Calculation and interpretation of the ir spectra of a number of N-acetylpyridinium salts

Based on calculation of frequencies and modes of normal vibrations of salts of N-acyl-4-dimethylaminopyridinium with N-acyl groups of different structures (acetyl, methoxycarbonyl, dimethylcarbamoyl), an interpretation is given of the IR spectra of the corresponding N-acyloinic cations. It is shown that the differences recorded in the experimental spectra of the salts are due to interaction between skeletal deformational vibrations of the aromatic ring and the deformational vibrations of acyl groups and to the manifestation of the characteristic vibrations of proper acyl groups. The stretching and deformational vibrations of the 4-dimethylamino group are insensitive to the nature of the acyl fragment. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 26–28, January–February, 2000.     

Symmetry of generalized mean-square vibration amplitudes and their effect on mean and equilibrium bond lengths in benzene, pyridine, and N-oxypyridine

Symmetry properties of generalized mean-square vibration amplitudes for plane six-membered rings belonging to the C_2v and D_6h symmetry groups are investigated. Corrections to average and equilibrium interatomic distances in benzene, pyridine, and N-oxypyridine are calculated. The character of the corrections in the series of these molecules and their deuterosubstituted analogs is investigated. Saratov State University, 83, Astrakhanskaya St., Saratov, 410601, Russia. Translated from Zhurnal Prikladnoi Spektroslopii, Vol. 65, No. 2, pp. 192–195, March–April, 1998.     

Role of geometrical prodan structures in the determination of possible centers of hydrogen bond formation

Using the method of intermediate neglect of differential overlap (INDO), quantum-chemical investigations of geometrical prodan structures with different rotation and deflection angles of methyl groups in the dimethylaminogroup of the molecule are performed. The charge distribution is studied for different conformations of the molecule. The possible centers of prodan interaction with proton-donor solvents are estimated. It is demonstrated that in addition to the oxygen and nitrogen atoms, the carbon atoms of the hydrocarbon chain and the aromatic prodan ring can interact with the solvent. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 10–16, January, 2008.     

Kinematic and electrooptical anharmonicity in the semiempirical intensity theory of IR and raman spectra of polyatomic molecules

Saratov State University, 83 Astrakhanskaya Str., Saratov, 410601, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 49–57, November–December, 1995.     

Allowance for resonances in solving inverse and direct spectroscopic problems in an anharmonic approximation. A scheme of processing for experimental data

The most important aspects in solving inverse and direct spectroscopic problems in the second order of perturbation theory in the presence of Coriolis, Fermi, and Darling-Dennison resonances are discussed. A scheme for obtaining unperturbed values of spectroscopic parameters is suggested which has some advantages over that proposed earlier in [6]. It is believed that this information can be useful to specialists in the field of applied spectroscopy. Saratov State Technical University, 77, Politechnicheskaya St., Saratov, 410054, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 249–255, March–April, 1997.     

Optical characteristics of alkali-halide crystals doped with nickel ions

Scientific-Research Institute of Mechanics and Physics at the Saratov State University, 112-A, Bolshaya Kozach'ya Str., Saratov, 410071, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 3, pp. 235–238, May–June, 1995.     

IR spectra of stigmastane series brassinosteroids differing in configuration and number of diol groups

