A comparative study of pyrenol and its trisulfonated derivative, pyranine, is undertaken to provide new clues for the understanding of the excited-state proton-transfer reaction (ESPT) of hydroxyarenes (ArOH*). A particular goal is to elucidate the nature of a transient intermediate involved in a three step mechanism of ESPT, as recently revealed in a dynamical study of excited pyranine in water. The present focus is on the reactant side, before the proton transfer occurs, and particular attention is given to the analysis of the nature of the electronic transitions and to the solute-solvent interactions in the ground and excited states of the ArOHs. Using both quantum chemical calculations and solvatochromism analyses, both (a) the role of electronwithdrawing substituents and H-bond interaction with the solvent in stabilizing the two lowest excited states, 1 L b and 1 L a , and (b) their relevance to the inversion of these two states are studied. The results allow the identification of the intermediate species in the three step mechanism of the ESPT of excited pyranine in water as a 1 L a state acid form, with appreciable charge-transfer character, as distinct from the 1 L b acid form reached in absorption. The results, which differ from more standard pictures of ESPT, are discussed within the perspective of a three valence bond form model for the ESPT process.

A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism. Graphical abstractThe synthesis of a series (bis)alkylamine silver(I) carboxylate complexes in nonpolar solvents were carried out and fully characterized both in the solid and solution. Carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination. The complexes form layered structures which thermally decompose forming nanoparticles stabilized only by aliphatic carboxylates.

Amorphous silicon carbonitride films were produced by remote hydrogen plasma CVD (RP-CVD) from Tris(dimethylamino)silane precursor. The effect of substrate temperature (T S ) on the kinetics of RP-CVD, chemical composition, structure, surface morphology, and properties of resulting films is reported. The T S dependence of film growth rate imply that RP-CVD is an adsorption-controlled process. The increase of T S from 30 to 400 8C causes the elimination of organic moieties from the film and the formation of SiÀC and SiÀN network structure. The structure-property relationships were determined. The films deposited at T S ¼ 300 8C appear to be dense materials exhibiting very small surface roughness, high hardness, and an extremely low friction coefficient. They seem to be suitable protective coatings for metal surfaces to increase their wear strength.