几种2-取代-4,5-双(α-呋喃基)噁唑的结构与光谱性质

在密度泛函DFT-B3LYP/6-31+G水平上对2-甲基-4,5-双(α-呋喃基)噁唑(化合物A)、2-苯基-4,5-双(α-呋喃基)噁唑(化合物B)、2-α-呋喃基-4,5-双(α-呋喃基)噁唑(化合物C)和2-α-呋喃乙烯基-4,5-双(α-呋喃基)噁唑(化合物D)S0基态进行构型优化,并用单取代组态相互作用方法(CIS)优化其S1激发态结构。从理论上探讨了A,B,C和D四种化合物的前线分子轨道能量、吸收和发射光谱等性质与结构的关系,并与实验值进行了对比,发现理论计算数据能够与实验结果一致,特别是采用纯密度泛函DFT-OLYP方法计算发射光谱时,理论计算数据与实验结果相差比混合密度泛函DFT-B3LYP方法更小。计算结果表明,分子共轭体系越大,前线轨道间能隙越小,吸收光谱红移越显著。     

电子传输材料1，3，4-噁二唑衍生物和1，2，4m三唑衍生物的DFT研究

采用密度泛函理论B3LYP方法，对1，3，4-噁二唑衍生物和1，2，4-三唑衍生物两类电子传输材料在中性、阴离子态和阳离子态下分别进行几何结构优化计算．结果表明，1，3，4-噁二唑衍生物的电子传输过程主要是分子内噁二唑上的N→O电子转移，1，2，4-三唑衍生物的电子传输过程主要是分子内三唑上N（双键）→N（单键）以及三唑环向与N相连的苯环电子转移．当其苯环上3位被拉电子基团取代后，其电子传输性能提高；而被给电子基团取代后，电子传输性能降低．     

含苯并咪唑环的1, 3, 4-噁二唑衍生物的核磁共振研究

在无水乙醇和KOH 存在下,将2-苯氧甲基苯并咪唑-1-乙酰肼(1)与CS₂反应,合成出了中间体5-(2-苯氧甲基苯并咪唑-1-亚甲基)-2-巯基-1,3,4-噁二唑(2),此中间体再与氯乙酰苯胺反应,得到一种新化合物-N-苯基-2-[5-(2-苯氧甲基苯并咪唑-1-亚甲基)-1,3,4-噁二唑-2-硫基]乙酰胺(3). 采用元素分析、IR及NMR技术确定了新化合物3的结构,并利用2D NMR技术对其trans和cis两种异构体的¹H和¹³C NMR谱带进行了全归属,给出了相应的偶合常数J值以及异构体所占的比例. 实验表明,新化合物3在DMSO中存在着trans和cis两种异构体的互变,并且trans异构体占主导,含量为64.5%, 而cis异构体的含量为35.5%.     

通过改变原子电负性调控异硫氰酸苯并恶唑荧光染料的激发态分子内质子转移过程和光物理性质

激发态分子内质子转移因其独特的光学性质而受到研究人员的青睐. 然而,关于改变原子电负性对激发态分子内质子转移过程和光物理性质影响的系统研究相对较少. 本文通过理论方法选择了一系列苯并噁唑异硫氰酸酯荧光染料(2-HOB、2-HSB 和2-HSeB),并通过改变氧族原子的电负性,系统地研究了激发态分子内质子转移过程和光物理性质. 计算的键角、键长、能隙和红外光谱分析表明,3个分子的分子内氢键强度依次为2-HOB<2-HSB<2-HSeB. 相应地,势能曲线的能垒大小为2-HOB>2-HSB>2-HSeB. 此外,计算的电子光谱表明,随着原子电负性的降低,发射光谱发生红移. 本工作将为基于激发态分子内质子转移性质的新型染料的合成和应用提供一定的理论指导.     

