固态多环芳烃化合物的THz时域光谱研究

利用太赫兹时域光谱技术室温下对芳烃化合物萘、联苯、葸、α-萘酚和β-萘酚在3-73cm^-1(0．1．2．2THz)频谱范围内进行了光谱测量。结果表明，多环芳烃化合物在此波段有不同的吸收特征。不能形成氢键的萘、联苯和蒽在67cm^-1(2．0THz)附近均有一吸收峰，这可能是由于分子之间的振动即晶格振动所引起的；而能够形成氢键的口一萘酚和卢．萘酚，其吸收峰可归结于分子间氢键的相互作用所引起的集体振动模式。1Hz时域光谱不仅能够鉴别分子结构存在微小差别的化合物而且还能鉴别同分异构体。     

新型4,4′-双取代-2,2′-二吡啶衍生物的合成及其光学性能

以4,4′-二甲基-2,2′-二联吡啶为原料,经酸化、酰氯化,酯化和缩合反应合成了两个新型的4,4′-双取代-2,2′-二吡啶衍生物—4,4′双(4,5-二苯基嗯唑-2-基)-2,2′-二吡啶(6a)和4,4′-双(4,5-二对甲氧基苯嗯唑-2-基)-2,2′-二毗啶(6b),其结构经1H NMR,IR和MS表征.用UV-Vis和荧光激发光谱测定了6a和6b的光学性能,结果表明,6a和6b的λmax分别为229 nm和238 nm;最大发射波长均为432 nm.     

手性氨基醇诱导联苯构象转化制备轴手性联苯化合物

在(S)-氨基丙醇及(R)-氨基丙醇手性臂的作用下, (M/P)-4,4'-二甲氧基-5,6,5',6'-二次甲二氧基-2-甲酸酯-2'-甲酰氨联苯经构型转化, 制备了光学纯轴手性联苯化合物(P, S)-3a 和(M, R)-3a. 测定了(P, S)-3a 的晶体结构及CD 光谱. 结果表明, 化合物(P, S)-3a 晶体属单斜晶系, P2(1)空间群, 晶胞参数为a＝12.122(2) Å, b＝8.9911(18) Å, c＝12.779(3) Å, β＝112.38(3)°, 在晶体中存在两组分子间氢键相互作用, 一组氢键由羟基氢与另一分子酰胺基团的羰基氧组成O-H…O,另一组由酰胺基团的NH 与另一分子酰胺基团的羰基氧构成N-H…O, 每一分子通过四个氢键与另外两个分子相连,构成棒状结构. 由CD 光谱确定了(M, R)-3b 的立体构型. 此外, 由(P, S)-3a 合成了轴手性化合物(P)-2,2'-二羟甲基-4,4'-二甲氧基-5,6,5',6'-二亚甲二氧基-联苯(6a).     

胆酸和脱氧胆酸分子的远红外与THz吸收光谱研究

胆酸和脱氧胆酸是胆汁酸中的主要成分, 是人体中重要的生物表面活性剂. 两种分子只相差一个羟基, 在远红外和太赫兹波段有不同的吸收光谱. 胆酸分子的太赫兹(THz)吸收光谱有1.26 THz(42 cm-1)和2.02 THz(67 cm-1)两个吸收峰, 脱氧胆酸分子的THz吸收光谱有1.13, 1.26, 1.69和2.17 THz(即38, 42, 56, 72 cm-1)等几个吸收峰. 两个分子的THz吸收光谱都包含有1.26 THz(42 cm-1) 峰, 反映出二者结构的相似性. 它们的远红外光谱都有部分频率相近的谱带, 但对比之下可以观察到峰位位移和相对峰强的改变. 指认了两种物质的某些可能与羧基振动有关的特征吸收峰. 为找出THz光谱隐含的信息, 利用Omnic程序采用二阶导数方法来处理THz光谱数据, 观察到多个子峰, 说明分子结构中可能存在更复杂的氢键状态. 实验结果表明, 远红外和THz吸收光谱是研究生物分子及鉴别生物分子结构的很好方法.     

