Raman Intensity of the v C=O Band in Hydrogen Bonded Complexes Involving Ethylformate and Phenol Derivatives

The hydrogen bonded complexes between carbonyl bases and hydroxylic derivatives have been extensively studied by infrared spectrometry; by comparison very little Raman data have been reported in the literature. Some qualitative measurements on the v _C=O band of acetone dissolved in water-tetrachloride mixtures have been performed by Singurel¹. Quantitative data on the absolute Raman intensity have been obtained for complexes involving cyclohexanone², acetone, acetophenone³ and methylacetate⁴. For these systems, hydrogen bond formation brings about a moderate intensity enhancement of the v _C=O band. In this work the Raman intensity of the v _C=O band of ethylformate (EtFo) complexed with phenol derivatives is investigated.     

Infrared Study (3700 - 3000 cm−1) of Hydrogen Bonds Involving Triphenyl Derivatives of Group V Elements

The hydrogen bonded complexes between hydroxylic derivatives and nitrogen bases have been extensively studied by infrared spectrometry but very few experimental results are available for bases involving other elements of group V. Some thermodynamic or spectroscopic data have however been reported for the interaction between alcohol derivatives or phenol and trialkyl- or triphenylphosphine derivatives^1–5 but the electron donor ability of the other compounds is not clearly established especially in the case of phenyl derivatives who have n-and π-electron-donor centers. In this case, the properties of the hydrogen bond can be investigated as a useful tool for the evaluation of the donor properties of the heteroatom and the nature of his interaction with the π ring system⁶. In this work, we have determined the thermodynamic constants and the frequency shifts of the ν_OH stretching vibration of hydrogen bonded complexes involving phenol derivatives and triphenylarsine. The influence of the acidity of the phenol molecules on the properties of the complexes is discussed. Some additional data are reported for complexes involving Ph₃X derivatives (X = N,P,Sb) and discussed as a function of the ionization potential of the heteroatom and the π-ring electrons.     

Raman spectroscopic study of synthetic reevesite and cobalt substituted reevesite (Ni,Co)6Fe2(OH)16(CO3)·4H2O

Raman spectroscopy, complemented with infrared spectroscopy of compounds equivalent to reevesite, formula (Ni,Co)₆Fe₂(OH)₁₆(CO₃)·4H₂O, with the ratio of Ni/Co ranging from 0 to 1, have been synthesised and characterised based on the molecular structure of the synthesised mineral. The combination of Raman spectroscopy with infrared spectroscopy enables an assessment of bands attributable to water stretching and brucite‐like surface hydroxyl units to be obtained. Raman spectroscopy shows a reduction in the symmetry of the carbonate anion, leading to the conclusion that the carbonate anion is bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Variation in the position of the carbonate anion stretching vibrations occurs and is dependent on the Ni/Co ratio. Water bending modes are identified in both the Raman and infrared spectra at positions greater than 1620 cm⁻¹, indicating that water is strongly hydrogen bonded to both the interlayer anions and the hydrotalcite surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared Study of the Interaction of Tetramethylthiourea and Dimethylthioformamide with Phenol Derivatives

Abstract

The hydrogen bonded complexes between hydroxylic bonds and oxygen or nitrogen bases have been extensively studied by infrared spectrometry. However, meager experimental results are available for sulfur participation in hydrogen bond formation. There seems little doubt that in thioamides - hydroxylic complexes, the donor site for hydrogen bonding is sulfur, particularly in view of the blue shift of the n → π? transition of the thiocarbonyl group in proton donor solvents ¹. This paper reports on a study of the equilibrium constants (K) and on the frequency shifts of the 1 v _OH stretching vibration of hydrogen bonded complexes between tetramethylthiourea (TMTU) or dimethyltnioformamide (DMTF) and some phenol derivatives.     

