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The reactions of 2,2'-pyridyl, (2-Py)C(O)C(O)(2-Py), with the Cd(II) compounds under various conditions are studied. The medium and nature of the anions exert a decisive effect on the compositions and structures of the formed cadmium complexes. The reaction of cadmium diacetate with 2,2'-pyridyl in an aqueous-alcohol medium in air affords coordination compound [Cd(Рic)(HO)] · HO ( I) (Pic is picolinate ion, COCHN), and its crystal structure is determined. The crystals are monoclinic: space group P2/ c, a = 7.499(1), b = 15.676(1), с = 12.719(1) Å, β = 94.79(1)°, V = 1490.0(2) Å3, Z = 4, ρ = 1.502 g/cm. The molecular packing of compound I is a supramolecular 3D framework consisting of discrete complexes [Cd(Pic)(HO)] linked by hydrogen bonds O-H...O. The coordination sphere of Cd contains two O atoms and two N atoms of the ligand and two water molecules. The coordination polyhedron of Cd is a distorted octahedron. [ABSTRACT FROM AUTHOR]

IR spectroscopy is applied to studying the effect of nonpolar and low-polar solvents on the molecular structure of solid-state quasi-one-dimensional strings formed through the chiral self-assembly from solutions of trifluoroacetylated homochiral amino alcohols (TFAAA). It is experimentally confirmed that in stable two-phase string/solvent gels and respective xerogels, solid-phase strings contain no solvent molecules as a structural element, experiencing, however, a weak disturbing influence of solvent molecules. It is shown that the process of spontaneous self-assembly of chiral strings in solutions is accompanied by the formation of a complex system of hydrogen bonds involving the C=O, N-H, and O-H functional groups of dissolved TFAAA molecules and by the displacement of solvent molecules to the periphery of the resulting quasi-one-dimensional strings. The results of the present work, together with data obtained by other experimental methods, indicate that TFAAA-based elementary strings have diameters of 1-2 nm, being crystalline, molecularly thin, quasi-one-dimensional objects. The amplitude of the thermally activated bending vibrations (transverse phonons) of elementary strings is sufficient to cause the entanglement of elementary strings, which leads to the formation of larger diameter supercoiled strings. [ABSTRACT FROM AUTHOR]

Using IR Fourier spectra and employing quantum-chemical calculations of electronic structure, spectra, and proton-acceptor properties, synthetic derivatives of aminophenol exhibiting biological activity in the suppression of herpes, influenza, and HIV viruses have been investigated from a new perspective, with the aim of establishing the spectral response of biological activity of the molecules. It has been experimentally established that the participation of the aminophenol hydroxyl group in intramolecular hydrogen bonds is characteristic of structures with antiviral properties. A quantum-chemical calculation of the proton-acceptor ability of the investigated aminophenol derivatives has shown that biologically active structures are characterized by a high proton-acceptor ability of oxygen of the hydroxyl group. A correlation that has been obtained among the formation of an intramolecular hydrogen bond, high proton-acceptor ability, and antiviral activity of substituted aminophenols enables us to predict the pharmacological properties of new medical preparations of the given class of compounds. [ABSTRACT FROM AUTHOR]

IR-Fourier spectra of solutions and crystals of biologically active benzaldehyde derivatives were studied. Specific features of the formation of intra- and intermolecular hydrogen bonds were analyzed. Spectral signatures that characterized participation of the hydroxyl OH group and also the OCH 3 and C=O groups in the formation of intramolecular hydrogen bonds of the three different types O–H···O–H, O–H···O–CH 3, and O–H···O=C were revealed. Intramolecular hydrogen bonds of the types O–H···O–H and O–H···O–CH 3 were absent for benzaldehyde derivatives in the crystal phase. Only hydroxyl and carbonyl groups participated in intermolecular interactions. This resulted in the formation of linear intermolecular dimers. Seven various configurations of the linear dimers were identified in solutions and crystals. [ABSTRACT FROM AUTHOR]

