聚醚型聚氨酯脲的氢键研究

简要评述了近年来有关聚醚型聚氨酯脲氢键研究进展，红外光谱中聚醚型氨酯脲的羰基谱带，特别是脲羰基谱带受化学组成，硬段的结构和制样条件等的影响，而呈现复杂的多重谱带特征，对于这些谱带目前已经作了较系统的归属。     

盐对甲醇微观结构的影响

利用拉曼光谱研究盐对甲醇微观结构的影响.比较了不同盐/甲醇体系的O—H伸缩谱段和C—O伸缩谱段的超额拉曼光谱,对比给出了阴、阳离子与甲醇的相互作用.O—H伸缩谱段的超额拉曼光谱明显地显示了阴离子与甲醇形成弱氢键,氢键强度排序为CH3OH-CH3OHCl--CH3OHNO3--CH3OHClO4--CH3OH,在这个波段内,基本观察不到阳离子与甲醇的相互作用.在C—O伸缩谱段内,阴阳离子均有显著的体现,且与它们作用的甲醇C—O伸缩振动频率有如下的关系:CH3—OH(阴离子)CH3—OH(体相)CH3—OH(阳离子).根据C—O伸缩谱段的超额拉曼光谱,拟合了该谱段的拉曼光谱,由分解的谱峰强度得到阴、阳离子第一溶剂化层中甲醇分子的数目,结果显示在该浓度(～0.005)下离子对第一溶剂化层以外的甲醇氢键网络结构没有明显影响.     

用红外光谱技术研究氢键的键合方式

氢键的形成能够使参与形成氢键的原化学键力常数降低,吸收频率移向低波数方向,同时吸收强度增加。为了介绍怎样利用红外光谱技术研究氢键的键合方式,本文以联酰胺衍生物为例,主要运用变温红外光谱技术分析NH伸缩振动波数、强度以及形成氢键的键长随温度的变化来研究羰基(C O)与氨基(H—N)之间的氢键形式。结果表明,本文举例中联酰胺基团中的C O与H—N以分子间氢键形式存在。     

聚醚氨酯的红外酰胺Ⅰ.谱带分析

通过对聚醚氨酯红外光谱酰胺-Ⅰ谱带的二级微商及傅里埃自解卷积处理,发现了位于1715cm~(-1)的新组分并可归属于无序的相间界面。应用差减光谱及曲线拟合对热处理试样的光谱谱带进行分析表明聚醚氨酯的加热/冷却过程是与可逆的无序/有序化过程及微相混合/分离过程有关的。新发现的1715cm(-1)组分强度的变化与无序/有序化过程是一致的。     

羟基硅烷氢键体系

根据红外及 Raman 光谱数据,羟基硅烷的羟基能相互稀合而形成分子间氢键。羟基硅烷与各种碱性化合物间的氢键体系,却直到最近才为 West 等所注意。他们根据羟基硅烷与二乙醚及对称三甲苯间氢键体系的 O—H 伸缩振动谱带位移Δv 以比较羟基硅烷与相应羟基碳烷(醇)中羟基的酸性。由于他们只采用两种碱性化合物,所以很难可靠地比较各羟基硅烷中羟基的酸性。     

青蒿素和类似过氧化合物的过氧基团振动频率的确认

青蒿素(arteannuin)是中药青蒿中抗疟的有效成分,它是一种含有过氧基团的新型倍半萜内酯,在红外光谱中的强吸收谱带831,881,1115cm~(-1)为过氧基团的特征振动频率.Philpotts等对870cm~(-1)附近的强红外吸收谱带为过氧基团振动频率曾提出疑点,特别是叔过氧基团化合物,它在800～900cm~(-1)范围内产生的强谱带归属于一C—O—基团的振动.而且过氧基团两侧取代基结构不同也将影响谱带的改变,拉电子基团会导致振动频率的波数增大,而推电子基团则使频率向低波数位移.本文用激光拉曼光谱并辅以红外光谱进行研究,比较了700～900cm~(-1)各谱带的谱型,相对强度和退偏振比等数据,并排除了倍半萜环振     

