Relative strength of hydrogen bond interaction in alcohol–water complexes

Hydrogen binding energies are calculated for the different isomers of 1:1 complexes of methanol, ethanol and water using ab initio methods from MP2 to CCSD(T). Zero-point energy vibration and counterpoise corrections are considered and electron correlation effects are analyzed. In methanol–water and ethanol–water the most stable heterodimer is the one where the water plays the role of proton donor. In methanol–ethanol the two isomers have essentially the same energy and no favorite heterodimer could be discerned. The interplay between the relative binding energy is briefly discussed in conjunction with the incomplete mixing of alcohol–water systems.     

Pressure induced changes in the Raman spectra of liquidn-alkanes and perfluoro-n-alkanes

The main effect of pressures up to 6 kbar on the Raman spectra of liquidn-alkanes and perfluoro-n-alkanes is a reduction of line widths indicative for a slowing-down of rotational motions about the long axes. There is no evidence for a change in the conformer populations.Dedicated to Prof. Dr. F. H. Müller at the end of his editorship of Colloid & Polymer Science.     

Polarized IR spectra of the hydrogen bond in acetic acid crystals

The paper presents the results of our investigations of the polarized IR spectra of the hydrogen bond in crystals of acetic acid, CH₃COOH, as well as in crystals of three deuterium isotopomers of the compound: CH₃COOD, CD₃COOH and CD₃COOD. The spectra were measured at 283 K and at 77 K by a transmission method using polarized light. Theoretical analysis of the results concerned the linear dichroic effects, together with the H/D isotopic and temperature effects observed in the solid-state IR spectra of the hydrogen and of the deuterium bond at the frequency ranges of the ν_O–H and the ν_O–D bands, respectively. Basic spectral properties of the crystals can be interpreted satisfactorily in terms of one of the quantitative theories of the IR spectra of the hydrogen bond, i.e. the “strong-coupling” theory or the “relaxation” theory when a hydrogen bond dimer model is used. From the spectra obtained it resulted that the strongest exciton coupling involved the closely spaced hydrogen bonds, belonging to different chains of associated acetic acid molecules. These results contradict the former explanation of the spectra within a model, which assumed a strong vibrational exciton coupling between four hydrogen bonds in a unit cell. On analyzing the spectra of isotopically diluted crystalline samples of acetic acid it has been proved that a non-random distribution of the protons and deuterons takes place in the hydrogen bond lattices. This non-conventional isotopic effect is a result of dynamical co-operative interactions involving hydrogen bonds in the system. Simultaneously it has been also found that in an individual hydrogen bonded chain in the crystals, distribution of the hydrogen isotope atoms H and D was fully random. The H/D isotopic “self-organization” mechanism most probably involves a pair of hydrogen bonds from each unit cell where each hydrogen bond belongs to a different chain.     

Stretching frequency distribution and hydrogen bond thermodynamics in water as calculated from ir spectra using the fluctuation model

This paper analyzes recent data on statistical distribution of OH vibration frequencies of liquid water calculated from the IR spectra of HOD molecules. The data are analyzed in terms of the hydrogen bond fluctuation concept. Two temperature invariant functions providing a reconstruction of the whole set of initial data and the statistical integral permitting one to calculate the configuration contributions to the internal energy, entropy, and heat capacity of liquid water over a wide temperature range are found and approximated analytically. The calculated heat capacity is in good agreement with thermophysical experimental data. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 3, pp. 532-539, May–June, 2000.     

Theory of the infrared spectra of the hydrogen bond in molecular crystals

A general model for the vibrational interactions of the hydrogen bonds in molecular crystals is presented. The energy and the intensity distributions of the IR spectra of the 1-methylthymine and uracil crystals are correctly reproduced.     

Effect of hydrogen bridge geometry on the vibrational spectra of water: Three-parameter potential of H bond

The ability of water molecules to form a three-dimensional network of hydrogen bonds basically determines both the intrinsic structure and unique properties of this liquid and also a character of interactions with other molecules. However, the dependence of the H bond energy on the geometry of its hydrogen bridge, namely on the R_O…_O length and non-linearity, is unknown, i.e. the deviations of O—H group directions and the lone pair forming this bond from optimum ones (angles (φ = H—_O…_O and χ = —_O…_O correspondingly). Even in computer simulation methods, the contribution of H bonds to the total interaction potential is not separated; that does not allow one to define unequivocally these bonds in a model and to analyze quantitatively the features of their networks. The purpose of this work is to fill in this gap by expressing the energy E through geometric parameters (R, φ, χ). The obtained solution quality is proved by an agreement between the distributions of OH vibrational frequencies (which are very sensitive to the H bond strength) calculated with its help and the shape of experimental spectra in a wide temperature range. Based on this, the distributions of H bond energies P(E, T) and of their bend angles P(φ, T) and P(χ, T) are also calculated. It is shown that the main contribution to spectra is made by the shortest bonds with their lengths close to a minimum of the potential E(R). Thus, the low-frequency slope of a band corresponds to slightly bent H bonds, while the central part relates to also short but sufficiently nonlinear H bonds. LongH bonds are responsible for only well known high-frequency Walrafens’s wing near 3620 cm^-1. Moreover, these weak bonds are very strongly bent.     

