Raman and DFT study of static,dynamic interactions and isotope effect in pyridazine + H2O/D2O systems

Polarized Raman and density functional theory (DFT) approach have been applied to study the static and dynamic properties of pyridazine (PRD) in H₂O(W) and D₂O(D) environment. The possible hydrogen bonded (HB) complexes of PRD with H₂O in gas phase and in the water solvation (using IEF-PCM and Onsager models) have been calculated using a B3LYP functional and 6-31+G(d,p)/6-311++G(d,p) basis sets. The static interaction in the PRD + H₂O complex leads to a blue shift in all the Raman modes of PRD and red shift in the O–H modes of water. The IEF-PCM solvation model gives the Raman wavenumbers closest to the experimental values. Raman spectra of ～962 and 1061 cm^?1 mode of PRD in the mixture of PRD + H₂O and PRD + D₂O at different mole fractions of PRD (x) have been measured. A difference in the wavenumber shift of the two modes of PRD is observed experimentally when PRD is diluted with H₂O and D₂O. The wavenumber shift at maximum dilution (x = 0.1), however, takes the same value in both H₂O and D₂O. In view of the similar chemical properties of H₂O and D₂O, the difference in the trend of the wavenumber shift is not trivial. It has been explained on the basis of relative values of dipole moments of H₂O, D₂O, and conjugated molecules of PRD with H₂O/D₂O calculated theoretically and the role of larger diffusive property of H₂O compared to D₂O. The dynamical process in the mixture of PRD+ H₂O/D₂O is discussed by studying the variation of the linewidth with concentration. A theoretical model, which is based on the fact that the concentration in microscopic volume fluctuates, fits the experimental results nicely.     

A Facile Strategy for the Construction of Purely Organic Optical Sensors Capable of Distinguishing D2O from H2O

Owing to the quite similar chemical properties of H₂O and D₂O, rational molecular design of D₂O optical sensors has not been realized so far. Now purely organic chromophores bearing OH groups with appropriate pK_a values are shown to display distinctly different optical responding properties toward D₂O and H₂O owing to the slight difference in acidity between D₂O and H₂O. This discovery is a new and facile strategy for the construction of D₂O optical sensors. Through this strategy, ratiometric colorimetric D₂O sensor of NIM‐2F and colorimetric/fluorescent dual‐channel D₂O sensor of AF were acquired successfully. Both NIM‐2F and AF can not only qualitatively distinguish D₂O from H₂O by the naked eye, but also quantitatively detect the H₂O content in D₂O.     

Intermolecular interaction fluctuations,vibrational coupling and spectral band shapes for liquid water

An analysis of the band shapes for liquid water in the framework of the H-bond fluctuation concept has revealed two temperature-independent functions able of describing IR- and Raman spectra for HOD from −200 to +300°C and also some water thermodynamic characteristics. Account taken of vibrational coupling explains the H₂O and D₂O spectra including the temperature dependence of their profiles.     

外偶极电场作用下H_2O,D_2O和T_2O的可逆分解电压

采用密度泛函B3P86方法和6-311++G(3df,3pf)基组,计算了在-0.05～0.05a.u.外偶极电场作用下,H2O,D2O,T2O,H2,D2,T2,O2的电子能量、核运动能量和熵值,在此基础上通过计算H2O(g)→H2(g)+O2(g)、D2O(g)→D2(g)+O2(g)、T2O(g)→T2(g)+O2(g)的焓变ΔH、熵变ΔS、Gibbs函数变化ΔG,最后得到了H2O,D2O,T2O的可逆分解电压Er.计算结果表明,外偶极电场存在时,H2O,D2O,T2O的Gibbs自由能变ΔG和可逆分解电压Er都有明显的变化,当外偶极电场正方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性增加;当外偶极电场负方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性减小;在相同外偶极电场作用下,Gibbs自由能变ΔG和可逆分解电压Er随H2O,D2O,T2O依次增加.     

Preparation,Crystal Structure,Vibrational Spectra,and Thermal Behavior of Rb2H2P2O6·2H2O

Single crystals of Rb₂H₂P₂O₆ · 2H₂O could be obtained from aqueous solutions of hypodiphosphoric acid and rubidium carbonate. Its crystal structure was determined by X‐ray diffraction and it crystallizes in the monoclinic space group P2₁/c with Z = 4. The salt‐like title compound consists of [H₂P₂O₆]^2– units in staggered P₂O₆‐skeleton conformation, Rb⁺ cations, and H₂O molecules, held together by intermolecular hydrogen bonds of the type O ··· O. The vibrational spectra (IR/FIR and Raman) of the rubidium salt were recorded and an assignment of the vibrational modes is proposed based on the point group C_2h for the P₂O₆‐skeleton of the anion. The thermal behavior of Rb₂H₂P₂O₆ · 2H₂O is dominated by a complex TG decay indicating a simultaneous H₂O delivery coupled with a disproportionation of [H₂P₂O₆]^2–, what is also supported by Raman spectra of heated samples.     