Hydrogen bonding in amylose/DMSO complexes studied by vibrational spectroscopy and density functional theory calculations

The intermolecular interactions in amylose/dimethyl sulfoxide (DMSO) complexes are discussed both experimentally and theoretically by means of Raman and infrared spectroscopies. The study is based on a preliminary analysis of well known systems such as pure liquid DMSO or DMSO in mixture with water: for such systems, an analysis of the CS stretching region is carried out both by means of Raman and infrared spectra. In particular, Raman spectra reveal a high sensitivity to the strength and to the type of interaction involving the DMSO molecules. These results, applied to the investigation of amylose‐DMSO complexes, show the presence of different hydrogen‐bonded complexes which coexist in this compound. In particular, DMSO molecules are identified both on the external surface of the V‐amylose helix, where they can interact via one hydrogen bond and in the inner channel of the helix where they can interact via two hydrogen bonds. The present findings open the possibility of applying vibrational spectroscopy to the characterization of inclusion compounds of amylose which are currently being involved in many fields of nanosciences. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopic Studies of Proton Transfer Equilibria In Hydrogen Bonded Complexes

Abstract

Recent studies on proton transfer equilibria for many hydrogen bonded complexes are discussed. These studies employ various spectroscopic techniques as infrared, ultraviolet, ¹H NMR, ¹³C NMR, ¹⁵N NMR and nuclear quadrupole resonance (NQR) spectroscopy. Special attention has been paid to Fourier transform infrared (FTIR), and it forms the main focus of this review, in particular for the study of proton transfer equilibria in proton sponges hydrogen bonded complexes. The influence of proton transfer equilibria on the physical, chemical and biological properties of hydrogen bonded complexes is shown. Some applications of proton transfer equilibria are also discussed.

     

Synthesis and Raman spectroscopic study of Mg/Al,Fe hydrotalcites with variable cationic ratios

Hydrotalcites of formula Mg₆(Al,Fe)₂(OH)₁₆(CO₃)·4H₂O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio have been successfully synthesised. The XRD patterns show variation in the d‐spacing attributed to the size of the cation. Raman and infrared bands in the OH stretching region are assigned to (1) brucite layer OH stretching vibrations, (2) water stretching bands and (3) water strongly hydrogen bonded to the carbonate anion. Multiple (CO₃)²⁻ symmetric stretching bands suggest that different types of (CO₃)²⁻ exist in the hydrotalcite interlayer. Increasing the cation ratio (Mg/Al,Fe) resulted in an increase in the combined intensity of the two Raman bands at around 3600 cm⁻¹, attributed to Mg OH stretching modes, and a shift of the overall band profile to higher wavenumbers. These observations are believed to be a result of the increase in magnesium in the structure. Raman spectroscopy shows a reduction in the symmetry of the carbonate, leading to the conclusion that the anions are bonded to the brucite‐like hydroxyl surface and to the water in the interlayer. Water bending modes are identified in the infrared spectra at positions greater than 1630 cm⁻¹, indicating that water is strongly hydrogen bonded to both interlayer anions and the brucite‐like surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Dussertite BaFe3+3(AsO4)2(OH)5—a Raman spectroscopic study of a hydroxy‐arsenate mineral

The mineral dussertite, a hydroxy‐arsenate mineral with formula BaFe³⁺₃(AsO₄)₂(OH)₅, has been studied by Raman spectroscopy complemented with infrared spectroscopy. The spectra of three minerals from different origins were investigated and proved to be quite similar, although some minor differences were observed. In the Raman spectra of the Czech dussertite, four bands are observed in the 800–950 cm⁻¹ region. The bands are assigned as follows: the band at 902 cm⁻¹ is assigned to the (AsO₄)³⁻ν₃ antisymmetric stretching mode, the one at 870 cm⁻¹ to the (AsO₄)³⁻ν₁ symmetric stretching mode, and those at 859 and 825 cm⁻¹ to the As‐OM^{2 + /3+} stretching modes and/or hydroxyl bending modes. Raman bands at 372 and 409 cm⁻¹ are attributed to the ν₂ (AsO₄)³⁻ bending mode and the two bands at 429 and 474 cm⁻¹ are assigned to the ν₄ (AsO₄)³⁻ bending mode. An intense band at 3446 cm⁻¹ in the infrared spectrum and a complex set of bands centred upon 3453 cm⁻¹ in the Raman spectrum are attributed to the stretching vibrations of the hydrogen‐bonded (OH)⁻ units and/or water units in the mineral structure. The broad infrared band at 3223 cm⁻¹ is assigned to the vibrations of hydrogen‐bonded water molecules. Raman spectroscopy identified Raman bands attributable to (AsO₄)³⁻ and (AsO₃OH)²⁻ units. Copyright © 2010 John Wiley & Sons, Ltd.     

