A Single Molecule of Water Encapsulated in Fullerene C
            <sub>60</sub>

Kurotobi, Kei; Murata, Yasujiro

doi:10.1126/science.1206376

Cited by 483 publications

(523 citation statements)

References 32 publications

(36 reference statements)

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“…The downfield shift of 0.05 ppm relative to empty C 60 deviates from the empirical correlation drawn previously between the van der Waals radius of the endohedral guest and a downfield 13 C chemical shift (H 2 O@C 60 , 0.11 ppm; H 2 @C 60 , 0.08 ppm; He@C 60 0.02 ppm). 2,3,30 A series of 19 F NMR spectra of HF@C 60 in the polycrystalline solid state were acquired at 263 K, using magic-angle spinning at a range of rotation frequencies, without 1 H decoupling ( Figure 2 and Supplementary Figures 5 and 6). All spectra display a prominent splitting due to a 1 H-19 F J-coupling of 506 ± 0.5 Hz.…”

Section: Resultsmentioning

confidence: 99%

“…1 The dihydrogen and water endofullerenes H 2 @C 60 , H 2 O@C 60 , and their isotopologues, have been synthesized by the procedure known as 'molecular surgery', in which synthetic operations are used to open a hole in the fullerene allowing encapsulation of the guest, followed by a suturing technique to reform the pristine fullerene shell. [2][3][4] Recently the approach has been extended to C 70 and C 59 N. [5][6][7] The confined molecules display quantization of their coupled translational and rotational degrees of freedom, and exhibit phenomena such as nuclear spin isomerism and orthopara conversion. [8][9][10][11][12] Recently it was shown that nuclear spin conversion of the encapsulated water molecules in H 2 O@C 60 leads to a change in the dielectric constant of the material.…”

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The dipolar endofullerene HF@C60

et al. 2016

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Abstract:The cavity inside fullerenes provides a unique environment for the study of isolated atoms and molecules. We report encapsulation of hydrogen fluoride inside C 60 using molecular surgery to give the endohedral fullerene HF@C 60 . The key synthetic step is the closure of the open fullerene cage while minimizing escape of HF. The encapsulated HF molecule moves freely inside the cage and exhibits quantization of its translational and rotational degrees of freedom, as revealed by inelastic neutron scattering and infrared spectroscopy. The rotational and vibrational constants of the encapsulated HF molecules were found to be redshifted relative to free HF. The NMR spectra display a large 1 H-19 F Jcoupling typical of an isolated species. The dipole moment of HF@C 60 was estimated from the temperature-dependence of the dielectric constant at cryogenic temperatures and showed that the cage shields around 75% of the HF dipole.Molecular endofullerenes consist of fullerene cages encapsulating small molecules, which are free to rotate and translate inside the cage. 1 The dihydrogen and water endofullerenes H 2 @C 60 , H 2 O@C 60 , and their isotopologues, have been synthesized by the procedure known as 'molecular surgery', in which synthetic operations are used to open a hole in the fullerene allowing encapsulation of the guest, followed by a suturing technique to reform the pristine fullerene shell. [2][3][4] Recently the approach has been extended to C 70 and C 59 N. [5][6][7] The confined molecules display quantization of their coupled translational and rotational degrees of freedom, and exhibit phenomena such as nuclear spin isomerism and orthopara conversion. [8][9][10][11][12] Recently it was shown that nuclear spin conversion of the encapsulated water molecules in H 2 O@C 60 leads to a change in the dielectric constant of the material. 13 One system of great interest is HF@C 60 , in which each fullerene cage contains a single hydrogen fluoride (HF) molecule. This material offers the possibility to study the spectroscopic properties of nearisolated and freely rotating HF molecules under a wide range of conditions, free from the complications of dimerization and hydrogen bonding. Predictions of the properties of HF@C 60 have been made using classical, 14 semiempirical 15,16 and quantum chemistry techniques. [17][18][19][20] Furthermore it has been postulated that endofullerenes containing freely rotating electric dipoles could exhibit ferroelectricity, due to cooperative alignment of the interacting electric dipole moments. 21 2The first examples of open-cage endofullerenes encapsulating a hydrogen fluoride molecule have recently appeared, including HF@1. 22,23 Herein we report the successful suturing of HF@1 to give the closed-cage species HF@C 60 . We present NMR, infrared, and neutron scattering data on HF@C 60 which show that the translational and rotational motions of the HF molecule inside the cage are quantized. Interactions with the cage modify the rotational and vibrational constants of the encapsula...

