Vibrational Spectra,Normal Coordinate Calculations,and Molecular Mechanics Calculations for 2, 3, 3-Trimethyl-1-Butene

Infrared and Raman spectra were obtained for 2, 3, 3-trimethyl-1-butene, and a vibrational assignment was made with the aid of normal coordinate calculations. Molecular mechanics calculations were also made to determine molecular parameters of the stable conformation. Values for the force constants of a forty-one parameter modified valence force field were obtained that will be used for other 2-methyl-1-alkenes that contain substituted methyl groups.     

Vibrational Spectra and Normal Coordinate Analysis for (S-Glutathionato) (2,2':6',2′-Terpyridine) Platinum(Ii) Chloride, [Pt(Trpy)Gs]Cl

The normal coordinate analysis of m(trpy)GS]CI (where trpy=2,2':6',2′terpyridine, GS= Glutathionato) has been carried out by using Urey-Bradley force field. According to the molecular structure, 222 internal coordinates were established and 162 theoretical vibrational frequencies agree well with the observed values with the average difference 3.44 cm^-1 and the maximum deviation 15.1 cm^-1.     

The Vibrational Spectra of a Series of Simple Phosphorus/Chromium Polyoxoanions

The infrared and Raman spectra of polycrystalline samples of K₂HPCr₂O₁₀, Na₃PCr₃O₁₃.3H₂0, K₃PCr₄O₁₆ and (NH₄)₃PCr₄O₁₆ were recorded and discussed. A general vibrational assignment for the internal vibrations of these species is proposed.

The structural characteristics of an interesting series of simple polyoxoanions of the PCr_nO^3- _3n+4 type have been determined recently^1–7. These species are essentially built from a central PO₄ -tetrahedron which share a different number of corners with CrO₄ -tetrahedra.

As part of our present studies on different physico-chemical properties of polyoxoanions, we have investigated the vibrational spectra of crystalline species containing the following anions: HPCr₂O^2- ₁₀, PCr₃O^3- ₁₃ and PCr₄O^3- ₁₆.

As the three species have some common structural features, their vibrational spectra can be analyzed and compared in terms of these common building elements, i. e., terminal CrO₃ and PO groups and POCr bridges.

The interatomic distances in the above mentioned units are also very similar in all the anions and the Cr-O distances are similar to those found in the normal (triclinic) form of K₂Cr₂O₇ ⁸.     

Vibrational Spectroscopic Analysis of L,D-Dipeptides

Raman and infrared spectra of Boc-D-Leu-L-Leu-OMe, Boc-L-Ile-D-aIle-OMe and its N-deuterated derivative have been obtained. Normal mode frequencies on the models of these dipeptides have been calculated and the conformationally sensitive amide I, II, III and V modes are compared with the experimentally observed frequencies. The calculated frequencies are in good agreement with the observed frequencies. It is observed that the amide frequencies in these dipeptides are not very sensitive to their backbone conformation. This is in contrast to the well established conformational dependence of the amide modes in peptides, polypeptides and proteins. The normal mode calculations on these peptides also show absence of mixing in amide I and II modes, and hence lack of appreciable splitting in these modes due to transition dipole coupling.

     

Vibrational and Conformational Analysis of 5-Methyl-2-Hexyne

Infrared and Raman spectra were obtained for 5- methyl-2-hexyne and wereinterpreted with the aid of normal coordinate calculations. The spectra and molecular mechanics calculations show the compound to exist in two spectroscopically distinguishable stable conformations, with the C₁ conformer being only a little more stable than the C_s, conformer. Vibrational assignments were made for both conformers.     

Vibrational Spectra and Normal Coordinate Analysis of Diamminediiodidezinc(II) with 15N and 2H Isotopic Substitution.

The Raman and IR. spectra of solid diamminediiodidezinc (II) with ¹⁵N and ²H isotopic substitution have been measured. The spectra have been interpreted assuming C_2v symmetry for the Zn(NH₃)₂I₂ complex structure. The skeletal stretching metal-ligand modes v_s(ZnN), v_as(ZnN), v_s(ZnI), v_as(ZnI) as well as the three bending modes δ(NZnN), δ(IZnI) and δ(IZnN) were assigned by comparison with the spectra of Zn(NH₃)₂C1₂ and Zn(NH₃)₂Br₂, and by the observed isotopic shifts of the frequencies. A normal coordinate analysis for the whole complex was carried out using the Local Symmetry Force Field Model.     

