Raman spectroscopic study on the structure of water in aqueous solution of zwitterionic surfactants

The structure and hydrogen bonding of water in aqueous solutions of various surfactants were analyzed using the contours of the O-H stretching in the polarized Raman spectra. From the relative intensity of the collective band (C value) corresponding to a long-range coupling of the O-H stretching in the aqueous surfactant solutions, the number of hydrogen bonds disrupted due to the presence of one surfactant molecule (N(corr) value) was evaluated. The N(corr) value for decylsulfobetaine was slightly negative, whereas those for ordinary ionic surfactants such as sodium dodecylsulfate and dodecyltrimethylammonium chloride were large positive values. Furthermore, the N(corr) for carboxybetaine surfactant was a small positive value. These results suggest that zwitterionic surfactants do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostriction effect by the proximity between the anionic and cationic groups.     

不同电解质体系水的拉曼谱的研究

通过一系列电解质体系水的拉曼光谱测量，得到了阴、阳离子种类和浓度引起的水伸缩振动和弯曲振动谱带丰富的变化信息，ＣｌＯ４＾－能有效地破坏水分子间的氢键，随着ＣｌＯ４浓度的增加，水分子间的氢键并非逐步被打断，而是氢键被破坏的水分子越来越多，从而使水分子有序度增大，这种氢键破坏方式符合水的混合模型（ＭｉｘｔｕｒｅＭｏｄｅｌ）ＳＯ＾２－４浓度的增对水的Ｒａｍａｎ光谱影响较小，是由于ＳＯ＾２－４与水分了间的     

Mechanism of the molecular mobility of water in the temperature range 298–359 K

The Raman spectra of liquid water in the region of O-H stretching vibrations were obtained in the temperature range 298–359 K. The Raman spectra were decomposed into the components using the XPSPEAK-4.1 program, and their temperature dependence was evaluated. The number of bifurcate hydrogen bonds and the percentage of rotational conformers containing bifurcate bonds were shown to increase with temperature. The defect mechanism of the molecular mobility of water on the hydrogen bond network in the temperature range 298–359 K was proposed.     

Water complexes of styrene and 4-fluorostyrene: a combined electronic, vibrational spectroscopic and ab-initio investigation

The binary complexes of water with styrene and fluorostyrene were investigated using LIF and FDIR spectroscopic techniques. The difference in the shifts of S 1 <-- S 0 electronic transitions clearly points out the disparity in the intermolecular structures of these two binary complexes. The FDIR spectra in the O-H stretching region indicate that water is a hydrogen bond donor in both complexes. The formation of a single O-H...pi hydrogen-bonded complex with styrene and an in-plane complex with fluorostyrene was inferred based on the analysis of the FDIR spectra in combination with ab initio calculations. The in-plane complex with fluorostyrene is characterized by the presence of O-H...F and C-H...O hydrogen bonds, leading to formation of a stable six-membered ring. The synergistic effect of O-H...F and C-H...O hydrogen bonds overwhelms the O-H...pi interaction in fluorostyrene-water complexes.     

Quantitative information about the hydrogen bond strength in dilute aqueous solutions of methanol from the temperature dependence of the Raman spectra of the decoupled OD stretch

We have obtained quantitative information about the hydrogen bond strength in pure water and in dilute aqueous solutions of methanol by analyzing the temperature dependence of Raman spectra of the decoupled OD stretch from 21 to 160 degrees C with the hydrogen bond energy dispersion method. A minimum at 2440 cm(-1) assigned to strong icelike hydrogen bonds and a maximum at 2650 cm(-1) due to maximally (but not completely) broken hydrogen bonds result in all cases. The energy of the minimum decreases upon addition of methanol due to formation of stronger water-methanol hydrogen bonds, whereas the energy of the maximum increases because water hydrogen atoms in the vicinity of the methyl group might participate in "more broken" hydrogen bonds than in bulk water.     

