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The infrared and Raman spectra of K 2 HPO 4 , K 2 HPO 4 ·3H 2 O and their deuterated derivatives were investigated between 10 and 550 K in the 4000-10 wavenumber range. For the anhydrous compound, two reversible phase transitions were evidenced and characterised at 150 and 450 K (180 and 450 K for the deuterated one). Above 450 K, the crystal is disordered, and the HPO 4 2− ions become spectroscopically equivalent. However, the strength of the hydrogen bonds remains practically the same as in the other phases and protonic conduction was not evidenced. K 2 HPO 4 ·3H 2 O shows two low temperature second order phase transitions at 165 and 200 K. These transitions consist of an ordering of the water molecules which are dynamically disordered at room temperature. The reversible anhydrous-trihydrate transition at 330 K is explained by rotational motions of the HPO 4 entities inside similar crystal frameworks.

In order to study the structure and dynamics of calcium–lead hydroxyapatites, Ca10−xPbx(PO4)6(OH)2, the Raman spectra of Pb10(PO4)6(OH)2 and Ca4Pb6(PO4)6(OH)2 are presented between 300 and 650 K in the 4000–10 cm−1 wavenumber range. For the two compounds, structural phase transitions are evidenced. The reversible structural transformation from monoclinic to hexagonal observed for Pb10(PO4)6(OH)2 occurs in two steps at 420 and 510 K. The hexagonal structure was not evidenced in the lead–calcium compound and only the first transition was observed near 420 K. At room temperature, OH− ions in pure lead hydroxyapatite (monoclinic form) are fully ordered within c-axis columns. An increase in temperature leads to a progressive disordering of these anions, resulting in the stabilisation of the hexagonal phase. Ca4Pb6(PO4)6(OH)2 has a disordered structure at room temperature compared with pure lead hydroxyapatite. The two broad ν OH− bands observed at 3567 and 3582 cm−1 confirm this interpretation. The existence of hydrogen bonds between the OH− and the nearest PO43− is also confirmed with Raman spectroscopy. Copyright © 2001 John Wiley & Sons, Ltd.

Infrared and Raman spectra of Cs 5 H 3 (SO 4 ) 4 ·H 2 O have been investigated in the 4000−10 cm −1 region between 450 and 90 K. An assignment of bands in terms of OH group, distorted sulphate ion and crystalline water group frequencies is proposed. One phase transition is observed at 415 K on heating and the spectral changes which occur between 150 and 240 K have been explained by progressive freezing out of the dynamically disordered acid hydrogen bonds and rotationally disordered water molecules on cooling. The spectroscopic results are compared with dielectric relaxation and NMR measurements on Cs 5 H 3 (SO 4 ) 4 ·H 2 O as well as with crystallographic data on the hexagonal high temperature phase of isomorphic Cs 5 H 3 (SeO 4 ) 4 ·H 2 O.

Blue pigments used by a 19th century French artist were analysed by Raman microspectrometry. The results are discussed in relation to the painting materials available at that time. This study is connected with an artistic study of the drawings, and allows the artistic and technical aspects of the work of this painter to be compared.

Raman and infrared spectra (4000–20 cm−1) of polycrystalline pyridine–oxalic acid complexes were investigated between 80 and 300 K and an assignment in term of group frequencies is given. The 2:2 and 2:3 compounds are spectroscopically identified and the OH…O and NH…O hydrogen bonds characterized. The spectroscopic results are consistent with crystallographic data. With the deuterated oxalic acid, only one 1:1 complex is obtained and its crystalline structure is different. From spectroscopic analysis, it is found to be built of infinite chains of hydrogenoxalate ions with strong OD…O hydrogen bonds (νOD about 1300 cm−1 and estimated Ro…o = 2.53 A). The pyridinium moiety (C5H5ND+) forms ND…O hydrogen bonds characterized by a νND frequency of 2130 cm−1 and an N…O distance of 2.75 A. Further, in this compound, one second-order phase transition is observed at 235 K and the structural modifications are discussed.

The Raman and infrared spectra of (NH4)3H(SeO4)2 and (ND4)3D(SeO4)2 were investigated between 20 and 400 K in the 4000–10 cm−1 frequency range. Five crystalline phases were characterized spectroscopically and structural information was obtained by comparison with results previously obtained on sulphate analogues. Phase III at room temperature is strongly disordered, mainly as regards the ammonium ions, and a decrease in temperature leads to a progressive ordering; however, parent and deuterated compounds show different phase sequences. Only the ferroelectric phase V shows the spectra characteristic of a fully ordered crystal. The mechanism of phase transitions, involving motions of NH4+ and selenate entities, and the behaviour of the strong OH…O hydrogen bond, present in the asymmetric (SeO4HSeO4)3− dimers, are discussed.

Raman and infrared spectra of 4-methyl-1,2,4-triazolethione showed that two crystalline phases, one stable and the other metastable, can be obtained from various crystallization processes. The metastable phase transforms into the stable phase at 395 K by an irreversible first-order phase transition. The two phases were characterized spectroscopically and structural properties are discussed. Copyright © 2000 John Wiley & Sons, Ltd.

