RUI: Syntheses of Porphyrinic Macrocycles with Altered Core Structures

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This project focuses on the development and study of synthetic methodology leading to meso-substituted porphyrinic macrocycles with altered core structures. Two structural motifs are a particular focus - the presence of one or more direct bipyrrole linkages as found in macrocycles such as corrole and [34]octaphyrin(1.1.1.0.1.1.1.0), and the presence of an sp3 hybridized meso-position as found in phlorin. Studies of these structural motifs will afford a family of molecules with intriguing structures and properties. In the course of the work, methods for the preparation of bipyrrole building blocks (e.g., diacylbipyrroles and conformationally locked bipyrroles) will be developed, and syntheses of a suite of mesosubstituted porphyrinic macrocycles (e.g., corrole, an octaphyrin, rosarin, a novel N-confused corrole, and phlorin) will be investigated. Promising reactions will be performed on a preparative scale to confirm the results of analytical experiments, as well as to provide suitable quantities for study of selected macrocycle properties (e.g., absorption, emission, stability, metal binding, anion binding).With this Research at Undergraduate Institutions award, the Organic and Macromolecular Chemistry Program is supporting the research of Dr. G. Richard Geier III, of the Department of Chemistry at Colgate University. The porphyrin molecule is responsible for reversibly binding oxygen to the oxygen storage and transport proteins, hemoglobin and myoglobin. Porphyrin-like molecules with altered core structures are of current interest, permitting experimental scrutiny of important and fundamental chemical questions, including aromaticity, metal binding, anion binding, photochemical reactions, electrochemical reactions, and catalysis. Studies of a wide variety of porphyrinic macrocycles add to our collective understanding of their properties, and to the potential for their application in industry and medicine. Key to these efforts is the development and refinement of synthetic methodology for the preparation of porphyrinic species. Professor Geier and his students are developing synthetic methods allowing the systematic exploration of the effects of ring expansion, contraction, isomerization, heteroatom modification, and other structural changes on the structures and chemistry of porphyrinic species. These studies also play a valuable role in training a large and diverse group of undergraduate students in the techniques of chemical synthesis and analysis.