Conformational Dynamics and Energetics of Carbon Nanohoops and their Ring-In-Ring Complexes

Carbon nanohoops are promising precursors for the bottom-up synthesis of carbon nanotubes, whose structural dynamics are not well understood despite their desirable materials properties. Here, we investigate the conformational landscape and energetics of cycloparaphenylenes (CPPs) and similar derivatives, including a methylene-bridged CPP and a carbon nanobelt. These nanohoops can form host-guest complexes with other rings, and understanding the dynamics of such assemblies is crucial for predicting their properties and identifying their potential applications. We used a combination of ion mobility mass spectrometry, tandem mass spectrometry, density-functional theory calculations and collision cross section simulations to characterise the single nanohoops and their ring-in-ring complexes, following their energetics and the conformational landscape of their disassembly from intact complexes to fragment ions. Our results show both rings and ring-in-ring complexes possess structural rigidity and reveal interesting trends in size, packing density, stability, and structure between [6]CPP, the methylene-bridged CPP and the carbon nanobelt as guests in ring-in-ring complexes, showing how mass spectrometry data can help to unravel the rules that govern the formation of such assemblies.