Development of a novel type of molecular switches based on expanded porphyrins using a combined and conceptual approach

Every day we use switches to turn electric appliances on and off and no computer could function without them. Molecular switches work in the same way, changing from one state to another depending on environmental influences such as light, pH, or voltage. However, as opposed to normal switches, molecular switches are extremely tiny and their application in nanotechnology, biomedicine and computer chip design opens up whole new horizons. Recently, the so-called expanded porphyrins have emerged as a promising class of pi-conjugated molecules that display unique electronic, optical and conformational properties. Interestingly, several expanded porphyrins switch between planar and twisted conformations encoding different photophysical properties. Such a change of topology involves a Hückel-Möbius aromaticity switch in a single molecule and it can be induced by solvent, pH and metalation. These features make expanded porphyrins suitable for the development of a novel type of molecular switches with practical applications. Despite its potential, the design of molecular switches based on the topological changes of expanded porphyrins has only been scarcely investigated. In this project, we aim to determine the multiple factors involved in the switching process of expanded porphyrins using computational chemistry, ultimately leading to the design of a novel type of molecular switches. Their potential as nonlinear optical and conductance switches will be explored for the first time.