Improving photocatalytic activity by appending a DABCO ring and a quinone to ruthenium polypyridyl complex

by James, Amy N.; Nguyen, Theresa; Zheng, Nan

By converting natural light energy into chem. energy, chemists are studying ways to take advantage of clean energy. The rising precedence of "green chem." has led to academic interest in the activity of photocatalysts and harnessing visible light in an efficient, accessible, and safe manner. Photochem. is an upcoming and fascinating field of study that has made significant progress, but also has great potential for future work. By utilizing light as a natural energy source, many reaction processes in chem. can be viewed with a new perspective. Ru(bpy)32+ is one of the most widely used photocatalysts. An efficient charge separation in its photoexcited state is critical for successful electron transfer between the photoexcited ruthenium complex and the substrate. However, the charge separation only has a lifetime of 200 ns. In order to prolong the lifetime of Ru(bpy)32+, I will be experimenting with two alterations of the ruthenium complex. One approach is to append 1,4-diazabicyclo[2.2.2.]octane (DABCO) to one of the bipyridine ligands. The DABCO ring acts as an electron donor to reduce the photoexcited ruthenium center into its original state, and thus create a relay to increase the charge separation's lifetime. The other approach is to attach a quinone to one of the bipyridine ligands. The Quinone group functions as an electron acceptor to oxidize the photoexcited bipyridine ligand, and therefore create a different type of relay that can also prolong the charge separation's lifetime. Overall, the appendage of specific organic mols. to one of the bipyridine ligands may be able to significantly increase the lifetime and catalytic efficiency of Ru(bpy)32+.