Improper hydrogen bonding and motional narrowing in binary mixtures of 2‐ and 3‐bromopyridine in methanol probed by polarized Raman study and DFT calculations

A concentration‐dependent Raman study of the ν(C Br) stretching and trigonal bending modes of 2‐ and 3‐Br‐pyridine (2Br‐p and 3Br‐p) in CH₃OH was performed at different mole fractions of the reference molecule, 2Br‐p/3Br‐p, from 0.1 to 0.9 in order to understand the origin of blue/red wavenumber shifts of the vibrational modes due to hydrogen‐bond formation. The appearance of additional Raman bands in these binary systems at ∼617 cm⁻¹in the case of 2Br‐p and at ∼618 cm⁻¹ in the case of 3Br‐p compared to neat bromopyridine derivatives were attributed to specific hydrogen‐bonded complexes formed in the mixtures. The interpretation of experimental results is supported by density functional calculations on optimized geometries and vibrational wavenumbers of 2Br‐p and 3Br‐p and a series of hydrogen‐bonded complexes with methanol. The parameters obtained from these calculations were used for a qualitative explanation of the blue/red shifts. The wavenumber shifts and linewidth changes for the ν(C Br) stretching and trigonal bending modes as a function of concentration reveal that the caging effects leading to motional narrowing and diffusion‐causing line broadening are simultaneously operative, in addition to the blue shift caused due to hydrogen bonding. Copyright © 2007 John Wiley & Sons, Ltd.     

Hydrogenated crystalline silicon fabricated at low-substrate temperatures by reactive sputtering in He-H2 atmosphere

Crystallized films of silicon containing about 5 at.% of bonded hydrogen have been fabricated by reactive sputtering in He and H₂ atmosphere at low substrate temperatures below 250°C. The structure was investigated by X-ray diffraction, Raman scattering, infrared and visible absorption measurements. The infrared spectra show two or three sharp absorption peaks at the stretching vibrational region of Si-H. The processes of both sputtering and crystallization are strongly affected by the presence of H₂.     

Raman spectroscopic study of the hydrogen‐arsenate mineral pharmacolite Ca(AsO3OH)·2H2O—implications for aquifer and sediment remediation

The removal of arsenate anions from aqueous media, sediments and wasted soils is of environmental significance. The reaction of gypsum with the arsenate anion results in pharmacolite mineral formation, together with related minerals. Raman and infrared (IR) spectroscopy have been used to study the mineral pharmacolite Ca(AsO₃OH)· 2H₂O. The mineral is characterised by an intense Raman band at 865 cm⁻¹ assigned to the ν₁ (AsO₃)²⁻ symmetric stretching mode. The equivalent IR band is found at 864 cm⁻¹. The low‐intensity Raman bands in the range from 844 to 886 cm⁻¹ provide evidence for ν₃ (AsO₃) antisymmetric stretching vibrations. A series of overlapping bands in the 300‐450 cm⁻¹ region are attributed to ν₂ and ν₄ (AsO₃) bending modes. Prominent Raman bands at around 3187 cm⁻¹ are assigned to the OH stretching vibrations of hydrogen‐bonded water molecules and the two sharp bands at 3425 and 3526 cm⁻¹ to the OH stretching vibrations of only weakly hydrogen‐bonded hydroxyls in (AsO₃OH)²⁻ units. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared Study of The Hydrogen Bond Complexes Involving 2,3-bis-(2-Pyridyl)-pyzazine and Proton Donors. Comparison with Monofunctional Heterocyclic N-Bases

The hydrogen bond complexes between phenols and 2,3-bis(2-pyridyl)-pyrazine BPP) are investigated by infrared spectroscopy in carbon tetrachloride solution. The formation constants for the complexes of 1–1 stoichiometry are higher than those predicted from the pK_a of BPP. This is also the case for other N-heteroaromatic bases (pyridazine, 2,2′-bipyrimidine) characterized by two vicinal equivalent nitrogen atoms. The thermodynamic and infrared data of the complexes show that BPP cannot be considered as a proton sponge.     

