Intramolecular hydrogen bonds in sulfur-containing aminophenols

IR Fourier spectroscopy methods have been adopted to study intramolecular interactions that occur in CCl₄ solutions of antiviral derivatives of aminophenol. Analysis of the IR spectra showed that intramolecular bonds O–H···N, O–H···O=C, N–H···O=S=O, and O–H···O=S=O can occur in these compounds depending on the substituent on the amino group. Not only the presence of intramolecular O–H···N, O–H···O=S=O, and N– H···O=S=O hydrogen bonds in 2-amino-4,6-di-tert-butylphenol derivatives containing a sulfonamide fragment but also conformational equilibrium among these types of intramolecular interactions are essential for the manifestation of high efficiency in suppressing HIV-infection in cell culture.     

Intramolecular hydrogen bonds and antioxidant activity of aminophenols

We have used IR Fourier spectroscopy to study intramolecular interactions in solutions of aminophenols in n-hexane. When the hydroxyl group in the molecule is ortho to the amino group, O-H⋯N and N-H⋯O intramolecular hydrogen bonds are formed in the aminophenols. Adding two tert-butyl groups to the benzene ring of ortho-aminophenols strengthens the O-H⋯N bond in the molecules, and prevents formation of an N-H⋯O bond. Additional acylation of the amino group in ortho-aminophenols leads to formation of an O-H⋯O=C intramolecular hydrogen bond. Formation of the above-indicated intramolecular hydrogen bonds in aminophenols affects the course of radiation-induced reactions occurring in n-hexane with participation of these compounds. The antioxidant properties of the aminophenols are enhanced when the hydroxyl groups in the molecules are found in the free state, and are diminished when strong O-H⋯N or O-H⋯O=C intramolecular hydrogen bonds are formed. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 577–582, September–October, 2007.     

Intramolecular hydrogen bonds in the phenylazomethine biomolecules

The FTIR spectra of the solutions of biologically active molecules (screened phenylazomethines) in CCl₄ are studied. The role of the OH- and N=C groups in the formation of the intramolecular H bonds is analyzed. The analysis of the FTIR spectra shows that three types of H bonds (O-H…O-H, O-H…N=C, and O-H…O-H…N=C) are possible in the molecules under study. A correlation of the H-bond formation in the phenylazomethine molecules and the antivirus properties of such molecules is revealed. The antivirus activity is observed for molecules that exhibit intramolecular O-H…O-H…N=C bonds in the absence of free hydroxyls. The antivirus activity decreases when the molecule contains additional OH groups that are not involved in H bonds.     

Manifestation of intramolecular hydrogen bonds in the IR spectra of bioactive aminophenols

The intermolecular interactions in solutions of aminophenols in CCl₄ are studied by the methods of IR Fourier spectroscopy. If the hydroxyl groups of aminophenol molecules occupy the ortho positions with respect to the amino groups of the molecules, the hydroxyl and amino groups are involved in intramolecular interactions with the formation of hydrogen bonds O-H...N and N-H...O. The introduction of two additional tert-butyl groups into the structure of the aminophenol molecule facilitates the formation of O-H...N bonds and impedes the formation of N-H...O bonds. The occurrence of the carbonyl group in the structure of aminophenols leads to the formation of intramolecular hydrogen bonds O-H...O=C. The introduction of the methyl groups into carbonyl-containing aminophenols transforms the O-H...O=C bond into the hydrogen bond N-H...O=C.     

Intramolecular hydrogen bonds in compounds of porphin type

NH modes are examined for porphins and simpler compounds. The NH frequency is found to vary smoothly in the sequence pyrrole to phihalocyanin, which cannot be explained in terms of an intramolecular hydrogen bond. The effects are ascribed to conjugation and formation of a macro ring.     

Hydrogen bonds of anti-HIV active aminophenols

Analysis of IR-Fourier spectra from solutions and crystals of antiviral sulfo-containing aminophenols has shown that various types of intramolecular and intermolecular interactions can occur in molecules of these compounds. Three types of intramolecular hydrogen bonds (O–H⋅⋅⋅N, O–H⋅⋅⋅O=S=O, and N–H⋅⋅⋅O=S=O) are formed in CCl₄ solutions of the sulfo-containing aminophenols. The formation of intermolecular H-bonds involving the NH- and OH-groups and the preservation of the intramolecular O–H⋅⋅⋅O=S=O H-bond are characteristic of the anti-HIV active aminophenol crystals. Spectral attributes are determined in order to distinguish between the anti-HIV active and inactive sulfo-containing aminophenols.     

