Spectroscopic investigation of macrocyclic poly (9,9-dimethyl-2-vinylfluorene) as an artificial light harvester

Three-dimensional crystal structures for the light harvesting antenna complexes of photosynthetic bacteria have recently been resolved [1]. This has led to a more profound understanding of how nature harvests sunlight in an efficient fashion. The antenna complex (LH2) is highly symmetric and the deployment of chromophores is cyclic. It is therefore of interest whether this architecture is important for the very rapid and efficient energy transfer - excitation hopping times at room temperature of ~100 fs have been reported [2]. In our investigations, the ring-like structure of LH2 is mimicked by novel two-dimensional macrocyclic polymers, which have recently been synthesized [3]. Such poly-vinyl aromatic polymers can be prepared with 10 – 50 chromophore groups (here the chromophore is 9,9 dimethylfluorene) that are pendent to the polymer backbone. In this report, the steady state and time-resolved spectroscopic properties of the macrocyclic polymers are compared with their linear analogs.