两个基于氮、膦混合配体的铜(Ⅰ)配合物的合成、光谱学性质和太赫兹时域光谱

在甲醇和二氯甲烷的混合溶剂中合成了2个新的铜(1)配合物,[Cu(bdppmapy)(2,2′-bipy)]BF4(1)和[Cu(bdppmapy)(2,2′-bipy)]I (2)(bdppmapy=N,N-二苯基膦甲基-2-氨基吡啶,2,2′-bipy=2,2′-联吡啶),通过X射线单晶衍射、元素分析、核磁共振氢谱、磷谱、荧光光谱和太赫兹时域光谱对2个配合物进行了分析和表征。1是由[Cu(CH3CN)4]BF4,bdppmapy和2,2′-bipy以1∶1∶1的比例混合得到的单核配合物。中心Cu(1)离子通过与双膦配体(bdppmapy)以及含氮配体(2,2′-bipy)的螯合作用形成变形四面体结构。与1相似,2由CuI,bdppmapy和2,2′-bipy以1∶1∶1的比例混合得到。在配合物2的非对称单元中,bdppmapy和2,2′-bipy配体分别与中心铜(1)离子螯合。荧光光谱表明所有的发射峰均源于金属-配体的荷移跃迁(MLCT)。太赫兹时域光谱的应用也为配合物研究提供了有用的信息。     

多重氢键自组装联萘酚和含氮化合物

作为相互识别的结果,(±)-2,2′-二羟基-1,1′-联萘酚可与4,4′,6,6′-四甲基-2,2′-联嘧啶、1,2-双(4-吡啶)乙烷、反式-1,2-双(4-吡啶)乙烯、4,4′-联吡啶-N,N′-双氧化物及双-2-吡啶基甲酮等多种含氮化合物分别形成外形良好的共晶化合物1,2,3,4及5.本文对5个共晶化合物的晶体...     

4,4′-二羟基联苯的合成

4,4′-二羟基联苯是染料的稳定剂和高聚物中间体,也是制备烷氧基取代的联苯液晶的重要前体。4,4′-联苯二磺酸钠盐的碱熔,在催化剂存在下4,4′-二卤代联苯(X=Cl,Br)的水解,以及烷基取代的4,4′-二羟基联苯的去烷基化等已有的制备方法均需较高的温度、特殊催化剂及设备。通过卤代芳烃催化配合的制备方法,成本较高。用联苯胺盐酸盐重氮化后再水解的制备方法,则认为重氮化时盐酸中不可含有硫酸,因为联苯胺硫酸盐不易溶解。     

一维配位聚合物{[Co(dpa)(H2O)4]·(dpdo)·(H2O)}n(H2dpa=2,2’-联苯二酸,dpdo=N,N’-二氧化-4,4’-联吡啶)的晶体结构和光谱性质

采用水热合成法制备了一个一维配位聚合物{[Co(dpa)(H2O)4].(dpdo).(H2O)}n(1)(H2dpa=2,2′-联苯二酸,dpdo=N,N′-二氧化-4,4′-联吡啶),通过红外光谱、紫外光谱、元素分析、XRPD、TGA和X-射线单晶衍射进行了表征。Co(Ⅱ)原子采取了畸变的八面体构型,6个配位氧原子分别来自于2个dpa2-配体和4个配位水分子。每一个dpa2-配体桥联2个Co髤中心,每一个Co(Ⅱ)原子与2个dpa2-配体配位进而形成了21螺旋链结构。借助溶剂水分子的连接作用,螺旋链之间通过多种O-H…O氢键作用形成了2D网格,通过dpdo和2D网格之间多种类型的氢键作用形成了三维超分子结构。测定了室温下聚合物1的固体荧光光谱。     

2,2’-二甲基-4,4’-联噻唑与CHCl3分子间相互作用的理论研究

采用量子化学从头算理论在MP2/6-31G(d,p)水平上对2,2’-二甲基-4,4’-联噻唑顺反异构体, trans-2,2’-二甲基-4,4’-联噻唑-CHCl3 (I), cis-2,2’-二甲基-4,4’-联噻唑-CHCl3 (II)形成的1∶1氢键复合物进行计算研究. 结果表明, 2,2’-二甲基-4,4’-联噻唑在气相条件下, 反式构象比顺式构象稳定. 氯仿与2,2’-二甲基-4,4’-联噻唑形成的复合物存在较强的氢键, 表现为氮原子的孤对电子与氯仿分子中C—H反键σ轨道的相互作用, 另外形成C—H…Cl弱相互作用, 氢键作用使2,2’-二甲基-4,4’-联噻唑的顺式结构在氯仿溶剂比反式结构更稳定.     

