A Synthetic Strategy for Cofacial Porphyrin-Based Homo- and Heterobimetallic Complexes

We present a straightforward and generally applicable synthesis route for cofacially linked homo- and heterobimetallic porphyrin complexes. The protocol allows the synthesis of unsymmetrical aryl-based meso-meso as well as beta-meso-linked porphyrins. Our method significantly increases the overall yield for the published compound known as o-phenylene-bisporphyrin (OBBP) by a factor of 6.8. Besides the synthesis of 16 novel homobimetallic complexes containing Mn-III, Fe-III, Ni-II, Cu-II, Zn-II, and Pd-II, we achieved the first single-crystal X-ray structure of an unsymmetrical cofacial benzene-linked porphyrin dimer containing both planar-chiral enantiomers of a Ni-2(II) complex. Additionally, this new methodology allows access to heterobimetallic complexes such as the Fe-III-Ni-II containing carbon monoxide dehydrogenase active site analogue. The isolated species were investigated by various techniques, including ion mobility spectrometry, DFT calculations, and UV/Vis spectroscopy. This allowed us to probe the influence of interplane distance on Soret band splitting.

Automated summary

A practical synthesis method for homo- and heterobimetallic porphyrin complexes was presented, leading to a notable increase in yield for known compounds and the discovery of new structures. Various techniques were used to investigate the isolated species, revealing the influence of molecular structure on UV/Vis absorption bands.