The influence of pressure on the infrared spectra of hydrogen-bonded solids. V. The formation of Fermi resonance 'windows'

1977 ◽  
Vol 30 (1) ◽  
pp. 71 ◽  
Author(s):  
SD Hamann
Keyword(s):  
Infrared Spectra ◽  
Isonicotinic Acid ◽  
Wave Functions ◽  
Fermi Resonance ◽  
Absorption Bands ◽  
Bending Vibrations ◽  
Low Frequencies ◽  
Stretching Vibrations ◽  
Solid Compounds ◽  
Smooth Transformation

Measurements have been made of the influence of pressure to 40 kbar on the infrared spectra of the normal and X-deuterated forms of seven solid compounds which have strong X-H...Y hydrogen bonds and whose spectra show very broad and intense X-H stretching bands at low frequencies. For two of the compounds, isonicotinic acid and nicotinic acid, compression causes the smooth transformation of superimposed absorption bands into Fermi resonance 'windows', or 'Evans holes'. The effect probably arises from increased overlap of the wave functions for in-plane ring-bending vibrations and X-H stretching vibrations.

The infrared spectra of theobromine salts

1967 ◽  
Vol 45 (23) ◽  
pp. 2899-2902 ◽  
Author(s):  
Denys Cook ◽  
Zephyr R. Regnier
Keyword(s):  
Hydrogen Bond ◽  
Nitrogen Atom ◽  
Infrared Spectra ◽  
Imidazole Ring ◽  
Free Base ◽  
Absorption Bands ◽  
Out Of Plane ◽  
Stretching Vibrations ◽  
Deformation Modes ◽  
Infrared Absorption Bands

From the infrared spectra of theobromine salts it is concluded that the salts are probably arranged in hydrogen-bonded centrosymmetric pairs involving [Formula: see text] interactions. [Formula: see text] anion− hydrogen bonds are formed by protonation of the free nitrogen atom (N9) in the imidazole ring. Infrared absorption bands arising from the former hydrogen bond constantly appear near 3 000 cm−1, whereas those from the latter shift from 2 580 to 3 300 cm−1, depending on the anion. In-plane NH and N+H deformation modes give bands near 1 485 and 1 160 cm−1, respectively. Out-of-plane NH modes have been located, but precise assignments are not possible.The assignments for some other bands which show deuteration shifts are detailed, and the carbonyl stretching vibrations which increase in frequency on protonation of the free base are identified.

Theoretical Modeling of the N-H and N-D Stretching Bands of Hydrogen-Bonded 1-Methylthymine Crystal and Its Deuterated Form

2006 ◽  
Vol 2 (4) ◽  
pp. 205-219
Author(s):  
Marek Boczar ◽  
Łukasz Boda ◽  
Marek J. Wójcik
Keyword(s):  
Hydrogen Bonds ◽  
High Frequency ◽  
Molecular Crystals ◽  
Low Frequency ◽  
Unit Cell ◽  
Fermi Resonance ◽  
Bending Vibrations ◽  
Theoretical Simulation ◽  
Stretching Vibrations ◽  
Centrosymmetric Dimers

Theoretical model for vibrational interactions in the hydrogen bonds in molecular crystals with four molecules forming two centrosymmetric dimers in the unit cell is presented. The model takes into account anharmonic-type couplings between the high-frequency N-H(D) and the low-frequency N•••O stretching vibrations in each hydrogen bond, resonance interactions (Davydov coupling) between equivalent hydrogen bonds in each dimer, resonance interdimer interactions within an unit cell and Fermi resonance between the N-H(D) stretching fundamental and the first overtone of the N-H(D) in-plane bending vibrations. The vibrational Hamiltonian, selection rules, and expressions for the integral properties of an absorption spectrum are derived. The model is used for theoretical simulation of the νs stretching bands of 1-methylthymine and its ND derivative at 300 K. The effect of deuteration is successfully reproduced by our model.

Infrared spectra and hydrogen bonding in some methyl α-glycopyranosides

1975 ◽  
Vol 28 (2) ◽  
pp. 335 ◽  
Author(s):  
AJ Michell
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Bending Vibrations ◽  
Ambient Temperatures ◽  
Out Of Plane ◽  
Stretching Vibrations ◽  
Plane Bending

Spectra in the OH stretching and out-of-plane bending regions of four methyl α-glycopyranosides of known crystal structure have been obtained at ambient and sub-ambient temperatures. Partial deuteration has been used to uncouple the stretching vibrations and assist in assignments of the out-of-plane bending vibrations.

scholarly journals Structure and theoretical infrared spectra of OH defects in quartz

2020 ◽  
Vol 32 (3) ◽  
pp. 311-323 ◽  
Author(s):  
Michael C. Jollands ◽  
Marc Blanchard ◽  
Etienne Balan
Keyword(s):  
Infrared Spectra ◽  
Density Functional ◽  
Broad Band ◽  
Atomic Scale ◽  
Fermi Resonance ◽  
Natural Environments ◽  
Natural Quartz ◽  
Absorption Bands ◽  
Oh Groups ◽  
Oh Defects

