效成分上,但具体如何定量分析其中青蒿素含量的研究工作却并不多,迫切需要一种简便、快速、无损的方法监控青蒿素的生产和使用。激光拉曼光谱是一种分子联合的光散射现象,能够提供样品分子的成分及结构,对研究青蒿素具有重要的意义。首先对青蒿素标准样品进行激光拉曼光谱定性分析测试,获得青蒿素标准品的拉曼特征图谱,这些标准图谱为以后分析中药复方制剂中的青蒿素奠定了基础。通过拉曼测试分析得到位于724 cm-1处的拉曼峰是与青蒿素中过氧基团直接相关的特性声子振动模式,可用于检测过氧桥键的存在,也是决定其抗疟活性的关键;而位于1 736 cm-1处的拉曼峰强度大、周围无其他振动峰干扰,是与青蒿素中内酯基团相关的特性声子振动模式,也可用来检测分析青蒿素。因此,拟采用青蒿素分子中位于724 cm-1处和1 736 cm-1两处的拉曼特征峰进行定性定量分析。然后,在实验室制备了一系列具有不同青蒿素质量百分数的青蒿素/面粉混合样品,确定出混合样品中青蒿素724 cm-1处和1 736 cm-1处拉曼光谱参数。并以峰面积比值A₇₂₄/A_{1 736}的平均值作为横坐标,青蒿素质量百分数作为纵坐标,拟合青蒿素质量百分数与峰面积比的函数关系,得到二次函数关系式为y=0.907 22x2+0.465 93x(0<x<0.9),相关系数r为0.992 65。最后,将该关系式用于中药复方制剂青蒿素哌喹片中青蒿素的含量检测分析,按照此方法计算得到的青蒿素含量值与真实值（14.29%）比较,相对误差较小（<10%）,可以初步建立起青蒿素含量的拉曼光谱测试方法。本文提出应用激光拉曼光谱技术,以期实现原位、无损和快速检测。在青蒿素标准样品实验研究基础上,确定青蒿素拉曼光谱参数和实验条件,建立起复方制剂中青蒿素含量的实验分析方法,为青蒿素的研究和应用开创新的局面。     

Raman study of temperature and pressure effects on vibrational relaxation in liquid CHCl3 and CDCl3

The Raman line shapes of the ν₁(A ₁)C-H and C-D stretching fundamentals in liquid CHCl₃ and CDCl₃ have been measured as a function of pressure from 1 bar to 4·5 kbar within the temperature range 30°C to 90°C. Densities have also been determined under the same experimental conditions. The vibrational relaxation rates are obtained from the isotropic component of the Raman band and the experimental results can be summarized as follows: (i) as T increases at constant density the vibrational relaxation rate increases; (ii) at constant T, the increase in density produces an increase in the relaxation rate; (iii) an increase in temperature at constant pressure results in an increased relaxation rate. The above three cases hold for the CDCl₃ liquid, whereas only (ii) may be stated for the CHCl₃ liquid.

The experimental vibrational data are interpreted in terms of the Kubo stochastic line-shape theory and the collinear-isolated-binary-collision model proposed by Fischer and Laubereau. Application of the Kubo formalism shows that vibrational dephasing is the dominant relaxation mechanism and that the modulation is fast both in liquid CHCl₃ and CDCl₃.

Interpretation in terms of the binary collision dephasing model leads to the following results: (i) the pure dephasing mechanism seems to be the dominant broadening mechanism for the isotropic Raman line shapes studied; (ii) the calculated dephasing rates as a function of density and temperature show agreement with the experimental data. In these calculations the elastic collision times are obtained from the modified Enskog theory.     

Concentration dependent Raman and IR study on salicylaldehyde in binary mixtures

A vibrational spectroscopic study of binary mixtures of salicylaldehyde (SA) in three different solvents (polar and nonpolar) is presented. The vibrational modes ν(CO), hydroxyl stretching mode (C OH) and aldehydic (C H) stretching vibration were analyzed. Changes in wavenumber position and full width half maximum have been explained for neat as well as binary mixtures with different volume fractions of the reference system, SA, in terms of inter‐ and intramolecular hydrogen bonding. The IR spectra of these mixtures have also been taken and compared with the Raman data. The spectral changes have been well explained using the concentration fluctuation model and solute–solvent interaction. Copyright © 2007 John Wiley & Sons, Ltd.     

3,5-二甲氧基苯甲醇振动光谱的研究

实验测量了3,5-二甲氧基苯甲醇(L₁OH)分子的拉曼和红外光谱,运用密度泛函理论(DFT)采用B3LYP混合泛函和6-311G(d, p)基函数组,计算了该分子的平衡构型和振动频率。结果表明：理论计算出的振动频率值和实验观测值吻合得较好。同时采用简正振动分析方法得到了各振动频率的势能分布(PED),从而对L₁OH分子的振动频率归属做出了全面指认。已有文献中还未见有对L₁OH分子振动光谱研究的报道。     

Density functional theory calculations and vibrational spectra of 3,5 dichloro hydroxy benzaldehyde and 2,4 dichloro benzaldehyde

The solid‐phase Fourier transform infrared (FT‐IR) and FT‐Raman spectra of 3,5 dichloro hydroxy benzaldehyde (DHB) and 2,4 dichloro benzaldehyde (DB) have been recorded in the regions 4000–400 and 4000–0 cm⁻¹, respectively. Theoretical information on the optimized geometry, harmonic vibrational wavenumbers as well as infrared and Raman intensities were obtained by means of density functional theory (DFT) using standard B3LYP/6–31G** level. This information was used in the assignment of the various fundamentals. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Copyright © 2008 John Wiley & Sons, Ltd.     

