Vibrational spectra of potassium hydrogen 3,4 furandicarboxylate and intramolecular H-bond

I.r. and Raman spectra of potassium hydrogen 3,4 furandicarboxylate are presented. An assignment of the band is proposed and the details of the hydrogen bond bonds are discussed by analogy with potassium hydrogen maleate. Anharmonic coupling between ν_as, OHO and ν_s OHO is found in the combination band at about 1000 cm⁻¹.     

A single crystal and polycrystalline study of potassium hydrogen malonate using inelastic neutron scattering

The incoherent ineleastic neutron scattering spectra of single and polycrystal samples of potassium hydrogen (deuterium) malonate have been obtained. These spectra have been assigned in concordance with optical spectra except for the location of the antisymmetric hydrogen bond stretch ν_as(OHO) which we observe at 470 cm⁻¹. The corresponding band in the spectrum of the deuterated sample occurs at 411 cm⁻¹. The CO₂ scissoring mode was also observed with significant intensity. These results are interpreted as a mixing of the two modes. This explains the rotation of ν_as(OHO) displacement vector. This vector lies, not along an O ⋯ O direction, but along a C ⋯ C direction.     

Near-infrared spectroscopy as an effective tool for monitoring the conformation of alkylammonium surfactants in montmorillonite interlayers

Application of near-infrared (NIR) spectroscopy to probing the arrangement of trimethylalkylammonium cations in montmorillonite interlayers has been demonstrated. Detailed analysis of the mid-IR (MIR) and NIR spectra of montmorillonite from Jelšový Potok (JP, Slovakia) saturated with surfactants with varying alkyl chain length (even numbers of carbon atoms from C6 to C18) was performed to show the advantages of the NIR region in characterizing surfactant conformations. The position of the ν_as(CH₂), (∼2930–2920 cm⁻¹), ν_s(CH₂) (∼2860–2850 cm⁻¹), 2ν_as(CH₂) (∼5810–5785 cm⁻¹), (ν + δ)_as(CH₂) (∼4340–4330 cm⁻¹) and (ν + δ)_s(CH₂) (∼4270–4250 cm⁻¹) signals was used as an indicator of the gauche/trans conformer ratio. For all bands, a shift toward lower wavenumber on increasing the alkyl chain length from 6 to 18 carbons suggests a transition from disordered liquid-like to more ordered solid-like structures of the surfactants. The magnitude of the shift was significantly higher for 2ν_as(CH₂) (28 cm⁻¹) than for ν_as(CH₂) (8 cm⁻¹) or ν_s(CH₂) (10 cm⁻¹), showing the NIR region to be a useful tool for examining this issue. Comparison of the IR spectra of crystalline alkylammonium salts and the corresponding organo-montmorillonites demonstrated a confining effect of montmorillonite layers on surfactant ordering. For each alkyl chain length the CH₂ bands of the organo-montmorillonites appeared at higher wavenumbers than for the unconfined surfactant, thus indicating a higher disorder of the alkyl chains. The wavenumber difference between corresponding samples was always higher in the NIR than in the MIR region. All these findings show NIR spectroscopy to be useful for conformational studies.     

Hydrogen bonding in potassium hydrogen maleate and some simple derivatives studied by inelastic neutron scattering spectroscopy

Inelastic neutron scattering spectra (300–2500 cm^?1) of KH(CHCO₂)₂, KD(CHCO₂)₂, KH(CDCO₂)₂ and KH(CHCO₂ · CClCO₂) have been obtained and the vibrations of the hydrogen bond, with the exception of ν₂(OHO), assigned. This is the first assignment of these vibrations in a centrosymmetric intramolecularly hydrogen bonded complex. ν_as(OHO) was found to be heavily mixed and to give rise to a strong doublet in the INS spectra.     

