Millimeter-Wave Spectroscopy, High-Resolution Infrared Spectrum, ab Initio Calculations, and Molecular Geometry of FPS

The transient thiophosphenous fluoride FPS was produced by pyrolysis of 2.5% F₂PSPF₂ in Ar at 1300–1800°C. High-resolution (≥0.004 cm⁻¹) Fourier transform infrared spectra of the a-type ν₁ and b-type ν₂ bands, centered respectively at 803.249 and 726.268 cm⁻¹, were measured and fitted to rotational and quartic centrifugal distortion parameters. The millimeter-wave spectrum, essentially b-type, was measured between 300 and 370 GHz in the ground state and in the ν₃ excited state for FP³²S and in the ground state for FP³⁴S. The frequencies were fitted to a Watson-type A-reduced Hamiltonian up to sextic distortion terms. High level ab initio calculations with large basis sets were performed on FPS and supported the first identification of its infrared and millimeter wave spectra. The calculated anharmonic force field provided precise ab initio rovibrational α constants which were combined with the experimental molecular parameters to determine an accurate equilibrium structure of the molecule: r_e(PS)=188.86 pm, r_e(PF)=158.70 pm, θ(FPS)=109.28°. The collision-controlled 1/e lifetime measured in a 10-Pa (1 : 20) F₂PSPF₂/Ar mixture was 2 s, more than two orders of magnitude larger than that of FPO under the same experimental conditions.     

20种氨基酸近红外光谱及其分子结构的相关性

旨在研究20种氨基酸的分子结构与其近红外光谱的相关性,为氨基酸近红外光谱在动物科学、食品和医药等方面的推广应用奠定一定的理论基础。应用岛津傅里叶变换红外光谱仪IRPrestige-21及其近红外附件FlexIRTM Near-Infrared Fiber Optics module,采集20种氨基酸标准物质在1 000～2 502 nm波长范围内的近红外光谱,分辨率8 cm-1,每个样品扫描3次,每次扫描50遍,取其平均值为氨基酸标准品的近红外光谱。根据氨基酸侧链基团的不同,分别比较脂肪族氨基酸、芳香族氨基酸和杂环氨基酸中各氨基酸分子结构与其近红外光谱的相关性。研究表明,20种氨基酸在1 000～2 502 nm区域有非常明显的近红外光谱吸收且差异显著。分子量较大的脂肪族氨基酸其近红外光谱受侧链基团的影响较大,而甘氨酸近红外光谱受羧基和氨基的影响较大;两种芳香族氨基酸近红外光谱的差异主要来自于苯环,酪氨酸苯环上的—OH基团降低了苯分子的对称性,导致更多振动吸收峰的出现;杂环氨基酸因其侧链上杂环分子基团构成不同,其近红外光谱在1 600～1 800 nm区域差异较大。综上,20种氨基酸主要存在4个特征光谱区：第1特征光谱区为1 050～1 200 nm主要由C—H基团的二级倍频构成;第2特征光谱区为1 300～1 500 nm主要由C—H基团的组合频构成;因侧链基团分子构成不同,在第3特征光谱区1 600～1 850 nm和第4特征光谱区2 000～2 502 nm表现出差异较大的特征吸收峰。因此,可以利用此4个近红外光谱特征区域对氨基酸进行定量和定性分析,提高氨基酸近红外光谱模型预测的准确性。     

四氨基钴酞菁的分子结构和红外光谱量子化学研究

四氨基钴酞菁作为一种很有前途的光敏剂,其光谱研究具有十分重要的意义。以密度泛函的B3LYP/3-21G*方法对四氨基钴酞菁的四种构型进行结构优化,计算出最稳定结构的能量,并模拟计算四氨基钴酞菁的红外光谱,模拟得出的红外光谱与实验所得的振动带有很好的拟合性。     

Nuclear Quadrupole Coupling Constants of Chlorine and Microwave Spectrum, Structure, and ab Initio Calculation of 1-Chloro-1,1,2-trifluoroethane