Vibrational multilevel quantum coherence due to anharmonic couplings in intermolecular hydrogen bonds

Femtosecond three-pulse photon-echo studies of acetic acid dimers in solution reveal multilevel coherence of O-H stretching excitations caused by the anharmonic coupling between the high-frequency stretching and low-frequency hydrogen-bond motions. We demonstrate for the first time that such multilevel coherence determines the nonexponential decay of the macroscopic O-H stretching polarization, whereas spectral diffusion processes play a minor role. The dephasing time of individual vibrational transitions contributing to the overall polarization is approximately 200 fs.     

Manifestation of intramolecular and intermolecular interactions in infrared absorption spectra of biologically active aminophenols

FTIR methods were used to study intramolecular and intermolecular interactions in solutions and the solid state of the biologically active aminophenols 2-anilino-4,6-di-tert-butylphenol, N-(3,5-di-tert-butyl-2-methoxyphenyl)aniline, and 2,4-di-tert-butyl-10H-1-phenothiazinol. An analysis of the IR spectra has shown that intramolecular interactions between the OH and NH groups occur in solutions of 2-anilino-4,6-di-tertbutylphenol in CCl₄ to form O-H⋯N hydrogen bonds. The NH groups in solutions of N-(3,5-di-tert-butyl-2-methoxyphenyl)aniline in CCl₄ are present in the non-associated state because of the absence of hydroxyl groups in the molecular structure. The OH and NH groups in solutions of 2,4-di-tert-butyl-10H-1-phenothiazinol in CCl₄ do not interact within the molecule due to a decrease in the conformational mobility of the molecular fragments due to the presence of the rigid C_Ar-S-C_Ar molecular bond in this compound. Intermolecular interactions involving the NH groups occur in the solid state of these compounds. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 68–73, January–February, 2008.     

Theoretical analysis of the IR and Raman spectra of acridone taking into account intermolecular hydrogen bonds

The geometric parameters, the force field, and the absolute intensities of the IR and Raman spectra of acridone, the hydrogen-bonded dimer of acridone, and its N-deuterated analogue are calculated quantum mechanically in terms of the density functional theory by the B3LYP/6-31G(d) method. The vibrational bands in the IR and Raman spectra of acridone are assigned and interpreted using the calculational data on acridone dimers and the data on the isotopic shifts of vibrational frequencies upon deuteration. The vibrations of acridone and anthraquinone are comparatively analyzed. Original Russian Text ￠ K.V. Berezin, T.V. Krivokhizhina, V.V. Nechaev, 2006, published in Optika i Spektroskopiya, 2006, Vol. 100, No. 1, pp. 20–27.     

Symmetric hydrogen bonds in ice X

Raman measurements on Ice VIII under pressures up to 50 GPa reveal strong line shifts, changes in isotope frequency ratio, intensity decreases, and the appearance of one new line around 38 GPa. These observations are consistent with the formation of symmetric hydrogen bonds and a new phase, Ice X, with cuprit structure.     

Slow neutron scattering and intermolecular excitations in liquid hydrogen

A simple analytical model for inelastic neutron scattering in liquid hydrogen with the effects of delayed diffusion and intermolecular vibrations with a single frequency parameter is proposed. Calculated results show good agreements with experimental results of total and differential scattering cross sections as well as the energy spectra of neutrons in liquid hydrogen moderators, and thus indicate the importance of the consideration of intermolecular excitations in the dynamics of liquid hydrogen.     

Compaction of intermolecular bonds in the macroscopic chiral phase of strings

The microstructure of a cured state characteristic of a wide variety of low-concentration homochiral solutions in comparison with that of the condensed phase formed in achiral solutions is studied using optical and atomic force microscopy and X-ray diffraction analysis.     

Intramolecular and intermolecular contributions to the spin-lattice relaxation of protons in benzene and cyclohexane

Temperature dependences are found for the intramolecular and intermolecular contributions to the spin-lattice relaxation of protons in benzene and cyclohexane by dilution in deuterated analogs. The intermolecular contribution in benzene is discussed on the basis of the model for the molecular distribution found from x-ray diffraction studies. The Hubbard correction to the intermolecular contribution is calculated on the basis of the experimental parameters corresponding to rotation and translation. The results imply discontinuous translational motion of molecules in both liquids.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 3, pp. 116–121, March, 1971.In conclusion the author thanks T. N. Khazanovich for useful advice.     

Oxygen nonstoichiometry and hydrogen bonds in BaTiO3

The origin of hydroxyl in the lattice of barium titanate as a consequence of the reaction of hydrogen with oxygen ions in the lattice is described. A band at the wave number 1770 cm^?1 was assigned to this hydroxyl in the infra-red spectrum. The samples were annealed in a stream of hydrogen and in sealed ampoules containing hydrogen or deuterium at temperatures above 900°C, and at 50 to 500° C when hydrogen plasma was used. The defect structure of the sample after prolonged annealing in hydrogen is discussed.