Issue 41, 2024

Polymorphism and flexibility of six-porphyrin nanorings in the solid state

Abstract

Butadiyne-linked porphyrin nanorings are fascinating nanometer-sized platforms for exploring electronic delocalization and aromaticity, and they mimic ultra-fast photosynthetic energy-transfer phenomena in plants and purple bacteria. However, little is known about how they interact in the solid state. Here, we compare the crystal structures of several pseudopolymorphs of a six-porphyrin nanoring template complex, and report the structure of the free-base nanoring co-crystallized with C60. The structures differ not only in the molecular packing; they also feature different molecular conformations. The template is slightly too small for the cavity of the nanoring, and this size mismatch can be accommodated by two types of distortion: either the zinc atoms are pulled away from the planes of the porphyrins, or the nanorings contract by adopting a ruffled conformation, with butadiyne links alternatingly above and below the plane of the six zinc centers. The template-bound ring forms sheets and tubular stacks with interdigitated aryl groups. Upon demetallation, the nanoring becomes more flexible, adopting a highly elliptical conformation on co-crystallization with C60. The structure of this free-base nanoring features infinite solvent filled channels with a channel diameter of 13.5 Å. The high porosity of these materials points towards possible applications as porous light-harvesting frameworks.

Graphical abstract: Polymorphism and flexibility of six-porphyrin nanorings in the solid state

Supplementary files

Article information

Article type
Edge Article
Submitted
06 Aug 2024
Accepted
17 Sep 2024
First published
18 Sep 2024
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2024,15, 16938-16946

Polymorphism and flexibility of six-porphyrin nanorings in the solid state

W. Stawski and H. L. Anderson, Chem. Sci., 2024, 15, 16938 DOI: 10.1039/D4SC05255B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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