联苯四甲酸及联吡啶构筑的一维链状银(Ⅰ)配合物的合成及晶体结构

采用水热法合成了一个新颖的配合物{[Ag(4,4′-bpy)][Ag2(H3btc)(H2btc)(4,4′-bpy)2].3H2O}n(1)(H4btc=联苯-2,2′,4,4′-四甲酸;4,4′-bpy=4,4′-联吡啶),并对其进行了元素分析、红外光谱和X射线单晶衍射测定。配合物1属于三斜晶系,空间群为P1,a=1.122 51(6)nm,b=1.554 01(8)nm,c=1.774 59(9)nm,β=91.641 0(10)°,V=2.830 8(3)nm3,Z=2,Dc=1.764 g.cm-3,μ=1.113 mm-1,F(000)=1 508,R1=0.045 0,wR2=0.086 2(I>2σ(I))。在1中,一维线性[Ag(4,4′-bpy)]+阳离子链包含在一维{[Ag2(H3btc)(H2btc)(4,4′-bpy)2]-阴离子双链与游离水分子通过分子间氢键组装成的三维超分子结构中。研究了配合物的热稳定性和电化学性质。     

腺嘌呤与富马酸共晶体的太赫兹光谱分析

利用太赫兹时域光谱(THz-TDS)技术在室温下对腺嘌呤、富马酸及两者的共晶体进行测量, 实验结果显示腺嘌呤与富马酸共晶体在0.92、1.24、1.52 THz处有明显的吸收峰, 与腺嘌呤和富马酸不同, 表明共晶体物相结构不同于原料. 根据腺嘌呤分子氢键供体与受体的结构特点, 使用密度泛函理论(DFT)对腺嘌呤与富马酸三种可能的共晶体结构进行模拟. 结果显示其中一种可能的共晶体结构在0.89、1.16、1.41 THz处存在特征吸收峰, 与实验结果较好吻合. 由此判断腺嘌呤与富马酸共晶体氢键形成位置为腺嘌呤的氨基与富马酸其中一个羧酸的碳氧双键形成氢键, 而此羧酸的羟基与腺嘌呤六元环上的邻位氮原子形成第二处氢键. 本文还结合理论模拟的结果对腺嘌呤与富马酸共晶体的特征吸收峰对应的相关振动模式进行了归属.     

Substituent Effects on the Low-Frequency Vibrational Modes of Benzoic Acid and Related Compounds

Well-resolved absorption spectra of benzoic acid and its derivatives with one hydrogen atom replaced by a substituent group CH3, OH, NH2 or NO2 were reported in the frequency region between 6 and 67 cm^-1 at room temperature with terahertz time-domain spectroscopy （THz-TDS）. These substances can be distinguished easily based on the terahertz absorption spectra. The measurements suggested that even minor changes in the molecular configuration and chemical composition lead to distinct differences in THz spectrum. Density functional theory （DFT） method was used to assist the analysis and assignment of the individual THz absorption spectra of benzoic acid and its methyl derivatives. Observed THz responses of samples can be assigned to the collective vibrations associated with intermolecular hydrogen bonds.     

Polarization and temperature dependent spectra of poly(3-hydroxyalkanoate)s measured at terahertz frequencies

Temperature-dependent terahertz (THz) absorption spectra of poly(3-hydroxyalkanoate)s (PHAs) were measured by using a Fourier transform far-infrared (FT-FIR) spectrometer and a THz time-domain spectrometer over a temperature range of 10 K to 465 K with a liquid helium cryostat and a heating cell. Clear differences were observed between the spectra of crystalline and amorphous polyhydroxybutyrate (PHB), indicating that the absorption peaks observed in the THz spectra originated in the higher-order conformation of PHB. The polarization spectra of a stretched PHB sample were measured, and the direction of the vibrational transition moment was determined. The temperature dependences of the spectra reveal frequency shifts and broadening of the absorption peaks with temperature, suggesting large anharmonicity of the vibrational potential. The temperature shift behaviour is quite different in each transition. Some of the transitions show a blue shift, which cannot be explained by a simple anharmonic potential model. Frequency shifts of the peaks were mainly observed below 10 THz, which suggests a large anharmonicity of the vibrational potential at lower frequencies.     

Terahertz time-domain spectroscopic investigation on quinones

Well resolved far-infrared spectra of 1,4-benzoquinone, 1,4-naphthoquinone, and 9, 10-anthraquinonme in polycrystalline form have been measured with terahertz time domain spectroscopy at room tem- perature. The characterizations of power absorption and index of refraction in the frequency range 0.3 -2.0 THz are presented. Theoretical calculation is applied to assist the analysis and assignment of individual THz absorption spectra of the p-quinones with semiempirical AM1, Hartree-Fock (HF), and density functional theory (DFT) method. Observed THz responses are assigned to the translational and torsional vibrations of p-quinone dimer held together by weak hydrogen bonds.     