Blue-shifted A-H stretching modes and cooperative hydrogen bonding. 1. Complexes of substituted formaldehyde with cyclic hydrogen fluoride and water clusters

The structures and vibrational spectra of the intermolecular complexes formed by insertion of substituted formaldehyde molecules HRCO (R = H, Li, F, Cl) into cyclic hydrogen fluoride and water clusters are studied at the MP2/aug-cc-pVTZ computational level. Depending on the nature of the substituent R, the cluster type, and its size, the C-H stretching modes of HRCO undergo large blue and partly red shifts, whereas all the F-H and O-H stretching modes of the conventional hydrogen bonds are strongly red-shifted. It is shown that (i) the mechanism of blue shifting can be explained within the concept of the negative intramolecular coupling between C-H and C=O bonds that is inherent to the HRCO monomers, (ii) the blue shifts also occur even if no hydrogen bond is formed, and (iii) variation of the acceptor X or the strength of the C-H...X hydrogen bond may either amplify the blue shift or cause a transition from blue shift to red shift. These findings are illustrated by means of intra- and intermolecular scans of the potential energy surfaces. The performance of the negative intramolecular coupling between C-H and C=O bonds of H(2)CO is interpreted in terms of the NBO analysis of the isolated H(2)CO molecule and H(2)CO interacting with (H2O)n and (HF)n clusters.     

IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex

Raman and infrared spectra of two polymorphous minerals with the chemical formula Fe3+(SO4)(OH)·2H2O, monoclinic butlerite and orthorhombic parabutlerite, are studied and the spectra assigned. Observed bands are attributed to the (SO4)2- stretching and bending vibrations, hydrogen bonded water molecules, stretching and bending vibrations of hydroxyl ions, water librational modes, Fe-O and Fe-OH stretching vibrations, Fe-OH bending vibrations and lattice vibrations. The O-H?O hydrogen bond lengths in the structures of both minerals are calculated from the wavenumbers of the stretching vibrations. One symmetrically distinct (SO4)2- unit in the structure of butlerite and two symmetrically distinct (SO4)2- units in the structure of parabutlerite are inferred from the Raman and infrared spectra. This conclusion agrees with the published crystal structures of both mineral phases.     

Correlation between the structure of water in the vicinity of carboxybetaine polymers and their blood-compatibility

The structure and hydrogen bonding of water in the vicinity of carboxybetaine homopolymer (poly[1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (PolyCMB), and a random copolymer of CMB and n-butyl methacrylate, Poly(CMB-r-BMA), with various molecular weights were analyzed in their aqueous solutions and thin film with contours of O-H stretching of Raman and attenuated total reflection infrared (ATR-IR) spectra, respectively. The relative intensity of the collective band (C value) corresponding to a long-range coupling of O-H stretchings of the Raman spectra for aqueous solution of Poly(CMB-r-BMA) was very close to that for pure water, which is in contrast with the smaller C value in aqueous solution of ordinary polyelectrolytes. The number of hydrogen bonds collapsed by the presence of one monomer residue (N(corr) value) of PolyCMB and Poly(CMB-r-BMA) (CMB, 45 mol %) (M(w), 1.14 x 10(4) and 1.78 x 10(4), respectively) could be calculated from the C value. The N(corr) values were much smaller than those for ordinary polyelectrolytes and close to those for nonionic water-soluble polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone). Furthermore, a water-insoluble Poly(CMB-r-BMA) with a large BMA content (M(w) = 347 kD, CMB 27 mol %) could be cast as a thin film (thickness, ca. 10 microm) on a ZnSe crystal for the ATR-IR analyses. At an early stage of sorption of water into the Poly(CMB-r-BMA) film, the O-H stretching band of IR spectra for the water incorporated in the film was similar to that for free water, which is in contrast with the drastic change in the O-H stretching band of water incorporated in polymer films such as poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PBMA). The theoretical vibrational frequency for water molecules hydrating a betaine molecule calculated by using a density functional method supported the experimental results. The adhesion of human platelets to Poly(CMB-r-BMA) films was much less than that to PMMA and PBMA. With an increase in the content of CMB residue, the number of platelets adhered to the Poly(CMB-r-BMA) film drastically decreased and then gradually increased, probably due to the increase in the roughness of the film surface. These results suggest that the carboxybetaine monomer residues with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules in both aqueous solution and thin film systems, resulting in the excellent blood-compatibility of the carboxybetaine polymers.     

