Interactions between a water molecule and C 60 in the endohedral fullerene H2O@C60

Rashed, Effat; Dunn, Janette L

Abstract

A water molecule encapsulated inside a C 60 fullerene cage behaves almost like an asymmetric top rotor, as would be expected of an isolated water molecule. However, inelastic neutron scattering (INS) experiments show evidence of interactions between the water molecule and its environment [Goh et al., Phys. Chem. Chem. Phys., 2014, 16, 21330]. In particular, a resolved splitting of the 1 01 rotational level into a singlet and a doublet indicates that the water molecule experiences an environment of lower symmetry than the icosahedral symmetry of a C 60 cage. Recent calculations have shown that the splitting can be explained in terms of electrostatic quadrupolar interactions between the water molecule and the electron clouds of nearest-neighbour C 60 molecules, which results in an effective environment of S 6 symmetry [Felker et al.]. We use symmetry arguments to obtain a simple algebraic expression, expressed in terms of a linear combination of products of translational and rotational basis functions, that describes the effect on a water molecule of any potential of S 6 symmetry. We show that we can reproduce the results of the electrostatic interaction model up to ≈ 12 meV in terms of two unknown parameters only. The resulting potential is in a form that can readily be used in future calculations, without needing to use density functional theory (DFT) for example. Adjusting parameters in our potential would help identify whether other symmetry-lowering interactions are also present if experimental results that resolve splittings in higher-energy rotational levels are obtained in the future. As another application of our model, we show that the results of DFT calculations of the variation in energy as a water molecule moves inside the cage of an isolated C 60 molecule, where the water molecule experiences an environment of icosahedral symmetry, can also be reproduced using our model.

Citation

Rashed, E., & Dunn, J. L. (2019). Interactions between a water molecule and C 60 in the endohedral fullerene H2O@C60. Physical Chemistry Chemical Physics, 21(6), 3347-3359. https://doi.org/10.1039/C8CP04390F

• Journal Article Type: Article
• Acceptance Date: Jan 18, 2019
• Online Publication Date: Jan 18, 2019
• Publication Date: Feb 14, 2019
• Deposit Date: Feb 6, 2019
• Publicly Available Date: Jan 19, 2020
• Journal: Physical Chemistry Chemical Physics
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 21
• Issue: 6
• Pages: 3347-3359
• DOI: https://doi.org/10.1039/C8CP04390F
• Keywords: fullerene, endohedral
• Public URL: https://nottingham-repository.worktribe.com/output/1524354
• Publisher URL: https://pubs.rsc.org/en/journals/journalissues/cp
• Additional Information: : This document is Similarity Check deposited; : Supplementary Information; : Effat Rashed (ORCID); : Janette L. Dunn (ORCID); : Single-blind; : Received 11 July 2018; Accepted 18 January 2019; Accepted Manuscript published 18 January 2019; Advance Article published 28 January 2019; Version of Record published 6 February 2019
• Contract Date: Feb 6, 2019