Vibrational spectra of Na, K, Mn2+, Ni2+ and Zn2+ salts of 1,2,4,5-benzenetetracarboxylic (pyromellitic) acid--a short hydrogen bond evidence

Five salts of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), [C6H2(COO)4H4], have been synthesized and investigated by infrared and Raman spectroscopy and by single crystal X-ray diffraction methods: sodium salt [Na2(H2O)2][C6H2(COO)4H2], potassium salt [K(H2O)3][C6H2(COO)4H3] and transition metal salts [M(H2O)6][C6H2(COO)4H2], which M = Mn, Ni and Zn. Crystal structures of all five compounds show short intramolecular asymmetric hydrogen bonds (SHB) between adjacent carboxyl groups with O...O distance average of 2.40 A. The Raman and infrared spectra reported indicate the presence of short hydrogen bonds in all salts, in agreement with the X-ray data. The O-H stretching mode [nu(OH)] had been observed at about 2500 cm(-1). Deuterated analogues were synthesized and their Raman spectra show that nu(OH)/nu(OD) ratio average is about unit. The symmetric [nu(sym)(O..H..O)] and asymmetric [nu(asym)(O..H..O)] stretching modes have been attributed about 300 and 870 cm(-1), respectively, in all salts, and for deuterated analogues, the ratio nu(OH)/nu(OD) to nu(sym)(O..H..O, O..D..O) is close to unit like it occurs in nu(OH). The vibrational modes, mainly SHB modes, are tentatively assigned by molecular orbital ab initio calculations of pyromellitic acid and anions [C6H2(COO)4H3]- and [C6H2(COO)4H2]2-. Geometry optimizations showed a good agreement with experimental data. Frequency calculation confirms the assignment of specific vibrational modes. Ab initio calculations show that nu(C=O) and nu(sym)(COO) are strongly coupled with in plane OH bending [delta(OH)]. In Raman spectra of deuterated analogues is observed a frequency shift of these bands.     

Infrared and Raman spectra of pyromellitic dithioanhydride

The i.r. spectrum of pyromellitic dithioanhydride has been measured from 4000 to 200 cm⁻¹; polarized i.r. spectra of single crystals have been also obtained. The Raman spectra of polycrystalline samples and solutions have been recorded and polarization of many lines has been determined. A detailed assignment of most of the fundamentals has been proposed on the basis of i.r. dichroism of the single crystals, Raman spectra and analogies with the spectra of related molecules.     

The infrared and Raman spectra of pyromellitic dianhydride

The infrared and Raman spectra of solid state samples of pyromellitic dianhydride have been measured. The infrared—Raman mutual exclusion rule has been observed and the frequencies have been tentatively assigned on the basis of D_2h symmetry. The values of the CO and skeletal ring stretching frequencies have been interpreted in terms of a conjugated π-system.     

Study of polarized IR spectra of the hydrogen bond system in crystals of styrylacetic acid

We have investigated the polarized IR spectra of the hydrogen bond system in crystals of trans-styrylacetic acid C(6)H(5)CHCHCH(2)COOH, and also in crystals of the following three deuterium isotopomers of the compound: C(6)H(5)CHCHCH(2)COOD, C(6)H(5)CHCHCD(2)COOH and C(6)H(5)CHCHCD(2)COOD. The spectra were measured at room temperature and at 77K by a transmission method. The spectral studies were preceded by determination of the X-ray crystal structure. Theoretical analysis of the results concerned linear dichroic effects, 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 nu(OH) and the nu(OD) bands, respectively. Basic spectral properties of the crystals can be interpreted satisfactorily in terms of the "strong-coupling" theory, when based on a hydrogen bond dimer model. This model sufficiently explained not only a two-branch structure of the nu(OH) and the nu(OD) bands, and temperature-induced evolution of the crystalline spectra, but also the linear dichroic effects observed in the band frequency ranges. A vibronic mechanism was analyzed, responsible for promotion of the symmetry-forbidden transition in the IR for the totally symmetric proton stretching vibrations in centrosymmetric hydrogen bond dimers. It was found to be of minor importance, when compared with analogous spectral properties of arylcarboxylic acid, or of cinnamic acid crystals. These effects were ascribed to a substantial weakening of electronic couplings between the hydrogen bonds of the associated carboxyl groups and the styryl radicals, associated with the separation of these groups in styrylacetic acid molecules by methylene groups in the molecules.     

Raman and polarized infrared spectra of pyridine-2-thione

Polarized i.r. spectra of oriented polycrystals and the i.r. and Raman spectra of polycrystalline samples of pyridine-2-thione have been obtained. The Raman spectra of a solution of pyridine-2-thione has also been measured and the polarization of many lines determined. The i.r. spectra of S-methyl and N-deuterated compounds have also been investigated. A complete assignment of all the observed peaks has been possible. The results are correlated with the assignments available for related systems.     