Vibrational Spectroscopic Characterization of the Arsenate Mineral Barahonaite: Implications for the Molecular Structure

The mineral barahonaite is in all probability a member of the smolianinovite group. The mineral is an arsenate mineral formed as a secondary mineral in the oxidized zone of sulphide deposits. We have studied the barahonaite mineral using a combination of Raman and infrared spectroscopy. The mineral is characterized by a series of Raman bands at 863 cm^?1 with low wavenumber shoulders at 802 and 828 cm^?1. These bands are assigned to the arsenate and hydrogen arsenate stretching vibrations. The infrared spectrum shows a broad spectral profile. Two Raman bands at 506 and 529 cm^?1 are assigned to the triply degenerate arsenate bending vibration (F ₂, ν₄), and the Raman bands at 325, 360, and 399 cm^?1 are attributed to the arsenate ν₂ bending vibration. Raman and infrared bands in the 2500–3800 cm^?1 spectral range are assigned to water and hydroxyl stretching vibrations. The application of Raman spectroscopy to study the structure of barahonaite is better than infrared spectroscopy, probably because of the much higher spatial resolution.     

Synthesis and Raman spectroscopic characterisation of hydrotalcite with CO32− and VO3− anions in the interlayer

Infrared and Raman spectroscopy were used to characterise synthetic mixed carbonate and vanadate hydrotalcites of formula Mg₆Al₂(OH)₁₆(CO₃)²⁻, (VO₄)³⁻·4H₂ O. The spectra were used to assess the molecular assembly of the cations and anions in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based on (1) the carbonate anion (2) the hydroxyl units and (3) water units. Bands were assigned to the hydroxyl stretching vibrations of water. Three types of carbonate anions were identified: (1) carbonate hydrogen‐bonded to water in the interlayer, (2) carbonate hydrogen‐bonded to the hydrotalcite hydroxyl surface and (3) free carbonate anions. It is proposed that the water is highly structured in the hydrotalcite, as it is hydrogen‐bonded to both the carbonate and the hydroxyl surface. The spectra were used to assess the contamination of carbonate in an open reacting vessel in the synthesis of vanadate hydrotalcites of formula Mg₆Al₂(OH)₁₆(CO₃)²⁻, (VO₄)³⁻·4H₂ O. Bands have been assigned to vanadate anions in the infrared and Raman spectra associated with V O bonds. Copyright © 2007 John Wiley & Sons, Ltd.     

Infrared and Raman study of the interaction between methyl acetate and phenol derivatives

In previous publications [1–3], we have been concerned with the influence of hydrogen bond formation on the Raman intensity of the carbonyl stretching vibration. It has been shown that hydrogen bond association of simple carbonyl bases (cyclohexanone, acetone, acetophenone) with proton donors such as phenol derivatives, hydrochlorid or hydrobromic acid brings about an intensity increase of the ν_CO Raman band; moreover, the intensity enhancement is linearly related to the enthalpy of complex formation. In the present work, these measurements are extended to the complexes formed between methyl acetate (MeAc) and phenol derivatives.

As suggested by the frequency lowering of the ν_CO vibration and the frequency increase of the ν_CO band, complex formation in solution takes place on the carbonyl function.From NMR [4–5] and UV data [6] it can also be concluded that protonation via hydrogen-bonded attachment occurs in solution predominantly at the carbonyl oxygen atom.Literature data for the thermodynamic quantities referring to esters with hydroxylic compounds are scarce. Consequently in this work, we have determined the equilibrium constants and the enthalpy of formation for complexes between MeAc and phenol derivatives. We also report the absolute intensity of the ν_CO Raman band in the free ester molecule and in the complexes, all measurements been made in a solvent of low polarity : carbontetrachloride.     