Vibrational spectroscopy investigation using density functional theory on 7‐chloro‐3‐methyl‐2H‐1,2,4‐ benzothiadiazine 1,1‐dioxide

The solid phase Fourier transform infrared (FTIR) and Fourier transform (FT) Raman spectral analysis of 7‐chloro‐3‐methyl‐2H‐1,2,4‐benzothiadiazine 1,1‐dioxide (diazoxide), an antihypertensive agent was carried out along with density functional computations. The optimized geometry, wavenumber and intensity of the vibrational bands of diazoxide were obtained by DFT‐B3LYP level of theory with complete relaxation in the potential energy surface using 6‐31G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational wavenumbers calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated wavenumbers are found to be in good agreement. The experimental spectra coincide satisfactorily with those of calculated spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

显微拉曼光谱在珍珠鉴定中的应用

本文用显微拉曼对三种珍珠 (天然海水珍珠、人工养殖海水珍珠、人工养殖淡水珍珠 )做了测试与分析。结果表明 :虽然主峰相同 ,然而这三种珍珠的拉曼谱有不可置疑的差别。另外 ,珍珠粉和整粒珍珠也有明显差异。测试中还发现 ,与拉曼谱同时记录到的光荧光谱也是有关珍珠的宝贵信息。因此 ,显微拉曼光谱仪记录到的材料振动谱和荧光谱为珍珠的分析研究及日常鉴定提供了可靠的信息资料。     

Far-Infrared and Raman Spectra of Crystalline Tetrapropylammonium Trichloromercurate(II)

The far-ir and Raman spectra of the tittle compound have been obtained at room and liquid nitrogen temperature. The spectra are consistent with a halogen bridged species and the vibrational modes are assigned in relation to the structure of the dimeric anionic complex. A symmetry lower than D_2h is proposed in agreement with preliminary X-ray diffraction results.     

抗癌新药安吖啶的近红外拉曼光谱及近红外表面增强拉曼光谱的研究

采用近红外表面增强拉曼光谱技术对抗癌新药安吖啶的结构进行了研究。     

Raman band shapes and the dynamics of liquid N2O4

The Raman spectra of the totally symmetric A _g modes, v ₁, v ₂ and v ₃, of the N₂O₄ molecule have been measured in the liquid state at 262, 279 and 297 K. The vibrational and the rotational correlation functions are calculated. The long-time exponential decay of the rotational correlation functions of all the A _g modes reflects an asymptotic diffusional behaviour of molecular reorientation. The rotational relaxation rate is found to increase with increasing temperature. A marked point of inflection from the short time inertial correlation to the long time exponential decay appears at about 0·35 ps for the v ₂ mode. This is an indication of orientational rebound arising from the librational motion in a temporary solvent cage. The isotropic bandwidth increases in the order v ₁ < v ₂ < v ₃, which is also the order of decreasing vibrational frequency. The temperature dependence of the peak frequency and of the bandwidth are also found to increase in the same order. These observations are analysed qualitatively in terms of two models of vibrational dephasing which take into account the effect of vibrational anharmonicity.     

Polarized Infrared and Raman Spectra and Ab-Initio Calculations of 2-(Methylthio)Benzothiazole

Abstract

The infrared spectra of 2-(methylthio)benzothiazole have been measured from 4000 to 180 cm^?1 for liquid and polycrystalline samples, polarized spectra of oriented films have also been obtained. the Raman spectra of polycrystalline and liquid samples have been investigated. the structural parameters, energies and vibrational frequencies have been calculated from ab-initio RHF calculations using the 6-31G?? basis set for various conformations. a detailed assignment of most of the observed bands has been proposed on the basis of the infrared dichroism, Raman polarization data and frequency calculations.     

四甲基环戊二烯铁和四甲基环戊二烯钌的振动光谱及简正坐标分析计算

本文采用简化一般价力场对Ｆｅ（Ｃ５Ｍｅ４Ｈ）２，Ｒｕ（Ｃ５Ｍｅ４Ｈ）２的振动光谱作了简正坐标分析计算，得到了一套合理的力常数，并对振动频率进行了指认。     

三硼酸铯和硼酸铯锂晶体的晶格振动光谱研究

本文对新型非线性光学晶体三硼酸铯（ＣｓＢ３Ｏ５∶ＣＢＯ）和硼酸铯锂（ＣｓＬｉＢ６Ｏ１０∶ＣＬＢＯ）进行了晶格振动光谱研究。首先对两种晶体的基本晶格振动模进行了对称性分类,记录了两种晶体低温下的拉曼光谱和室温下的红外反射光谱,对晶体的晶格振动模进行了认定,将振动模归属于平面六元环（Ｂ３Ｏ６）和四面体（ＢＯ４）。然后比较了ＣＢＯ,ＣＬＢＯ和ＬＢＯ（ＬｉＢ３Ｏ５）三种晶体的晶格振动光谱,讨论了阳离子对振动光谱的影响。另外,还讨论了硼酸盐晶体晶格振动模ＬＯ ＴＯ分裂的大小与晶体非线性光学系数之间的关系。     

Theoretical analysis of the structure of excited electronic states, Raman, and resonance Raman spectra of indole in the isolated state and aqueous solution

The structure of the first excited electronic states of indole has been calculated for the isolated state and aqueous solution. The vibrational spectra of isolated indole have been calculated by the DFT method in the harmonic and anharmonic approximations. The resonance Raman spectra of indole have been calculated quantum mechanically in the Herzberg-Teller approximation. The effect of hydrogen bonds on the structure and vibrational (Raman and resonance Raman) spectra of indole has been analyzed.