Monitoring selected hydrogen bonds in crystal hydrates of amino acid salts: combining variable-temperature single-crystal X-ray diffraction and polarized Raman spectroscopy

Predicting behaviour of hydrogen bonds with varying temperature, in particular-correlating donor-acceptor distances in the O-H···O hydrogen bonds with the frequencies of O-H stretching vibrations is important for understanding dynamics of biomolecules and phase transitions in crystals. A commonly used correlation suggested earlier in the literature is based on statistical analysis of different compounds [A. Novak, Structure and Bonding, 1974, 18, 177; K. Nakamoto, M. Margoshes, R. E. Rundle, J. Am. Chem. Soc., 1955, 77, 6480]. The present study is a rare example when correlations between geometry and energy parameters have been found for selected individual hydrogen bonds in the same crystalline compound at multiple temperatures. The properties of several types of O-H···O hydrogen bonds in bis(DL-serinium) oxalate dihydrate and DL-alaninium semi-oxalate monohydrate have been studied by a combination of variable-temperature single-crystal X-ray diffraction and polarized Raman spectroscopy. The changes in the hydrogen bonds geometry could be compared with the changes of the corresponding spectral modes. The correlation suggested by Novak is roughly followed, better for medium and weak, than for short hydrogen bonds. Fine details of spectral changes differ for individual bonds. The way how H-bonds are affected by cooling depends on their environment in the crystal structure. Short O-H···O hydrogen bonds in bis(DL-serinium) oxalate dihydrate expand or remain almost unchanged on cooling, whereas in DL-alaninium semi-oxalate monohydrate all strong H-bonds are compressed under these conditions. The distortion of individual hydrogen bonds on temperature variations is correlated with the anisotropy of lattice strain.     

Proton dynamics in the strong chelate hydrogen bond of crystalline picolinic acid N-oxide. A new computational approach and infrared, raman and INS study

Infrared, Raman and INS spectra of picolinic acid N-oxide (PANO) were recorded and examined for the location of the hydronic modes, particularly O-H stretching and COH bending. PANO is representative of strong chelate hydrogen bonds (H-bonds) with its short O...O distance (2.425 A). H-bonding is possibly well-characterized by diffraction, NMR and NQR data and calculated potential energy functions. The analysis of the spectra is assisted by DFT frequency calculations both in the gas phase and in the solid state. The Car-Parrinello quantum mechanical solid-state method is also used for the proton dynamics simulation; it shows the hydron to be located about 99% of time in the energy minimum near the carboxylic oxygen; jumps to the N-O acceptor are rare. The infrared spectrum excels by an extended absorption (Zundel's continuum) interrupted by numerous Evans transmissions. The model proton potential functions on which the theories of continuum formation are based do not correspond to the experimental and computed characteristics of the hydrogen bond in PANO, therefore a novel approach has been developed; it is based on crystal dynamics driven hydronium potential fluctuation. The envelope of one hundred 0 --> 1 OH stretching transitions generated by molecular dynamics simulation exhibits a maximum at 1400 cm-1 and a minor hump at approximately 1600 cm-1. These positions square well with ones predicted for the COH bending and OH stretching frequencies derived from various one- and two-dimensional model potentials. The coincidences with experimental features have to be considered with caution because the CPMD transition envelope is based solely on the OH stretching coordinate while the observed infrared bands correspond to heavily mixed modes as was previously shown by the normal coordinate analysis of the IR spectrum of argon matrix isolated PANO, the present CPMD frequency calculation and the empirical analysis of spectra. The experimental infrared spectra show some unusual characteristics such as large temperature effects on the intensity of some bands, thus presenting a challenge for theoretical band shape treatments. Our calculations clearly show that the present system is characterized by an asymmetric single well potential with no large amplitudes in the hydronium motion, which extends the existence of Zundel-type spectra beyond the established set of hydrogen bonds with large hydronic vibrational amplitudes.     

Simulating infrared spectra and hydrogen bonding in cellulose Iβ at elevated temperatures

We have modeled the transformation of cellulose Iβ to a high temperature (550 K) structure, which is considered to be the first step in cellulose pyrolysis. We have performed molecular dynamics simulations at constant pressure using the GROMOS 45a4 united atom forcefield. To test the forcefield, we computed the density, thermal expansion coefficient, total dipole moment, and dielectric constant of cellulose Iβ, finding broad agreement with experimental results. We computed infrared (IR) spectra of cellulose Iβ over the range 300-550 K as a probe of hydrogen bonding. Computed IR spectra were found to agree semi-quantitatively with experiment, especially in the O-H stretching region. We assigned O-H stretches using a novel synthesis of normal mode analysis and power spectrum methods. Simulated IR spectra at elevated temperatures suggest a structural transformation above 450 K, a result in agreement with experimental IR results. The low-temperature (300-400 K) structure of cellulose Iβ is dominated by intrachain hydrogen bonds, whereas in the high-temperature structure (450-550 K), many of these transform to longer, weaker interchain hydrogen bonds. A three-dimensional hydrogen bonding network emerges at high temperatures due to formation of new interchain hydrogen bonds, which may explain the stability of the cellulose structure at such high temperatures.     