C60异噁唑环衍生物的结构、电子光谱和非线性光学性质的研究

应用半经验AM1量子化学方法研究了8种C60异噁唑环衍生物的结构,以AM1优化几何构型为基础,用ZINDO/CIS方法计算了目标分子的电子光谱.结果表明,异噁唑环的引入导致HOMO与LUMO间的能级差减小, C60母体与加成基团之间存在分子内电荷转移.计算所得电子光谱值与实验结果较吻合,几种化合物在400nm以上均产生非C60特征吸收峰,这些峰是电荷从加成基团向C60部分转移产生的.用FF/AM1方法计算了分子非线性光学系数α、β、γ值,在所得计算结果上推测了影响体系非线性光学系数效应的因素.     

2-乙氧基苯腈的激发态和离子态光谱

首次报道了2-乙氧基苯腈的双色共振双光子电离(2-color REMPI)光谱和质量分辨阈值电离(MATI)光谱,确定了2-乙氧基苯腈分子基态到第一电子激发态的激发能和精确的绝热电离能分别为(34 092±2)和(69 796±5) cm^-1。结合密度泛函理论计算和Franck-Condon光谱模拟对实验结果进行了分析并对振动谱带进行了归属。与苯腈相比,乙氧基取代使得光谱谱带变得丰富且复杂,许多乙氧基的振动模被观察到。这些实验和理论结果为相关的科学研究和应用开发提供重要参考资料。     

2-(2-苯并噁唑啉酮-3-甲基)-6-芳基-咪唑[2,1-b][1,3,4]噻二唑的NMR谱研究

许多文献已报道,含有咪唑[2,1-b][1,3,4]噻唑环的衍生物具有抗癌、抗结核、抗菌、抗真菌、抗惊厥、止痛等活性. 该文合成了一个新的在医药方面具有潜在应用价值的咪唑[2,1-b][1,3,4]噻二唑衍生物,即2-(2-苯噁唑啉酮-3-甲基)-6-苯基-咪唑[2,1-b][1,3,4]噻二唑,并利用2D NMR技术对其¹H NMR 和¹³C NMR谱进行了全归属.      

C砷异噁唑环衍生物的结构、电子光谱和非线性光学性质的研究

应用半经验AM1量子化学方法研究了8种C60异噁唑环衍生物的结构，以AMl优化几何构型为基础，用ZINDO／CIS方法计算了目标分子的电子光谱．结果表明，异噁唑环的引入导致HOMO与LUMO间的能级差减小，C60母体与加成基团之间存在分子内电荷转移．计算所得电子光谱值与实验结果较吻合，几种化合物在400nm以上均产生非C60特征吸收峰，这些峰是电荷从加成基团向C60部分转移产生的．用FF／AM1方法计算了分子非线性光学系数α、β、γ值，在所得计算结果上推测了影响体系非线性光学系数效应的因素．     

电子传输材料1,3,4-恶二唑衍生物和1,2,4-三唑衍生物的DFT研究

采用密度泛函理论B3LYP方法,对1,3,4噁二唑衍生物和1,2,4三唑衍生物两类电子传输材料在中性、阴离子态和阳离子态下分别进行几何结构优化计算.结果表明,1,3,4噁二唑衍生物的电子传输过程主要是分子内噁二唑上的N→O电子转移,1,2,4三唑衍生物的电子传输过程主要是分子内三唑上N(双键)→N(单键)以及三唑环向与N相连的苯环电子转移.当其苯环上3位被拉电子基团取代后,其电子传输性能提高;而被给电子基团取代后,电子传输性能降低.     

2-(2-羟基苯亚甲基)胺基-3-氰基吡啶的结构和光谱性质

实验以水杨醛、2-氨基-3-氰基吡啶为原料,合成了Schiff碱2-(2-羟基苯亚甲基)胺基-3-氰基吡啶并测定了Schiff碱的红外和拉曼光谱.利用密度泛函理论B3LYP方法在6-311++G~(**)基组上对合成的Schiff碱进行了几何构型的优化、红外光谱及拉曼光谱的计算,得到了分子的优势构象的结构参数、频率值及对应的强度.对实验和理论计算的光谱数据进行了对比,对分子的振动模式进行了全面归属,结果表明理论计算与实验测试数据相吻合.此外,还计算了其前线分子轨道,得到了HOMO-LUMO能隙相关的数据,为Schiff碱类化合物的结构分析和光谱检测技术提供了参考依据.     

