Chemistry Letters, Vol.33, No.2, 178-179, 2004
Intramolecular proton transfer inducing a Biszwitterion structure in a N-4 Schiff base
X-ray and NMR evidences of a sulfonated and tetradentate N-4 Schiff base pointed out unusual iminium groups. This produces amide groups and the protons transfer leads to an overall biszwitterion structure.