Photostability of hydrophobic amides of pyridinecarboxylic acid as copper extractants from chloride media

Galvanic corrosion inhibition from aspect of bonding orbital theory in Cu/Ru barrier CMP

In this report, the galvanic corrosion inhibition between Cu and Ru metal films is studied, based on bonding orbital theory, using pyridinecarboxylic acid groups which show different affinities depending on the electron configuration of each metal resulting from a π-backbonding. The sp² carbon atoms adjacent to nitrogen in the pyridine ring provide π-acceptor which forms a complex with filled d-orbital of native oxides on Cu and Ru metal film. The difference in the d-orbital electron density of each metal oxide leads to different π-backbonding strength, resulting in dense or sparse adsorption on native metal oxides. The dense adsorption layer is formed on native Cu oxide film due to the full-filled d-orbital electrons, which effectively suppresses anodic reaction in Cu film. On the other hand, only a sparse adsorption layer is formed on native Ru oxide due to its relatively weak affinity between partially filled d-orbital and pyridine groups. The adsorption behaviour is investigated through interfacial interaction analysis and electrochemical interaction evaluation. Based on this finding, the galvanic corrosion behaviour between Cu and Ru during chemical mechanical planarization (CMP) processing has been controlled.

Photodegradation of Hydrophobic Pyridineketoximes in Toluene and Heptane

The goal of the research was to study the reactivity of the hydrophobic 2- and 3-pyridineketoximes under exposure to UV-VIS light. The photodegradation was conducted in both toluene and heptane for 10 h under atmosphere of argon. Ten-hour irradiation experiments demonstrated that the pyridineketoximes underwent the facile E-Z photoisomerization, photo-Beckmann rearrangement, and to a lesser extent, the photosubstitution to the pyridine ring. From LC-MS and NMR analysis of the irradiated solutions, it was found that the photosubstitution proceeded to give the corresponding 6-substituted 2- or 3-pyridylketoxime via the replacement of the ring hydrogen by the benzyl or heptyl group. The photo-Beckmann rearrangement led to the formation of the corresponding amides, but also other products formed in the photo-decomposition reaction.

Degradation of organothiophosphorous extractant Cyanex 301

The resistance of extractants to light is important during industrial extraction processes. A photodegradation of the organothiophosphorous extractant Cyanex 301 in toluene and hexane as organic diluent and the identification of possible degradation products using FT-IR and GC-MS techniques were performed. The influence of copper(II) and cobalt(II) ions on the stability of the extractant under UV-vis light exposure was also studied. The changes in the percentage composition of individual components of the extractant depended on the types of organic diluents and copper or cobalt ions. During this process, copper complex irradiation precipitation of black powder and photooxidation of toluene were observed. Based on these results we proposed a hypothetical mechanism of photodegradation of extractant Cyanex 301.