The microwave spectrum of the ³⁵Cl and ³⁷Cl isotopic species of 1-chloro-1,1,2-trifluoroethane (HCFC-133b) has been investigated in the frequency region 10 to 50 GHz using a Stark modulation microwave spectrometer. A pulsed jet Fourier transform microwave spectrometer was also used for the measurement of hyperfine splittings. A least-squares analysis of the observed b-type Q- and R-branch transition frequencies gave rotational and centrifugal distortion constants and components of the chlorine nuclear quadrupole coupling constant tensors in the principal axes system as follows: A=4625.161 (3) MHz, B=2004.127 (2) MHz, C=1875.813 (2) MHz, Δ_J=0.144 (9) kHz, Δ_JK=1.0748 (8) kHz, Δ_K=1.57 (1) kHz, δ_J=0.01376 (4) kHz, δ_K=−0.146 (4) kHz, χ_aa=−57.958 (10) MHz, χ_bb=21.231 (11) MHz, and χ_cc=36.727 (11) MHz for ³⁵ClCF₂CH₂F species, and A=4607.684 (6) MHz, B=1960.565 (2) MHz, C=1834.823 (2) MHz, Δ_J=0.106 (7) kHz, Δ_JK=1.022 (3) kHz, Δ_K=1.48 (1) kHz, δ_J=0.0142 (2) kHz, δ_K=−0.18 (2) kHz, χ_aa=−46.268 (11) MHz, χ_bb=17.319 (13) MHz, and χ_cc=28.950 (13) MHz for ³⁷ClCF₂CH₂F species. The structural parameters are calculated from the observed six rotational constants by assuming the partial structure of ab initio calculation. The electronic properties of the C-Cl bond are evaluated from the observed nuclear quadrupole constants of chlorine. These molecular properties are compared with those of other related molecules.     

Inversion and internal rotation in methyl-d-amine: Microwave spectrum

The microwave spectrum of CH₂DNH₂ has been observed in the 8–74 GHz region. The spectrum shows that this molecule takes essentially two distinguishable conformers, trans and gauche forms, although a small amount of coupling between them can be detected. For each line of the trans form a small inversion splitting has been found. It is 93.97 MHz at K = 0 and a periodic function of K. The mean frequencies of the inversion pairs of lines are well explained as the frequencies of a rigid rotor. The gauche spectrum is extremely complicated; each rotational line splits into four because of inversion and gauche-gauche tunneling interactions. The analysis was carried out based on the theory developed in the preceding paper. Tunneling energy parameters of internal-rotation, ?_gg and ?_tg, and inversion, δ_gg and δ_tg, were determined as ?_gg = 3476.6 MHz, ?_tg = 3233.1 MHz, δ_gg = 2790.6 MHz and δ_tg = 3052.7 MHz. Energy difference between trans and gauche conformers ΔE_tg was estimated to be 7.060 cm^?1 from these values of parameters and also on the basis of the observed anomaly in the Q branch series of trans form which is due to an accidental degeneracy between the K = 1 level of trans and K = 2 level of gauche. The effects on the internal-rotation of other internal motions have also been discussed.     

Infrared Spectra and Transmission of Substituent Effects Through the Arylazomethine Group in Aromatic Schiff Bases

The IR frequencies and integrated intensities of the nitrile group of two series of aromatic Schiff bases have been measured. The data obtained are compared with the Hammett σ constants as well as with the calculated dipole moment derivatives of the nitrile group. An evaluation of the transmission coefficient Π of the arylazomethine group is reported.     

H_2O/C复合微粒子群的光学截面及红外发射率光谱的计算

本文利用 A.L.Aden和 M.Kerker微粒子 Mie散射理论 ,计算了 H2 O/C复合微粒子群的光学截面 ,对混合后的 H2 O/C粒子群的发射率光谱进行了计算     

Raman,Infrared and 1H-NMR Spectra of Hexamethyldisilylchalcogenides

The Raman, infrared and ¹H-NMR spectra of (CH₃)₃ -X-Si (CH₃)₃ (X=O,S,Se,Te) were measured, and the assignment was carried out by comparison with those of the structurally related compounds, (CH₃)₃ SiCl and (CH₃)₃ Si-Si (CH₃)₃. The vibrational spectra of (CH₃)₃ Si-X-Si (CH₃)₃ can be interpreted in terms of a non-rigid D_3d symmetry with internal rotations, because those of skeletones of the molecules indicate the lack of coincidence between Raman and infrared frequencies. The ¹H-NMR spectra also support a non-rigid D_3d model, because only one band for CH₃ group appears.     