Vibrational anharmonicity and Fermi resonances in CHF2Cl

The infrared spectrum of CHF₂Cl has been recorded between 15 000 and 350 cm⁻¹. The Fermi resonance between levels involving ν₄ and 2ν₆ is analysed in bands extending from 800 cm⁻¹ to 7000 cm⁻¹ leading to a best value of k₄₆₆ = ± 14.98 cm⁻¹. In conjunction with the recent results of Amrein, Dubal and Quack, Molec. Phys. 56,727 (1985); estimates are reported for 38 out of 45 possible x_ij constants. A variation in the relative intensity of the two Q branches associated with ν₁, on cooling the gas cell, indicates that a hot band contributes to the upper branch at 3024.55 cm⁻¹. However, other evidence suggests that the latter arises also from the combination ν₂ + ν₇ + ν₉, in a very weak, close resonance with ν₁ at 3021.27 cm⁻. A number of anomalous band contours are reported.     

Vibrational spectra and structure of triphenyltin halides

The solid state IR and Raman spectra of SnPh₃Br do not show any band at 338 cm⁻¹, and there is not C_3ν point group inversion between ν_as SnC₃ and ν_s SnC₃ for SnPh₃X (X  Cl, Br). The presence or absence of a band around 338 cm⁻¹ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh₃ groups.     

Vibrational (i.r. and Raman) spectra and conformational studies of 1-formyl-3-thiosemicarbazide

The i.r. and Raman spectra (30–4000 cm⁻¹) of 1-formyl-3-thiosemicarbazide (FTSC) and deuterated ftsc-d₄, have been studied. Most of the vibration modes reveal pairs of bands and show strong temperature dependence. A band group {ν(NNH₂)} at ∼ 1100 cm⁻¹ exhibits well resolved doublet (1095 and 1112 cm⁻¹) structure below 100 k. The intensity in the 11 12 cm⁻¹ band decreases regularly (band disappears at 150 K) with the rise in temperature. Two new bands at 955 and 1070 cm⁻¹ appear while measured above 400 K. The system eventually exists in several conformers in simultaneous equilibria. Moreover, a few bands {e.g. ν(CO), ν(CS) and ν(CH)} that show strong intensifies in i.r. exhibit weak (or zero) intensifies in the Raman and vice-versa. The features (characteristic of u and g vibration species) could be explained by a C_2h pseudo symmetry space group proposed for the system. Both the FTSC and FTSC-d₄ represent strong molecular associations. This favours the maximum abundance in the dimer stabilized conformers.     

Matrix-isolation infrared spectra of oxy(tetraphenylporphyrinato)iron(II) containing CS2 and SO2 as axial ligands

The IR spectra of cocondensation products of Fe(TPP) with CS₂/Ar exhibit the ν(CS₂) of Fe(TPP)(CS₂) at 1522 cm⁻¹ which is 7 cm⁻¹ lower than that of free CS₂. When Fe(TPP) was cocendensed with O₂/CS₂/Ar, the bands characteristic of Fe(TPP)(CS₂)O₂ (ν(CS₂), 1519 cm⁻¹ and ν(O₂), 1190 cm⁻¹) were observed in addition to those of Fe(TPP)(CS₂) and Fe(TPP)O₂ (ν(O₂), 1195 cm⁻¹). These assignments were confirmed by ¹²CS₂/¹³CS₂ isotope shifts and warm-up experiments. A S-bonded structure in which the linear CS₂ molecule is weakly coordinated to the Fe atom has been proposed for these adducts. The IR spectra of cocondensation products of Fe(TPP) with SO₂/Ar exhibit bands characteristic of Fe(TPP)(SO₂) (1342, 1146) and Fe(TPP)(SO₂)₂ (1332 and 1142) in addition to those of SO₂ monomer ((1355*, 1351*) and (1152*, 1148*)), SO₂ dimer (1344, 1151) and SO₂H₂O (1343 and 1150 cm⁻¹). Here, the numbers in brackets indicate the SO₂ stretching frequencies, ν₃ and ν₁, respectively, and the asterisks denote those split by the matrix effect. The cocodensation products of Fe(TPP) with O₂/SO₂/Ar exhibit new bands at 1328 (ν₃), 1142(ν₁) and 1188 cm⁻¹ (ν(O₂)). The O-bonded structure in which the bent SO₂ molecule is coordinated to the Fe atom via the terminal oxygen has been proposed, based on small shifts of the ν₃ and ν₁ vibrations upon coordination.     

