The vibrational spectrum of ethanol monomer trapped in argon and nitrogen matrices has been recorded in various conditions of temperature and irradiation. The structures and vibrational properties of the anti and gauche conformers have been investigated by ab initio calculations according to the DFT method. The comparison between observed and calculated frequencies allows an explanation of the matrix data and a proposal of a complete assignment for both conformers. The striking spectral changes observed in nitrogen matrices upon temperature cycling in the range 8−30 K are interpreted in term of anti → gauche conversion. In contrast with these observations, the spectrum obtained in an argon matrix is unsensitive to thermal effects, the anti form being the only one to be stabilized. Monochromatic irradiations in the OH and CO stretching regions were carried out with the purpose of inducing photorotamerization. In all cases only changes of trapping sites were observed, despite an interconversion barrier lower than the energy of the absorbed photons.

A study of the self-assembly of nonane-alkanedithiol monolayers on gold in n-hexane and ethanol solvents is presented. Self-assembled monolayers (SAMs) are characterised by reflection-absorption infrared spectroscopy (RAIRS), sum frequency generation (SFG) and spectroscopic ellipsometry (SE) measurements. Data obtained for alkanethiols SAMs are also shown for comparison. The measurements show that nicely organized HSC9SH SAMs can be obtained in n-hexane provided that N2-degassed solutions are used and all preparation steps are performed in the absence of ambient light. SFG measurements show that these SAMs have free standing SH groups. Use of an un-degassed and/or light-exposed n-hexane solutions leads to a worse layer organization. Preparation in ethanol, even in degassed solutions with processing in the dark, leads to poorly organized layers and no sign of free -SH groups was observed.

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Selective vibrational excitations of OH stretching modes of ethanol dimers trapped in solid argon or nitrogen were carried out in the range 3550-3500 cm -1 . This proved an efficient means to interconvert these dimers and thus to characterize several conformers by their most specific vibrational modes. The structures, energies, and vibrational properties of four minima of the potential energy surface have been investigated by the density functional method. These minima correspond to an open chain dimer where both proton donor (PD) and proton acceptor (PA) subunits are either anti-or gauche-ethanol, with well-differentiated vibrational spectra in the domains 1400-1240 and 1100-1020 cm -1 . The comparison between calculated and observed spectra in these domains enables the anti or gauche character of both PD and PA to be distinguished. In argon matrix four dimeric species were identified after deposition. All of them are sensitive to irradiation at the νOH frequency of their PD moiety, with simple conversion schemes for two of them. On one hand, the most abundant one, characterized by νOH bands at 3660.1 and 3527.2 cm -1 , is found to be anti-anti. Upon irradiation at 3527 cm -1 , it is converted into an unstable gauche-gauche form, not present before irradiation, which spontaneously reconverts into its precursor in the dark. On the other hand, another conformer with νOH frequencies at 3665.4-3536.2 cm -1 , also anti-anti, is converted upon irradiation at 3536 cm -1 into a new form whose identification is rendered difficult by the small number of bands assigned. In nitrogen not less than seven νOH bands in the range 3520-3470 cm -1 are assignable to dimers. Irradiations at various νOH PD frequencies are very efficient to interconvert these species whose structures are discussed on the same grounds as in the case of argon matrix. However the greater complexity of the conversion processes precludes a full assignment of the spectra except for the most abundant species for which the data are complete enough to conclude an anti-gauche structure.