Synthesis of Heterobimetallic Porphyrin Tubes for Modulation of Small Molecule Catalysis and Host-Guest Chemistry

Authors: Owen Szeglowski, Timothy Cook, John Pinti

SUNY Campus: SUNY Buffalo

Presentation Type: Poster

Location: UU 111

Presentation #: 74

Timeslot: Session C 1:45-2:45 PM

Abstract: Motivated by the ever-increasing demand for energy, the Cook lab has been continually exploring the use of polynuclear porphyrin architectures as catalysts for small molecule activation. Historically, metallic molecular clips have been employed to facilitate the assembly of these prisms, however it is attractive to eliminate these structural metals, as they are associated with higher costs and reduced acid stability. Herein, we report the synthesis and characterization of a tetra-porphyrin tube bridged by organic pyridinium-based linkers (Figure 1). These tubes can be post-synthetically metalated with a series of first-row transition metals, including Zn, Ni, and Co. Uniquely, as these tubes are the result of two distinct porphyrin moieties, they provide an ideal candidate for a heterobimetallic system, such as Zn2-Co2-tube. By controlling the metal sites present in this architecture, we can modulate the activity of the porphyrin tubes for catalysis of the oxygen-reduction reaction (ORR), in which the Co4-tube has the lowest overpotential, followed by the Zn2-Co2-tube, and finally the Zn4-tube. Beyond this, the size of the architectures makes them ideal candidates for host-guest chemistry. To probe this, encapsulation of C60 and C70 was studied via absorbance and fluorescence routes, where the structures were found to asymmetrically accommodate the fullerenes, breaking the internal symmetry of the molecule and thus splitting the proton resonances further when encapsulated.