Internal Rotation, Quadrupole Coupling, and Structure of (CH3)3SiCl Studied by Microwave Spectroscopy and ab Initio Calculation

The microwave spectrum of (CH₃)₃SiCl and its isotopic species (CH₃)₃Si³⁷Cl, (CH₃)₃²⁹SiCl, (CH₃)₃³⁰SiCl, and (¹³CH₃)(CH₃)₂SiCl has been studied in the frequency range of 3 to 40 GHz. The barrier to internal rotation, the chlorine quadrupole coupling, and the structure were determined. Ab initio calculation were compared with the experimental results.     

甲胺水合离子团簇的结构模型及红外光谱研究

本文利用量子化学计算方法,研究了甲胺和水复合离子团簇[(CH₃NH₂)(H₂O)_n]⁺的几何结构、能量和红外光谱,揭示了结构生长模型、氢键作用机制和质子转移机理. 研究结果表明,在[(CH₃NH₂)(H₂O)_n]⁺团簇中,甲胺甲基上的一个氢原子转移到氨基上,形成分子内质子转移的CH₂NH₃⁺离子核心结构模型,水分子作为氢键受体,与质子化氨基NH₃⁺形成氢键. CH₃NH₂⁺离子核心结构模型没有CH₂NH₃⁺离子核心结构模型稳定. 在团簇的红外光谱中,CH振动、自由NH振动、氢键结合的NH振动和OH振动模式在CH₃NH₂⁺和CH₂NH₃⁺两种离子核心结构模型的理论计算红外光谱中明显不同,因此可用于鉴别甲胺水合离子团簇的结构模型,有助于理解甲胺和水复合团簇的氢键网络结构.     

基质隔离红外光谱结合理论计算研究第五族金属原子和硫化氢反应

利用基质隔离红外光谱结合理论计算,研究了激光溅射获得的第五族金属原子和硫化氢分子的反应. 结果表明金属原子插入H₂S的H-S化学键形成HMSH分子(M=V,Nb,Ta). 对Nb和Ta该HMSH分子重排为H₂MS分子. HMSH分子和H₂S进一步反应生成H₂M(SH)₂分子. 通过D₂S和H₂³⁴S同位素标定确定了产物的分子结构,同时我们用DFT(B3LYP和BPW91)理论计算预测了产物分子的能量、结构和振动频率. 通过DFT IRC计算研究了第五族金属原子和₂S分子的反应机理. HVSH分子通过光照解离为VS和H₂,然后通过退火可以发生VS和H₂复合反应. 计算表明HVSH释放H₂需要16.9 kcal/mol的活化能及吸热13.5 kcal/mol.     

Infrared and Raman spectra of Histidine: an ab initio DFT calculations of Histidine molecule and its different protonated forms

The infrared spectra of Histidine molecule have been recorded in the Nujoll mull as well as in aqueous solution in the range 400–4000 cm⁻¹. The Raman spectrum of the same molecule has also been measured. The different protonated/deprotonated forms of imidazole ring which contains different forms of Histidine1, Histidine2, Histidine3 and Histidine4 have been studied with DFT and RHF methods using several basis sets. A comparison of energies of the two neutral tautomers (Histidine1 and Histidine2) indicates that Histidine1 is more stable as compared to Histidine2 while Histidine3 (imidazolium cation) is the most stable in gas phase. The selected geometrical parameters and theoretically calculated frequencies for the above-mentioned form of Histidine were also proposed. The observed IR and Raman bands of Histidine molecule are assigned to different modes on the basis of calculated frequencies, their intensities and available literature values.     

Infrared Spectra of Crystalline,Glassy and Liquid Methanol at High Pressures

Abstract

Mid-infrared spectra in the range 400–1800 cm^?1 of methanol samples in diamond anvil cells at ambient temperature and pressures up to 11 GPa are reported. The freezing pressure is confirmed to be 3.6 GPa, and the spectra of the resulting metastable glass are very similar to those of the liquid. When maintained at high pressure, the glass spontaneously transforms to an ordered crystalline phase which is stable over the range 3.6 to 11 GPa. Small changes in peak wavenumbers for 14 internal modes as a function of pressure are observed, indicating that distortion of the molecules is minimal. A slight decrease for the C-O-H bending mode is attributed to charge transfer from the molecular 0-H bond to the strengthening intermolecular hydrogen bond.     

