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.     

Raman spectra of potassium, rubidium, and thallium hydrogen phthalates

The polarized Fourier-transform Raman spectra of oriented single crystals of K, Rb, and Tl hydrogen phthalates, as well as of deuterated potassium hydrogen phthalate, are studied in the range 50–3300 cm^?1 in different scattering geometries. The frequencies of internal vibrations in the spectra of these compounds are assigned to vibrations of the orthophenylene and carboxyl groups. The replacement of K with Rb or Tl leads to an insignificant low-frequency shift of vibrations. A multiband structure of OH(D) stretching vibrations is observed in the range 1900–2800 cm^?1 in the spectra of all hydrogen phthalates, which is caused by Fermi-resonance interactions. A number of additional bands are observed in the spectrum of deuterated potassium hydrogen phthalate, which indicates that deuterium atoms partially replace hydrogen atoms in both the orthophenylene and the carboxyl groups.     

Raman and infrared study of phyllosilicates containing heavy metals (Sb,Bi): bismutoferrite and chapmanite

The kaolinite‐like phyllosilicate minerals bismutoferrite BiFe³⁺₂Si₂O₈(OH) and chapmanite SbFe³⁺₂Si₂O₈(OH) have been studied by Raman spectroscopy and complemented with infrared spectra. Tentatively interpreted spectra were related to their molecular structure. The antisymmetric and symmetric stretching vibrations of the Si O Si bridges, δ SiOSi and δ OSiO bending vibrations, ν (Si O_terminal)⁻ stretching vibrations, ν OH stretching vibrations of hydroxyl ions, and δ OH bending vibrations were attributed to the observed bands. Infrared bands in the range 3289–3470 cm⁻¹ and Raman bands in the range 1590–1667 cm⁻¹ were assigned to adsorbed water. O H···O hydrogen‐bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Manifestation of structure and intermolecular interactions of biologically active brassinosteroids in infrared spectra

We have analyzed the IR spectra obtained for steroidal phytohormones 24-epibrassinolide, 24-epicastasterone, 28-homobrassinolide, and 28-homocastasterone. The characteristic frequencies of the stretching vibrations of the hydrocarbon groups CH₃, CH₂, and CH and also the C=O groups in the spectra of brassinolides are higher than in the spectra of castasterones, which makes it possible to identify them from the IR spectra. Study of the spectra of these brassinosteroids in different media (pressed samples in KBr, films, solutions in CHCl₃ and CDCl₃) allowed us to establish the presence of intermolecular interactions in which C=O and OH groups, OH-OH groups participate, and also the possible formation of intramolecular hydrogen bonds between the OH groups of the molecules. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 610–616, September–October, 2007.     

Concentration dependences of IR absorption spectra in the range of stretching vibrations of OH groups of congruent lithium-niobate crystals doped with zinc and magnesium

The concentration behavior of the parameters of spectral lines that correspond to stretching vibrations of OH groups in the IR absorption spectra of LiNbO₃:Zn (0.04–4.46 mol % ZnO) and LiNbO₃:Mg (0.19–5.91 mol % MgO) crystals has been studied. It has been found that, in the range of threshold concentrations of Zn²⁺ and Mg²⁺ doping cations, the line parameters experience a jump. In this case, the widths of some lines decrease, which indicates the ordering of OH groups in the crystal. It has been shown that nonstoichiometric crystals are characterized by the occurrence of different positions of OH groups and different values of the quasi-elastic constants of O–H bonds in the crystal structure. In the stoichiometric LiNbO₃ crystal, all the positions of OH groups are the same, and the quasi-elastic constants of O–H bonds are identical.     

枪晶石变温拉曼光谱及其固液相微结构研究

枪晶石在传统冶金连铸保护渣中起着十分重要的作用。采用紫外激光光源和电荷耦合器件(CCD)探测器,测定了枪晶石晶体和高温拉曼光谱(温度范围:298~1 723 K),观察了其在变温状态(升温和降温过程)下的特征谱变化。谱图结果显示,枪晶石熔态微结构单元与固态的相比更为多元化,表明熔体状态下多种团簇结构共存。同时,利用枪晶石晶胞结构模型,通过Dmol3密度泛函(DFT)理论计算了其分子振动频率,将其与实验值相结合,确定了特征谱峰的归属,为进一步采用拉曼光谱法原位研究保护渣中枪晶石的结构变化与行为特征提供了重要依据。     