氢稀释对纳米晶硅薄膜晶化特性的影响及薄膜生长机理

以SiH₄与H₂作为前驱气体,采用射频等离子增强化学气相沉积技术制备了纳米晶硅薄膜.利用Raman散射和红外吸收光谱等技术,对不同氢稀释比条件下薄膜的微观结构和键合特性进行了研究.结果表明,随着氢稀释比增加,薄膜的晶化率明显提高,而氢稀释比过高时,薄膜晶化率呈现减少趋势.红外吸收光谱分析表明,纳米晶硅薄膜中氢的键合模式与薄膜的晶化特性密切相关.随着氢稀释比增加,薄膜中整体氢含量和SiH₂键合密度明显减少,而在高氢稀释比条件下,氢稀释比增加导致薄膜中SiH₂键合密度和整体氢含量增加.     

Optical modulation in nematic phase of halogen substituted hydrogen bonded liquid crystals

A series of halogen-substituted hydrogen-bonded liquid crystalline complexes have been designed and synthesised. A successful attempt has been made to form complementary hydrogen bonding between the dodecyloxy benzoic acid (12BAO) and halogen-substituted benzoic acids and the physical properties exhibited by the individual complexes are studied. The complexes obtained are analysed by polarising optical microscope (POM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dielectric studies. The formation of complementary hydrogen bond is confirmed through FTIR spectra. An interesting feature of this series is the observation of a field-induced transition (FiT) in nematic phase. Another interesting phenomenon is the observation of a new smectic X phase (worm-like texture) in all the synthesised complexes. Dielectric relaxation studies in the smectic C phase of these hydrogen bonded complexes along with the Arrhenius and the Cole–Cole plots are discussed. Optical tilt angle in smectic C phase and the corresponding fitted data analysis concur with the Mean field theory prediction.     

Interpretation of the vibrational spectra of polycrystalline adenine

The infrared and Raman spectra of the tetramer of the adenine N₉H are calculated and analyzed. The vibrational spectra of polycrystalline adenine are interpreted. It is demonstrated that the method for calculating the vibrational spectra of molecular complexes formed by hydrogen bonds can be used for interpreting the vibrational spectra of polyatomic molecules in the solid state.     

Raman Spectroscopic Study of the Copper Silicate Mineral Apachite Cu9Si10O29 · 11H2O

ABSTRACT

Apachite, Cu₉Si₁₀O₂₉ · 11H₂O, is a mineral named after the American Indian Apache tribe. Raman and infrared spectroscopy have been used to characterize the molecular structure of apachite. The structure of the mineral shows disorder, which is reflected in the difficulty in obtaining quality Raman spectra. Raman spectroscopy clearly shows the presence of OH units in the apachite structure, which attests the formula to be not correct. Both Raman and infrared spectroscopy show the presence of water in the apachite structure. Different water molecules are present with different hydrogen bonding strengths. A suggested formula might be Cu₉Si₁₀O₂₃(OH)₁₂ · 5H₂O.

The Raman band at 967 cm^?1 is assigned to the –SiO₃ symmetrical stretching vibration and the bands at 997 and 1096 cm^?1 are assigned to the ν₃ –SiO₃ antisymmetric stretching vibrations. An intense Raman band at 673 cm^?1 with a shoulder at 663 cm^?1 is assigned to the ν₄ Si-O-Si bending modes. Raman spectroscopy complemented with infrared spectroscopy enabled a better understanding of the molecular structure of apachite.     

Raman spectroscopy of dawsonite NaAl(CO3)(OH)2

Raman spectroscopy both at 298 and 77 K complemented with infrared spectroscopy was used to study the structure of dawsonite. Previous crystallographic studies concluded that the structure of dawsonite was a simple one; however, both Raman and infrared spectroscopy show that this conclusion is incorrect. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions, showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred around 950 cm⁻¹ in both Raman and infrared spectra show that the OH units in the dawsonite structure are non‐equivalent. Calculations using the position of the Raman and infrared OH stretching vibrations enabled estimates of the hydrogen‐bond distances of 0.2735 and 0.27219 pm at 298 K, and 0.27315 and 0.2713 pm at 77 K to be made. This indicates strong hydrogen bonding of the OH units in the dawsonite structure. Copyright © 2007 John Wiley & Sons, Ltd.