Theoretical study of the polarized infrared spectra of the hydrogen bond in 2‐furoic acid crystal dimer

This work presents a theoretical simulation of ν_{O? H} and ν_{O? D} band shapes in the polarized infrared spectra of 2‐furoic acid dimer crystals measured at liquid‐nitrogen temperature. The line shapes are studied theoretically within the framework of the anharmonic couplings between low‐frequency hydrogen‐bond vibrations and degenerate excited states of high‐frequency hydrogen vibrations in hydrogen‐bonded dimers and the anharmonic coupling between the first excited state of the fast mode and the harmonics or band combinations of some low‐frequency bending modes, which lead to Fermi resonances.This approach takes into account the adiabatic approximation, the intrinsic anharmonicity of the low‐frequency mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, and the direct and indirect damping of the fast‐stretching modes of the hydrogen bonds and of the bending modes. The infrared spectral density was calculated within the linear response theory by Fourier transform of the autocorrelation function of the transition dipole moment operator of the fast mode. Numerical results show that mixing of all these effects allows satisfactory reproduction of the main features of the experimental IR line shapes of crystalline H‐ and D‐bonded 2‐furoic acid at liquid‐nitrogen temperature and for different polarizations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Strong vibrational exciton coupling effects in polarized IR spectra of the hydrogen bond in 2-thiopyridone crystals

This paper presents the results of investigation on polarized IR spectra of the hydrogen bond in 2-thiopyridone crystals. The spectra were measured in the frequency range of the NH and ND bond stretching vibrations, for two different crystalline forms, having developed ab or bc crystal faces. The spectra exhibited extremely strong vibrational exciton coupling effects characterized by a large Davydov-splitting (correlation field splitting), whose existence was confirmed by a strong difference between the polarized spectra of the two forms of 2-thiopyridone crystals. It was shown that extremely strong exciton interactions involving the translationally non-equivalent hydrogen bonds in the unit cell are responsible for these effects. Isotopic dilution in the crystals caused the disappearance of the spectral effects, ascribed to the inter-dimer exciton couplings, and the simultaneous retaining of the dimeric character of the “residual” ν_NH and ν_ND bands. This spectral behavior of the isotopically diluted crystals was interpreted as the result of the dynamical co-operative interactions involving the hydrogen bonds in the lattice. These interactions lead to a non-random distribution of the protons and deuterons in the cyclic hydrogen bond dimeric systems and in consequence to the so-called H/D isotopic “self-organization” effects in the crystal spectra. The fine structure of the “residual” ν_NH and ν_ND bands is also influenced by such non-conventional spectral effects as the selection rule breaking for IR transitions, as well as the “reversal” exciton coupling effect for centrosymmetric hydrogen bonded dimers. This statement is supported by model calculations of the analyzed band shapes. They are performed in terms of the “strong-coupling” theory which assumes a strong anharmonic coupling involving different frequency hydrogen bond normal vibrations in the dimers, namely the high-frequency NH stretching and the low-frequency ν_N⋯S hydrogen bond stretching vibrations.     

Influence of molecular electronic properties on the IR spectra of dimeric hydrogen bond systems: polarized spectra of 2-hydroxybenzothiazole and 2-mercaptobenzothiazole crystals

We have studied the polarized IR spectra of the hydrogen-bonded molecular crystals of 2-hydroxybenzothiazole (HBT) and 2-mercaptobenzothiazole (MBT). The crystal structure of 2-hydroxybenzothiazole was determined by X-ray diffraction. The polarized spectra of the crystals were measured, in the frequency ranges of the ν_N-H and ν_N-D bands, at room temperature, and at 77 K. In both systems an extremely strong H/D isotopic effect in the spectra was observed, involving reduction of the well-developed ν_N-H band fine structure to a single prominent ν_N-D line only. The two ν_N-H bands were also shown to exhibit almost identical properties, band shapes, temperature and dichroic properties included. The spectra were quantitatively reconstituted, along with the strong isotopic effect, when calculated using the ‘strong-coupling’ theory, assuming the centrosymmetric dimers of HBT or MBT to be the structural units responsible for the crystalline spectral properties. The similarity of the spectra of the two crystalline systems was considered to be a result of longer-distance couplings between the proton vibrations in the dimers, via the aromatic ring electrons. When investigating the ‘residual’ ν_N-H band shapes for crystals isotopically diluted by deuterium, we observed some ‘self-organization’ effects in the spectra, indicating the energetically favored presence of two identical hydrogen isotopes in each hydrogen bond dimer.     

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.     