The vibrational spectra of a series of HF solutions in acetone (1:20-8.9:1) are analyzed with the help of special techniques. It is shown that three types of strong heteroassociates (HAs) with 1:1, 4:1, and ≥10:1 stoichiometric ratios of the molecules are formed in the HF-(CH)CO binary liquid system. The concentration ranges of the existence of HAs in the solution and the stretching vibrational frequency of their constituent HF molecules are estimated. The density functional method (B3LYP/6-31++G( d,p)) is used to calculate the optimal configurations and IR spectra of the (HF)·((CH)CO) molecular complexes ( m = 1, 2, 4, 8, n = 1, 2) of different structure. The relative stability of the latter is studied. By comparing the calculated and experimental data, the composition (2:2 and 4:1) and structure of two types of HAs are determined. [ABSTRACT FROM AUTHOR]

FTIR spectra of pharmacologically active molecules of benzoic acid and its derivatives have been measured in CCl solutions and in microcrystals. Features of the formation of intra-and intermolecular hydrogen bonds have been analyzed. Spectral attributes have been revealed that characterize the participation of a carboxyl group in different types of intermolecular interactions with the formation of cyclic, linear, and criss-cross dimers. Mechanisms of the intermolecular interactions are shown to be defined by the character of the substituents attached to the benzene ring in the para- and meta-positions relative to the carboxylic group. [ABSTRACT FROM AUTHOR]

IR Fourier spectra of pharmacologically active sterically hindered phenols in CCl solutions are studied. A relationship between the absorption intensity in the spectral range of the free vibrations of OH-groups and the antimicrobial activity of the phenols is discovered. If the hydroxyl groups are in an ortho-position within a molecule, then intramolecular hydrogen bonds are formed. The hindered phenols with nonassociated hydroxyl groups are the most pharmacologically active. [ABSTRACT FROM AUTHOR]

nalysis 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 CCl 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. [ABSTRACT FROM AUTHOR]

The IR spectrum and structure of methyl-β-D-glucopyranoside have been studied theoretically taking into account the influence on them of the hydrogen bond formed in the sample. Density-functional theory with the B3LYP functional in basis 6-31G( d) was used to minimize the energies and calculate the structures, electro-optical parameters, force constants, frequencies of normal harmonic vibrations, and intensities in IR spectra of the simplest H-bonded dimeric complexes of methyl-β-D-glucopyranoside. The calculated spectra of H-bonded complexes were compared with those of the free molecule and the experimental spectrum in the range 400-3700 cm. Conclusions about the structure of methyl-β-D-glucopyranoside were made. The interpretation of its IR spectrum was refined. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The micro-structure, and IR spectrum of water molecules in 1-butyl-3-methylimi- dazolium tetrafluoroborate([Bmim]BF4)/water mixture with different concentrations (x1 = 25.0%, 50.0%, 75.0%, and 90.0%) were studied with molecular dynamics simulation at room temperature. It was shown that water molecules tend to be isolated from each other in mixtures with more ions than water molecules in pure water. With the increase of the molar fraction of water in the mixture, the rotation bands and the bending bands of water display red shift from 566.2 to 651.4 cm-1 and from 1638.4 to 1683.2 cm-1 respectively, whereas the O–H stretch bands show blue shift from 3519.8 to 3452 cm-1, which agree well with the experimental results. This suggests that the molecules are hindered and their motions are difficult and slow, due to the hydrogen-bond interactions and the inharmonic interactions between the inter- or intra-molecular modes of water molecules. [ABSTRACT FROM AUTHOR]

The aim of this work was to determine the structure of stable heteroassociates (HAs) with the stoichiometric ratios 1:2, 2:1, and 4:1 of molecules formed in the HF-(C2H5)2O binary liquid system. The stretching frequencies of HF molecules found for each HA using a special procedure for processing IR spectra were compared with the calculated frequencies V HF of the stable molecular complexes (HF)m ((C2H5)2O)n ( m = 1, 2, 4, 8; n = 1, 2) with different topologies by the density functional method (B3LYP/6-31++G( d,p)). As a result, it was shown that the most stable (among H-bonded complexes with the same stoichiometric ratio of molecules) HAs HF((C2H5)2O)2, (HF)4 ((C2H5)2O)2, and (HF)8-((C2H5)2O)2 formed in HF solutions in diethyl ether. All of them had a cyclic structure and a common peculiarity of structure: only one lone electron pair of the oxygen atom of the (C2H5)2O molecules is involved in hydrogen bonding. [ABSTRACT FROM AUTHOR]