Vibrational Spectra of 4-Benzoylpiridine and the 18O Substituted Derivative

Abstract

Infrared and Raman spectra of 4-benzoylpiridine (4BP) and its ¹⁸O substituted derivative have been recorded in the solid and in the molten state. Polarized Raman spectra in the molten state have also been measured. The assignment of the vibrational bands is performed on the basis of isotopic shifts, group vibrational concept and polarization features of the normal modes. The previous assignment of the in- and out-of-plane deformations of the carbonyl group and the fundamentals below 700 cm^?1 are questioned and corrected.     

Infrared Spectra of the Anion-Radicals of Benzophenone and Some of Its Isotopic Isomers

Abstract

Band assignment of the infrared spectra of the anion-radicals of benzophenone-d_O, -d₁₀ and ¹⁸O has been given on the basis of isotopic shifts. The frequency of the ν_C=O band decreases by ca. 270 cm^?1 with the transformation of neutral keton into anion-radical, due to the strong electron-withdrawing character of the carbonyl group; frequencies of the other modes decrease slightly, down to 30 cm^?1.     

基于密度泛函理论的尼克酸分子振动光谱分析

实验测量了尼克酸分子的拉曼和红外光谱,用B3LYP混合泛函和cc-PVDZ基组计算了尼克酸分子的平衡构型、振动频率、拉曼和红外强度。采用GAR2PED程序对尼克酸分子进行了简正振动分析,依据所得势能分布对尼克酸分子的振动频率进行了理论归属,弥补了以往文献缺少对其振动模式贡献进行定量研究的不足,提供了更多的振动光谱信息。     

Vibrational Investigations of Polyoxometalates - 5 - Valence Force Field Calculations of 1-Metalo-5-tungstates NbVW5 VIO19 3- AND MoVIW 5 VIO19 2- : Influence of the Oxidation State of the Metal Atoms

Normal coordinate treatments of NbW₅O₁₉ ^3- and MoW₅O₁₉ ^2-, two polyoxoanions related to the Lindqvist structure, were performed by assuming the transferability of the internal force field of the parent hexatungstate W₆O₁₉ ^2-. The valence force fields were discussed according to the nature of the M' atom (Nb (V) or Mo (VI)) considered as a perturbing element in the tungstic framework.     

Vibrational spectra and potential energy distributions for 1‐benzyl‐1H‐imidazole by normal coordinate analysis

The Fourier‐transform (FT) Raman and infrared (IR) spectra of the crystallized novel pharmaceutical molecule 1‐benzyl‐1H‐imidazole (BI) were recorded and analyzed. The geometry, intermolecular hydrogen bond, and harmonic vibrational wavenumbers of BI were investigated with the help of B3PW91 density functional theory (DFT) methods. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The aromaticities of the imidazole and phenyl rings were studied using the standard harmonic oscillator model of aromaticity (HOMA) index. Natural bond orbital (NBO) analysis on BI was carried out to demonstrate the various intramolecular interactions that are responsible for the stabilization of this molecule leading to its medicinal activity. The potential energy profile corresponding to the torsion around the bridge bonds connecting the two rings was drawn to explain the steric and/or electronic effects using potential energy surface (PES) scan studies. The pronounced double‐bond localization in the imidazole ring upon intermolecular H‐bonding appears to be the cause for its enhanced aromaticity. Copyright © 2008 John Wiley & Sons, Ltd.     

亚已基硫脲分子的拉曼、红外光谱和简正振动分析

实验测量了亚乙基硫脲分子的拉曼和红外光谱, 用量子化学方法计算了分子的几何构型以及振动频率, 以实验频率为标准对分子内力场进行了标度, 采用简正振动分析方法得到了各振动频率的势能分布, 从而对亚乙基硫脲分子的振动频率归属做出了全面指认。     

Normal Coordinate Analysis of 3-Bromo-1,3-Dinitroazetidine

Abstract

The infrared spectrum of 3-bromo-1,3-dinitroazetidine was interpreted with the aid of normal coordinate calculations. A seventy-two parameter modified valence field was used in those calculations, and the observed wave numbers were fit with an average error of 2.5 cm^?1. An assignment of the bands in terms of symmetry coordinates is given. Many of the force constants were transferred to 1-acetyl-3,3-dinitroazetidine to aid in normal coordinate calculations for that compound.     

