Reorganization of the intramolecular hydrogen bonding network in 1,14-di(arylamino)-5,10-di(ethoxycarbonyl)-tripyrrins

Abstract

Recently we have reported that 1,14-diaminated tripyrrins form a double helical structure via interstrand hydrogen bonding interaction in non-polar solvents. In this work, ethoxycarbonyl-substituted 1,14-di(arylamino)tripyrrins were prepared by nucleophilic substitution reaction. The structure has been revealed by X-ray analysis to be a ([Formula: see text]-syn, [Formula: see text]-syn) conformer stabilized by intramolecular hydrogen bonding between the pyrrolic NH proton and the ester carbonyl oxygen atom. This conformer was likely formed as a meta-stable state in solution since thermal isomerization into a ([Formula: see text]-syn, [Formula: see text]-syn) conformer was observed in DMSO via NH tautomerization.