Infrared spectra of hydrogen bond a general theoretical model

For the IR spectra of the hydrogen bond a general theoretical model is presented which puts on equal footing the Fermi resonance and the coupling between the high and low frequency modes. The fundamental hamiltonian is derived and its spectral consequences studied in detail. The theoretical IR spectra of the hydrogen bond are obtained and the relative roles of both mechanisms are quantitatively studied and discussed.     

Potential of hydrogen bond in water. Comparison of the theory with vibrational spectra and results of molecular dynamics simulations

Potential of hydrogen bond is the function which relates its energy to geometrical parameters of hydrogen bridge: its length R(O…O) and angles between direction O…O and OH group [φ (H-O…O)] and/or lone pair of proton accepting oxygen atom [χ(-O…O)]. Previously we have suggested an approach to design such potentials based on the approximate numerical solution of a reverse problem of the spectrum band shape in the frames of the fluctuation theory of hydrogen bonding. In the given work this method is applied to construction of the two-parameter potentials that depend on parameters {R(O…O), φ (H-O…O} or {φ (H-O…O), χ (-O…O)}. Using them, the spectra of OH vibrations of HOD molecules in a liquid phase are calculated theoretically in good agreement with experiment in the temperature range up to 200 °C. Distributions of angles P(φ, T), P(χ, T), and energies P(E) are calculated also. The same distributions and spectra are independently calculated on the basis of the geometrical parameters of the hydrogen bridges obtained from molecular dynamics models of water. The shapes of the spectral contours and their temperature evolution calculated for computer models turned out to be similar to experimental ones only for the potential that includes the length of H-bond R(O…O).     

Relevance of hydrogen bond definitions in liquid water

To evaluate the relevance of treating the hydrogen bonds in liquid water as a digital (discrete) network and applying topological analyses, a framework to optimize the fitting parameters in various hydrogen bond definitions of liquid water is proposed. Performance of the definitions is quantitatively evaluated according to the reproducibility of hydrogen bonding in the inherent structure. Parameters of five popular hydrogen bond definitions are optimized, for example. The optimal choice of parameters for the hydrogen bond definitions accentuates the binary nature of the hydrogen bonding and the intrinsic network topology of liquid water, especially at the low temperature region. The framework provides a solid basis for network analyses, which have been utilized for water, and is also useful for designing new hydrogen bond definitions.     

水分子与聚苯胺间氢键的形成对电子性质的影响

用量子化学SCF-LCAO-MO AM1方法, 对于水分子与聚苯胺(PAn)间氢键体系进行了结构优化, 从理论上系统地研究了聚苯胺分子链不同位置形成氢键的可能性以及成键方式。运用晶体轨道EHMACC方法, 对具有不同氢键结构的PAn体系进行了能带结构计算, 揭示了水分子存在和氢键的形成对PAn掺杂导电性能的贡献。氢键形成后, 能带结构变化表明有利于导电能力的提高。     

液态水氢键的分析方法及研究进展

氢键已经发现了100多年,迄今为止它仍然是科学研究的重要课题。氢键的研究涉及从无机到有机众多学科,例如材料科学、生物化学、分子医学等。液态水是一种重要的化学溶剂,它很多特殊的性质都源于水分子间形成的氢键体系。特别是最近几年,水体系间氢键的研究取得了巨大的进步,关于氢键本质的新认识不断被提出。本文以水为例,重点介绍水体系中氢键的分析方法及研究进展,以期对氢键的研究有一个整体的认识。     

A short hydrogen bond investigation by polarized Raman spectra of Co2+ and Zn2+ salts of pyromellitic acid