双原子分子电子光谱的振动结构分析

从电子振转能级的光谱项出发,分析了双原子分子电子振动谱带序和电子振动谱带列的规律,并归纳出德兰德斯表(Deslandres table)及其主要性质。以C₂分子电子振动光谱的斯簧谱带系作为实例,说明了如何对电子振动光谱的测量值进行标识,并将它们按振动结构规律整理成德兰德斯表,从而获得有关分子光谱不同态的非谐性常数、振动频率等重要参数以及任意谱带的波数公式。     

The Vibrational Spectra of 9-Fluorenone and Some of Its Isotopic Isomers

Abstract

Vibrational spectra of 9-Fluorenone, 9-Fluorenone-¹⁸O and 9-Fluorenone-d₈ have been recorded in the solid state and solutions in the infrared and (4000–100 cm^?1) and in the Raman (4000–50 cm^?1). Differential infrared linear dichroic spectra have also been measured. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes.     

2-巯基噻二唑的拉曼、红外光谱、DFT计算和简正振动分析

采用B3LYP混合泛函和6-311G基函数组,并对重原子和轻原子使用离散函数和极化函数,利用密度泛函理论计算了2-巯基噻二唑的分子振动频率。实验测量了2-巯基噻二唑分子的拉曼、红外光谱,以实验频率为标准对分子内力场进行了标度,采用简正振动分析方法得到了各振动模的势能分布,从而对该分子的振动频率归属做出了全面指认。     

Vibrational Analysis of 2,3-Dimethyl-1-Butene

Infrared and Raman spectra were obtained for 2,3-dimethyl-1-butene. The spectra showed the presence of two stable conformations. Vibrational assignments were made for both conformers with the aid of normal coordinate calculations. Values for the force constants that were obtained will be used in the future as the initial values for other substituted 1-alkenes, such as 2-isopropyl-3-methyl-1-butene.     

Vibrational Spectra of Arsenates and Phosphates of the Type Kcaln(XO4)2

The infrared and Raman spectra of polycrystal-line samples of different compounds of the types KCaLn(AsO₄)₂ and KCaLn(PO₄)₂, belonging to the hexagonal LaPO₄, structural modification, were recorded and discussed. A complete vibrational assignment, based on a factor group analysis, is proposed. The influence of the different lanthanide cations on the internal vibrations of the XO₄ groups is briefly discussed and some comparisons with related compounds are also made.

It is well known that simple lanthanide arsenates, phosphates, vanadates and cnromates (V) of the type LnXO₄ belong to two different structural types.     

The Vibrational Spectra and Normal Coordinate Analysis of Semiconducting Y2BaCuO5

Both infrared (FTIR) and Raman spectra have been measured for the green semiconducting Y₂BaCuO₅ (2:1:1) in the Y-Ba-Cu-O system. Factor group analysis and normal-coordinate-analysis calculations have been conducted for this phase in order to determine the symmetries, the wavenumber locations and the eigenvector nature of its first-order modes of vibration along with the appropriate set of modified GVF force constants. The predicted vibrational spectral results are in good agreement with the experimentally observed FTIR and Raman spectral data. The generated force constants are interpreted along with those for related phases on the basis of structure.     

Vibrational Assignment of N-Phenylphthalimide and 15N-Phenylphthalimide

Abstract

The i.r. spectra of N-phenylphthalimide and ¹⁵N-phenylphthalimide have been measured in 4000–100 cm^?1 frequency range as KBr and polyethylene pellets and as chloroform solutions. The Raman spectra (4000–50) cm^?1 of microcrystalline powder of the of the same compounds have also been investigated.

A detailed assignment of most of the observed frequencies has been proposed on the basis of the group vibrational concept, isotopic shift data and analogies with the spectra of related molecules. Some literature data have been discussed and some frequencies are reassigned.