Control of the association behavior by molecular design is one of the most essential benefits in artificial supramolecular systems. 1,14‐Dianilinotripyrrin has recently emerged as a novel conjugated molecule which forms a double helix in non‐polar solvents with the aid of multiple interstrand hydrogen bonding interactions. In this work, we investigated the substituent effects at the 5,10‐positions of tripyrrin on their association thermodynamics. This study illuminated two key findings; 1) electronic tuning by the para‐substituents reduce the entropic costs thereby slightly improve the association constants, and 2) ortho‐substituents force the tripyrrin core to be relatively planar, which significantly decreases the association constant due to less feasible π‐stacking.

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.

Control of the association behavior by the molecular design is one of the most essential benefits in artificial supramolecular systems. 1,14-Dianilinotripyrrin has recently emerged as a novel conjugated molecule which forms a double helix in non-polar solvents with the aid of multiple interstrand hydrogen bonding interactions. In this work, we investigated the substituent effects at the 5,10-positions of tripyrrin on their association dynamics. This study illuminated two key findings; 1) electronic tuning by the para-substituents reduce the entropic costs thereby slightly improve the association constants, and 2) ortho-substituents force the tripyrrin core to be relatively planar, which significantly decrease the association constant due to less feasible π-stacking.

Control of the association behavior by the molecular design is one of the most essential benefits in artificial supramolecular systems. 1,14-Dianilinotripyrrin has recently emerged as a novel conjugated molecule which forms a double helix in non-polar solvents with the aid of multiple interstrand hydrogen bonding interactions. In this work, we investigated the substituent effects at the 5,10-positions of tripyrrin on their association dynamics. This study illuminated two key findings; 1) electronic tuning by the para-substituents reduce the entropic costs thereby slightly improve the association constants, and 2) ortho-substituents force the tripyrrin core to be relatively planar, which significantly decrease the association constant due to less feasible π-stacking.