Exciton Dynamics and Charge Diffusion in Supramolecular Porphyrin Polymers

Abstract Controlling chromophore aggregation across nano- to mesoscale dimensions provides a powerful strategy for tailoring the properties of π-conjugated materials and accelerating advances in organic optoelectronic technologies. Because exciton generation, migration, and dissociation in organic assemblies are governed by molecular packing, precise control over nanoscale order is critical for defining structure−function relationships in organic semiconductors. In this context, one-dimensional supramolecular polymers offer compelling design platforms, where assembly pathways and packing geometries can be leveraged to modulate excitonic coupling, promote delocalization, and direct transport. Although porphyrin superstructures with J-type excitonic coupling have been widely studied as models for efficient energy migration, the excited-state processes of H-type porphyrin assemblies remain comparatively underexplored, despite the structural robustness of these constructs and their potential to promote directional exciton and charge diffusion. Here, we address this gap using a novel zinc porphyrin derivative PZn-OTEG-OH, which undergoes cooperative supramolecular polymerization to form one-dimensional aggregates with H-like photophysics. Ultrafast pump−probe transient absorption measurements in solution reveal that the supramolecular polymer exhibits a nanosecond excited-state lifetime together with diffusive exciton migration over nanometer length scales. In the solid state, the preorganized aggregate translates into an interconnected fibrillar network, in contrast to the comparatively featureless films obtained from monomeric solution. Solid-state electrochemical measurements reveal only modest shifts in redox inflection potentials between monomer- and aggregate-derived films, whereas chronoamperometry indicates faster charging dynamics and an increased apparent diffusion coefficient for the aggregate-derived films. Together, these results demonstrate that cooperative H-like porphyrin assemblies can integrate efficient exciton migration in solution with enhanced charge accumulation in the solid state, establishing a molecular design strategy for light-harvesting organic semiconducting materials.