含R2dtc配体和V=O基的金属簇红外光谱研究

本文报道两类含Ｒ２ｄｔｃ配体的金属簇的红外光谱特点及某些规律,含Ｒ２ｄｔｃ的立方簇合物在４００－５００ｃｍ＾－１有较宽而弱的吸收,可归结于Ｍ－μ３Ｓ振动。Ｍ－Ｓｄｔｃ在３３０－３８０ｃｍ＾－１,Ｃ－Ｎ振动在１４７０－１５１０ｃｍ＾－１。二甲基ｄｔｃ配体立方的ｖ（Ｃ－Ｎ）与ｖ（Ｃ＝Ｓ）比值他二烷基ｄｔｃ立方烷的相应振动分别蓝移和红移,可归结于甲基超共轭效应所致。「Ｖ２Ｃｕ２Ｓ４（Ｒ２ｄｔｃ）２（ＰｈＳ）２」＾２－和「ＶＣｕ４Ｓ４（Ｒ２ｄｔｃ）ｎ（ＰｈＳ）４－ｎ」＾３－（ｎ＝０,１,２）的Ｍ－μ３Ｓ振动分别出现在４８０和４６５ｃｍ＾－１,可作为区别两类化合物的一个指标。另一类含（Ｒ２ｄｔｃ）２Ｖ２Ｏ２（μ－Ｓ）２单元的金属簇中,Ｖ－Ｏ伸缩频率在８４４－９７０ｃｍ＾－１范围内,（Ｅｔ４Ｎ）「Ｖ２Ｓ２Ｏ３（Ｅｔ２ｄｔｃ     

Infrared Absorption,Nuclear Magnetic Resonance and Electronic Spectra of N-Hydroxyureas and Carbamates

During the course of investigating the anticancer activities of new compounds, we have synthesized a series of novel cyclic N-hydroxyurea derivatives and several carbamate intermediates^1–3. Infrared absorption, nuclear magnetic resonance, and electronic absorption spectra were examined in order to confirm the identities and to study the molecular structure of these compounds.     

基于二维红外技术研究氧化羧甲基纤维素钠/胶原的相互作用及热稳定性

采用氧化羧甲基纤维素钠(OCMC)作为交联剂,对胶原溶液进行改性并采用二维红外技术分析OCMC与胶原之间的相互作用及其对胶原热稳定性的影响.一维红外图谱显示OCMC交联改性对胶原的主要特征吸收峰即酰胺Ⅰ,Ⅱ和Ⅲ带的峰位与强度无明显影响;改性前后胶原的酰胺Ⅲ带与1455 cm-1处吸光度的比值AⅢ/A1455均接近于1....     

双核过渡金属羰基配合物团簇离子的红外光谱、结构和成键

Binuclear transition metal carbonyl clusters serve as the simplest models in understanding metal-metal and ligand bonding that are important organometallic chemistry catalysis. Binuclear first row transition metal carbonyl ions are produced via a pulsed laser vaporization/supersonic expansion cluster ion source in the gas phase. These ions are studied by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Density functional theory calculations have been performed on the geometric structures and vibrational spectra of the carbonyl ions. Their geometric and electronic structures are determined by comparison of the experimental IR spectra with the simulated spectra. The structure and the metal-metal and metal-CO bonding of both saturated and unsaturated homonuclear as well as heteronuclear carbonyl cluster cations and anions are discussed.     

The Raman and Infrared Spectra and Structures of Ethyl Chloride,Bromide and Iodide

The Raman, infrared and proton NMR spectra of the liquid molecules, C₂H₅-X(X[dbnd]Cl, Br, I) have been recorded. And the molecular structures have been studied on the basis of these spectra. Consequently a non-rigid structure in which a CH₂ group rotates freely with respect to the three hydrogen atoms of CH₃ group is established.