Masked alkynes for synthesis of threaded carbon chains

18 January 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Polyynes are chains of sp1 carbon atoms with alternating single and triple bonds. As they become longer, they evolve towards carbyne, the 1D allotrope of carbon, and they become increasingly unstable. It has been anticipated that long polyynes could be stabilized by supramolecular encapsulation, by threading them through macrocycles to form polyrotaxanes, but, until now, polyyne polyrotaxanes with many threaded macrocycles have been synthetically inaccessible. Here we show that masked alkynes, in which the CC triple bond is temporarily coordinated to cobalt, can be used to synthesize polyrotaxanes, up to the C68 [5]rotaxane with 34 contiguous triple bonds and four threaded macrocycles. This is the length regime at which the electronic properties of polyynes converge to those of carbyne. Cyclocarbons constitute a related family of molecular carbon allotropes, and cobalt-masked alkynes also provide a route to [3] and [5]catenanes built around cyclo[40]carbon and cyclo[80]carbon, respectively.

Keywords

polyyne
rotaxane
carbyne
cyclocarbon
catenane
alkyne
cobalt
carbon
allotrope

Supplementary materials

Title
Description
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Title
Supplementary Information
Description
General Methods, Synthetic Protocols, GPC Traces, X-Ray Crystal Structures, UV-Visible Absorption Spectra, Raman Spectra, Comparison of NMR Spectra, Solid-State Thermal Stability, NMR Spectra and Mass Spectra
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