Fluorescent Dendrimeric Molecular Catalysts Demonstrate Unusual Scaling Behavior at the Single-Molecule Level

Abstract

A series of surface-supported molecular palladium catalysts were synthesized using a dendrimeric attachment motif to incorporate multiple BODIPY fluorophores for single-molecule fluorescence microscopy. An unusual fluorescence intensity scaling law was observed, whereby the addition of multiple fluorophores did not result in a substantial increase in single-molecule brightness. Possible quenching mechanisms are discussed, and simulations of photophysical population dynamics are used to identify singlet–triplet annihilation as the likely origin of the scaling law. This work is a conspicuous example of how the availability of different photophysical kinetic pathways can have substantial influence on molecular design rules, with implications for light-harvesting strategies.