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Talewar SK, Pardo LC, Headen TF, Halukeerthi SO, Chikani B, Rosu-Finsen A, Salzmann CG. Hydrophobic hydration of the hydrocarbon adamantane in amorphous ice. Faraday Discuss 2024; 249:69-83. [PMID: 37794776 PMCID: PMC10845010 DOI: 10.1039/d3fd00102d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/19/2023] [Indexed: 10/06/2023]
Abstract
Hydrophobic molecules are by definition difficult to hydrate. Previous studies in the area of hydrophobic hydration have therefore often relied on using amphiphilic molecules where the hydrophilic part of a molecule enabled the solubility in liquid water. Here, we show that the hydrophobic adamantane (C10H16) molecule can be fully hydrated through vapour codeposition with water onto a cryogenic substrate at 80 K resulting in the matrix isolation of adamantane in amorphous ice. Using neutron diffraction in combination with the isotopic substitution method and the empirical potential structure refinement technique, we find that the first hydration shell of adamantane is well structured consisting of a hydrogen-bonded cage of 28 water molecules that is also found in cubic structure II clathrate hydrates. The four hexagonal faces of the 51264 cage are situated above the four methine (CH) groups of adamantane whereas the methylene (CH2) groups are positioned below the edges of two adjoining pentagonal faces. The oxygen atoms of the 28 water molecules can be categorised on the basis of symmetry equivalences as twelve A, twelve B and four C oxygens. The water molecules of the first hydration shell display orientations consistent with those expected for a clathrate-hydrate-type cage, but also unfavourable ones with respect to the hydrogen bonding between the water molecules. Annealing the samples at 140 K, which is just below the crystallisation temperature of the matrix, removes the unfavourable orientations and leads to a slight increase in the structural order of the first hydration shell. The very closest water molecules display a tendency for their dipole moments to point towards the adamantane which is attributed to steric effects. Other than this, no significant polarisation effects are observed which is consistent with weak interactions between adamantane and the amorphous ice matrix. FT-IR spectroscopy shows that the incorporation of adamantane into amorphous ice leads to a weakening of the hydrogen bonds. In summary, the matrix-isolation of the highly symmetric adamantane in amorphous ice provides an interesting test case for hydrophobic hydration. Studying the structure and spectroscopic properties of water at the interface with hydrophobic hydrocarbons is also relevant for astrophysical environments, such as comets or the interstellar medium, where amorphous ice and hydrocarbons have been shown to coexist in large quantities.
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Affiliation(s)
- Sukhpreet K Talewar
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Luis Carlos Pardo
- Grup de Caracterització de Materials, Departament de Física, EEBE, Universitat Politècnica de Catalunya, and Barcelona Research Center in Multiscale Science and Engineering, C/Eduard Maristany 10, E-08019 Barcelona, Spain
| | - Thomas F Headen
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, OX11 0QX, UK
| | - Siriney O Halukeerthi
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Bharvi Chikani
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Alexander Rosu-Finsen
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Christoph G Salzmann
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
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Rosu-Finsen A, Davies MB, Amon A, Wu H, Sella A, Michaelides A, Salzmann CG. Medium-density amorphous ice. Science 2023; 379:474-478. [PMID: 36730416 DOI: 10.1126/science.abq2105] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Amorphous ices govern a range of cosmological processes and are potentially key materials for explaining the anomalies of liquid water. A substantial density gap between low-density and high-density amorphous ice with liquid water in the middle is a cornerstone of our current understanding of water. However, we show that ball milling "ordinary" ice Ih at low temperature gives a structurally distinct medium-density amorphous ice (MDA) within this density gap. These results raise the possibility that MDA is the true glassy state of liquid water or alternatively a heavily sheared crystalline state. Notably, the compression of MDA at low temperature leads to a sharp increase of its recrystallization enthalpy, highlighting that H2O can be a high-energy geophysical material.
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Affiliation(s)
| | - Michael B Davies
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.,Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | - Alfred Amon
- Department of Chemistry, University College London, London WC1H 0AJ, UK
| | - Han Wu
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Andrea Sella
- Department of Chemistry, University College London, London WC1H 0AJ, UK
| | - Angelos Michaelides
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK.,Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
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Halukeerthi SO, Shephard JJ, Talewar SK, Evans JSO, Rosu-Finsen A, Salzmann CG. Amorphous Mixtures of Ice and C 60 Fullerene. J Phys Chem A 2020; 124:5015-5022. [DOI: 10.1021/acs.jpca.0c03439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Siriney O. Halukeerthi
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Jacob J. Shephard
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Sukhpreet K. Talewar
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - John S. O. Evans
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom
| | - Alexander Rosu-Finsen
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - Christoph G. Salzmann
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom
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