Synthesis of triple stranded porphyrin nanobelts.

Rodríguez-Rubio, Arnau; Zhu, He; Man Cheung, Ka; Rončević, Igor; Gödde, Lene A; Hergenhahn, Janko; Field, Joshua L; Gupta, Prakhar et al. · Science · 2025

basic_science · Level V

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Abstract

Molecular nanobelts are fascinating analogs of carbon nanotubes. Their rigid geometries and strongly coupled π-electrons have the potential to generate a wave function resembling that of a quantum ring. Here, we report the synthesis of triple stranded nanobelts consisting of 8 to 12 edge-fused porphyrin units with diameters of 21 to 32 angstroms. We synthesized these nanobelts by nickel-mediated coupling of <i>meso</i>-bromoporphyrins to form singly linked nanorings, followed by oxidation with gold(III) chloride. Experimental <sup>1</sup>H nuclear magnetic resonance spectra, supported by computational simulations, revealed that belts containing odd numbers of porphyrins, with circuits of 90 or 110 π-electrons, display global aromatic ring currents, whereas even-numbered belts, with 80, 100, or 120 π-electrons, are globally antiaromatic.