Sterically Allowed H‐type Supramolecular Polymerizations

Abstract The functionalization of π‐conjugated scaffolds with sterically demanding substituents is a widely used tactic to suppress cofacial (H‐type) stacking interactions, which may even inhibit self‐assembly. Contrary to expectations, we demonstrate herein that increasing steric effects can result in an enhanced thermodynamic stability of H‐type supramolecular polymers. In our approach, we have investigated two boron dipyrromethene (BODIPY) dyes with bulky phenyl ( 2 ) and mesityl ( 3 ) meso ‐substituents and compared their self‐assembly in nonpolar media with that of a parent meso ‐methyl BODIPY 1 lacking bulky groups. While the enhanced steric demand induces pathway complexity, the superior thermodynamic stability of the H‐type pathways can be rationalized in terms of additional enthalpic gain arising from intermolecular C−H⋅⋅⋅F−B interactions of the orthogonally arranged aromatic substituents, which overrule their inherent steric demand. Our findings underline the importance of balancing competing non‐covalent interactions in self‐assembly.