Experimental and theoretical study of the polarized infrared spectra of the hydrogen bond in 3‐thiophenic acid crystal

This article presents the results of experimental and theoretical studies of the v_{O H} and v_{O D} band shapes in the polarized infrared spectra of 3‐thiophenic acid crystals measured at room temperature and at 77 K. The line shapes are studied theoretically within the framework of the anharmonic coupling theory, Davydov coupling, Fermi resonance, direct and indirect damping, as well as the selection rule breaking mechanism for forbidden transitions. The adiabatic approximation allowing to separate the high‐frequency motion from the slow one of the H‐bond bridge is performed for each separate H‐bond bridge of the dimer and a strong nonadiabatic correction is introduced via the resonant exchange between the fast‐mode excited states of the two moieties. The spectral density is obtained within the linear response theory by Fourier transform of the damped autocorrelation functions. The approach correctly fits the experimental line shape of the hydrogenated compound and predicts satisfactorily the evolution in the line shapes with temperature and the change in the line shape with isotopic substitution. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Infrared and resonance enhanced Raman spectra of some metal vic-dioximes with short hydrogen bonds

Infrared and enhanced Raman spectra were recorded of bis(2,3-butanonedioximato-N,N′) nickel (II) and palladium (NiDMG, PdDMG) as well as the i.r. spectra of bis(ethanedialdioximato-N,N′) nickel (II) (NiHG), bis(2,3-pentanonedioximato-N,N′) nickel (II) (NiEMG), and of bis(2,3-butanonedioximato-N,N′) copper (II) (CuDMG). The mutual exclusion of i.r. and Raman active modes of NiDMG and PdDMG prove the existence of an inversion centre whereas the coupling of the in-plane OH deformation with two skeletal modes of CN stretching character indicates that the molecular symmetry is likely to be C_2h only. The B _u OHO stretching mode has been identified in the nickel complexes with a strong, broad band near 900 cm⁻¹. The resonance Raman enhancement is observed mainly with skeletal vibrations of CN character and, less, with those having NO character. The effects of high pressure upon i.r. spectra were observed. The possible symmetry of the hydrogen bond is discussed.     

The infrared and Raman spectra of guanidinium salts

The i.r. and Raman spectra of guanidinium chloride, guanidinium perchlorate, and the deuterated derivatives of these salts, have been determined as solids and in solutions.     

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.     

IR and polarized Raman spectra of strontium tartrate trihydrate

The IR and polarized Raman spectra of SrC₄H₄O₆ · 3H₂O have been recorded and analysed. The factor group analysis of the divalent tartrate ion has been carried out on the basis of C₂ symmetry. As the ion possesses lower symmetry in the crystal, splittings have been observed for the different vibrational modes. Separate bands in the bending region of water suggest the existence of three crystallographically different water molecules in the crystal, which is confirmed by deuterium substitution.     

Infrared and Raman spectra of cytosine and cytidinium salts

Studies of the infrared and Raman spectra of cytidinium salts are presented. They are supplemented by the measurements of the infrared spectra of the c     

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.     

Adsorption of Co2+ and Zn2+ on cryptomelane-type hydrous managese dioxide

Co²⁺ and Zn²⁺ ions are adsorbed on cryptomelane-type MnO₂ by exchange with surface protons and with structural ions (probably K⁺ and/or Mn²⁺) in the oxide. The latter sites are responsible for the much higher capacity to these cations, compared to Na⁺. At all pH values, two straight lines expressing the presence of mainly two groups of sites with distinctly different adsorption energies are located in the Langmuir plots for both Co²⁺ and Zn²⁺. The apparent capacities of the two groups increase with the increase of pH, indicating the involvement of protons in the adsorption process over the whole concentration range. The higher Co²⁺ capacity at relatively low pH, compared to the Zn²⁺ capacity, is probably due to a more exchange with the structural ions. Crytomelane type MnO₂ seems to be a quite heterogenous ion adsorbent whose adsorption sites could be approximated to two groups only.     

The polarized infrared and Raman spectra of crystalline ammonium trifluoromethanesulphonate

The infrared and Raman spectra of NH₄CF₃SO₃ were obtained and analysed and an assignment was proposed for the observed bands. The assignment of some anion bands was supported by means of the polarized spectra of monocrystals. The fundamental frequencies of the anion were used for a normal coordinate calculation.     

Pressure response of Raman spectra of water and its implication to the change in hydrogen bond interaction

In situ Raman spectroscopic measurements of water in the region of OH vibration were conducted up to 0.4 GPa at 23 and 52 degrees C. The frequencies of the decomposed OH stretching bands initially decreased with increasing pressure, reached a minimum at 0.15 GPa and increased up to 0.3 GPa and then decreased, which corresponds to the variations of the strength of hydrogen bonding. This variation was observed at 23 degrees C, but not at 52 degrees C, which suggests a change in pressure dependence on the hydrogen bond interaction between these two temperatures. Based on the equilibration model between hydrogen-bonded and nonhydrogen-bonded molecules, the present experimental results indicate that the pressure variation of the viscosity depends on the ratio of hydrogen-bonded molecules, rather than the strength of hydrogen bonding between molecules.