The concentration dependence of normalized absorbance (to the total number of moles of components in one liter) of HF solutions in acetonitrile (1:12–10:1) is analyzed. It is found that in the binary liquid system (BLS) under study molecular complexes with stoichiometric 1:1 and ∼10:1 ratios of molecules occur along with the heteroassociates (HAs) found previously with the ratio HF:CH3CN of 4:1. For each of the HAs the concentration range at which it is formed in BLS is evaluated, and the positions of HF stretching vibrational bands are found. Optimum configurations and vibrational frequencies of molecular complexes (HF) m ·(CH3CN) n ( m = 1–6, n = 1–2) of various topology are calculated using the density functional method (B3LYP/6-31 ++ G ( d, p)). Their relative stability and the structure peculiarities are studied; complexation tendencies in the HF-CH3CN system are revealed. The structure of HAs with 1:1 and 4:1 stoichiometric ratios of molecules is determined by comparing the results of calculations and experiment. [ABSTRACT FROM AUTHOR]

We used infrared spectroscopy methods to study the molecular structure of tissues from human organs removed during surgery. The IR spectra of the surgical material from breast, thyroid, and lung are compared with data from histological examination. We show that in malignant neoplasms, a change occurs in the hydrogen bonds of protein macromolecules found in the tissue of the studied organs. We identify the spectral signs of malignant pathology. [ABSTRACT FROM AUTHOR]

Density functional theory (B3LYP/6-31G*) is applied to calculate structures, energy, dipole moment, polarizability, frequencies of normal vibrations in the harmonic approximation and intensities in vibrational spectra of 2-, 3-, and 4-biphenylmethanol molecules and their H-complexes that can form in crystalline, amorphous, and liquid phases. Based on the analysis of simulation results, the effect of the position of a methanol group in the molecule on its vibrational spectrum is discussed. The structure forming role of a hydrogen bonds in biphenylmethanols and the possibility of realization of two polymorphic modifications in 2-biphenylmethanol are stated. These modifications are: metastable monoclinic, in which each of four molecules of the unit cell is a link of a chain H-associate; and stable triclinic, in which four molecules of the unit cell organize an H-complex in the form of a cyclic tetramer. It is found that crystalline samples of 3-and 4-biphenylmethanols consist of chain H-associates. A glass-like sample of 2BPhM being a mixture of H-complexes consisting of cyclic tetramers and chain associates contains crystalline nuclei of triclinic and monoclinic polymorphous modifications in the supercooled state. In a liquid sample of 2BPhm, chain H-associates and free molecules are realized. [ABSTRACT FROM AUTHOR]

This contribution provides the theoretical background for the structure-determining role of hydrogen bonding in the formation of a near-surface layer of titania nanocrystallites, previously revealed by the authors in the investigation of IR experimental spectra of two-component solid mixtures of nanocrystalline titanium dioxide with benzophenone or 4-pentyl-4′-cyanobiphenyl. DFT calculations (B3LYP) in 6-31+G( d) basis set is used to simulate the structure and IR spectra of free molecules of water, 4-pentyl-4′-cyanobiphenyl, benzophenone and their H-complexes formed in the near-surface layers of titania nanocrystallites due to presence of water adsorbed on their surfaces. Using the results of simulation and analysis of IR spectrum bands corresponding to stretching vibrations of polar bonds O-H, C=O, C≡N, the formation mechanism of near-surface layers of titania nanocrystallites in the considered heterogeneous two-component systems is theoretically substantiated: they are formed by hydrogen-bonded complexes involving components of the mixture and water. [ABSTRACT FROM AUTHOR]

IR spectroscopy methods (experiment, theoretical simulation) have been applied to study the structural features and intermolecular interactions in a two-component heterogeneous nano-size system benzophenone-titanium dioxide (BPh-TiO2). IR spectra of the sample were recorded at room temperature within the range 400–4000 cm−1. The spectra display hydrogen bonding determining the intermolecular interactions between titanium dioxide, BPh molecules, and water in the near-surface layers of nanocrystalline TiO2 particles. IR spectra of free BPh molecules, water, model H-complexes of BPh with water, and the fragment of hydrated titania surface (BPh...HOH and BPh...Ti≡) have been simulated. Experimental and theoretical spectra were analyzed in the region of stretching vibrations of carbonyl, hydroxyl, and other groups sensitive to a variation of intermolecular interactions. It is found that hydrogen bonding in the near-surface layers of nanocrystalline TiO2 particles in the two-component heterogeneous nanosystem BPh-TiO2 gives rise to the formation of complexes BPh-O-Ti(OH)-O-, BPh...HOH, along with complexes of-O-Ti(OH)-O-with water and pure water complexes. [ABSTRACT FROM AUTHOR]

