Understanding self-assembly across scales in BODIPY derivatives: from supramolecular aggregation in solution to optical-waveguiding crystalline materials

Abstract

Molecular self-assembly constitutes a useful tool to construct discrete and functional nanostructures with well-defined properties. Nevertheless, understanding supramolecular order in solution and its transmission to the solid state for the same scaffold remains challenging and the impact of this transition in the properties of the resulting supramolecular architectures is still underexplored, thus limiting the application of self-assembly in fields like organic electronics. Herein we explore the supramolecular aggregation process of a chiral BODIPY derivative in solution, its features in solid state, and its potential application as optical waveguide. In solution, this derivative follows a time-dependent self-assembly process, ultimately leading to aggregates of increasing dimensionality with propensity to precipitate, from which a certain degree of crystallinity can be inferred. The subsequent formation of single crystals confirms the preservation of key supramolecular features from solution to the solid state. Notably, the one-centimeter-long crystals obtained present active optical waveguiding behavior in the NIR with a remarkable optical loss coefficient, the first optical loss reported for BODIPY crystals. These results highlight the value of studying self-assembly across different scales and demonstrate the potential of BODIPY-based systems for the development of optical waveguides with remarkable performance.