A vibrational-spectroscopic study of the SO2−H2O system

Raman and infrared spectra of gaseous SO₂ and SO₂ dissolved in H₂O and D₂O have been recorded. Although the results are in general agreement with previous work, some new infrared data is presented, as well as results on the effect of phase and solvent change on the infrared and Raman spectra. Previous workers have used the technique of vibrational spectroscopy to investigate the structure of the pyrosulfite ion in solution. The present study indicates that it is difficult to make conclusive statements concerning the structure of this ion on the basis of present and previous work. Solutions containing the sulfite ion have also been studied. Spectral differences between previous studies have been investigated, and an earlier study by Bernstein is essentially substantiated, although the present work does indicate, some discrepancy in the 900–1100-cm^? region for this ion.     

Freezing-point of mixtures of H 2 16 O and H 2 18 O

Freezing-point depression of mixtures of H ₂ ¹⁶ O and H ₂ ¹⁸ O were measured. The results showed that the freezing point of the mixture rose linearly with an increase in the molal concentration of H ₂ ¹⁸ O. The results suggested the formation of a solid solution of H ₂ ¹⁶ O and H ₂ ¹⁸ O by freezing, similar to that formed by H ₂ O–D ₂ O, and that H ₂ ¹⁸ O behaves as a different molecule than H ₂ ¹⁶ O.     

Asymmetry of H2O Molecules in the Liquid State and Its Consequences

The correlations between the geometrical parameters of the O–H...O hydrogen bridge and the stretching frequency _OH are refined by using neutron diffraction and vibrational spectroscopy data. The distribution functions of the interatomic distances r _OH and intermolecular distances R _O...O in water in the range from –40 to 100°C were calculated from the Raman spectra of HOD. The extent of asymmetry of H₂O molecules in the liquid state, caused by fluctuations of the local environment of two OH groups, and its manifestations in the structure and vibrational spectra of water are analyzed.     

Tetracyanonickelate compounds as sorptive materials and the substitution of their H2O content by D2O

The compounds NiNi(CN)₄·3,5H₂O and Ni(NH₃)₂Ni(CN)₄·H₂O have been studied to examine the possibility of substituting their H₂O or NH₃ content by D₂O. Contact with D₂O was performed after heating the compounds to several temperatures. Depending on the degree of decomposition of the original compounds different ranges of substitution were possible. In such manner the compounds NiNi(CN)₄·3,5D₂O, NiNi(CN)₄·5D₂O, Ni(NH₃)₂Ni(CN)₄·D₂O, and Ni(D₂O)₂Ni(CN)₄·D₂O were prepared and thermally they were less stable than the original ones. The substitution by D₂O is in agreement with the sorptive properties of the original tetracyanonickelate against different organic compounds using GC, since these could substitute the guest component and sometimes also the ligands during their decomposition.     

Raman spectra of single H2O molecules isolated in cavities of crystals

The vibrational (Raman) spectra of H₂O molecules isolated in cavities of beryl, cordierite, bikitaite, natrolite, scolecite, lawsonite, and hemimorphite have been measured in the temperature range of 4–295 K. The influence of van der Waals and hydrogen bonds on the values of frequency, intensity, and half-width of stretching and bending modes of H₂O is considered. The spectra of translational vibrations of H₂O molecules in crystal cavities are discussed. For the firsts time, the ratio between the frequencies of translation and stretching vibrations of H₂O and the dependence of frequencies of bending vibrations on the angle H-O-H in H₂O molecule are presented.     

Derivative analysis of Raman spectra of liquid water in the OH (D) stretching region

Second derivative analysis of Raman spectra of H₂O, D₂O and HOD in liquid phase at room temperature for parallel and perpendicular polarized modes in the OH and OD stretching regions is reported. Five components obtained at approximately 3215, 3375, 3455, 3535 and 3640 cm⁻¹ for the second derivative plots of Raman spectra of liquid water are explained as due to the presence of three types of associated water species with (i) both OH bonds involved in moderately strong hydrogen bonds (SS), (ii) both OH bonds involved in weak hydrogen bonds (WW), and (iii) one OH bond involved in strong and one in weak hydrogen bonds (SW) respectively. The derivative plots obtained for Raman spectra of D₂O and HOD also contain features expected to be present on the basis of this model.     