IR spectra of steroid phytohormones of the stigmastane series (22R, 23R)-28-homocastasterone and (22R,23R)-28-homosecasterol and their isomers (22S,23S)-28-homocastasterone and (22S,23S)-28-homosecasterol have been analyzed. The 28-homocastasterone molecule contains diol groups in ring A and in the side chain whereas that of 28-homosecasterol has one diol group in the side chain. The lack of two OH groups in ring A of homosecasterol compared to homocastasterone results in the appearance of stretching vibrational bands of H–C= (ν_max = 3025 cm^–1) and –C=C (ν_max = 1656 cm^–1) groups of ring A. Substantial changes are observed in the area of OH stretching vibrations. Homocastasterones pressed in KBr possess twice as many OH groups as homosecasterols such that absorption band total intensities in IR spectra of both isomers caused by H-bonds of the diol groups in the side chain amount to 65% whereas the share of the 2α,3α group is only 35% of the total intensity. Hence the contribution from the side-chain OH groups of the studied brassinosteroids to the integral optical density of the bands exceeds that from the ring-A OH groups. In dilute CHCl3 solutions of the brassinosteroids, the conformations of the brassinosteroid side chains are not the same. As a result, intramolecular H-bonds of different energy are created. The optical density D_max in band maxima of free OH groups for homocastasterones is three times higher than that for the corresponding band maxima of homosecasterol. This implies that D_max for bands of free OH groups of the homocastasterone ring-A diol group is greater, in contrast with the relatively greater D_max for bands of homosecasterol side-chain OH groups bound by an intermolecular H-bond. The homocastasterone diol groups also form intramolecular Hbonds more actively. The lack of the diol group in ring A of the homosecasterols does not affect the frequencies of the C=O stretching vibrations. This leads to the conclusion that the C=O group forms intermolecular H-bonds only with the side-chain OH groups of brassinosteroids pressed in KBr.     

Infrared spectra of brassinolide and castasterone steroid phytohormones and their 24-epi derivatives

Absorption bands in IR spectra of brassinolide, castasterone, and their 24-epi derivatives in the frequency range 3800–1000 cm^–1 have been interpreted. A number of spectral features distinguishing brassinolide from castasterone have been found. The conducted analysis shows that the structural differences manifest themselves in IR spectra of the investigated brassinosteroids in the region of stretching vibrations of CO–H, C=O, C–OH, C–O–C, CH₃, CH₂, and CH groups. The main distinctions in IR spectra of brassinolides and castasterones are due to the B ring structure.     

Stepwise aromatic nucleophilic substitution in continuous flow. Synthesis of an unsymmetrically substituted 3,5-diamino-benzonitrile library

Aromatic or heteroaromatic ring precursors with 2–3 identical functionalities are often used in sequential derivatization depending on the reactivity difference or the selective execution of the reaction such as nucleophilic aromatic substitution. Continuous flow chemistry offers an enhanced parameter space (pressure and temperature) with rapid parameter optimization that ensures selectivity in many cases. We developed a flow chemistry procedure to carry out a stepwise aromatic nucleophilic substitution of difluoro-benzenes having an activating group in meta position to the fluorines. The mono-aminated products were obtained in high yield and selectivity in an extremely short reaction time, while applying higher temperature, longer reaction zone (or time), and employing higher excess of another amine reactant, the subsequent introduction of the second amino group was also successfully achieved leading to an unsymmetrically substituted 3,5-diamino-benzonitrile library.     

Calculation and analysis of the frequencies of normal vibrations of 2,3-Di-O-nitro-methyl-β-D-glucopyranoside

A calculation of the frequencies and forms of the normal vibrations of the 31-atom molecule 2,3-di-O-nitromethyl-β-D-glucopyranoside has been performed. Particular emphasis has been placed on the interpretation of the strongest bands in the spectrum of 2,3-di-O-nitro-methyl-β-D-glucopyranoside, which are due to vibrations of the nitrate groups. The present work has been reported at the IV International Congress of theoretically competent chemists, Jerusalem (Israel), July 7–12, 1996. B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 724–728, November–December, 1997.     

Intramolecular hydrogen bonding and structure of stereoisomeric 20(22)-hydroxy-22(23)-isoxazolinyl steroids

We have used IR spectroscopy and the quantum chemical AM1 method to study stereoisomeric 22(23)-isoxazolinyl steroids with a hydroxyl group at C₂₀ or C₂₂, in order to establish the spectral features that will allow us to identify their stereoisomers. We have carried out a conformational analysis of isoxazolinyl steroid stereoisomers, and we have calculated the populations of their stable conformers. We have assigned the bands in the IR spectra of the stereoisomers in the region of the stretching vibrations of OH groups, and have analyzed the possibility of intramolecular hydrogen bond formation between the OH groups and proton-acceptor centers of the isoxazoline ring. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 145–151, March–April, 2006.     

