Toward the Synthesis of a Topologically Non-Planar Porphyrin

Abstract

The purpose of this research is to synthesize and to investigate the properties of a topologically non-planar porphyrin. When topology, an area of mathematics concerned with spatial properties that are preserved under deformation, is applied to chemistry, the bonds of a molecule can be stretched and bent, but not broken. A topologically planar molecule is one that has been deformed to become planar without any crossing over between bonds. In order to have a topologically non-planar porphyrin, a macrocyclic organic molecule that consists of four pyrroles attached to each other by methine bridges, two straps must be introduced to bridge the molecule. The addition of a metal center to the molecule results in a topologically non-planar porphyrin. An initial strap and a metal center have been introduced in separate experiments to porphyrins, both giving promising results. However, the small amount of porphyrins synthesized using previously developed methods proved to be an increasing problem. Consequently, new synthetic schemes are being used in order to increase the amount of porphyrin produced. The new synthetic route is based on a more efficient synthesis of the critical aldehyde for the porphyrin synthesis, 2-(methoxymethyl)benzaldehde. This aldehyde is combined with pyrrole to form a dipyrromethane. Lastly, the dipyrromethane is combined with 2-(bromomethyl)benzaldehyde to form the porphyrin. The ultimate goals of this project include: 1) demetallation of the porphyrin to reverse the topological property of the molecule, 2) studying the light absorbing properties of these porphyrins by incorporating electron donating and withdrawing groups into the straps, and 3) investigating the potential topological chirality of strapped porphyrins.