Absolute infrared band intensities and air broadening coefficient for spectroscopic measurements of formic acid in air

The absolute infrared intensities of the ν₂, ν₃ and ν₆ bands of formic acid have been evaluated in a 480 L White cell system using FTIR and ion chromatography techniques. The values obtained are, respectively; (4.2 ± 0.2) × 10⁻¹⁷ cm molec⁻¹ for the ν₆ band, (4.8 ± 0.2) × 10⁻¹⁷ cm molec⁻¹ for the ν₃ band and (0.57 ± 0.04) × 10⁻¹⁷ cm molec⁻¹ for the ν₂ band. The air broadening coefficient of transitions in the ν₆ band, has been measured using a tunable diode laser spectrometer, equal to (0.101 ± 0.005) cm⁻¹ atm⁻¹ (half width at half maximum). A computer search has been performed to find absorption lines of formic acid suitable for second derivative tunable diode laser measurement of this gas in ambient air.     

Spectroscopic studies of the reaction of iodine with the mixed oxygen—nitrogen cyclic base 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane

The reaction of iodine with the interesting mixed oxygen—nitrogen cyclic base 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (TODACOD) has been investigated spectrophotometrically in the solvent 1,2-dichloroethane. The spectra indicate the formation of the pentaiodide ion, I⁻₅, judging from its two strong absorptions around 360 and 290 nm. Elemental analysis for the solid iodine—(TODACOD) complex indicate that the (TODACOD) base—iodine ratio is 1:3 in agreement with the ratio concluded from the photometric titration plots based on the absorptions of the formed polyiodide ion. Therefore, the formed iodine complex is formulated as [(TODACOD)I]⁺.I⁻₅. The formation of the I⁻₅ species was also confirmed by the resonance Raman spectrum of the solid product. The Raman spectrum can be explained entirely by the presence of the bent I⁻₅ ion with C_2υ structure. The vibrations of I⁻₅ ion are ν_s(II); outer, ν_s(II); inner, ν_as(II); outer, and ν_as(II); inner and are assigned as expected at 164, 110, 137 and 87 cm⁻¹, respectively.     

Vibrational analysis of sodium α-, β- and γ-hydroxybutyrates. Inter- and intramolecular hydrogen bonds

The infrared and Raman spectra of sodium α-, β- and γ-hydroxybutyrates and their deuterated analogues are examined in the 4000-100 cm⁻¹ range and an assignment of the fundamental vibrations is given. Based on the localization of the asymmetric stretching vibrations ν_asOH and the out-of-plane vibration γOH, inter- and/or intramolecularly hydrogen-bonded forms are proposed: the low frequencies of ν_asOH (<3200 cm⁻¹) and high frequencies of γOH (≈800 cm⁻¹) argue in favour of the existence of intramolecular hydrogen bonding. Sodium α-hydroxybutyrate exhibits as a chelate ring with an intramolecular hydrogen bond between hydroxyl and carboxyl groups, whereas sodium, β-hydroxybutyrate has the two association forms with inter- and intramolecular hydrogen bonds. Sodium γ-hydroxybutyrate exists as a hydrogen-bonded polymer, with an intermolecular hydrogen bond between the hydroxyl groups and between the hydroxyl and carbonyl groups. At a crystallization temperature above 50°C, only the α- salt showed a structural change indicating the existence of intra- and intermolecular hydrogen bonds. This result is confirmed by differential scanning analysis.     

An inelastic neutron scattering study of hydrogen bonding in potassium hydrogen dichloromaleate

The inelastic neutron scattering (INS) spectrum (350–2000 cm^?1) of potassium hydrogen dichloromaleate (solid slate) has been obtained. Two of the normal modes of vibration of the hydrogen bond [γ(OHO) and δ(OHO)] were observed and assigned. No INS band v_as(OHO) was observed in the region 500–1300 cm^?1. This conflicts with expectations from infrared data.     

