Aromaticity and through-space electronic coupling in [2]catenanes comprising two intertwined, globally electron-delocalized octaphyrinoid rings

14 January 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

π-Conjugated molecules with nontrivial topologies, such as catenanes and knots, offer unique aromaticity and through-space electronic and magnetic interactions absent in traditional planar π-systems. However, their synthesis remains challenging, with prior examples showing only localized aromaticity in individual benzenoid rings. Here, we report the synthesis of a [2]catenane comprising two intertwined octaphyrinoid rings, each with 34 globally delocalized π-electrons, achieved using a passive metal-template strategy with 2,2’-dipyrromethene as the directing ligand. Experimental and theoretical studies reveal nearly orthogonal spatial arrangement of the rings in neutral catenane, stabilized by multiple [NH···N] and [S···N] close contacts. These rings exhibit global aromaticity with entangled magnetic shielding interactions. Upon four-electron oxidation, the system converts to a tetracation with two globally antiaromatic (32π) rings, where through-space bonding interactions minish the antiaromatic destabilization. Notably, counterions also affect (anti)aromaticity of the tetracations in single-crystal state, highlighting a dynamic interplay between molecular topology, electronic structure, and external interactions.

Keywords

Catenane
Aromaticity
Porphyrinoid
through-space
mechanically interlocked molecules

Supplementary materials

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Description
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Supplementary Information
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Synthetic procedures and characterization data, additional spectra, DFT calculation details, and X-ray crystallographic data.
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