Pyrrole-Based Zwitterionic π-Electronic Systems That Form Self-Assembled Dimers.

Pyrrole-based zwitterionic π-electronic systems including a phenylcarboxylate (benzoate) anionic site and an N-methyl pyridinium cation unit were synthesized. Spectroscopic and theoretical examinations revealed the intermolecular hydrogen-bonding interactions of the pyrrole NH group and the 3-pyridinium and 3-benzoate ortho-CH moieties of zwitterions with a carboxylate anion to form self-assembled dimers. The self-assembled dimers were found to exist in equilibrium with the corresponding monomers in DMSO, whose dimerization ability was examined by concentration-dependent measurements.