Electronic spectra and predissociation of jet-cooled CH3O and CH3O-Ar in the Ã2A1 state

The òA₁-X̃²E electronic spectrum of jet-cooled methoxy radical has been examined by the LIF technique. Two newly discovered vibrational bands of 2930 and 1390 cm⁻¹ are assigned to ν₁ (totally symmetric C-H stretching) and a degenerate ν₅ mode, respectively. The predissociation, CH₃O → CH₃ + O in the òA₁ state is newly elucidated and the threshold energy is deter- mined as 5100 cm⁻¹ from the potential minimum. For the CH₃O-Ar complex, the threshold energy is reduced by about 100 cm⁻¹.     

The analysis of high-resolution spectra of the ν2 and ν5 bands of CH335Cl and CH337Cl

The ν₂ and ν₅ bands of CH³₃⁵Cl and CH³₃⁷Cl between 1300 and 1600 cm⁻¹ have been analysed using a Fourier transform spectrum with 0.006 cm⁻¹ resolution. For CH³₃⁵Cl, the microwave data and 1200 lines from the IR spectrum with J⩽ 50 were fitted with an overall r.m.s. error of 0.00079 cm⁻¹ using the method of predicative observations. A similar fit for 900 lines of CH³₃⁷Cl gave an overall r.m.s. error of 0.00055 cm⁻¹, providing erroneous microwave data on the ν₅ level are omitted. Improved molecular constants are reported for both isotopic species. As expected, the values for ν₂ and ν₅ are little affected by chlorine isotopic substitution.     

Infrared spectroscopic studies of hydrogen-bonded complexes in cryogenic sulutions

We have measured the ν_s(OH) band parameters of the IR absorption spectra for a wide variety of hydrogen-bonded (HB) complexes of CH₃OH(D), CF₃CH₂OH, and (CF₃)₃COH(D) with some simplest representatives of various classes of bases in Xe and Kr in the temperature range 120–270 K. The ν_s(OH) absorption bands of the HB complexes in solution in atomic solvents have been demonstrated to be narrower by a factor of 2 to 4 than in molecular solvents at the same temperature. The fact that the ν_s(OH) bandwidths in Xe and in the gas phase at similar temperatures are practically the same indicates that these bandwidths are in both cases governed mainly by the contribution of “hot transitions” from a sequence of excited levels of the ν_β low-frequency bending mode of the hydrogen bond. The other characteristic features revealed for the complexes under study in liquid Xe and Kr at ν_s(OH) frequency shifts up to 500 cm⁻¹ include: (1) slight temperature dependence of the ν_s(OH) bandwidth (0.1–0.3 cm⁻¹/K), (2) almost “normal” isotope frequency ratio ν_s(OH)/ν_s(OD) (1.34–1.36) and (3) low ν_s(OH) temperature shift values (0.1–0.4 cm⁻¹/K).     

The NH stretching region of some imides and thioimides

The multiplet structure of νNH and νND bands of solid phtalimide, monothiophtalimide, dithiophtalimide, isatin, saccharin and of their deuterated analogues has been explained as being a result of Fermi resonance of the fundamentals of νNH and νND with combinations and/or overtones. The submaxima of 3080 and 2970 cm⁻¹ of saccharin as well as pronounced doublet of 2465 and 2345 cm⁻¹ of d-phtalimide move to lower frequency in the low temperature ir spectra, while the “windows” remain fixed at 3045 and 2380 cm⁻¹, respectively. These examples could be a striking demonstration of Evans type Fermi resonance.     