Optical and luminescence characteristics of BaF2 and BaF2:Tm in vacuum UV and UV spectral regions

The spectral characteristics of BaF₂ and BaF₂:Tm crystals and ceramics are compared. The vacuum UV (VUV) and UV absorption spectra and excitation spectra of core-valence and exciton luminescence are investigated. The main exciton and electron-hole processes responsible for the structure of recorded spectra are considered.     

Fingerprint IR spectroscopy to probe amino acid conformations in the gas phase

We report the infrared (IR) absorption spectra of different conformational isomers of gas phase amino acid molecules in the molecular fingerprint region of 330-1500 cm(-1). The IR absorption spectra for three conformers of the amino acid tryptophan show absorption bands that uniquely identify the conformational structure of the molecule and that are well matched by density functional theory calculations. The present observations hold great promise for future identification of conformational folding of larger molecules by means of their IR absorption characteristics.     

利用2DCOS进行多组分混合气体傅里叶变换红外光谱分析中同分异构体谱峰的辨别

在利用傅里叶变换红外光谱进行混合气体定量分析中,针对烃类尤其是同分异构体等构成的混合气体其谱图特征相似、吸收峰严重交叠,不易进行特征吸收成分的判别和特征变量选择的问题,为增强谱峰分辨力,采用广义二维相关光谱和傅里叶变化红外光谱对烃类混合气体分析中同分异构体进行辨别,以异丁烷和正丁烷的红外光谱及受浓度扰动组成的光谱组为例进行二维相关红外光谱分析。通过观察全波段和主吸收峰波段单组分气体的傅里叶变换红外光谱,可知其谱图相似,吸收峰严重交叠,如果混合在一起,将基本无法辨别何种分子结构及成分。通过广义二维相关光谱的变换,其二维相关光谱的同步谱和异步谱可以清晰地辨别出异丁烷和正丁烷的特征吸收峰及其各自强度,实验结果可知,异丁烷在2 893,2 954和2 977 cm-1,正丁烷在2 895和2 965 cm-1具有强的吸收特征谱线。分析结果初步验证了二维红外相关光谱在多组分混合气体傅里叶变换红外光谱定量分析中谱分辨率增强方面的应用。     

Optical properties of six isomers of three dimensionally delocalized <Emphasis Type="Italic">π</Emphasis>-conjugated carbon nanocage

First-principles GW+Bethe-Salpeter method employing all-electron mixed basis approach is applied to hydrocarbon molecules consisting of 78–198 atoms and its theoretical accuracy and performance are evaluated. Based on the confirmed accuracy/reliability of our method, we simulated the UV–vis absorption spectra of previously reported six possible isomers [E. Kayahara et al., Nat. Chem. 4, 2694 (2013)]. We also attempted to identify the most stable isomers of recently synthesized ball-shaped carbon nanocages by taking into account available experimental spectra. The best agreement with the experiment is found for the most unstable isomer, labelled as T. Our simulation strongly suggests that the external experimental conditions such as solution and finite temperature affect stability.     

紫外光辐照对偶氮苯光谱特性的影响

采用紫外可见吸收、稳态荧光光谱和荧光衰减测量技术,观察了4-硝基-4'-氨基偶氮苯(NAA)在氯仿溶液中的光致变色现象及分子的跃迁能级和能级寿命。结果表明:NAA分子的顺反异构化反应并非一级反应;分子处于反式异构体和顺式异构体的跃迁能分别为255.6,240.2 kJ/mol;分子处于反式异构体的能级寿命为0.02 ns,处于顺式异构体的能级寿命为3.54 ns。顺反异构体的含量、NAA分子之间及NAA分子与溶剂分子之间的相互作用影响NAA分子激发态的能级寿命。     

Quick detection of contaminants leaching from polypropylene centrifuge tubes with surface‐enhanced Raman spectroscopy and ultraviolet absorption spectroscopy

