Polarized vibrational spectra of betaine monohydrate single crystal

The polarized infrared and Raman spectra of betaine monohydrate single crystal were measured and discussed in relation to the crystal structure. An assignment of the observed bands to the internal vibrations of the betaine and water molecules is proposed.     

Structural and polarized vibrational studies of pentacaesium trihydrogentetraselenate monohydrate

Polarized IR and Raman spectra of single crystal were measured at room and at low temperature. The polarized IR spectra were measured by transmission and specular reflection method. The IR-microscope was used for vibrational measurement of small monocrystals. Assignment of the bands is proposed on the basis of oriented gas model approximation. The polarized vibrational spectra are discussed in relation to the crystal structure and possible proton conductivity and phase transition.     

Synthesis and crystal structure of thorium bis(hydrogenphosphate) monohydrate

Microcrystals of Th(HPO 4) 2.H 2O were hydrothermally obtained from a Th(NO 3) 4-CO(NH 2) 2-H 3PO 3-H 2O system ( T = 180 masculineC). The structure [orthorhombic, Pbca, a = 9.1968(2) A, b = 18.6382(2) A, c = 8.7871(2) A], unlike alpha-Zr(HPO 4) 2.H 2O-type layered compounds, consists of a three-dimensional framework with PO 4 tetrahedra coordinated to Th atoms. The water molecule is also coordinated to the Th atom and projected toward small channels running along the directions of the a and c axes. The ThO 6O(w) environment could be described as a highly distorted pentagonal bipyramid.     

N‐(2‐Hydroxyethyl)ethylenediammonium hydrogenphosphate monohydrate

The title compound, C₄H₁₄N₂O²⁺·HPO₄^2?·H₂O, contains alternating interleaved layers of hydrogenphosphate and N‐(2‐hydroxyethyl)ethyl­enedi­ammonium moieties. The water mol­ecules are associated with channel‐like voids in the structure and a network of hydrogen bonds stabilizes the crystal packing.     

DFT studies of the structure, vibrational and NMR spectra of 2-amino-pyridine betaine monohydrate

Four of the most stable conformers of 2-amino-pyridine betaine (1-carboxymethyl-2-amino-pyridinium inner salt) monohydrates, 2-NH₂PB·H₂O, and one anhydrous were analyzed by the B3LYP/6-31G(d,p) calculations and compared with the X-ray data. Two types of optimized conformers can be distinguished: (a) with NH₂ and COO groups and (b) an imino tautomer with NH and COOH groups. A common feature of the optimized molecules are intramolecular hydrogen bonds between the COO⁻ and H₂N or COOH and HN groups. In the crystal both NH₂ and COO groups participate in intermolecular hydrogen bonds. The probable assignments of the anharmonic experimental solid state vibrational frequencies of 2-NH₂PB·H₂O and 2-ND₂PB·D₂O (conformer 2) based on the calculated B3LYP/6-31G(d,p) harmonic frequencies have been made. Correlations between experimental chemical shifts for 2-NH₂PB, its hydrochloride and 1-carboxyethyl-2-amino-pyridinium inner salt (¹³C and ¹H in D₂O) and GIAO/B3LYP/6-31G(d,p) calculated isotropic shielding constants, δ_exp=a+bσ_calc, are reported. Good linear regression between experimental and theoretical results for ¹³C was obtained. Only in 2-NH₂PB the hydrogen at -position is outside the linear correlation.     

Ab initio structural and vibrational investigation of sulfuric acid monohydrate

We employ ab initio methods to find stable geometries and to calculate potential energy surfaces and vibrational wavenumbers for sulfuric acid monohydrate. Geometry optimizations are carried out with the explicitly correlated coupled-cluster approach that includes single, double, and perturbative triple excitations (CCSD(T)-F12a) with a valence double-ζ basis set (VDZ-F12). Four different stable geometries are found, and the two lowest are within 0.41 kJ mol(-1) (or 34 cm(-1)) of each other. Vibrational harmonic wavenumbers are calculated at both the density-fitted local spin component scaled second-order M?ller-Plesset perturbation theory (DF-SCS-LMP2) with the aug-cc-pV(T+d)Z basis set and the CCSD-F12/VDZ-F12 level. Water O-H stretching vibrations and two highly anharmonic large-amplitude motions connecting the three lowest potential energy minima are considered by limiting the dimensionality of the corresponding potential energy surfaces to small two- or three-dimensional subspaces that contain only strongly coupled vibrational degrees of freedom. In these anharmonic domains, the vibrational problem is solved variationally using potential energy surfaces calculated at the CCSD(T)-F12a/VDZ-F12 level.     

The dehydration process in the dl‐phenylglycinium trifluoromethanesulfonate monohydrate crystal revealed by XRD,vibrational and DSC studies

Thermal analysis, X‐ray diffraction and temperature‐dependent IR spectroscopy were used to study the dehydration process of crystalline dl ‐phenylglycinium trifluoromethanesulfonate monohydrate (PGTFH), C₈H₁₀NO₂⁺·CF₃SO₃^?·H₂O. PGTFH dehydrates in one step centred at 353 K and crystallizes in the monoclinic space group C2/c, whereas the anhydrous compound (PGTF) crystallizes in the triclinic space group P. The dehydration process in PGTFH is preceded by a weakening of both the noncovalent aromatic–aromatic interactions and the packing contacts. This process is accompanied by the breakage of medium‐strength O—H…O hydrogen bonds between ions inside layers and a reorganization of the ions within the layers. This reorganization results in the formation of two different ion pairs (dl ‐phenylglycinium trifluoromethanesulfonate) and the formation of a new hydrogen‐bond network. The dehydration process does not destroy the nature of the crystal structure. Both crystals, i.e. hydrated and anhydrous, have a layered structure, although the layers of each crystal are arranged somewhat differently.     

