Structural Mediation of Interlayer Excitation Transport in Zirconium−Phosphonate Multilayers

We report on our investigation of interlayer excitation transport in zirconium−phosphonate (ZP) multilayer structures. We find that dipolar (Förster) excitation transfer between energetically overlapped oligothiophene chromophores in adjacent layers does not play a significant role in determining the relaxation dynamics of these systems. This finding is not consistent with the predictions of the Förster model, and we account for this discrepancy by considering the spatial modulation of the dielectric response of the ZP multilayer assemblies. The presence of polarizable Zr−bis(phosphonate) layers between layers of donor and acceptor chromophores serves to screen dipolar D−A coupling. Intralayer excitation transfer within individual chromophore aggregates dominates population relaxation dynamics in these systems. We also find that spacing the chromophore-containing layers away from the primed substrate surface does not eliminate chromophore aggregation. We discuss these data in terms of the dominant factors in the formation of ZP layers.