Air-liquid interfaces of aqueous solutions containing ammonium and sulfate: spectroscopic and molecular dynamics studies

Investigations of the air-liquid interface of aqueous salt solutions containing ammonium (NH(4)(+)) and sulfate (SO(4)(2-)) ions were carried out using molecular dynamics simulations and vibrational sum frequency generation spectroscopy. The molecular dynamics simulations show that the predominant effect of SO(4)(2-) ions, which are strongly repelled from the surface, is to increase the thickness of the interfacial region. The vibrational spectra reported are in the O-H stretching region of liquid water. Isotropic Raman and ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopies were used to study the effect of ammonium and sulfate ions on the bulk structure of water, whereas surface sum frequency generation spectroscopy was used to study the effect of these ions on the interfacial structure of water. Analysis of the interfacial and bulk vibrational spectra reveal that aqueous solutions containing SO(4)(2-) perturb the interfacial water structure differently than the bulk and, consistent with the molecular dynamics simulations, reveal an increase in the thickness of the interfacial region.     

Lifetimes and the dynamics of hydrogen bonds in liquid water

Based on Raman spectra of light, heavy, and half-heavy water in the region of O-H and O-D stretching vibrations and on the independent-oscillator model, it is shown that a peculiarity of the liquid state of water is the nonequivalence of O-H groups of water molecules in hydrogen bonding. The structure of liquid water and the mechanism of its molecular mobility are considered in this context.     

Effect of temperature and water content on the structure of 1,2-propanediol and 1,3-propanediol: Near-infrared spectroscopic study

Effect of temperature and water content on the structure of 1,2-propanediol (12PD) and 1,3-propanediol (13PD) in the liquid phase has been studied by Fourier-transform near-infrared (FT-NIR) spectroscopy. In addition, the spectra of both diols in CCl₄ solutions at various concentrations were measured. The experimental spectra were analyzed by two-dimensional (2D) correlation approach and chemometric methods. The present results give no evidence that 12PD form the intramolecular hydrogen bonding. In contrast, significant amounts of 13PD molecules in diluted CCl₄ solution is involved in the intramolecular hydrogen bonding. At higher concentrations the intramolecular hydrogen bonds are broken and replaced by the intermolecular ones. The structure of pure liquid propanediols is determined by the intermolecular hydrogen bonding. Unlike for monohydroxyl alcohols, addition of water to propanediols leads to faster temperature-induced breaking of the hydrogen-bonded associates. However, variation of water content at constant temperature does not influence the structure of both diols. In this respect behavior of propanediols is similar to that of the monohydric alcohols. The molecules of water in the mixtures are hydrogen bonded to the diols and act as a double proton donor. This bonding appears to be stronger than that in bulk water.     

Theoretical model for a tetrad of hydrogen bonds and its application to interpretation of infrared spectra of salicylic acid

Theoretical model of vibrational interactions in hydrogen-bonded salicylic acid dimer is presented which takes into account the adiabatic couplings between high- and low-frequency O-H and O...O stretching vibrations, resonance interactions between both intermolecular hydrogen bonds and between inter- and intramolecular hydrogen bonds, and Fermi resonance between the O-H stretching fundamental and the first overtone of the O-H in-plane bending vibrations. The model is used for theoretical simulation of the nu(s) stretching bands of salicylic acid and its OD derivative at 300 K. The effect of deuteration is successfully reproduced by our model. Infrared, far infrared, Raman, and low-frequency Raman spectra of the polycrystalline salicylic acid and its deuterated derivative have been measured. The geometry and experimental frequencies are compared with the results of density-functional theory calculations performed at the B3LYP6-31 ++ G**, B3LYP/cc-pVTZ, B3PW916-31 ++ G**, and B3PW91/cc-pVTZ levels. O-H, O-D, and O...O stretching frequencies are used in theoretical simulation of the nu(s) stretching bands.     

Hydrogen bonds in solid hydroxides, a bond valence approach

The bond valences s_OH due to the O-H bonds of OH⁻ ions in solids have been calculated indirectly from intermolecular H?O distances, viz. those within the Wigner Seitz cell around the respective hydrogen atom, by using the equation s_OH=1−∑s_H?O. The bond valences thus derived are an excellent measure of the strength of O-H bonds [J. Mol. Struct. 351 (1995) 205]. This is shown by their almost linear correlation with the wave numbers of the stretching modes of matrix isolated OD⁻ ions observed with IR or Raman experiments. In the case of very weak or lacking hydrogen bonds, this correlation fails because then other interionic bonding phenomena than hydrogen bonds as metal-oxygen interactions and hydrogen-hydrogen repulsion etc. gain in importance or dominate finally and, hence, partly or fully determine the wave numbers of the OD stretching modes, which, however, still remain a measure of the respective bond strengths. The relation of the distances r_OH, the bond valences s_OH, and the stretching modes ν_OD of both free, gaseous OH⁻ ions and H₂O molecules and those embedded in crystalline matrices is discussed.     