胃和结直肠癌的傅里叶变换红外光谱研究

利用傅里叶变换红外光谱仪及带ATR探头的中红外光纤系统测定了手术切除的胃癌、结直肠癌及相应的正常组织共31对标本粘膜面的反射红外光谱. 结果表明, 与正常组织相比, 癌组织的红外光谱发生明显变化: (1) 与脂类相关的谱带2955, 2920, 2870, 2850和1740 cm-1出现几率明显低于正常组织(P<0.001), I1460/I1400(I为峰强度)明显降低(P<0.001), 表明癌组织的脂类相对含量降低; (2) 与蛋白质相关谱带N—H和O—H明显红移(P=0.025), 表明N—H和O—H的氢键化程度增加, 癌组织的I3375/I1460, I1640/I1460和I1550/I1460明显升高(P<0.01), 表明癌组织的蛋白质相对于脂类的含量增加, 癌组织的HW1550/I1550(HW为半高宽)明显升高(P=0.036), HW1550则明显降低(P=0.05), 表明癌组织中蛋白质的二级结构发生显著变化; (3) 与醣类相关谱带中癌组织的I1160/I1460降低(P=0.002), 结合组织化学染色, 推测可能是癌组织表面的糖蛋白明显减少造成的, 而I1120/I1460升高(P=0.019)则可能是癌组织表面的糖原颗粒增加所致. (4) 与核酸相关谱带中癌组织的PO的反对称伸缩振动蓝移(P=0.033), 表明癌组织中磷酸基团的氢键化程度降低. 研究结果表明, 红外光谱有望成为诊断恶性肿瘤的有力工具.     

稀土HEH[EHP]固体配合物的红外光谱

本文制备了La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y等十五种稀土与2-乙基己基膦酸单(2-乙基己基)酯的固体配合物,测定了4000-100cm~(-1)的FT-IR光谱,对其主要红外光谱吸收带进行了归属。指认150cm~(-1)为Ln-O键的伸缩振动带,250cm~(-1)附近的谱带为COPO,CCPO骨架扭曲振动与Ln-O键的耦合振动带。结果表明配合物为多聚体系,PO_2与稀土离子可能为桥式配位形式。Ln-O键基本上为离子键。     

密度泛函理论及光谱对CuCl2溶液中微团簇的研究

利用密度泛函理论和拉曼光谱对氯化铜溶液第一溶剂化层中的微团簇进行了研究。采用B3LYP方法对溶液中可能存在的团簇构型进行优化,从动力学和热力学方面分析得出溶液中团簇结构信息。理论拉曼光谱在100~500 cm~(-1)主要为Cu—O的伸缩振动峰,3400~4000 cm~(-1)范围内为O—H的对称和不对称伸缩振动。实验光谱在200~340 cm~(-1)出现明显新峰,位于2500~4000 cm-1的O—H伸缩振动峰随着溶液浓度的增加,峰的强度逐渐减小,峰形有明显变化。实验光谱和理论光谱验证和比对,表明溶液的实验光谱中产生的新峰为Cu—O振动,CuCl_2水溶液中产生短程离子相互作用及溶剂化现象,且随着溶液浓度的增加,溶剂化数目减小。     

四(对-硝基苯基)卟啉配合物的红外和拉曼光谱

本文研究了四(对-硝基苯基)卟啉及其Cr(Ⅲ)、Mn(Ⅲ)、Fe(Ⅲ)、Co(Ⅱ)、Ni(Ⅱ)、Cu(Ⅱ)、Zn(Ⅱ)配合物的3500～220cm~(-1)的红外光谱和1700～100cm~(-1)的拉曼光谱.谱带归属表明,～250cm~(-1)谱带是M—N伸缩振动和卟啉环变形振动的复合振动.金属敏感带出现在～1600、～1582、～1547、～1284、～1190、～355和～245cm~(-1)处,其中二价金属配合物金属敏感带频率按Ni>Co>Cu>Zn顺序递减.用金属半径和d_x~2 y~2电子排斥作用解释了金属敏感带变化规律.     

Hydrogen bonding and crystallization in biodegradable multiblock poly(ester urethane) copolymer

The hydrogen bonding and crystallization of a biodegradable poly(ester urethane) copolymer based on poly(L ‐lactide) (PLLA) as the soft segment were investigated by FTIR. On slow cooling from melt, the onset and the progress of the crystallization of the urethane hard segments were correlated to the position, width, and relative intensity of the hydrogen‐bonded N? H stretching band. The interconversion between the “free” and hydrogen‐bonded N? H and C?O groups in the urethane units in the process was also revealed by 2D correlation analysis of the FTIR data. The crystallization of the PLLA soft segments was monitored by the ester C?O stretching and the skeletal vibrations. It was revealed that the PLLA crystallization was restricted by the phase separation and the urethane crystallization, and at cooling rates of 10 °C/min or higher, the crystallization of the PLLA soft segments was prohibited. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 685–695, 2009     