The crystalline structure of 2-biphenylmethanol has been investigated by the radiographic method at room temperature, and its IR transmission spectra were measured in the 400–4000 cm−1 range. Structural-dynamic models of free molecules of 2-biphenylmethanol, biphenyl and methanol, hydrogen-bonded complexes of 2-biphenylmethanol with methanol and a tetramer of methanol molecules have been built by the density functional method (B3LYP/6-31G*). The structure, the energy, mechanical and electro-optical parameters, the frequency and intensity of normal vibrations in IR spectra of each of the mentioned molecular systems were calculated. The crystalline structure of 2-biphenylmethanol, its features determined by the hydrogen bond formation in the crystal has been found, its structure-forming role and energy were assessed, and IR spectra interpreted on the basis of single crystal X-ray diffraction data, the analysis of measured IR spectra, and results of molecular modeling. [ABSTRACT FROM AUTHOR]

Plane vibrations and intensities of the IR spectra of the ketone and enol forms of cytosine and deuterocytosine in various phase states are calculated and analyzed. It is shown that in a crystalline state and an aqueous solution cytosine forms a hydrogen bond of two types: C2=O8...HN1 and C2=O8...HN10, with a stronger intermolecular interaction in both phases being implemented by the hydrogen bonds between the O8 and N1 atoms. A satisfactory interpretation of the spectrum of the isolated molecules of cytosine, with the simultaneously existing ketone and enol tautomeric forms, is possible in the presence of the structural isomers of the enol form that differ in the position of multiple bonds. [ABSTRACT FROM AUTHOR]

Calculations of the frequencies and absolute intensities of the IR bands of plane vibrations of thymine and N1,N3-deuterothymine in various phase states have been carried out. It has been shown that in the polycrystalline state thymine forms hydrogen bonds C2=O8...HN1 and C2=O8...HN3, and in an aqueous solution the intermolecular interaction is realized by means of the hydrogen bonds O8...HO and O...HN1. [ABSTRACT FROM AUTHOR]

We have measured the parameters of the bands of the stretching vibrations νOH (frequency width, peak and integral intensities) in the IR spectra of a large number of H‐complexes of 1,1‐diphenylethanol [(C6H5)2C(CH3)OH] with solvents of different protophilic forces, for which systematic data are not available. The enthalpies of formation of the H‐complexes and the protogenic properties of the alcohol indicated were estimated, and also correlations between spectral characteristics were established. [ABSTRACT FROM AUTHOR]

The IR band structure and intensities, as well as normal vibration frequencies, are calculated by the density functional method using the Becke exchange functional and the Lee-Yang-Parr (B3LYP) correlation functional with the 6-311+G(d,p) basis set for pyridine and water molecules and for 1:1 and 1:2 hydrogen-bonded complexes (pyridine...H2O and pyridine...D2O). The structures of the hydrogen-bonded complexes are established. The characteristicity of the fundamental vibration frequencies and absolute IR intensities of pyridine in its hydrogen-bonded complexes is analyzed. The solvent effect is investigated within the framework of the self-consistent reactive field (SCRF) model. The thermodynamic characteristics of complexation are calculated using the modified G1, G2, and G2(MP2) models and the B3LYP/6-311+G(d,p) theoretical method including the basis set superposition error (BSSE). [ABSTRACT FROM AUTHOR]

By the method of IR spectroscopy the hydrogen bonds of 1,1‐diphenylethanol (DPE) depending on the concentration in the CCl4 solution and temperature have been investigated. It has been found that hydrogen bonds in crystalline DPE form a tetramer, and in a solution with a concentration of 0.5 mole/liter, cyclic dimers are formed which, with increasing concentration, pass into a cyclic tetramer. [ABSTRACT FROM AUTHOR]

The IR absorption spectra of thin nitrobenzene, ethylene glycol, and glycerin layers in an electric field are investigated. It was established that the spectrum change and electro-optical effects depend on the molecular structure of these liquids. [ABSTRACT FROM AUTHOR]