The Raman spectra and cross-sections of H2O, D2O, and HDO in the OH/OD stretching regions

We report the OH and OD stretching regions of the vapor phase Raman spectra of H₂O, and of a D₂O/HDO mixture, at room temperature. Also, the corresponding spectrum of H₂O at ∼2000 K in a methane/air flame is reported. These spectra are interpreted in terms of transition moments of the molecular polarizability, based on high-level ab initio calculations of the polarizability surface, and on variational wavefunctions considering the rotational-vibrational coupling in full. As a byproduct of this analysis several tables have been compiled including scattering strengths and assignments for individual rotational transitions of the three species. From these tables the Raman spectra in the OH/OD stretching regions can be simulated over the range of temperatures up to 2000 K for H₂O, and up to 300 K for D₂O and HDO.     

Raman spectroscopic investigations of natural jennite from Maroldsweisach,Bavaria, Germany

A full‐range pattern (100–3700 cm⁻¹) analysis of natural jennite was performed for the first time by Raman spectroscopy, applying a polarized laser at a wavelength of 532 nm. A prominent structural feature of jennite is the preferred orientation of Si‐tetrahedron and Ca‐octahedron chains parallel [010]. The latter ones are additionally coupled to H₂O molecules and OH groups. This arrangement leads to a strong dependence on orientation for the intensity ratios of mainly three different regions in the Raman spectra: 180–210, 950–1050 and 3100–3650 cm⁻¹. These sections can be assigned to Ca–O lattice vibrations, Q² Si–tetrahedron stretching and O–H vibrations of H₂O molecules and Ca–OH structures, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl titanate mineral betafite (Ca,U)2(Ti,Nb)2O6(OH): effect of metamictization

Raman spectra of the uranyl titanate mineral betafite were obtained and related to the mineral structure. A comparison is made with the spectra of uranyl oxyhydroxide hydrates. Observed bands are attributed to the (UO₂)²⁺ stretching and bending vibrations, U–OH bending vibrations and H₂O and (OH)^? stretching, bending and libration modes. U–O bond lengths in uranyls and O?H···O bond lengths are calculated from the wavenumbers assigned to the stretching vibrations. Raman bands of betafite are comparable with those of the uranyl oxyhydroxides. The mineral betafite is metamict as is evidenced by the intensity of the UO stretching and bending modes being of lower intensity than expected and by bands that are significantly broader.     

Interpretation of infrared spectra for ion-exchange systems

Analytical expressions for the frequencies of stretching OH vibrations of hydrated ions are obtained. The expressions are applied to the interpretation of the experimental IR spectra of cation exchanger KU-2, heterogeneous cation-exchange membrane MK-40, and to the Nafion membrane. The comparison of the experimental and theoretical spectra gives evidence of the existence of water molecules located between fixed and mobile ions, i.e., of the dissociation of ion pairs.     

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.     

Temperature investigations of Raman spectra of stoichiometric and congruent lithium niobate crystals

In the temperature range 100–450 K, we have investigated Raman spectra of congruent and stoichiometric LiNbO₃ crystals. We have found that, in this temperature range, frequencies and widths of all the spectral lines depend linearly on temperature. However, the width of the line that corresponds to vibrations of the A₁(TO) symmetry of Li⁺ ions depends on temperature much more weakly than the width of the line that corresponds to vibrations of the A₁(TO) symmetry of Nb⁵⁺ ions. This fact indicates that the anharmonicity of vibrations of Nb⁵⁺ ions along the polar axis is much stronger compared to vibrations of Li⁺ ions. It is likely that this anharmonicity is noticeably contributed by O^2? ions, which are characterized by an anharmonic potential, vibrations of which, according to calculations from first principles, are mixed with vibrations of Nb⁵⁺ ions. The anharmonicity of vibrations of O^2? ions is evidenced by a strong temperature dependence of the width of the line that corresponds to vibrations of the A₁(TO) symmetry of O^2? ions perpendicularly to the polar axis. We have found that the temperature dependence of the intensity of lines that correspond to fundamental vibrations is nonmonotonic. At the same time, the temperature dependence of the intensity of “superfluous lines” is strictly linear. It is likely that this behavior of the intensities of lines of fundamental vibrations is related to the occurrence of clusters and microstructures in the crystal structure.     