A Raman spectroscopic study of the uranyl phosphate mineral bergenite

Raman spectroscopy at 298 and 77 K of bergenite has been used to characterise this uranyl phosphate mineral. Bands at 995, 971 and 961 cm-1 (298 K) and 1006, 996, 971, 960 and 948 cm-1 (77K) are assigned to the nu1(PO4)3- symmetric stretching vibration. Three bands at 1059, 1107 and 1152 cm-1 (298 K) and 1061, 1114 and 1164 cm-1 (77 K) are attributed to the nu3(PO4)3- antisymmetric stretching vibrations. Two bands at 810 and 798 cm-1 (298 K) and 812 and 800 cm-1 (77 K) are attributed to the nu1 symmetric stretching vibration of the (UO2)2+ units. Bands at 860 cm-1 (298 K) and 866 cm-1 (77 K) are assigned to the nu3 antisymmetric stretching vibrations of the (UO2)2+ units. UO bond lengths in uranyls, calculated using the wavenumbers of the nu1 and nu3(UO2)2+ vibrations with empirical relations by Bartlett and Cooney, are in agreement with the X-ray single crystal structure data. Bands at (444, 432, 408 cm-1) (298 K), and (446, 434, 410 and 393 cm-1) (77 K) are assigned to the split doubly degenerate nu2(PO4)3- in-plane bending vibrations. The band at 547 cm-1 (298 K) and 549 cm-1 (77 K) are attributed to the nu4(PO4)3- out-of-plane bending vibrations. Raman bands at 3607, 3459, 3295 and 2944 cm-1 are attributed to water stretching vibrations and enable the calculation of hydrogen bond distances of >3.2, 2.847, 2.740 and 2.637 A. These bands prove the presence of structurally nonequivalent hydrogen bonded water molecules in the structure of bergenite.     

含氮杂冠醚双亲聚合物纳米球的制备及性能

设计、合成了含氮杂冠醚和腺嘌呤的双亲聚合物,聚[N,N-二乙氧基-1,10-二氮杂-18冠-6-5-甲基-腺嘌呤-异酞酸酯](PCASE).SEM观测到在水溶液中该聚合物与5-氟尿嘧啶(5-flu)小分子识别后自发聚集成直径约140～210nm的纳米球,用动态光散射测得水溶液中PCASE/5-flu纳米球的粒径主要集中在120～230nm范围内,FTIR研究了PCASE/5-flu纳米球内聚合物PCASE中腺嘌呤与底物5-氟尿嘧啶的分子识别,结果表明,识别后5-氟尿嘧啶环上C(2)=O伸缩振动峰从1724cm-1位移至1718cm-1,且聚合物中腺嘌呤NH2峰3324cm-1消失,出现了一个新的NH2峰3432cm-1,说明5-氟尿嘧啶环上C(2)=O与聚合物PCASE中腺嘌呤上NH2间形成了氢键.变温红外谱显示,识别后的羰基峰1718cm-1随温度的升高逐渐向高波数回移,并最终稳定在5-氟尿嘧啶环上C(2)=O识别前的1724cm-1处,且识别后产生的新NH2峰3432cm-1随温度的升高逐渐减弱至消失,表明所形成的氢键断裂.     

酰胺水化作用的富里埃红外光谱研究及其SCFPPP计算

本文用富里埃红外光谱仪研究了酰胺水化作用引起的红外光谱变化。用SCFPPP方法对五种酰胺进行了计算。含水酰胺的羰基伸缩振动频率向低波数的位移与酰胺和水分子间的氢键强度成正比。其氢键强度与羰基上氧原子的净电荷密度成正比,与酰胺分子的HOMO轨道能量成反比。     

含氮杂冠醚和核酸碱基双亲聚合物的合成及性能

设计合成了含氮杂冠醚和胸腺嘧啶的双亲聚合物聚[N,N-二乙氧基-1,10-二氮杂-18冠-6-5-甲基-胸腺嘧啶-异酞酸酯](PCTSE). 用SEM观测到其在水溶液中自发聚集成直径为150~220 nm的纳米球; 用动态光散射测得PCTSE纳米球水溶液的粒径分布主要集中在130~240 nm, 用FTIR研究了PCTSE/腺嘌呤中胸腺嘧啶与底物腺嘌呤的分子识别作用, 结果表明, 聚合物中胸腺嘧啶环上C₄=O伸缩振动峰从1670 cm^-1位移至1664 cm^-1, 表明胸腺嘧啶与腺嘌呤间形成了氢键. 变温红外光谱表明, 该峰又随温度的升高逐渐向高波数位移, 最后位移到识别前的1670 cm^-1处, 表明所形成的氢键断裂.     