Abstract. The infrared spectra of natural quartz, and synthetic quartz produced in conditions relevant to natural environments, generally contain some association of OH-stretching absorption bands at 3596, 3585, 3483, 3431, 3379 and 3313 cm−1, and/or a broad band at ∼ 3400 cm−1. In this study, a series of OH-bearing defects has been theoretically investigated from first principles within the density functional theory framework. The optimized structure, infrared spectroscopic properties and relative energy of defect configurations have been determined. Comparison with experimental observations enables the identification of atomic-scale configurations related to the experimentally observed OH-stretching bands. Consistent with previous interpretations, the results confirm the assignment of the bands at 3596 and 3483 cm−1 to OH defects associated with B3+ substituting for Si4+ and to OH defects associated with Li+ cations located in the structural channels, respectively. They also confirm the assignment of the bands at 3313 and 3379 cm−1 to OH associated with the Al3+-for-Si4+ substitution and, by implication, the previously given interpretation of the 3431 cm−1 band in terms of Fermi resonance. The band at 3585 cm−1 does not appear to be related to a hydrogarnet-type defect, as has been proposed previously, but potentially corresponds to isolated OH− groups bridging two Si atoms, where the charge compensation is ensured by a nonlocal mechanism.

C=O Stretching vibrations in Raman and infrared spectra of simple esters

1982 ◽  
Vol 47 (8) ◽  
pp. 2027-2036 ◽  
Author(s):  
Jiří Dybal ◽  
Jan Štokr ◽  
Bohdan Schneider
Keyword(s):  
Infrared Spectra ◽  
Methyl Acetate ◽  
Butyl Acetate ◽  
Dielectric Constants ◽  
Fermi Resonance ◽  
Conformational Structure ◽  
Infrared And Raman Spectra ◽  
Tert Butyl ◽  
Acetate Methyl ◽  
Stretching Vibrations

Infrared and Raman spectra of methyl acetate, tert-butyl acetate, methyl pivalate and tert-butyl pivalate were measured in the liquid and crystalline states and solutions of different dielectric constants. In these molecules, the bands of the C=O str. vibrations are not affected by conformational structure. The shape and position of the band of the C=O str. vibration in methyl acetate are primarily determined by intermolecular order created by interactions of the permanent dipoles of the molecules. In methyl pivalate and in tert-butyl acetate, the shape of the carbonyl band is mainly determined by Fermi resonance.

Assignment of the Carbon-Hydrogen Stretching and Bending Vibrations of Poly(Methyl Methacrylate) by Selective Deuteration

1979 ◽  
Vol 33 (6) ◽  
pp. 555-561 ◽  
Author(s):  
Stoil K. Dirlikov ◽  
Jack L. Koenig
Keyword(s):  
Fourier Transform ◽  
Methyl Methacrylate ◽  
Infrared Spectra ◽  
Fourier Transform Infrared ◽  
Methyl Groups ◽  
Bending Vibrations ◽  
Poly Methyl Methacrylate ◽  
Selective Deuteration ◽  
Stretching Vibrations ◽  
The Fourier Transform

The C—H stretching and C—H bending vibrations of the methylene, α-methyl, and ester methyl groups of poly(methyl methacrylate) are discussed and assigned on the basis of the infrared spectra of its three deuterated derivatives: PMMA—CD3—OCD3, PMMA—CD2—OCD3, and PMMA—CD2—CD3. The digital analog of PMMA is obtained by coaddition of the Fourier transform infrared spectra of the deuterated PMMA derivatives. The experimental and digital PMMA spectra are compared in the regions of the C—H stretching and C—H bending vibrations: the agreement in frequency is excellent and the relative intensities are practically the same in the C—H stretching vibrations region. However, their relative intensities strongly differ in the C—H bending region.

Infrared spectra of compounds with the methoxymethyl protecting group

1986 ◽  
Vol 51 (1) ◽  
pp. 90-100 ◽  
Author(s):  
Soňa Vašíčková ◽  
Vladimír Pouzar ◽  
Ivan Černý ◽  
Pavel Drašar ◽  
Miroslav Havel
Keyword(s):  
Infrared Spectra ◽  
Strong Absorption ◽  
Protecting Group ◽  
Absorption Bands ◽  
Stretching Vibrations

Infrared spectra of a series of compounds containing the CH3OCH2O- (MOM-O-) group have been studied. All the spectra exhibit three characteristic strong absorption bands due to coupled stretching vibrations of C-O-C-O-C grouping in the region 1 200 - 1 000 cm-1.

