Encapsulation of Molecular Hydrogen in Fullerene C
            <sub>60</sub>
            by Organic Synthesis

Komatsu, Kôichi; Murata, Michihisa; Murata, Yasujiro

doi:10.1126/science.1106185

Cited by 593 publications

(505 citation statements)

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“…The temperature dependences of T 1 for H 2 and H 2 @C 60 were investigated in detail for toluene-d 8 ( Figure 1) and for benzene-d 6 , 1,1,2,2-tetrachloroethane-d 2 , 1,2-dichlorobenzene-d 4 , and chloroformd 1 . Striking features of the data are the occurrence of a maximum for T 1 at ∼240 K for both the H 2 and H 2 @C 60 in toluene-d 8 and a ratio of T 1 values which is nearly independent of temperature.…”

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Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

et al. 2006

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We report an investigation of the nuclear spin-lattice relaxation of H 2 and H 2 @C 60 1 as a function of solvent and temperature. These studies explore and compare the nature of the interactions of a guest H 2 molecule confined transiently within the walls of a solvent cavity and a guest H 2 molecule encapsulated within the walls of the C 60 cavity.The relaxation time (T 1 ) of H 2 has been extensively studied in the gas phase and in liquid hydrogen at low temperatures. 6 The values of T 1 are 10-20 times smaller for H 2 @C 60 than for H 2 even though the ratios of T 1 for H 2 and H 2 @C 60 are similar in all the solvents.The temperature dependences of T 1 for H 2 and H 2 @C 60 were investigated in detail for toluene-d 8 ( Figure 1) and for benzene-d 6 , 1,1,2,2-tetrachloroethane-d 2 , 1,2-dichlorobenzene-d 4 , and chloroformd 1 . Striking features of the data are the occurrence of a maximum for T 1 at ∼240 K for both the H 2 and H 2 @C 60 in toluene-d 8 and a ratio of T 1 values which is nearly independent of temperature. A maximum of the value of T 1 with temperature is also found in 1,1,2,2-tetrachloroethane-d 2 and chloroform-d 1 . For benzene-d 6 and 1,2-dichlorobenzene-d 4 in the available range of temperatures, only a decrease of T 1 with increasing temperature was observed.This kind of dependence of T 1 on temperature is uncommon, although a maximum of T 1 has previously been observed for small molecules such as H 2 O, 7 HCl, and HBr in solution, 8,9 and it is consistent with two relaxation mechanisms with different temperature dependences dominating in turn below and above 240 K for both H 2 and H 2 @C 60 . Since the value of T 1 for both H 2 and H 2 @C 60 does not significantly change in going from benzene-h 6 to benzened 6 (Table 1), the dominating interactions determining H 2 and H 2 @C 60 nuclear relaxation must be intramolecular. Furthermore, the intramolecular dipole-dipole interaction and spin-rotation interaction are known 2 to be responsible for the relaxation of gaseous H 2 and their magnitude has been measured for H 2 in molecular beams. 10 Therefore it is likely that the relaxation of H 2 in solution also depends on the competition between intramolecular dipole-dipole interaction and spin-rotation interaction.The contribution to 1/T 1 (in extreme narrowing conditions) from intramolecular dipolar and spin-rotation interaction may be estimated by eq 1 2 and eq 2, 11,12 respectively:where γ H is the magnetogyric ratio for the proton, r is the equilibrium internuclear distance of H 2 (0.74 Å), C is the spinrotation coupling constant (7.16 × 10 5 rad s -1 ), 10 I is the moment of inertia of H 2 (4.6 × 10 -48 kg m 2 ), and k B is the Boltzmann constant. The correlation times τ dip and τ sr are measures of the timedependent fluctuations in the orientation and angular velocity of H 2 , respectively. Both correlation times are expected to be functions of viscosity and temperature which depend on the details of the motion of H 2 molecules and the surrounding medium. 11 Qualitatively, the dipole-...

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Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

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“…In recent years some remarkable complexes have been synthesised in which a hydrogen molecule is permanently trapped inside a fullerene cage [1][2][3] . These endohedral H 2 -fullerene complexes are superb model systems for understanding quantum molecular dynamics.…”

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“…Therefore to measure the spectrum of the entrapped H 2 alone it was expedient to record INS spectra from both H 2 -filled and empty cage samples under identical conditions and to determine the difference spectrum. Samples with high purity were prepared using published synthetic procedures [1,2] The H 2 @ATOCF sample mass was 492mg, equivalent to 0.46mmol H 2 . The existence of a -13.25 meV neutron energy gain peak at a temperature of 2.5K proves that the sample is not in full thermal equilibrium.…”

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Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

et al. 2009

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“…The physical properties of hydrogen endofullerenes have also been probed by nuclear magnetic resonance [1,8,9]. What has enabled the experimental investigations is the synthetic organic breakthrough, known as 'molecular surgery', by Komatsu and co-workers [10,11] for producing macroscopic amounts of H 2 @C 60 and HD@C 60 .…”

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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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Encapsulation of Molecular Hydrogen in Fullerene C ₆₀ by Organic Synthesis

Cited by 593 publications

References 23 publications

Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

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

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Encapsulation of Molecular Hydrogen in Fullerene C 60 by Organic Synthesis

Cited by 593 publications

References 23 publications

Nuclear Relaxation of H2 and H2@C60 in Organic Solvents

Nuclear Relaxation of H2 and H2@C60 in Organic Solvents

Quantum Translator-Rotator: Inelastic Neutron Scattering of Dihydrogen Molecules Trapped inside Anisotropic Fullerene Cages

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

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Encapsulation of Molecular Hydrogen in Fullerene C ₆₀ by Organic Synthesis

Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

Nuclear Relaxation of H₂ and H₂@C₆₀ in Organic Solvents

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