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The photo-stability of hydrophobic esters of pyridine-3-carboxylic acid and pyridine-3,5-dicarboxylic acid containing 2-ethylhexyl-, octyl-, and dodecyl-substituents which are model extractants of copper from chloride media were studied together with the photo-degradation of their copper complexes. The results indicate that UV light degraded the esters of both pyridine-3,5-dicarboxylic acid and pyridine-3-carboxylic acid. The degree of degradation depended on the structure of the ester, the type of solvent, and the presence of oxygen, water or hydrochloric acid in the solution during exposure to visible or UV-visible light. Photo-reactions between the solvent and the esters were also observed. Copper has a considerable influence on the photo-stability of the esters.

Mass spectrometric decompositions of complexes of nicotinic acid esters and amides with copper are discussed. Liquid secondary ion mass spectrometry (LSIMS) was used as an ionisation technique and metastable ion spectra were recorded by using B/E linked scans. The fragmentation pathways consist mainly of the loss of one ligand molecule and also the cleavage of amide or ester bonds. It may be possible, on the basis of cleaved neutral fragments, to determine the site of coordination in the gas phase. It was also found that the presence of a chlorine atom affects the fragmentation pathways of complexes.