Ratchet-free solid-state inertial rotation of a guest ball in a tight tubular host
Overview of the press release
Dynamics of molecules in the solid state holds promise for connecting molecular behaviors with properties of bulk materials. Solid-state dynamics of fullerene (C60) has previously been explored to reveal the presence of unique rotational motions. However, intimate intermolecular contacts between the polyhedral molecules result in restricted motions of a ratchet phase at low temperatures, which provides an interesting yet challenging problem in controlling the solid-state dynamics of molecules. Here we show that a tubular host for C60 liberates the solid-state dynamics of the guest from the motional restrictions. Although the intermolecular contacts between the host and C60 were present to enable a tight association with a large energy gain of –14 kcal mol–1, the dynamic rotations of C60 were simultaneously enabled by a small energy barrier of +2 kcal mol–1 for the reorientation. The solid-state rotational motions that were dictated by the single energy barrier halted at a very low temperature of 50 K and, at a high temperature of 335 K, reached a non-Brownian, inertial regime with an extremely rapid rotational frequency of 213 GHz. Supramolecular methods adopting non-directional van der Waals interactions should be of interest to explore solid materials possessing unique dynamic characteristics.
Figure: Crystal structures of a ball-in-tube molecular bearing. The inner ball rotates rapidly at a speed of inertial motions.
Journal Nature Communications Title Ratchet-free solid-state inertial rotation of a guest ball in a tight tubular host Authors Taisuke Matsuno, Yusuke Nakai, Sota Sato, Yutaka Maniwa & Hiroyuki Isobe* DOI 10.1038/s41467-018-04325-2 Paper link https://doi.org/10.1038/s41467-018-04325-2
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