Cobalt and zinc salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C(6)H(2)(COO)(4)H(4)], have been synthesized and investigate by polarized Raman spectroscopy. These compounds present short intramolecular hydrogen bonds (SHB) between adjacent carboxyl groups. Raman spectra indicate the presence of this interaction in both salts. Three specific vibrational of SHB modes have been investigated: O-H-O symmetric [nu(sym)(OHO)] and asymmetric [nu(asym)(OHO)] stretching modes and O-H stretching mode [nu(O-H)], which they were observed around 300, 850 and 2500 cm(-1), respectively. In crystallographic point of view, the cobalt salt presents a symmetric SHB while the zinc salt presents an asymmetric SHB. In cobalt salt all three vibrational modes of O-H-O groups in polarized Raman spectra occur in A(g) orientation although in zinc salts two of them are observed in A(g) orientation and one in B(g). Spectra analysis indicate that nu(sym)(OHO) mode is observed as A(g) to cobalt salt and B(g) to zinc salt. This mode occurs in a crowded spectral region and its identification was made by deconvolution techniques. Comparing spectra of the two salts, it is observed a small difference in relative intensity and wavenumber shift of nu(sym)(OHO) (deviance of 43 cm(-1)) and nu(OH) (deviance of 21 cm(-1)) modes due probably to differences in O...O distance between salts and in orientation of pyromellitate anion in unit cell. The nu(asym)(OHO) mode does not present significant wavenumber shift due difference in SHB. The nu(OH) band presents a great potential for hydrogen bond studies due to the fact that in its vibrational region (around 2500 cm(-1)) it is not observed other vibrational modes of these compounds.     

Spectral characterization of hydrogen bond network dynamics in water

Some computational aspects of the characterization of the complex hydrogen bond network dynamics using power spectral analysis are discussed. In the case of hydrogen-bonded liquids, the tagged molecule potential energy is shown to be a useful quantity for capturing the behavior of the networked liquid on different lengths and time scales. The computation of the tagged potential energy for rigid-body effective pair potentials, such as the TIP5P-E and SPC-E models, is discussed. The more structured nature of the TIP5P-E potential, compared to the SPC/E potential, shows up as differences in the high-frequency librational band of the power spectra of the tagged molecule potential energies. The static distributions of the tagged molecule potential energies are also more structured in the case of TIP5P-E, rather than SPC/E, water. The overall behavior of the key power spectral features remains the same in both the models. The possibility of detailed characterization of the power spectrum, and therefore of the underlying dynamics, using a model-based parametric fitting procedure for the power spectra is also discussed. We show that a parametric fitting can allow one to test alternative models of the dynamics underlying the liquid state dynamics.     

Topological building blocks of hydrogen bond network in water

Basic three-dimensional units of the network, called fragments, are introduced to characterize the hydrogen bond (HB) network structure of water. Topological differences among normal liquid water, water at low temperature, and water under high pressure are elucidated by their fragment statistics. Water at low temperature has almost defect-free network and is filled with stable fragments with small distortion. It is found that there exists a certain way on how fragments mutually aggregate. Well-formed aggregates heterogeneously constitute very stable network structures. HB network rearrangements occur scarcely inside these aggregated domains but take place in their surface areas. The heterogeneity of HB structure and rearrangement in water is thus explained in terms of the fragment structure and its rearrangements. The fragment analysis thus elucidates the intermediate-range order in water HB network.     

Effects of dynamical couplings in IR spectra of the hydrogen bond in N-phenylacrylamide crystals

This article presents the investigation results of the polarized IR spectra of the hydrogen bond in N-phenylacrylamide crystals measured in the frequency range of the proton and deuteron, ν(N-H) and ν(N-D), stretching vibration bands. The basic spectral properties of the crystals were interpreted quantitatively in terms of the "strong-coupling" theory. The proposed model of the centrosymmetric dimer of hydrogen bonds facilitated the explanation of the well-developed, two-branch structure of the ν(N-H) and ν(N-D) bands as well as the isotopic dilution effects in the spectra. The vibronic mechanism of the generation of the long-wave branch of the ν(N-H) band ascribed to the excitation of the totally symmetric proton vibration was elucidated. The complex fine structure pattern of ν(N-H) and ν(N-D) bands in N-phenylacrylamide spectra in comparison with the spectra of other secondary amide crystals (e.g., N-methylacetamide and acetanilide) can be accounted for in terms of the vibronic model for the forbidden transition breaking in the dimers. On the basis of the linear dichroic and temperature effects in the polarized IR spectra of N-phenylacrylamide crystals, the H/D isotopic "self-organization" effects were revealed.     

Raman spectra of bis(2-ethylhexyl) hydrogen phosphorodithioate

Conclusions The Raman spectra of bis(2-ethylhexyl) hydrogen phosphorodithioate were studied. The frequencies of the principal vibrations of the acid phosphorodithioate were assigned.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1267–1271, June, 1976.The authors thank coworkers of the extraction laboratory for the samples and I. K. Korobeinicheva for making it possible to record the spectra on the PH-1 instrument.