Spectroscopic manifestations of isotope substitution in ultrasound jet-cooled complex molecules and their van der waals complexes

It is shown that, upon formation of ultrasound jet-cooled var der Waals complexes of polar molecules of 9-cyanoanthracene, 3-aminophthalimide, and 3-amino-N-methylphthalimide with water molecules, pronounced manifestations of isotope substitution in the ligand molecules take place, which manifest themselves in shifting 0–0-transitions by 5–7 cm⁻¹ and changes in frequencies of intramolecular vibrations. Spectroscopic effects of isotope substitution of atoms of the amino group are established for substituted phthalimides. We propose a new mechanism of the effect of isotope substitution on frequencies of electronic transitions which cannot be reduced to the known one (realized by means of changes in values of the zero vibrational energy) and is based instead on the change in the charge density distribution in the molecule. Belarusian State University, 4, F. Skorina Ave., Minsk 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 148–154, March–April, 1997.     

Fluorescence excitation spectra of jet-cooled carbazole complexes with monohydric alcohols

We have analyzed the fluorescence excitation spectra of carbazole complexes with a single molecule of methyl, deuterated methyl, ethyl, and propyl (1-propanol and 2-propanol) alcohols, cooled in a supersonic jet. We have determined the shifts in the fluorescence excitation spectra of the complexes relative to the frequency of the purely electronic transition of unbound carbazole. They occur as a result of formation of hydrogen bonds between the N-H group of the carbazole and the OH group of the alcohols. The frequencies of stretching vibrations of the hydrogen bonds with different alcohols vary within the range 150–157 cm⁻¹, while the frequencies of the bending vibrations vary in the range 21–22.9 cm⁻¹. From the shape of the rotational contours of the bands for the purely electronic and vibronic transitions of the complexes, we determined that they belonged to rotational conformers. We calculated the equilibrium configurations of the complexes in the ground state. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 756–760, November–December, 2007.     

Interpretation of IR spectra of the N-acethyl-4-dimethylaminopyridinium salts

In a harmonic approximation we calculate the frequencies of normal vibrations and their modes for a salt cation of N-acethyl-4-dimethylaminopyridinium hexachlorstibiate and of its three deuteroderivatives obtained on deuteration over a CH₃-group, over a ring, and over a ring and a CH₃-group. From the results of calculation, an interpretation of the IR spectra of the salts considered is carried out. To whom correspondences should be addressed. L. M. Litvinenko Institute of Physical and Organic Chemistry and the Chemistry of Coal, National Academy of Sciences of Ukraine, 70, R. Luxemburg Str., Donetsk, 340114, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 158–162, March–April, 1999.     

Theoretical interpretation of spectral signs of an oxymethyl group in the IR spectrum of methyl-β-D-glucopyranoside

For the first time, we have assigned the observed absorption bands and interpreted the IR spectrum of methyl-β-D-glucopyranoside in detail in the 1500–800 cm⁻¹ region, based on a full calculation of the frequencies and absolute intensities of the normal vibrations of the molecule and their comparison with the experimental data. We have identified two groups of spectral signs indicating an oxymethyl substituent has replaced the hydroxyl group on the C₍₁₎ atom in the glucopyranoside: absorption bands of medium intensity due to the characteristic vibrations of the substituent, and intense bands due to an unusual “interaction” between many structural moieties. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 721–727, November–December, 2006.     

