In this research program, self-assembling arrays of molecules will be constructed that are photoactive and will mimic some of the essential features of natural light harvesting complexes. Porphyrin chromophores will be assembled so as to form antennae that facilitate energy migration between porphyrin molecules and subsequent energy transfer to a trap, where a chemical reaction can be initiated. Each antenna will be assembled by spontaneous self-association, by multi-point hydrogen bonding of heterocycles that are covalently bonded to the porphyrin ring. One, two, or four such heterocycles will be bonded to a single porphyrin ring such that dimers, polymolecular ribbons, cyclomers, and three- dimensional supramolecular arrays will result. In this manner, highly oriented structures will be formed in solution, in a mesophoric phase, or in the solid state, each of which has discrete porphyrin chromophores positioned within the critical distance for excitation energy migration and transfer. %%% This grant from the Organic Dynamics Program supports the research of Dr. Anthony M. Harriman at the University of Texas, Austin. The harvesting of light energy for the synthesis of molecules by plants, whereby chlorophyll is the energy harvesting system, is of obvious importance. This is a complex process in nature, where an array of chlorophyll molecules are assembled for the task of light harvesting. The porphyrin ring portion of chlorophyll is the light absorbing unit. In this project, porphyrin rings will be self-assembled and the transfer of light energy from the porphyrin ring to an appended energy trapping moiety will be studied. This system will serve to mimic the natural light harvesting system.
