Work

Synthesis of Tetra-Porphyrin Tubes for Catalysis and Host–Guest Chemistry

Year: 2026

Type: article

Abstract: We report a reaction between tetra-3-pyridyl and tetra-3-bromomethylphenyl porphyrins forming a tetra-porphyrin tube with alkylpyridinium linkers (24 h, 26% yield). The free-base tube (FB4-tube) was characterized using NMR, HR-MS, UV–vis, and single-crystal X-ray diffraction. Metalating the tolyl porphyrin prior to synthesis afforded Zn2FB2-tube which was further metalated with Co(II) to a heterobimetallic tetranuclear Zn2Co2-tube. FB4-tube was subsequently metalated with zinc(II) and cobalt(II) giving homometallic tetranuclear cores. Cobalt porphyrins are catalysts for the Oxygen Reduction Reaction (ORR); therefore, we evaluated the tubes as homogeneous ORR catalysts. The Co4-tube showed an Ecat1/2 of −1.0 V vs FcH+/FcH. The tubes were evaluated for ORR selectivity via reduction with ferrocene. The Co4-tube had a selectivity of 81.7% for H2O versus H2O2 while that of the heterobimetallic tube was 37.8%. The former depleted O2 at ∼4 times the rate. Porphyrin cages with large cavities have been used to sequester fullerenes. The FB4-tube encapsulated C60 with a binding constant KC60⊂tube of 2.33 ± 0.03 × 105 M–1. Binding was verified via NMR, HR-MS, and electronic absorption spectroscopy. Tetra-porphyrin architectures are rare, and this facile synthesis of homometallic and heterobimetallic variants may populate a wide library of tetranuclear cores for catalysis and supramolecular chemistry.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.5c05469

Authors: John C. Pinti, Owen Szeglowski, Allison M. Zamudio, Rachel L. Snider, Matthew R. Crawley, Timothy R. Cook

Institution: University at Buffalo, State University of New York

Language: English

Topic: Porphyrin and Phthalocyanine Chemistry

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, Division of Chemistry