Protonation of Porphocyanine - A New Expanded Tetrapyrrolic Macrocycle
Xie, L. and David Dolphin
Can. J. Chem.
The porphocyanine nucleus contains six nitrogen atoms, four of which are theoretically capable of accepting a proton in acidic solution. However, only the monoprotonated and diprotonated forms have been observed. These two forms were characterized by their visible and fluorescence spectra. PKa values of 6.0 ± 0.1 and 4.4 ±0.1 were determined by spectrophotometric titration The monoprotonated monocationic form can be observed in methanol.