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

The dipolar endofullerene HF@C60

et al. 2016

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“…Central to these studies is the notion that the displacement of a high-energy water cluster from a receptor drives guest association, and in some cases, subsequent catalysis. However, despite the abundance of structural data documenting diverse water clusters encapsulated in various host cavities, mechanistic descriptions of the dynamic processes between water and host are rare (24)(25)(26)(27)(28)(29)(30)(31)(32).…”

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Protein-like proton exchange in a synthetic host cavity

Hart‐Cooper

Sgarlata

Perrin

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The mechanism of proton exchange in a metal-ligand enzyme active site mimic (compound 1) is described through amide hydrogendeuterium exchange kinetics. The type and ratio of cationic guest to host in solution affect the rate of isotope exchange, suggesting that the rate of exchange is driven by a host whose cavity is occupied by water. Rate constants for acid-, base-, and watermediated proton exchange vary by orders of magnitude depending on the guest, and differ by up to 200 million-fold relative to an alanine polypeptide. These results suggest that the unusual microenvironment of the cavity of 1 can dramatically alter the reactivity of associated water by magnitudes comparable to that of enzymes.W ater-mediated proton transfer in molecular cavities plays an essential role in the function of nature's remarkable metabolic machinery (1, 2). Of the broad diversity of enzymecatalyzed reactions, those involving transfer of hydrogen are ubiquitous and of high fundamental importance (3). For instance, ATP synthase employs an internal chain of water molecules to mediate proton transfer across an electrochemical gradient (4, 5). This process drives ATP synthesis, which allows organisms to broadly meet their basic energy needs. Recent studies of tunneling in enzymatic hydron transfer reactions have other far-reaching and broad implications, namely the importance of the dynamic enzyme motions in driving catalysis (6, 7).Of the methods used to study hydron transfer, kinetic studies of the mechanisms of amide hydrogen-deuterium exchange (HDX) have helped to elucidate the dynamic interactions between water and protein surfaces that are central to the unique capabilities of enzymes (8-13). Noncovalent interactions, such as electrostatic effects and hydrogen bonding, have also been shown to exert a significant influence on amide HDX rates. These properties are manifest in amide HDX rate constants that can vary by a factor of a billion for residues on the same protein (8). How these variations arise, and how such a property could be harnessed to drive enzyme-like reactivity, remain challenging questions.In a growing effort to emulate the efficacy of biological receptors and enzymes, studies of the preparative, guest-binding, and catalytic properties of synthetic assemblies have been pursued (14-21). Whereas guest encapsulation has been reported in a variety of media, association processes of organic guests are generally more thermodynamically favorable in water (22, 23). Central to these studies is the notion that the displacement of a high-energy water cluster from a receptor drives guest association, and in some cases, subsequent catalysis. However, despite the abundance of structural data documenting diverse water clusters encapsulated in various host cavities, mechanistic descriptions of the dynamic processes between water and host are rare (24-32).As part of the broader field of synthetic hosts previously mentioned, our group has developed a class of biologically inspired, anionic K 12 Ga 4 L 6 assemblies that exhibit cat...

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“…Besides H 2 @C 60 , the theoretical study of which will be reported shortly, this includes molecular hydrogen in clathrate hydrates [19,29,30], metal-organic frameworks [31][32][33][34][35] and zeolites [36,37], among others. Finally, methodological extensions are in progress in our group to the INS spectra of nanoconfined polyatomic molecules such as methane [38] and water [39].…”

Section: Discussionmentioning

confidence: 99%

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

Lawler

et al. 2013

Phil. Trans. R. Soc. A.

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One contribution of 13 to a Theo Murphy Meeting Issue 'Nanolaboratories: physics and chemistry of small-molecule endofullerenes' . We report rigorous quantum calculations of the inelastic neutron scattering (INS) spectra of HD@C 60 , over a range of temperatures from 0 to 240 K and for two incident neutron wavelengths used in recent experimental investigations. The computations were performed using our newly developed methodology, which incorporates the coupled five-dimensional translation-rotation (T-R) eigenstates of the guest molecule as the initial and final states of the INS transitions, and yields highly detailed spectra. Depending on the incident neutron wavelength, the number of computed INS transitions varies from almost 500 to over 2000. The low-temperature INS spectra display the fingerprints of the coupling between the translational and rotational motions of the entrapped HD molecule, which is responsible for the characteristic splitting patterns of the T-R energy levels. INS transitions from the ground T

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A Single Molecule of Water Encapsulated in Fullerene C ₆₀

Cited by 483 publications

References 32 publications

The dipolar endofullerene HF@C60

The dipolar endofullerene HF@C60

Protein-like proton exchange in a synthetic host cavity

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

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A Single Molecule of Water Encapsulated in Fullerene C 60

Cited by 483 publications

References 32 publications

The dipolar endofullerene HF@C60

The dipolar endofullerene HF@C60

Protein-like proton exchange in a synthetic host cavity

HD in C 60 : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence

Contact Info

Product

Resources

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A Single Molecule of Water Encapsulated in Fullerene C ₆₀

HD in C ₆₀ : theoretical prediction of the inelastic neutron scattering spectrum and its temperature dependence