FTIR studies on protonation of selected aromatic polyimines

• Protonation of aromatic polyazomethines by methanesulphonic and p-chlorophenol proceeds according to two different ways.
• Protonation by methanesulphonic acid causes decrease in conjugation because SO3 groups interact with polymer phenyl rings.
• Protonation by p-chlorophenol causes increase in conjugation due to lack of interactions with the phenyl ring from polymer.

Protonation of selected aromatic polyazomethines by methanesulfonic acid and p-chlorophenol were investigated using FTIR spectroscopy. The influence of the protonation agent on the conjugation effect in polymers is discussed. To explain the observed differences in the protonation effects, geometry optimization was performed for systems of model compounds and protonation agents. For the model compounds the appropriate bis-Schiff bases consisting of two imine groups placed between three phenyl rings were used for calculations.