Interfacial water on organic substrates at cryogenic temperatures: hydrogen bonding and quantification in the submonolayer regime.

Water molecules were used to probe the physical and chemical properties of a model hydrophilic organic organized layer. To this end, H2O adsorption on mercaptoundecanoic acid self-assembled monolayers (SAMs) was investigated at the molecular level under ultra-high vacuum by high resolution electron energy loss spectroscopy (HREELS), through the sensitivity of the water OH stretching modes to the molecular environment. The water interfacial layer formation and structure were studied upon deposition at 28 K. A direct sensitive quantification in the submonolayer regime (10-80% of completion) was achieved by the sole measurement of the OH stretching mode frequencies, and the dominant basic (-COO-)/acidic (-COOH) forms of the terminal functions could be probed. The surface densities of the water interfacial layer and the SAM terminal functions were measured independently, and demonstrated to be comparable. This means that the SAM terminal functions provided anchors for water adsorption through two hydrogen bonds and that the SAM acted as a template even at 28 K. Upon annealing at 110 K, the water molecules were observed to form clusters of higher molecular density, dewetting the supporting substrate. Finally, the vanishing of the supporting substrate vibrational signature, due to the masking effect by the deposited water layer, was used to estimate the depth probed by HREELS through water layers to be 11 ± 2 Å.

DOS and electron attachment effects in the electron-induced vibrational excitation of terphenylthiol SAMs.

Low energy electron scattering on terphenylthiol (TPT, HS-(C6H4)2-C6H5) self-assembled monolayers (SAMs) deposited onto gold was investigated using high resolution electron energy loss spectroscopy (HREELS) by recording specular elastic and inelastic excitation functions. The electron elastic reflectivity could be directly compared to the sample density-of-states (DOS) above vacuum level. A high reflectivity region was observed in the range 7.2-8.6 eV. Inelastic excitation functions were studied to get insights into the mechanisms involved in the excitation of a selection of vibrational modes (dipolar and impact scattering). In particular, a resonant mechanism was observed in the excitation of the stretching mode ν(CC) at 196 meV. The purely resonant contribution to the electron-induced excitation of the stretching modes ν(CH) (379 meV) could be extracted from the overtone excitation. It is located at 7.2 eV above the vacuum level and is characterized by a width of 3.4 eV.

Investigation of the reactivity of arylamines, organo-hydrazines and tolylisocyanate towards [PW12-xMxO40]n- Keggin anions.

Reaction of K7[A,alpha-PW9Mo2O39] with Na2MoO4.2H2O in a mixture of water/dioxane/hydrochloric acid and further precipitation with (Bu4N)Br provided (Bu4N)3[A,alpha-PW9Mo3O40](3). Analogous reaction with K7-xNax[alpha-PW11O39] is an alternative to the synthesis of (Bu4N)3[alpha-PW11O39{MoVIO}]2. Multinuclear NMR and ESI mass spectrometry have been used to interpret the reaction of (Bu4N)x[alpha-PW11O39{ReO}](x=3 1; x=4 1I), (Bu4N)x[alpha-PW11O39{MoO}](x=3 2; x=4 2I) and (Bu4N)3[A,alpha-PW9Mo3O40]3 by organohydrazines, arylamines, tolylisocyanate and tetraphenylphosphine imide.