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The Raman spectrum of liquid ethyldibromosilane, CH 3 CH 2 SiHBr 2 , was recorded at various temperatures between 298 and 218 K, and the spectrum of the crystal was obtained at 210 K from a sample sealed in a capillary. Additional spectra of the amorphous and annealed crystals, which were deposited on a copper finger cooled with boiling liquid nitrogen, were recorded. The infrared spectra were recorded of the vapor and amorphous and crystalline solid in the range 4000-50 cm −1 and mid-infrared spectra isolated at 4.8 K in argon and nitrogen matrices were also observed. These vibrational spectra show that two conformers, anti and gauche, are present in the vapor and in the liquid, but only the anti conformer remains in the crystalline solid. Three conformer pairs in the Raman spectrum of the liquid phase were used to obtain the enthalpy difference, which gave an average value of 128 ± 17 cm −1 (1.53 ± 0.2 kJ mol −1 ) with the anti form lower in energy. At ambient temperature it is estimated that there is 52 ± 2% of the gauche conformer present in the liquid. The optimized geometries, infrared and Raman intensities, and scaled vibrational wavenumbers for the anti and gauche conformers were obtained from ab initio MP2/6-31G(d) calculations with full electron correlation. The conformational energy difference was also obtained from ab initio MP2/6-311 + G(d,p) calculations which gave a predicted energy difference of 97 cm −1 with the anti form the conformer of lower energy. These spectroscopic and theoretical results are discussed and compared with the corresponding quantities for some similar molecules.

Infrared spectra of 1,1,1-trifluoropropyltrifluorosilane (CF 3 CH 2 CH 2 SiF 3 / were obtained in the vapour, amorphous and crystalline solid phases in the range 4000-50 cm −1 . Additional spectra in argon and nitrogen matrices at 4.8 K were recorded before and after annealing to temperatures of 20-36 K. Raman spectra of the compound as a liquid were recorded at various temperatures between 298 and 163 K and spectra of the amorphous and crystalline solids were obtained. The spectra revealed the existence of two conformers (anti and gauche) in the fluid phases and in the matrices. When the vapour was shockfrozen on a cold-finger at 78 K and subsequently annealed to 120-150 K, 12 mostly weak Raman bands vanished in the crystal. Much smaller variations were observed in the corresponding infrared spectra after annealing. However, the spectra indicated the existence of two different crystals, formed after annealing the amorphous solid to 120 and to 150 K; both crystals contained the same conformer (anti). Raman and IR spectra of 1,1,1-trifluoropropyltrifluorosilane in cyclohexane, carbon tetrachloride and acetonitrile revealed conformational displacements with solvent polarity. From intensity variations between 298 and 223 K of the Raman pair 639/665 cm −1 , 1H • .gauche-anti/ = 3.4 ± 0.3 kJ mol −1 was obtained in the liquid. Annealing experiments indicate that the anti conformer also has a lower energy in argon and nitrogen matrices; moreover, the low-energy conformer is present in the crystal. The spectra of both conformers have been interpreted in detail. Ab initio calculations at the HF/6-311(d), HF/6-311 G (3df,3pd) and MP2/G-31(d) levels gave optimized geometries, infrared and Raman intensities and scaled vibrational wavenumbers for the anti and gauche conformers. The conformational energy difference derived was 5.3 kJ mol −1 with anti being the low-energy conformer.

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The H/D exchange process in the imidazolium-based room temperature ionic liquids (RTILs) 1-decyl-3-methyl-imidazolium bromide- and chloride ([C10mim][Br] and [C10mim][Cl]) in D2O solutions of various concentrations was studied applying (1)H, (13)C NMR, and Raman spectroscopy. The time dependencies of integral intensities in NMR spectra indicate that the H/D exchange in [C10mim][Br] at very high dilution (10(-4) mole fraction of RTIL) runs only slightly faster than in [C10mim][Cl]. The kinetics of this process drastically changes above critical aggregation concentration (CAC). The time required to reach the apparent reaction saturation regime in the solutions of 0.01 mole fraction of RTIL was less 10 h for [C10mim][Br], whereas no such features were seen for [C10mim][Cl] even tens of days after the sample was prepared. The H/D exchange was not observed in the liquid crystalline gel mesophase. The role of anions, self-aggregation (micellization), and mesophase formation has been discussed. Crucial influence of Br(-) and Cl(-) anions on the H/D exchange rates above CAC could be related to the short-range ordering and molecular microdynamics, in particular that of water molecules. The concept of the conformational changes coupled with the H/D exchange in imidazolium-based ionic liquids with longer hydrocarbon chains can be rejected in the light of (13)C NMR experiment. The revealed changes in (13)C NMR spectra are caused by the secondary ((13)C) isotope effects not being the signal shifts due to the conformational trans-gauche transition.

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Calcium hydroxyapatite containing amorphous phosphate phase (ACP-CaHA) and nano-structured hydroxyapatite (CaHA) have been prepared by two sol-gel synthesis routes. The structural organization of hydroxyl groups in both materials has been determined by means of 1 H MAS NMR and FTIR spectroscopy. It has been shown that the amount of structural -OH groups in nano-structured CaHA is significantly higher than that from adsorbed water and vice versa in ACP-CaHA. A precise signal shape analysis has been carried out for both studied samples. The 31 P NMR signals have been found being Voigt-shaped in the wide-line as well as in MAS spectra. The 1 H and 31 P spin-lattice and spin-spin relaxation time measurements have revealed that the fast spin motion takes place in ACP-CaHA. The corresponding correlation time τ ~ 7 · 10 -7 s at ~300 K has been determined. The effect of MAS rate on the 31 P signal shape also confirms that this motion runs in the time scale of microseconds or even nanoseconds. The magnitude of the anisotropic broadening 1220 ± 20 Hz determined for nano-structured CaHA is very close to the maximum of the dipolar 1 H-31 P coupling distribution profile estimated using CP MAS kinetics. The dynamics of 1 H-31 P spin interactions in nano-structured CaHA (τ ~ 3.3 · 10 -5 s) is much slower than in ACP-CaHA.