Effect of methylation on wavenumber shift of ring breathing mode of pyrimidine in the solution of H2O and D2O by employing Raman difference spectroscopic technique and DFT approach

The relative structural and dynamic properties of hydrogen-bonding between Pyrimidine (Pmd) + H₂O and Pmd + D₂O, and 4-Methylpyrimidine (Mpmd) + H₂O and Mpmd + D₂O are investigated experimentally by linear Raman spectroscopy using Raman difference spectroscopic (RDS) technique. The focus has been given to the ring breathing mode (ν₁). The effect of methylation on the Pmd ring has been studied in terms of wavenumber shift (Δν), peak-position and linewidth variation with mole fraction of the solvent. The wavenumber shift has been calculated by assuming the Voigt profile of the Raman band. In order to explain our experimental results, we have optimized single Pmd and 4Mpmd molecules and their various complexes with H₂O and D₂O in the stoichiometric ratio of 1:1, 1:2, 1:3 and 1:4 by employing DFT/B3LYP functional with 6-311+G(d,p) basis set using Gaussian software. There is a good correspondence between experimental and theoretical results. Our result reveals that with RDS technique, Δν of a band up to 1/100th of the FWHM can be measured precisely.     

Effects of temperature and pressure on the near-infrared spectra of HOD in D2O

The near-infrared absorption spectra (9500 to 11000 cm^–1) of HOD, 20 mol% in D₂O were measured at temperatures between 4 and 55°C and pressures up to 500 MPa. From the analysis of the spectra, the following conclusions are drawn. (1) At temperatures below about 38°C, the ice I-like bulky structure is destroyed to form the dense structure which reflects the high-pressure ice-like structure as the pressure is increased. (2) At temperatures above about 38°C, the bulky structure hardly remains at atmospheric pressure and the formation of dense structure proceeds monotonically with increasing pressure. The results and conclusion obtained in the present paper agrees with those obtained for pure H₂O water in the previous investigation.     

Vibrational frequencies of (H2O) n and (D2O) n clusters for n = 2 and 8: possible relevance to inelastic neutron scattering of ice

Hartree-Fock plus MP2 corrections are reported for the vibrational frequencies in (H₂O)₂ and (D₂O)₂ and in the cubic octamers (H₂O)₈ and (D₂O)₈. The motivation was the inelastic incoherent neutron scattering of ice as studied experimentally by Li et al. (J.-C. Li, D. Londono, D.K. Ross, J.L. Finney, S.M. Bennington and A.D. Taylor (1992). J. Phys. Cond. Matter, 4, 2109). Some contact is made between our results and these experiments, and also with earlier infrared and Raman studies of Bertie and coworkers.     

Atmospheric pressure chemical ionization and fragmentation of aminomonosaccharides in H2O and D2O

Aminomonosaccharides (glucosamine, galactosamine, and mannosamine) in H₂O and D₂O were ionized by atmospheric pressure chemical ionization (APCI) and their fragmentation patterns were investigated to identify them. All the aminomonosaccharides showed the same fragment ions but their relative ion intensities were different. Major product ions generated in H₂O were [M + H]⁺, [M + H – H₂O]⁺, and [2M + H – 3H₂O]⁺, while in D₂O were [M_D6 + D]⁺, [M_D6 + D – D₂O]⁺, and [2M_D6 + D – D₂O – 2HDO]⁺. At a high fragmentor voltage above 120 V, the relative ion intensities of the major product ions showed different trends according to the aminomonosaccharides. For the use of H₂O as solvent and eluent, the order of the ion intensity ratio of [M + H – H₂O]⁺/[2M + H – 3H₂O]⁺ was galactosamine > mannosamine > glucosamine. When using D₂O as solvent and eluent, the order of the ion intensity ratios of [M_D6 + D – D₂O]⁺/[M_D6 + D]⁺ and [2M_D6 + D – D₂O – 2HDO]⁺/[M_D6 + D]⁺ was mannosamine > galactosamine > glucosamine. It was found that glucosamine, galactosamine, and mannosamine could be distinguished by the specific trends of the major product ion ratios in H₂O and D₂O. Copyright © 2009 John Wiley & Sons, Ltd.     