The conventional ab initio method at the closed restricted Hartree-Fock level (RHF) and the density functional theory (DFT) approach at the B3-LYP level, using the 6-31+G* basis set, are applied to predict the molecular structure and the energetic and the vibrational properties (harmonic wave numbers, force fields and potential energy distributions) of the 3,4'-bi-1,2,4-triazole and of two deuterated derivatives (ND and ND(CD)(3)). The theoretical results are compared to the Raman and infrared vibrational data. Using both methods, there is a very good agreement between theory and experiment concerning not only the wave numbers but also the isotopic shifts. This accordance allows us to validate the calculated structure of bTA. This molecule is characterized by an aromatic structure in which two triazolic rings are linked by a CN bond, intermediary between a single and double bond, in a planar conformation. From a methodological point of view, the B3-LYP method predicts more accurate structure and harmonic vibrational wave numbers than the RHF method.

Infrared and Raman spectra of crystalline pyrrole and pyrrole-d5 were recorded in the range 5–4000 cm−1. The behaviour of internal and external modes was studied as a function of temperature between 200 and 5 K. Two phase transitions were observed at 67 and 30 K and their mechanism is discussed. For the incommensurate phase, between 67 and 30 K, the amplitude and phase modes were identified at about 20 and 10 cm−1, respectively; for the first, a critical exponent of 0.30 was determined. No evidence of NH … π hydrogen bond participation in the transitions has been detected.

Six red quinacridone pigments have been studied and characterised by electronic, infra–red and Raman spectroscopic techniques. The pigment colour can be correlated to the crystal structure rather than in terms of intramolecular substituent effects. Study of the pigments in paint formulations shows the complementary nature of these techniques; in particular, Raman spectra are very useful for pigment identification while infra–red spectroscopy is useful for characterising resins.

The infrared and Raman spectra of various flourinated ethylamines have been obtained for different phases. Emphasis has been put on the conformational behaviour in inert gas matrices. Some preliminary results for 2-fluoroethylamine and 2,2,2-trifluoroethylamine are given in the present communication. The two gauche conformers of 2-fluoroethylamine which are observed in the vapour phase are also present in the argon and nitrogen matrices. A conformational change, possibly to an anti conformer, is observed after a few hours in the argon matrix. For 2,2,2-trifluoroethylamine no conformational change is observed in the matrices.

Infrared and Raman spectra of the BaF(HF 2 ) crystal and its 10 and 50% deuterated derivatives at 300 and 90 K have been investigated in the 4000 to 20 cm −1 range. An assignment of internal and lattice vibrations has been proposed. Vibrational spectra are consistent with a centrosymmetric P 2 1 / m space group and Z =2. They show that the (FHF) − ion is not centrosymmetrical, in spite of a short F…F distance; a force field calculation has been performed in order to determine the FH and H…F distances, which are equal to 1.08 and 1.20 A, respectively, in agreement with the 1 H and 19 F NMR data. The ν 3 (H)/ν 3 (D) isotope frequency ratio indicates a negative or zero isotope effect on the F…F distance, which is observed for the first time for a strong asymmetric hydrogen bond.

The Raman spectra of a purine single crystal have been studied in the 200 to 5 cm−1 region. Far infrared spectra of oriented needles have been recorded for comparison in the 250 to 15 cm−1 range. Sixteen of the twenty-one expected lattice vibrations have been observed and asigned to their symmetry species. Normal coordinate calculations for the purine crystal have been carried out, the atom-atom intermolecular potentials being identical with those of 1,2,4-triazole with the exception of the H…N interaction.

Infrared and Raman spectra of crystalline deltic acid and its deuterated derivative have been studied between 4000 and 20 cm −1 . In order to specify vibrational assignment of ring and CO modes based on C 2v molecular symmetry, valence force field calculation was undertaken. It appears that the results obtained for simpler disubstituted cyclopropenones can be applied to deltic acid. So, the highest frequencies about 1930 and 1610 cm −1 involve nearly equal mixture of ring and CO stretching. Two different, strong but asymmetric OH OC hydrogen bonds occur in crystal.

Raman spectrometry complemented by infrared spectrometry have been used to study the modifications of the acetylcholine (Ach) molecule during the course of its non-enzymatic hydrolysis in the pH range 6 to 12. The evolution with time of Ach Raman spectra, in the 600–1800 cm−1 frequency range, has been related to the course of the reaction and the final products have been identified. The rate constant has been determined using the relative intensities of vibrations associated with the Ach molecule and with the products of the reaction. The calculated value was in agreement with the value obtained by the pH-stat method.

The infrared and Raman spectra of crystalline deltic acid and its deuterated derivative have been investigated in the 4000–20[Formula: see text]cm−1 range. An assignment of all the intramolecular fundamentals has been proposed assuming a C2v molecular symmetry. The crystal symmetry is likely to be described by the [Formula: see text] or P2/m space group with Z = 2. Deltic acid molecules probably form infinite chains linked with two very strong, asymmetric, and different OH … O hydrogen bonds, with O … O distances estimated at 2.49 and 2.56 Å.