Intramolecular coupling of BrO stretching vibrations in solid bromates, infrared and Raman spectroscopic studies on M(BrO3)2.6H2O (M = Mg, Co, Ni, Zn) and Ni(ClO3)2.6H2O

Infrared and Raman spectra of the isostructural cubic halate hexahydrates M(BrO3)2.6H2O (M = Mg, Co, Ni, Zn) and Ni(ClO3)2.6H2O (space group, Pa3; Z = 4) are presented. They are discussed with respect to the strength of the O-H...OXO2 hydrogen bonds (hydrogen bond acceptor capability, synergetic effect) and the order of the BrO stretching modes. In the case of undistorted bromate ions, e.g. at C3 lattice sites, the order of the symmetric (v1) and asymmetric (v3) XO stretching modes is v1 < v3 as for ClO3- but in contrast to IO3- with v1 > v3. The relative order of v1 and v3 of halate ions is mainly governed by the specific masses of the halogen atoms and the angles of the XO3- ions. The latter decrease in the sequence ClO3- (107degrees) > BrO3-> IO3- (< 100 degrees). The Raman scattering intensities of the asymmetric XO stretching modes v3 of the title compounds are unusually low (< 5% those of v1).     

Coherent low-frequency motions of hydrogen bonded acetic acid dimers in the liquid phase

Ultrafast vibrational dynamics of cyclic hydrogen bonded dimers and the underlying microscopic interactions are studied in temporally and spectrally resolved pump-probe experiments with 100 fs time resolution. Femtosecond excitation of the O-H and/or O-D stretching mode gives rise to pronounced changes of the O-H/O-D stretching absorption displaying both rate-like kinetic and oscillatory components. A lifetime of 200 fs is measured for the v=1 state of the O-H stretching oscillator. The strong oscillatory absorption changes are due to impulsively driven coherent wave packet motions along several low-frequency modes of the dimer between 50 and 170 cm(-1). Such wave packets generated via coherent excitation of the high-frequency O-H/O-D stretching oscillators represent a clear manifestation of the anharmonic coupling of low- and high-frequency modes. The underdamped low-frequency motions dephase on a time scale of 1-2 ps. Calculations of the vibrational potential energy surface based on density functional theory give the frequencies, anharmonic couplings, and microscopic elongations of the low-frequency modes, among them intermolecular hydrogen bond vibrations. Oscillations due to the excitonic coupling between the two O-H or O-D stretching oscillators are absent as is independently confirmed by experiments on mixed dimers with uncoupled O-H and O-D stretching oscillators.     

Structure of water incorporated in sulfobetaine polymer films as studied by ATR-FTIR

The structure and hydrogen bonding of water in the vicinity of a thin film of a sulfobetaine copolymer (poly[(N,N-dimethyl-N-(3-sulfopropyl)-3'-methacrylamidopropanaminium inner salt)-ran-(butyl methacrylate)], poly(SPB-r-BMA)), were analyzed with band shapes of O-H stretching of attenuated total reflection infrared (ATR-IR) spectra. The copolymer could be cast as a thin film, of approximate thickness 10 microm, on a ZnSe crystal for the ATR-IR spectroscopy. At an early stage of sorption of water into the polymer film, the O-H stretching band of the IR spectra for the water incorporated in the film was similar to that for free water. This is consistent with the tendency for another zwitterionic polymeric material, poly[(2-methacryloyloxyethylphosphorylcholine)-ran-(butyl methacrylate)] (poly(MPC-r-BMA). It is, however, contradictory to the drastic change in the O-H stretching band for water incorporated into films of polymers such as poly(2-hydroxyethyl methacrylate), poly(methyl methacrylate) and poly(butyl methacrylate). These results suggest that polymers with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules incorporated in the thin films. The investigation into the blood-compatibility of both the poly(SPB-r-BMA) and the poly(MPC-r-BMA) films indicate a definite correlation between the blood-compatibility of the polymers and the lack of effect of the polymeric materials on the structure of the incorporated water.