Study on character of interactions between Cu(I) and Ag(I) chelates with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and (neutral, anionic) micelles. Chelates of Cu(I) and Ag(I) as new micellar probes

The interactions between chelate and micelle was investigated using Cu(I) and Ag(I) chelates with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in cationic, non-ionic and anionic surfactants media. It was found that Cu(I) and Ag(I) chelates with 5-Br-PADAP are bound to different parts of micelle; the Cu(I) one to a hydrophobic core of non-ionic and anionic micelles and the Ag(I) one in a double layer of anionic micelle. Both chelates were exploited in order to examine some micellar properties. By means of Cu(I) chelate, the anhydrous character of the micellar core, the shift in micellar pH, the shift in the redox potential, the stability of the micellar core upon the addition of methanol, and the cationic character of mixed micelle (TX-100+CTAB) were examined. On the other hand, by means of the Ag(I) chelate, the micellar electrostatic potential of anionic micelle and its change upon the addition of external salt or methanol was investigated. The Co(III)/Co(II) chelates with 5-Br-PADAP were used as the parallel system to Cu(II)/Cu(I) system in order to confirm the shift in pH at the interface of sodium dodecyl sulfate micelle. It was shown that the change of oxidation state of metal ions plays the crucial role in the characterisation of properties of micelles. In this way, the anhydrous character of the micellar core, the shift in the micellar pH, the cationic character of the mixed micelle were confirmed.