Low-frequency vibrational Raman and i.r. spectrum of crystalline cystosine monohydrate

Raman scattering and i.r. transmission measurements were performed on oriented single crystals of cytosine monohydrate (CMH) at frequencies below 400 and 150 cm⁻¹ respectively. Frequency shifts caused by partial deuteration were also measured. The spectra were interpreted with the help of a lattice dynamical model containing only ‘line-of-sight’ interactions. The observed Raman frequencies in CMH were found to be significantly higher than corresponding ones previously measured in 1-methylthymine. These differences in frequencies are thought to be due to the additional hydrogen bonding provided by water molecules in CMH. A brief discussion is given of the implications of our measurements for interpyrimidine bonding in DNA.     

Synthesis,crystal structure,vibrational and dielectric properties of di-benzyl-ammonium selenite monohydrate

The new hybrid compound [C₆H₅CH₂NH₃]_2·SeO_3·H₂O was synthesized and found to crystallize in the triclinic space group P$\overline{1}$. This structure can be described as an alternation between organic and inorganic chains connected by two types of N−HO and O−HO hydrogen bonds. The two and antiparallel cations [C₆H₅CH₂NH₃]⁺are arranged in a face-to-face pattern with a distance of 3.911(10)Å between them, indicating the existence of π-π interaction. The thermal properties show that the mass losses take place in three steps, which correspond to dehydration and degradation of the title compound. The IR and Raman spectra prove the existence and independence of the organic and inorganic groups as well as a water molecule. The equivalent circuit is modeled by a combination series of two parallel R–CPE circuits. Dielectric studies show that this material is ionic-protonic conductor at low temperature and becomes electronic one at high temperature.     

Diguanidinium hydrogenarsenate monohydrate and its deuterated analogue vibrational, DSC and X-ray investigations

The crystal structure of diguanidinium hydrogenarsenate monohydrate has been found to belong to the P42(1)/c space group of the tetragonal system, with Z = 8, a = 17.114(2) A, c = 7.3500(10) A. In this complex, a network of hydrogen bonds links water molecules and hydrogenarsenate ions. The hydrogenarsenate ions form hydrogen-bonded chains along the crystallographic c-axis. Detailed vibrational studies have been carried out (FTIR and FT-Raman on powder samples, polarized FTIR microscope on a small single crystal at room temperature). The vibrational spectra are discussed in relation to the crystal structure. Calorimetric (DSC) studies have been performed, but no phase transition was found in the temperature range 100-350 K.     

Vibrational spectral studies of L-methionine L-methioninium perchlorate monohydrate

The infrared and laser Raman spectra of L-methionine L-methioninium perchlorate monohydrate were recorded at room temperature and the vibrational assignments of the observed wave numbers were made. The presence of both the carbonyl and the ionized carboxylic groups has been identified in the title complex. The L-methionine and L-methioninium the cation have different conformations. This together with the different environment has seen by the two -CH(2)- groups in each skeleton cause several of the group wave numbers to occur as doublets or as broad bands. The perchlorate anion was found to be in the T(d) symmetry in the methionine environment. The coordination to other ligands in the crystal through hydrogen bonding does not affect this symmetry. The extensive intermolecular hydrogen bonding in the crystal was identified by the shifting of bands due to the stretching and bending modes of the various functional groups. Fermi resonance has also been observed.     

Polarized vibrational spectra of Prussian Blue films: Spectroscopic evidence of columnar growth

We describe the preparation of Prussian Blue films with several thicknesses, and their characterization by means of cyclic voltammetry and polarized reflection FTIR spectroscopy. The electrochemical experiments demonstrated a direct relationship between the film thickness and its intrinsic conductivity. The vibrational spectra showed asymmetrical bands in the vicinity of the cyanide stretching band. The s-polarization bands showed a shift to higher frequencies, while the p-polarization bands showed a downshift with increasing film thickness. The presence of shifted cyanide stretching bands in the s- and p-polarizations is attributed to the columnar shape of Prussian Blue grains formed in the growth process.     

Infrared and Raman spectroscopic studies of l-valine l-valinium perchlorate monohydrate

FT-IR and FT-Raman spectra were recorded and analyzed for l-valine l-valinium perchlorate monohydrate crystals. The wave number assignments have been made for the functional groups, viz. COOH, COO(-), --[NH(3)](+), C--(CH(3))(2), C--C--N and C--H. One of the two amino acid residues remains in the zwitterionic form while the other residue exists in the cationic form. The symmetry of the ClO(4)(-) anion has been found to be lowered corresponding to ClO(2) group. The hydrogen bonds that prevail between amino acid residues, perchlorate anion and water molecule influence the wave numbers of several stretching and deformation modes to deviate from the expected values.     

Electronic and vibrational spectral studies of substituted mercaptopyrimidines

The vibrational spectra (i.r., far i.r. and Raman) of 4,6-dimethyl-2-mercaptopyrimidine and 4,6-dihydroxy-2-methylmercaptopyrimidine have been reported along with their assignments. Hydrogen bonding and tautomeric behaviour are discussed. Electronic spectra in various solvents at different pH values are recorded. The effect of a change of solvent on the electronic transitions of both compounds is explained along with the bathochromic and hypsochromic shifts observed when the neutral form of the compound is changed to the anionic or cationic form.     

Thermal degradation and spectroscopic studies of single-crystalline organometallic calcium adipate monohydrate

Journal of Thermal Analysis and Calorimetry - Calcium adipate monohydrate single crystals were grown by single gel diffusion technique using silica gel as a medium of growth. The powder X-ray...