scholarly journals Infrared, 1H and 13C NMR Spectra of N,N-Dichloroarylsulphonamides, 4-X-C6H4SO2NCl2 (X = H, CH3, C2H5, F, Cl or Br) and i-X, j-YC6H3SO2NCl2 (i-X, j-Y = 2,3-(CH3)2, 2,4-(CH3)2, 2,5-(CH3)2, 2-CH3, 4-Cl, 2-CH3, 5-Cl, 3-CH3, 4-Cl, 2,4-Cl2 or 3,4-Cl2)

2003 ◽  
Vol 58 (9-10) ◽  
pp. 563-568
Author(s):  
B. Thimme Gowda ◽  
K. Jyothi ◽  
N. Damodara
Keyword(s):  
Infrared Spectra ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Empirical Correlations ◽  
Absorption Bands ◽  
1H And 13C Nmr ◽  
Modes Of Vibration ◽  
Stretching Vibrations ◽  
Electron Donating Groups ◽  
Infrared Absorption Bands

Several mono- and di-substituted N,N-dichloroarylsulphonamides of the configuration, 4-XC6H4SO2NCl2 (where X = H, CH3, C2H5, F, Cl or Br) and i-X, j-YC6H3SO2NCl2 (where i- X, j-Y = 2,3-(CH3)2, 2,4-(CH3)2, 2,5-(CH3)2, 2-CH3,4-Cl, 2-CH3,5-Cl, 3-CH3,4-Cl, 2,4-Cl2 or 3,4-Cl2), respectively, were prepared, characterised and their infrared spectra in the solid state and NMR spectra in solution state were measured and correlated. Comparison of the infrared spectra of the N,N-dichloroarylsulphonamides with the corresponding arylsulphonamides and Nchloroarylsulphonamides revealed that the infrared absorption bands in the ranges, 790 - 735 cm−1 and 595 - 546 cm−1 are due to N-Cl asymmetric and symmetric stretching vibrations, respectively, and that the effect of ring substitution on the N-Cl frequencies is not consistent. The frequencies in the ranges 1384 - 1333 cm−1 and 1181 - 1143 cm−1 are, respectively, assigned to S=O asymmetric and symmetric modes of vibration. The effect of substitution in the phenyl ring in terms of electron withdrawing and electron donating groups is non-systematic. Since the chemical shift depends on the electron density around the nucleus, empirical correlations relating the chemical shifts to the structures have been considered. The chemical shifts of aromatic protons and carbons in all the N,Ndichloroarylsulphonamides have been calculated by adding substituent contributions to the shift of benzene. Considering the approximation made, the agreement between the calculated and experimental chemical shifts is good.

Preparation and infrared spectra of some ammine complexes of ruthenium(II) and ruthenium(III)

1967 ◽  
Vol 45 (12) ◽  
pp. 1337-1341 ◽  
Author(s):  
A. D. Allen ◽  
C. V. Senoff
Keyword(s):  
Solid State ◽  
Infrared Spectra ◽  
Absorption Bands ◽  
Ammine Complexes ◽  
Stretching Vibrations

The infrared spectra of the complexes [Ru(NH3)6]X2 and [Ru(NH3)6]X3, where X = Cl−, Br−, I−, BF4− and [Ru(NH3)5X]X2, where X = Cl−, Br− and I−, have been measured in the solid state between 4 000 – 250 cm−1. Assignments have been made for the observed absorption bands. The metal–nitrogen stretching vibrations were observed between 485–424 cm−1 for the ruthenium(III) complexes but were not observed for the ruthenium(II) complexes in this region.

Intramolecular Hydrogen Bonds and Fermi Resonance in N-Substituted N'-(2-Fluorobenzoyl)thiourea Derivatives

1994 ◽  
Vol 59 (4) ◽  
pp. 951-956 ◽  
Author(s):  
Oľga Hritzová ◽  
Dušan Koščík
Keyword(s):  
Hydrogen Bond ◽  
Perturbation Theory ◽  
Hydrogen Bonds ◽  
Bond Strength ◽  
Infrared Spectra ◽  
Fermi Resonance ◽  
Absorption Bands ◽  
Thiourea Derivatives ◽  
Hydrogen Bond Strength ◽  
Intramolecular Hydrogen

The presence of intramolecular NH...O=C bonds was proved in N-substituted N'-(2-fluorobenzoyl)thiourea derivatives by analysis of their infrared spectra. The intramolecular vibrational effects bring about a shift of the ν(NH) vibrational band to lower frequencies to the extent that the band gets into a vicinity to the δ(NH) overtone and Fermi resonance occurs between them. In addition, the ν(NH) vibration is also affected by Fermi resonance with the ν(CO) + δ(NH) combination. Double absorption bands were observed in the ν(CO) region for some of the derivatives. Based on perturbation theory applied to three-level interactions and using the Langseth and Lord equations, the band frequencies corrected for Fermi resonance were calculated and the hydrogen bond strength was examined in the compounds studied.

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