The i.r. and Raman spectra of polycrystalline 2-pyridinethione, 3-pyridazinethione, 2,4-dithiouracile and corresponding N -deuterated derivatives have been investigated in 4000-40 cm −1 range. Solutions in various solvents were also examined. An assignment for all intramolecular fundamentals is given. Only the “thio” form was observed even in apolar solvents. A metastable solid phase has been shown-up for the deuterated 2,4-dithiouracile. In these compounds, the strength of NH ⋯ S hydrogen bonds are similar to NH ⋯ O interaction of corresponding “oxo” molecules and characterised by νNH frequencies about 2900 cm −1 .

The i.r. and Raman spectra of room temperature phase (phase II) of (NH 4 ) 3 H(SO 4 ) 2 and (ND 4 ) 3 D(SO 4 ) 2 as polycrystalline samples and single crystals have been investigated between 4000 and 30 cm −1 . An assignment of internal and external modes is given in terms of group frequencies and symmetry types. This crystal contains non-centrosymmetric dimers (SO 4 HSO 4 ) 3− where sulphate ions are associated by strong asymmetric OH … O hydrogen bonds; they are characterized by two strong Raman bands at 1078 and 966 cm −1 , and a νOH frequency at about 1250 cm −1 . The acidic proton is statistically disordered around the crystallographic symmetry centre while all of the NH + 4 ions show an important dynamical orientational disorder.

The i.r. and Raman spectra of various crystalline phases of the trans linear quinacridone and some methylated and chlorinated derivatives have been investigated between 4000 and 200 cm−1. Each of these pigments has been characterized spectroscopically and an assignment for intramolecular fundamentals is given in terms of group frequencies. The strength and length of NH ⋯ O hydrogen bonds have been assessed from the vNH frequency and correlated with the pigment colour which is principally determined by intermolecular interactions rather than by the substituent hypso(batho)chromic effect. The NH ⋯ O distance increases from 2.87 A for the red compounds to 2.93 A for the purple ones.

The i.r. Raman spectra of crystalline 4,5,6-trimethyl 2-pyrimidone and seven deuterated derivatives have been investigated between 4000 and 180 cm −1 . Aqueous and CHCl 3 solutions were also examined. An assignment for intramolecular fundamentals is given, as well as a distinction between the most characteristic of each methyl group. The methylation and protonation effects are discussed. Furthermore, a 1 1 adduct of this pyrimidone and potassium halides is observed and characterized; it contains a strong NH…X − hydrogen bond.

The i.r. and Raman spectra of crystalline 2-pyrimidone, its hydrochloride and corresponding N -deuterated derivatives have been investigated between 4000 and 200 cm − . Aqueous solutions were also examined. An assignment for all intramolecular fundamentals is given. Effects of the protonation on the C=O group and on the ring are discussed as well as strength and characteristics of the hydrogen bonds NH … O and NH … Cl − .

The Raman and infrared spectra of (NH4)3H(SO4)2 crystal were investigated in the range 20–300 K. An assignment of bands due to internal and external vibrations is given. The crystalline phases designated II, III, V and VII were identified and characterized spectroscopically. Hydrogen bonding, the nature and degree of structural (dis)order and the mechanisms of the phase transitions are discussed. The NH4+ ions show an important orientational disorder and become fully ordered in phase VII only. They are involved in all transitions and seem the main cause of the ferroelectricity at low temperature.

The i.r. and Raman spectra of polycrystalline acridinone and N -deuterated derivatives have been investigated between 4000 and 200 cm −1 ; solutions in various solvents were also examined. An assignment for intramolecular fundamentals is given in terms of group frequencies and symmetry type. The strength and characteristics of the NH⋯O hydrogen bonds are discussed as well as the crystal structure.

Summary Inelastic Election Tunneling Spectrometry (IETS) yielded useful information on the interaction of Acetylcholine and its analog β-Methylacetylcholine with an alumina surface. The spectra obtained are discussed in comparison with infrared and Raman spectra of the same molecules in solid state and in aqueous solutions studied previously by the authors. It is shown that under certain conditions AL 2 O 3 catalyses the hydrolysis of molecules as does the Acetylcho-Line-esterase enzyme on the postsynaptic membrane or a basic aqueous medium with a pH greater than 9.

The Tieschitz H3 chondrite contains 0.25% bulk carbon1 but concentrations of as much as 2–6% (ref. 2) occur in black, 10–20 µm-wide rims around chondrules that are thought to have accreted before the agglomeration of the stone2–5. These rims are extremely fine-grained and compact, the main constituent being an iron-rich olivine (Fa 60–65) as shown by a Debye–Sherrer X-ray diffractogram, in good agreement with the FeO/FeO + MgO matrix value2,6. To further our understanding of the rim composition and of the thermal history of the stone, we used the MOLE Raman laser microprobe7 to characterize the carbon constituent. We report here that it is a highly disordered graphite with a progressive ordering as shown by samples heated to temperatures between 300 and 600 °C. Tieschitz could not have been heated to more than 300–350 °C.