Impact of boron desymmetrization on supramolecular polymerization of BODIPY dyes

Abstract

Supramolecular polymers are often investigated for highly symmetric and planar molecules, such as typically explored BF₂-substituted BODIPY dyes. However, it is surprising that the possibility of desymmetrizing the sp³ hybridized boron centre of BODIPY dyes has remained unexplored in the context of supramolecular polymerization. Herein, we synthesized a new BODIPY derivative 2 with two different substituents at the boron (fluorine and phenyl), resulting in a system with two different π-surfaces, and analyzed its supramolecular polymerization in non-polar media. Notably, this symmetry reduction increases the complexity of the self-assembly by enabling the formation of an intermediate assembled state, which cannot be found in the symmetrical model BODIPY 1 with a BF₂ group. Different experimental and theoretical studies suggest that significant steric effects together with multiple potential intermolecular stacking modes of the BODIPY dyes lead to discrete nanoparticle intermediates that ultimately transform into more-ordered H-type supramolecular polymers at lower temperatures. Our results introduce a new design strategy for controlled supramolecular polymerization.