Anomalous surface‐enhanced Raman scattering (SERS) peaks were identified for liquid sample stored in polypropylene (PP) centrifuge tubes for months. We observed unexpected Raman peaks during experiments with thiamine hydrochloride aqueous solutions stored in PP tubes for 2 months. In order to identify the contaminants, we have performed SERS experiments on deionized (DI) water stored in PP centrifuge tubes for 2 months and compared them with those from fresh DI water sample. We have also carried out ultraviolet (UV) absorption spectra for both fresh and contaminated water. We believe that the water is contaminated because of chemicals leaching from the PP tube. From the gas chromatography‐mass spectrometry data, the main contaminants were found to be phthalic acid (PA) and its derivatives. Further SERS and UV absorption experiment for PA correlated well with the anomalous peaks identified earlier. We qualitatively confirmed the identification and quantitatively estimated the concentration of the suspect contaminants as between 1 and 10 µM with both SERS and UV absorption spectroscopy. With UV absorption spectroscopy, we precisely estimated the concentration as 2.1 µM . We have shown that the sample in PP tube can be contaminated by the leaching chemicals upon long‐term storage, and suggest SERS and UV absorption spectroscopy as two quick and simple techniques to detect the contamination. Copyright © 2011 John Wiley & Sons, Ltd.     

基于光谱吸收法和荧光法的甲烷和二氧化硫检测系统的研究

根据污染气体的光谱吸收特性与荧光特性,设计了一套时分复用检测系统,既可以使用光谱吸收法检测甲烷和二氧化硫又可以使用荧光法检测二氧化硫。系统采用组合可切换光源、共用光路、气室及信号处理部分,首先进行光谱吸收和荧光的特性测量,然后进行光谱吸收法检测甲烷与二氧化硫浓度实验,以及紫外荧光法检测二氧化硫浓度实验。经过光谱吸收和荧光的特性测量得出吸收法测二氧化硫和甲烷的吸收峰处的激发波长分别为280nm和1.64μm,荧光法测二氧化硫最佳激发波长为220nm。经光谱吸收法实验可得甲烷浓度与相对强度的线性关系和二氧化硫浓度与输出电压的线性关系,线性度分别为98.7%,99.2%;经荧光法实验可得二氧化硫浓度与电压成线性关系,线性度达到了99.5%。研究表明,该系统能使用于污染气体的光谱吸收检测和紫外荧光检测。将两种测量方式组合在一起,降低了成本与体积,同时此系统也可用于其他气体的检测,有一定的应用价值。     

Quantum mechanical interpretation of the IR Spectrum of 2-deoxy-D-ribose in the oh group stretching vibration region

Within MP2/6-311++G(d,p)//DFT B3LYP/6-31 G(d,p) theory, taking into account the anharmonicity of the vibrations, we have calculated the vibrational spectra of all the conformers of the furanose, pyranose, and linear forms of the 2-deoxy-D-ribose molecule. Based on the calculation, we have interpreted the experimental IR spectrum of this molecule in the region of stretching vibrations of the OH groups. For the α and β anomers of the pyranose form of the molecule, we observe and explain the difference between the populations realized in the experiment and the calculated thermodynamic equilibrium values. We present the structures of the eight isomers of 2-deoxy-D-ribose determining its IR spectrum in a low-temperature inert matrix.     

Recording holograms on color centers in CaF2:Na crystals by light with different wavelengths

The absorption spectra and holographic characteristics of a CaF₂:Na crystal sample are measured at different wavelengths within the absorption band of colloidal centers, along with the same characteristics of the samples with holograms after their irradiation by incoherent UV light. Results of the study confirm the diffusion-and-drift mechanism of recording holograms on color centers in ionic crystals.     

Nondestructive readout of a three-dimensional photochromic optical memory with a near-infrared differential phase-contrast microscope

A three-dimensional (3D) rewritable optical memory using photochromic material is described for high-density memory. The bits are recorded in a 3D volume of photochromic material. A transformation of the photochromic molecule between two isomers with different absorption spectra can be stimulated by irradiation with appropriate wavelengths. We show that a nondestructive readout of photochromic memory is possible by use of a small difference in the refractive index of the photochromic isomers in the near-IR range. For this purpose a near-IR laser-scan differential phase-contrast microscope is used. Experimental results of 3D recording and nondestructive reading are presented.