Infrared spectra of S-and R-isomers of biologically active brassinosteroids

Comparative analysis of IR spectra of S-and R-isomers differing in the configuration of OH groups in the side chain of biologically active 24-epi-and 28-homocastasterones and 24-epi-and 28-homobrassinolides is carried out. Stretching vibration frequencies of H-bonded OH groups of isomers of corresponding brassinosteroids practically coincide. The optical density in maxima of these bands is higher in spectra of the R-isomers. Alteration in the configuration of the OH groups weakly influences also the band intensities of CH3, CH₂, and CH groups. Band intensities of stretching vibrations of associated C=O groups of S-and R-isomers also neglibibly differ from each other. Their frequency characteristics do not experience substantial changes. These features differ considerably in IR spectra of castasterones and brassinolides. For castasterones, the difference in frequencies of band maxima of free and bound C=O groups amounts to ∼15 cm⁻¹; for brassinolides, 23 cm⁻¹. Intensities of both bands are approximately equal in spectra of castasterones. The band intensity of free C=O groups of brassinolides is considerably lower than that of H-bonded ones. The above spectral differences can be used to identify these brassinosteroids. Frequencies of both symmetric and antisymmetric deformation vibrations of CH₃ and CH₂ groups are close in spectra of all brassinosteroids studied. The frequency of CH₂ in a CH₂-OC group belongs only to brassinolides; of deformation vibrations of CH in a CH-C=O group, to castasterones. The frequency of stretching vibrations of C-O-C and C-O groups is observed only in spectra of brassinolides. In the region 1130–900 cm⁻¹ of IR spectra of brassinosteroids, stretching vibrations of CC, CCH, and C-OH groups are predominantly observed. In the frequency range 1130–995 cm⁻¹, the optical density of band maxima of S-isomers is higher than that of R-isomers, which can be used to identify isomers. At the same time frequencies of corresponding bands of isomers practically coincide. Differences in the structure of the side chain of brassinosteroids do not influence essentially the frequency characteristics of the IR spectra. The exception is the band related to stretching vibrations ν(C23-OH) of the side chain which features a considerable frequency ν_max ≈ 983 cm⁻¹ only in spectra of R-isomers of homocastasterone and brassinolide. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 623–630, September–October, 2008.     

Effect of intravenous laser irradiation on the molecular structure of blood and blood components

We present the results of a spectral study of the effect of low-intensity laser radiation on the molecular structure of blood and blood components. Analysis of the Fourier transform IR absorption spectra of blood confirmed the changes we observed previously in the oxygen transport characteristics of blood with intravenous exposure to the emission from a He-Ne laser. We show that structural and conformational changes in the hemoglobin tetramer, initiated by laser-induced photoreactions between Hb and oxygen, lead to characteristic changes in the shape and intensity of the IR bands for NH stretching vibrations, and also the amide I and amide II absorption bands. In the IR spectra of irradiated blood samples, we note increased absorption in the bands for stretching vibrations of the phosphate groups (945–1280 cm⁻¹), which is evidence for an increase in the nucleic acid content (DNA, RNA). In the spectra of plasma and erythrocytes prepared from irradiated blood, there are no changes in this region of the IR spectrum. At the same time, in the IR spectra of samples of irradiated plasma, the intensity of the bands for stretching vibrations of the CH₂ groups increases substantially. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 106–112, January–February, 2006.     

Using the coordinates of the mass centers of atomic groups in analyzing vibrations of large molecules

We show that in describing the vibrations of molecules it is worthwhile to use coordinates that include the mass centers of atomic groups. We note special features of the program implementation of the approach in application to the earlier devised set of “Spectrum-structure” and LEV programs. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 42–47, January–February, 2000.     

Study of the electro-absorption spectrum of a nickel acceptor exciton in a ZnO:Ni crystal based on a calculation of vibrations associated with a Ni+1 impurity

Localized vibrations in ZnO crystals due to the substitution impurity Ni⁺¹ are modeled. The calculations were performed in the shell model using a recursive method for vibrations with A ₁ and E type symmetry. Numerical calculations allowed us to analyze the vibronic structure in the electro-absorption spectra for nickel acceptor excitons in ZnO:Ni. Fiz. Tverd. Tela (St. Petersburg) 41, 986–990 (June 1999)     

Generation-mode operation of the tunnel diode stimulated by external microwave radiation

We show that oscillations in the generating circuit are stimulated under the action of microwave radiation when bias voltage, which is smaller than peak voltage, is applied to the diode. In this case, the frequency and amplitude of the generation stimulated by microwave radiation depend on the radiation power level. Saratov State University, Saratov, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 10, pp. 1009–1012, October 1999.