Teaching Interests: Organic Chemistry, Molecular Nanotechnology
Research Interests: Studies of porphyrinoid synthetic methodology and porphyrinoid properties.
Research in the Geier laboratory is directed towards the investigation of methodology for the preparation of a variety of porphyrinoids. Successful syntheses of porphyrinic species facilitate studies of macrocycle properties—such as stability, spectroscopy, metal binding, and catalysis.
Porphyrins perform diverse functions in Nature (Figure 1). For example, the characteristic red color of blood and green color of plants are due to porphyrinoids (heme and chlorophyll respectively). The rich diversity of porphyrin function arises from the variety of mechanisms available for the fine tuning of macrocycle properties. The identity of the central metal ion and axial ligands are important. The protein matrix surrounding the porphyrin ring also influences macrocycle properties. And of particular interest to our research group, the core structure of the porphyrin can be substituted, reduced, heteroatom modified, isomerized, expanded, and/or contracted relative the prototypical porphyrin structure.
Structural alterations to the porphyrin macrocycle gives rise to a large family of molecules that display diverse and complementary properties (Figure 2). Some of the general structures shown in Figure 2 are found in Nature. Others have been created in the laboratory in an effort to produce porphyrinoids of fundamental interest, and materials useful for a wide range of commercial applications including molecular electronic devices, solar energy, photodynamic cancer therapy, ion selective sensors, and catalysis.
In the Geier research group, we have a number of ongoing projects involving many of the macrocycles shown in Figure 2. Presently, we are exploring the series of compounds shown in Figure 3. The central core of the porphyrinoids differ in subtle, but profound ways which may impact metal binding and properties of the metal chelates. To forward these efforts, our group has contributed methodology for the preparation of corroles (J. Org. Chem. 2004, 69, 4159-4169), phlorin (J. Org. Chem. 2007, 72, 4084-4092), and 5-isocorrole (J. Org. Chem. 2010, 75, 553-563). The phlorin prepared by our group is noteworthy as it is one of the most stable phlorins known towards degradation in light and air. Preliminary metal binding experiments have been successfully carried out on a 5-isocorrole in collaboration with the Ziegler group at The University of Akron (Dalton Trans. 2011, 40, 4384-4386). Further investigation of the coordination chemistry of these porphyrinoids, and studies of catalysis mediated by the metalloporphyrinoids are ongoing. We also continue to target additional novel porphyrinoids in our synthetic investigations.
Throughout our studies, we utilize a broad range of experimental techniques including preparative organic synthesis, parallel analytical-scale reactions, analytical chromatographic methods (GC, HPLC) and preparative chromatography, and a variety of spectroscopic tools (NMR, UV-vis, IR, fluorimetry, EI-MS, CI-MS, and LD-MS).
Please make an appointment with Professor Geier to discuss current research opportunities in the Geier laboratory.
Excellent reviews of many topics germane to this research may be found in The Porphyrin Handbook, Kadish, K.M.; Smith, K.M.; Guilard, R., eds. Academic Press, 2000; and in The Colours of Life, Milgrom, L. R., Oxford University Press: New York, 1997.