On the Search for H5O2+centered Water Clusters in the Gas Phase

In searching for H₅O₂⁺-centered water clusters, we employed vibrational predissociation spectroscopy and ab initio calculations. Structures of the clusters were characterized by the free- and hydrogen-bonded-OH stretches of ion cores and solvent molecules. Systematic examination of H⁺(H₂O)_5–7 in a supersonic expansion reveals the presence of both cyclic and noncyclic forms of H₅O₂⁺-centered water clusters. The proton transfer intermediate H₅O₂⁺(H₂O)₄ was identified, for the first time, by its characteristic hydrogen-bonded-OH stretches of the ion core at 3178 cm^?1. Also discovered at n = 7 is the H₅O₂⁺-containing five-membered ring isomer, whose existence is evidenced by the observation of a bonded-OH stretching doublet at 3544 and 3555 cm^?1 of the solvent molecules. The observations are in accord with ab initio calculations which forecast that H₅O₂⁺(H₂O)₄ and H₅O₂⁺(H₂O)₅ are, respectively, the lowest-energy isomers of protonated water hexamers and heptamers.     

Peroxide Coordination of Tellurium in Aqueous Solutions

Tellurium–peroxo complexes in aqueous solutions have never been reported. In this work, ammonium peroxotellurates (NH₄)₄Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂ ( 1 ) and (NH₄)₅Te₂(μ‐OO)₂(μ‐O)O₅(OH)?1.28 H₂O?0.72 H₂O₂ ( 2 ) were isolated from 5 % hydrogen peroxide aqueous solutions of ammonium tellurate and characterized by single‐crystal and powder X‐ray diffraction analysis, by Raman spectroscopy and thermal analysis. The crystal structure of 1 comprises ammonium cations and a symmetric binuclear peroxotellurate anion [Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂]^4?. The structure of 2 consists of an unsymmetrical [Te₂(μ‐OO)₂(μ‐O)O₅(OH)]^5? anion, ammonium cations, hydrogen peroxide, and water. Peroxotellurate anions in both 1 and 2 contain a binuclear Te₂(μ‐OO)₂(μ‐O) fragment with one μ‐oxo‐ and two μ‐peroxo bridging groups. ¹²⁵Te NMR spectroscopic analysis shows that the peroxo bridged bitellurate anions are the dominant species in solution, with 3–40 %wt H₂O₂ and for pH values above 9. DFT calculations of the peroxotellurate anion confirm its higher thermodynamic stability compared with those of the oxotellurate analogues. This is the first direct evidence for tellurium–peroxide coordination in any aqueous system and the first report of inorganic tellurium–peroxo complexes. General features common to all reported p‐block element peroxides could be discerned by the characterization of aqueous and crystalline peroxotellurates.     

H 2 O-D2O Solvent Isotope Effect on Excess Molar Volumes of 3-Methylpyridine Solutions

Densities of 3-methylpyridine (3-MP) + water and 3-methylpyridine + heavy water were measured in the 3-MP mole fraction range 0.002–0.04 from 298 to 318 K. The excess molar volumes of 3-MP + D₂O mixtures were found to be more negative than those of 3-MP + H₂O mixtures. The partial molar volume of 3-MP at infinite dilution is smaller in D₂O than in H₂O which suggests that 3-MP causes a structure-breaking effect in water which is more pronounced in D₂O. It was found that the volume change with concentration in dilute solutions of 3-MP in water and heavy water can be adequately described by the pair-wise interaction of the solute molecules. The molal volume second-virial coefficient, V _xx , is positive indicating that the water molecules are less structured in the cospheres of the solute pairs than in the bulk solvent. The temperature dependence of V _xx displays a maximum at around 308 K in the case of D₂O solutions, whereas V _xx increases almost linearly with temperature in H₂O solutions.     

Ab initio valence-bond calculations of H2O

The first and second bond dissociation energies for H₂O have been calculated in anab initio manner using a multistructure valence-bond scheme. The basis set consisted of a minimal number of non-orthogonal atomic orbitals expressed in terms of gaussian-lobe functions. The valence-bond structures considered properly described the change in the molecular system as the hydrogen atoms were individually removed to infinity. The calculated equilibrium geometry for the H₂O molecule has an O-H bond length of 1.83 Bohrs and an HOH bond angle of 106.5°. With 49 valence-bond structures the energy of H₂O at this geometry was ?76.0202 Hartrees. The calculated equilibrium bond length for the OH radical was 1.86 Bohrs and the energy, using the same basis set, was ?75.3875 Hartrees. After correction for zero point energies the calculated bond dissociation energies are: H₂O → OH + H, D₁=75.38 kcal/mole and OH → O+H, D₂=54.79 kcal/mole.     

Vibrational analysis of chlorinated methylphosphonic acids: Part 2. Vibrational analysis of CHCl2PO3H2 and its anions

The vibrational spectra (IR and Raman) of CHCl₂PO₃H₂ and its anions in H₂O and D₂O solutions are reported. The IR spectra of the solid dibasic sodium and potassium salts, the solid normal and O-deuterated monobasic sodium and potassium salt and the solid normal and O-deuterated acid are discussed. The principal results of the normal coordinate analysis of the compounds are tabulated.