Raman spectroscopic study of the uranyl titanate mineral brannerite (U,Ca,Y,Ce)2(Ti,Fe)2O6:effect of metamictisation

Raman spectra of the uranyl titanate mineral brannerite were analysed and related to the mineral structure. A comparison is made with the Raman spectra of uranyl oxyhydroxide hydrates. The observed bands are attributed to the TiO and (UO₂)²⁺ stretching and bending vibrations, U OH bending vibrations, as well as H₂O and (OH)⁻ stretching, bending and libration modes. U O bond lengths in uranyls and O H···O bond lengths were calculated from the wavenumbers assigned to the stretching vibrations. Raman bands of brannerite are in harmony with those of the uranyl oxyhydroxides. The mineral brannerite is metamict, as is evidenced by the intensity of the UO stretching and bending modes being of lower intensity than expected and with bands that are significantly broader. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Vibrational study of squaric acid

Infrared and Raman spectra of polycrystalline squaric acid and its deuterated derivative have been investigated at various temperatures in the 3600–30 cm^-1 range. Two infrared active lattice modes have been identified at 230 and 125 cm^?1 in the spectra at room temperature phase. A new assignment of some intramolecular vibrations involving OH and CO group is proposed. The behaviour of intramolecular and lattice bands as a function of temperature and phase transition is discussed.     

Infrared and Raman spectra of M2Cu2O5 (M=Y,Ho)

We report both Raman and infrared reflectivity spectra of M₂Cu₂O₅ (M=Y, Ho) at room temperature in the spectral range of 30–1000 cm^–1.37 (31) ir and 18 (15) Raman active modes of Y₂Cu₂O₅ (Ho₂Cu₂O₅) are observed. A factor group analysis has been performed to identify the symmetries of the observed modes. Comparing the vibrational spectra of these compounds we conclude that the phonons above 300 cm^–1 originate from the Cu–O vibrations and those under 300 cm^–1 from M–O vibrations.Alexander von Humboldt Foundation fellow     

A Raman spectroscopic study of bukovskýite Fe2(AsO4)(SO4)(OH)· 7H2O,a mineral phase with a significant role in arsenic migration

The Raman spectrum of bukovskýite [Fe³⁺₂(OH)(SO₄)(AsO₄)· 7H₂O] has been studied and compared with that of an amorphous gel containing specifically Fe, As and S, which is understood to be an intermediate product in the formation of bukovskýite. The observed bands are assigned to the stretching and bending vibrations of (SO₄)²⁻ and (AsO₄)³⁻ units, stretching and bending vibrations and vibrational modes of hydrogen‐bonded water molecules, stretching and bending vibrations of hydrogen‐bonded (OH)⁻ ions and Fe³⁺ (O,OH) units. The approximate range of O H···O hydrogen bond lengths was inferred from the Raman spectra. Raman spectra of crystalline bukovskýite and of the amorphous gel differ in that the bukovskýite spectrum is more complex, the observed bands are sharp and the degenerate bands of (SO₄)²⁻ and (AsO₄)³⁻ are split and more intense. Lower wavenumbers of δ H₂O bending vibrations in the spectrum of the amorphous gel may indicate the presence of weaker hydrogen bonds compared to those in bukovskýite. Copyright © 2011 John Wiley & Sons, Ltd.     

Vibrational study of phase transitions and conductivity mechanism in H3OUO2PO4.3 H2O (HUP)

Infrared and Raman spectra of polycrystalline H₃OUO₂PO₄.3 H₂O (HUP) have been envestigated at various temperatures between 50 K and 300 K. The most temperature sensitive bands corresponding to PO₄ and H₂O librations, U-OPO₃ stretching and OH stretching vibrations indicate four different phases of HUP and allow to propose a phase transition mechanism from a quasiliquid state of protonated species in R.T. phase to a fully ordered crystal below 100 K. Protonic conductivity mechanism of room and low temperature phases is discussed.     

Vibrational spectra and crystal lattice dynamics of hexahydrates of zinc potassium and ammonium sulfates

The IR spectra and polarized Raman spectra of crystals of hexahydrates of zinc potassium and ammonium sulfates have been obtained experimentally at 93 K and at room temperature. The frequencies and modes of normal vibrations of the octahedral complex [Zn(H₂O)₆]²⁺ have been calculated. The assignment of the observed lines of the internal and external vibrations of the crystal cell has been made by calculations and by factor-group analysis. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 162–168, March–April, 2000.