Characterization of parallel and antiparallel G-tetraplex structures by vibrational spectroscopy

A series of G-rich oligonucleotides able to form tetraplexes has been studied by FTIR spectroscopy. Characteristic markers of the formation of guanine tetrads are given. Moreover, we propose a new marker discriminating between parallel and antiparallel tetraplexes: the position of the C6O6 guanine carbonyl stretching vibration. In intermolecular parallel tetrameric structures formed by four separate strands this absorption is observed at 1693 cm-1 while for antiparallel tetrameric structures, either intramolecular or formed by dimerization of hairpins, this vibrational mode is observed at 1682 cm-1. These shifts to higher wavenumbers, when compared to the position of a free guanine C6O6 carbonyl stretching vibration observed at 1666 cm-1(Deltanu=27 cm-1 for parallel tetraplexes and Deltanu=16 cm-1 for antiparallel tetraplexes) reflect different strand orientations in the structures. This marker has been used to evidence the possibility of an antiparallel-parallel tetraplex reorganization for Oxytricha nova d(G4T4G4) and d((G4T4)3G4) and human d(G3T2AG3) telomeric sequences induced by Na+/K+ or Na+/Ca2+ ion exchange. Formation of the guanine tetrads, characterization of the phosphate geometries and of the sugar conformations have also been obtained by FTIR for the different tetraplexes.     

Experimental evidence for intramolecular blue-shifting C-H...O hydrogen bonding by matrix-isolation infrared spectroscopy

Experimental evidence for intramolecular blue-shifting C-H...O hydrogen bonding is presented. Argon matrix-isolation infrared spectra of 1-methoxy-2-(dimethylamino)ethane exhibit a band at 3016.5 cm-1. Spectral behavior with annealing indicates that this band is assigned to the most stable conformer, trans-gauche-(trans|gauche'), with an intramolecular C-H...O hydrogen bond. Density functional calculations show that this band arises from the stretching vibration of the C-H bond participating in the formation of the C-H...O hydrogen bond. The C-H bond is shortened by 0.004 A, and the C-H stretching band is blue-shifted by at least 35 cm-1 on the formation of the hydrogen bond. The (C)H...O distance is calculated as 2.38 A, which is shorter than the corresponding van der Waals separation by 0.3 A.     

Infrared spectra and ab initio calculations for the F- -(CH4)n (n = 1-8) anion clusters

Infrared spectra of mass-selected F- -(CH4)n (n = 1-8) clusters are recorded in the CH stretching region (2500-3100 cm-1). Spectra for the n = 1-3 clusters are interpreted with the aid of ab initio calculations at the MP2/6-311++G(2df 2p) level, which suggest that the CH4 ligands bind to F- by equivalent, linear hydrogen bonds. Anharmonic frequencies for CH4 and F--CH4 are determined using the vibrational self-consistent field method with second-order perturbation theory correction. The n = 1 complex is predicted to have a C3v structure with a single CH group hydrogen bonded to F-. Its spectrum exhibits a parallel band associated with a stretching vibration of the hydrogen-bonded CH group that is red-shifted by 380 cm-1 from the nu1 band of free CH4 and a perpendicular band associated with the asymmetric stretching motion of the nonbonded CH groups, slightly red-shifted from the nu3 band of free CH4. As n increases, additional vibrational bands appear as a result of Fermi resonances between the hydrogen-bonded CH stretching vibrational mode and the 2nu4 overtone and nu2+nu4 combination levels of the methane solvent molecules. For clusters with n < or = 8, it appears that the CH4 molecules are accommodated in the first solvation shell, each being attached to the F- anion by equivalent hydrogen bonds.     

Thermal stability of lysozyme Langmuir-Schaefer films by FTIR spectroscopy

Fourier transform infrared spectroscopy has been applied to study the thermal stability of multilayer Langmuir-Schaefer (LS) films of lysozyme deposited on silicon substrates. The study has confirmed previous structural findings that the LS protein films have a high thermal stability that is extended in a lysozyme multilayer up to 200 degrees C. 2D infrared analysis has been used here to identify the correlated molecular species during thermal denaturation. Asynchronous 2D spectra have shown that the two components of water, fully and not fully hydrogen bonded, in the high-wavenumber range (2800-3600 cm-1) are negatively correlated with the amine stretching band at 3300 cm-1. On the grounds of the 2D spectra the FTIR spectra have been deconvoluted using three main components, two for water and one for the amine. This analysis has shown that, at the first drying stage, up to 100 degrees C, only the water that is not fully hydrogen bonded is removed. Moreover, the amine intensity band does not change up to 200 degrees C, the temperature at which the structural stability of the multilayer lysozyme films ceases.