Photoexcited States of UV Absorbers,Benzophenone Derivatives

The UV absorption, phosphorescence and phosphorescence‐excitation spectra of benzophenone (BP) derivatives used as organic UV absorbers have been observed in rigid solutions at 77 K. The triplet–triplet absorption spectra have been observed in acetonitrile at room temperature. The BP derivatives studied are 2,2′,4,4′‐tetrahydroxybenzophenone (BP‐2), 2‐hydroxy‐4‐methoxybenzophenone (BP‐3), 2,2′‐dihydroxy‐4,4′‐dimethoxybenzophenone (BP‐6), 5‐chloro‐2‐hydroxybenzophenone (BP‐7) and 2‐hydroxy‐4‐n‐octyloxybenzophenone (BP‐12). The energy levels and lifetimes of the lowest excited triplet (T₁) states of these BP derivatives were determined from the first peak of phosphorescence. The time‐resolved near‐IR emission spectrum of singlet oxygen generated by photosensitization with BP‐7 was observed in acetonitrile at room temperature. BP‐2, BP‐3, BP‐6 and BP‐12 show photoinduced phosphorescence enhancement in ethanol at 77 K. The possible mechanism of the observed phosphorescence enhancement is discussed. The T₁ states of 2‐hydroxy‐5‐methylbenzophenone, 4‐methoxybenzophenone and 2,4′‐dimethoxybenzophenone have been studied for comparison.     

Vibrational spectra of copper sulfate hydrates investigated with low-temperature Raman spectroscopy and terahertz time domain spectroscopy

In this paper, the vibrational spectra of copper sulfate hydrates (CuSO(4)·xH(2)O, x = 5, 3, 1, 0) have been investigated with low-temperature Raman spectroscopy and terahertz time domain spectroscopy (THz-TDS). It is found that the four groups of Raman bands between 90 and 4000 cm(-1) can be assigned to lattice vibration as well as intramolecular vibrations of a copper complex, sulfate group, and water molecules. The variation of vibrational spectra during the dehydrated process are discussed in detail considering the transformation of the crystal structure, especially the bands between 3000 and 3500 cm(-1), which are attributed to the ν(1) and ν(3) modes of water molecules. In addition, as a complement of Raman spectra, the THz spectra at 0.1-3 THz indicate the absorption due to the low-frequency lattice vibration and hydrogen bond.     

Charge transfer interaction and terahertz studies of a nonlinear optical material L-glutamine picrate: A DFT study

Charge transfer interaction, vibrational spectra, and DFT computation of l-glutamine picrate has been analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. The natural bond orbital analysis confirms the occurrence of strong intramolecular hydrogen bonding in the molecule. Terahertz time-domain spectroscopy was used to detect the absorption spectra in the frequency range from 0.025 to 2.8 THz. The vibrational modes found in molecular crystalline materials should be described as phonon modes with strong coupling to the intramolecular vibrations.     

Terahertz absorption spectra of some saccharides and their metal complexes

In this work, THz absorption spectra of some saccharides and their metal complexes were measured. The main purpose of this work is to investigate the M-O vibrations, intermolecular and intramolecular hydrogen bonds and other vibrations in the FIR region using powerful spectroscopic techniques adopting the metal-sugar complexes prepared in our laboratory. The M-O vibrations in the FIR spectra of metal-sugar complexes indicate the formation of metal complexes. The THz spectrum of glucose below 100cm(-1) was measured at first to confirm the THz experimental method. Characteristic absorption bands in the spectra of various samples are observed. THz spectra of saccharides below 100cm(-1) often have several absorption bands, and different saccharides have various absorption peaks in the THz region, which may be used to distinguish different saccharides. The differences in the number of bands observed are related to different structures of the samples, and these absorption bands are related to the collective motion of molecules. But the THz spectra of their metal complexes are different from the ligands, and no band appears in the region below 50cm(-1) at the present experimental condition, which indicates that THz spectroscopy may also be helpful to identify the formation of metal-sugar complexes, and the changes after complexation in the THz spectra below 100cm(-1) may be related to different metal ions. The metal-sugar complexes with similar crystal structures resemble mid-IR spectra, but their THz spectra may have some differences.     

含硫氨基酸的太赫兹光谱

利用太赫兹时域光谱(THz-TDS)技术研究室温条件下多晶含硫氨基酸L-蛋氨酸(Met)和L-半胱氨酸(Cys)的光谱特性, 得到相应的吸收谱和折射率谱, 表明含硫氨基酸在THz波段具有区别于其它氨基酸的显著特征. 在实验测量的有效光谱范围0.2～2.8 THz内, L-蛋氨酸的THz吸收峰分别位于1.06, 1.88和2.70 THz; L-半胱氨酸的吸收峰分别位于1.40, 1.70, 2.33和2.61 THz, 两种氨基酸的平均折射率均为1.44. 利用GAUSSIAN 03软件包中的Hartree-Fock理论计算了蛋氨酸双分子的低频振动谱, 表明了与蛋氨酸各吸收峰对应的分子微观振动模式, 并对实验光谱进行了解析讨论.