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The splitting of the T2 stretching vibration into B2 and E modes on passing from Td to D2d symmetry is discussed for M2XO4 molecules (M = Li, Na, K, Cs, In and T1. X = Cr, Mo, W and S). Correlations between XO stretching force constants, OXO bond angles and cation polarizabilities are made.

The infrared and Raman spectra of some cyclopentadienyl compounds of the transition metals, namely Ti(C5H5)Cl3 and M(C5H5)2Cl2 (M = Ti, Zr and Hf), are reported and discussed. The infrared spectra of the gaseous species isolated in argon matrices at 10 K provide structural information about the single molecules. Particular attention has been paid to the low-frequency region in order to achieve more reliable assignments for the internal-rotation modes. The structural data and the fundamental frequencies derived from the spectra are employed in a calculation of the thermodynamic functions for these compounds in the ideal gas state.

The structure of the bridging carbonyls in H 2 FeRu 3 (CO) 13 was investigated by IR spectroscopy in crystal and solutions. On basis of data handling procedures performed on the CO stretching region of the bridged carbonyls, symmetry and bond angles have been estimated.

FTIR measurements were carried out on matrix-isolated calcium dihalide vapours. CaF 2 , CaCl 2 , CaBr 2 and CaI 2 samples were vaporized at temperatures ranging from 1100 K to 1700 K and the vapours were trapped in argon and krypton matrices. Bands of monomers, dimers and in one case of a more complex aggregate were observed. The spectra were interpreted on the basis of polarizable ion model calculations. Regarding the structure of the dimer molecule, D 2h symmetry was established from the experimental measurements and theoretical results. A trimer molecule was found for CaF 2 and a D 2d symmetry structure is suggested for it.

Infrared and Raman spectra of triptycene are reported for both the solid and pseudo-gaseous phases in the range 20–4000 cm−1. Spectroscopic data are interpreted on the basis of D3h global symmetry. The entropy of the vapour is calculated at 400 K and good agreement found with the thermochemical value.

The IR spectra (300–4000 cm −1 ) of bis-(N,N-diethyldithiocarbamato)-nickel(II) as N 2 matrix and oriented polycrystalline layer are reported. All the observed bands are assigned and classified on the grounds of their polarisation in the symmetry classes of D 2h , the highest possible molecular symmetry. Remarkably, polarisation of the absorptions around 1000 cm −1 rules out the assignment to any C-S stretching, in contrast with previous assignments. The room temperature crystal spectra do not show evidence for crystal splitting. The matrix spectrum shows features related to the existence of rotamers around the H 2 C-N bond, which give useful assistance in the assignment.

In this paper are reported the infrared spectra of the gaseous ternary oxides Li, Na, K, Rb, Cs, Tl perrhenates, Li, Na and Cs molybdates and tungstates and Li, Na, K and Tl chromates in nitrogen, matrices at 10K over the frequency range 200–4000 cm −1 . The results are compared with those of the corresponding solids and free anions. The observed spectra suggest that the vibrational properties of these species may well be described as ion pairs in which the coordinated anion is not detectably polarized by the alkali metal cation.

Vibrational frequencies, force constants and geometrical parameters of the oxides of group VIB elements in rare gas matrices are compared with those in the gas phase. Bonding in these species is discussed.

The surface reaction of [(η-C 5 H 5 )Fe(CO) 2 ] 2 adsorbed on hydrated silica and alumina has been studied by FTIR spectroscopy. Hydrogen bonding of one or both bridging carbonyls of the molecule with the surface hydroxo groups, protonation on metalmetal bonds, and forming adducts with Lewis acidic sites of the surface have been taken into consideration, and a series of surface species was detected suggesting a co-existence of most above surface reactions. Cyclopentadienyl group has stabilised FeFe frame, cleavage of metalmetal bond in a small rate was only detected.

The infrared spectrum of monomeric uracil, trapped in Ar and N 2 cryogenic matrices, is presented and compared with the infrared and Raman spectra recorded for this same compound in associated forms, as observed in its pure solid state and in solution. The monomeric molecules are all in the 2,4-diketotautomeric form and are planar, as can be deduced indirectly from the absence of band multiplicity due to conformeric equilibrium. The assignment is based on comparison with previous works on uracil and with matrix isolation studies on other cis - and trans -imides and is supported by spectral comparison with N,N -dideuterouracil trapped in the same cryogenic matrices. With few exceptions, the assignment is consistent with that obtained by theoretical approaches. On passing from an Ar to an N 2 matrix, the bands due to νNH and γNH shift to lower and higher wavenumbers, respectively, as a result of a specific interaction between the NH groups and the N 2 molecules.

The polarisation behaviour of the infrared absorptions of a single crystal of bis-(dimethyldithiophosphato) nickel(II) with (001) as the predominant face is studied. Because only a and b polarisation can be measured on (001), the b 2u and b 3u normal modes, which are polarised on b , cannot be distinguished, whilst the b 1u modes are observed on a . The most characteristic absorptions of the compound are assigned on the basis of the polarisation results. The comparison of the crystal with the solution spectrum indicates that the absorptions at 396 and 357 cm −1 undergo crystal field splitting in the solid.

The IR and Raman spectra of gaseous and solid CH 3 TiX 3 and CD 3 TiX 3 species (X = Cl, Br, I) are reported. The gas phase spectra have been recorded between 4000 and 20 cm −1 at pressures of 1 atm and 4 atm at 350 K and the Raman spectra of the solid phase recorded at 4.2 K. Internal rotation barriers and thermodynamic functions have been calculated.

The reaction of magnesium and oxygen atoms in argon, krypton, xenon and oxygen matrices at 20.4° K was studied by infrared spectroscopy between 200 and 4000 cm −1 . The appearance of a band in the magnesium-oxygen stretching region, reproducible in all the matrices, indicates that reaction takes place. Oxygen-13 isotopic substitution suggests that the absorption is due to Mg 3 O 3 , whose formation is supported by the crystal structure of the solid phase. The force constants are calculated as f R = 2.3 mdyne/A and F ϕ / R 2 = 0.44 mdyne/A assuming a planar six-membered ring of alternate magnesium and oxygen atoms with bond angles O-Mg-O 100° and Mg-O-Mg 140°.

Infrared spectra of Li 2 SO 4 , Cs 2 SO 4 , Tl 2 SO 4 , In 2 MoO 4 and Tl 2 MoO 4 molecules isolated in nitrogen matrices at 12 K have been obtained. D 2d symmetry of these species is proposed. The splitting of the v 3 ( F 2 ) mode on passing from T d to D 2d symmetry is briefly discussed.