The coordination chemistry of model phenolic ligands (pyrocatechol, salicylic acid, and 2,2'-biphenol) that are able to form respectively five-, six-, or seven-membered rings with titanium(IV) alkoxides is investigated. With pyrocatechol, a polynuclear complex containing 10 Ti atoms was characterized with a not very common doubly bridging mu3-(O,O,O',O') coordination mode. With salicylic acid, a monomeric tris(chelate) complex was obtained. With 2,2'-biphenol, a polynuclear complex containing six Ti atoms was obtained showing both mu2-(O,O') and mu2-(O,O,O') coordination modes for the ligands. Intermolecular interactions in the solid state for these three new compounds are also quantitatively discussed using the partial charge model.
Confocal micro-Raman spectroscopy has been applied for vibrational investigations on a sol-gel derived hybrid polymer coating. In order to characterize the dimensions of the focus inside the coating, the substrate, and the coating/substrate, a model that considers both the refraction and diffraction effects has been developed. A coating of ∼20.2 μm thickness applied to polycarbonate substrate has been investigated. The spatial distribution of the Raman intensity in the focal volume was studied at different depths within the sample and the Raman response at the corresponding levels has been calculated. The selection in depth of the Raman response, given by the confocal pinhole, was also taken into account. In comparing the prediction of this theoretical model to the empirical results, a good agreement has been observed.
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