Frequency Generation in Natural Light Harvesting Systems and the Dynamics of Novel Tripyrrolic Pigments
(Seminar was cancelled and will be rescheduled for a later time.)
Efficient energy transfer in many photosynthetic pigment-protein aggregates is mediated by excitonic coupling and delocalization. By directly exploiting exciton-exciton interactions using frequency generation ultrafast electronic spectroscopy, it is possible to connect the spatial, temporal and dynamic landscapes of these complex systems. These measurements reveal the relationship between delocalized excitations even in spectrally congested aggregates, providing a novel and generalizable means to understand relaxation in strongly coupled systems. In photosynthetic aggregates, the component pigment molecules determine the overall properties of the complex including the efficiency of energy transfer. Through the design of synthetic analogs of these pigment molecules, we may be able to construct biologically inspired light harvesting systems with controlled, tunable properties. Using ultrafast nonlinear spectroscopy, we have studied the dynamics of a novel series of tripyrrindione molecules. These molecules are related to numerous linear or macrocyclic oligopyrroles, including tetrapyrrolic porphyrins in heme, that appear in many natural light harvesting complexes. These molecular systems are tunable and redox active, potentially providing new pathways to controllable and efficient energy and charge transfer.