A re-examination of the infrared and ultraviolet spectroscopy of trifluoroacetyl fluoride and trifluoroacetyl chloride: An experimental and theoretical study

The fundamental IR vibrational modes of trifluoroacetyl fluoride CF₃C(O)F and trifluoroacetyl chloride CF₃C(O)Cl have been re-examined by ab initio molecular orbital calculations and compared with literature assignments. Several bands of the IR spectrum are reassigned. The Q-branch and integrated absorption cross-sections have been measured for ν₁, ν₃, ν₄ and ν₁₁ fundamental bands for both pressurized and unpressurized samples on each molecule. The UV absorption spectra of CF₃C(O)F and CF₃C(O)Cl show a structureless continuum with a maximum at 21Onm (σ_max=3.20±0.02 × 10⁻²⁰ cm² molecule⁻¹) and 255 nm (σ_max=7.66±0.26 × 10⁻²⁰ cm² molecule⁻¹), respectively. The nature of the electronic transition giving rise to the UV absorption spectrum for CF₃C(O)F and CF₃C(O)Cl has been examined by ab initio molecular orbital calculations. It is attributed to the A¹A″←X¹A′ electronic transition.     

Near infrared absorption spectrum of perfluoro-t-butanol/acetonitrile complexes at low temperatures: Fermi resonances and simultaneous transitions

Interactions between perfluoro-t-butanol (PFTB) and acetonitrile-d₃ (AN) in a mixture of freons are studied between 298 and 88 K in liquid or vitreous states. In the conditions of the experiment, a mean 1:2 stoichiometry [PFTB⋯(AN)₂] is inferred from previous matrix measurements. A ν_OH shift of about 160 cm⁻¹ is observed in this temperature range: it is mainly ascribed to solvent effects on the complex. In fact, the dν_OH/dT coefficient increases at low temperature on account of specific solvation of the complex by the freon Br atoms. The ν_OH + τ_OH combination wavenumber is little dependent on the state of PFTB, near 3900 cm⁻¹. A comparatively strong simultaneous transition involving the PFTB ν_OH mode and a ν_CN mode of neighbouring AN molecules is observed. Weaker bands could also be explained by such transitions involving a combination level of PFTB and a ν_CN vibration. Strong Fermi resonances are displayed in the 2ν_OH region when the ν_OH band is located around 3100 cm⁻¹, either in pure AN or in freons at low temperature. The levels interacting with 2ν_OH are ternary combinations and quaternary overtones mainly involving the COH bend and the CO stretch. These resonances are favoured by a strong increase of the OH stretching vibration anharmonicity.     

Vibrational spectroscopic characterization of the phosphate mineral hureaulite – (Mn,Fe)5(PO4)2(HPO4)2·4(H2O)

This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn_3.23, Fe_1.04, Ca_0.19, Mg_0.13)(PO₄)_2.7(HPO₄)_2.6(OH)_4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm⁻¹ assigned to PO stretching vibrations of HPO₄²⁻ units. The Raman band at 989 cm⁻¹ is assigned to the PO₄³⁻ stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm⁻¹ are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO₄²⁻ and PO₄³⁻ units. A set of Raman bands at 531, 543, 564 and 582 cm⁻¹ are assigned to the ν₄ bending modes of the HPO₄²⁻ and PO₄³⁻ units. Raman bands observed at 414, and 455 cm⁻¹ are attributed to the ν₂ HPO₄²⁻ and PO₄³⁻ units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.     

The ab initio calculation of the band origin and vibrational frequencies of the Ã-X̃ system of HNCl using the non-rigid bender hamiltonian

A three-dimensional fit of ab initio MRD CI potential data has been made for the lowest two electronic states of the HNC1 molecule (X̃ ²A″ and à ²A'), and the corresponding vibrational frequencies and rotational energies have been computed using the non-rigid bender Hamiltonian. For the ground state the vibrational frequencies obtained are ν₁ = 2942 cm⁻¹, ν₂ = 1232 cm⁻¹, and ν₃ = 549 cm⁻¹, while the corresponding values for the first excited state are 3524,947 and 836 cm⁻¹ respectively. We calculate T_c(à ²A') 16200 cm⁻¹, T_o(òA') = 16400 cm⁻¹, and the Franck-Condon maximum, Ã(0,3,1)-X̃(0,0.0), is calculate at 19200 cm⁻¹(5200 Å).