Electron Delocalization Pathways in Porphyrin Nanostructures

The development of efficient electronic devices, such as computer chips and LEDs, has been the driving force of countless technological advances. We have now reached the edge of what is possible with conventional materials (metals and silicon), and further miniaturization requires exploitation of quantum phenomena at the nanoscale. The Anderson group is focused on building porphyrin-based nanostructures (tapes and rings) which behave similar to metals, exhibiting exotic properties such as small band gaps, ultrafast energy delocalization, and nanoscale ring currents. In some cases, their electrical conductivity can be controlled by quantum interference. This makes them excellent candidates for molecular wires, transistors, and light-absorbing or light-emitting devices. This project proposes quantum-mechanical simulations of porphyrin nanostructures with the goal of understanding and predicting their behavior. Our first objective is to identify proper methods for describing these systems. Then, we will answer questions that are difficult to explore experimentally, such as: What are the limits of aromaticity? Through which chemical bonds does the electrical current flow? How do the electronic, optical, and magnetic properties depend on the molecular structure and the metal center (and its spin)? Can we predict quantum interference by following electron delocalization pathways? Finally, we will systematically screen the properties of porphyrin-based polymers with different linkers and metal centers, determining suitable candidates for molecular wires. The project will show how to accurately describe nanoscale systems of interest to molecular electronics, give a new perspective on electron delocalization and quantum interference in extended conjugated systems, and identify new synthetic targets for molecular wires and electrical circuits. It will provide fundamental understanding of phenomena such as ultrafast energy migration and nanoscale aromaticity.