Nonmetallic Endofullerenes and the Endohedral Environment: Structure, Dynamics, and Spin Chemistry

Lawler, Ronald G.

doi:10.1007/978-3-319-47049-8_12

Cited by 10 publications

(4 citation statements)

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“…Thee xperimental 13 Cr esonance is a1 :4:6:4:1 quintet with chemical shift d C = À13.63 ppm. [49] The 1 Hspin-lattice relaxation time constant of 12 CH 4 @C 60 was found to be T 1 = 1.4904 AE 0.0005 sat295 K. Measurement of T 1 as afunction of temperature indicates aclear increase in relaxation rate constant (T 1 À1 )w ith increasing temperature. This is alarge deshielded shift of the cage 13 CNMR resonance in comparison with the effect of smaller molecular endohedral species (HF@C 60 , Dd =+0.04 ppm, [17] H 2 @C 60 , Dd =+ 0.08 ppm, [16] and H 2 O@C 60 , Dd =+0.11 ppm [15,16] ), consistent with the large size of methane.Correlation of Dd with the van der Waals radius of the enclosed species has been described for the inert gas@C 60 series.…”

Section: Angewandte Chemiesupporting

confidence: 79%

“…This is alarge deshielded shift of the cage 13 CNMR resonance in comparison with the effect of smaller molecular endohedral species (HF@C 60 , Dd =+0.04 ppm, [17] H 2 @C 60 , Dd =+ 0.08 ppm, [16] and H 2 O@C 60 , Dd =+0.11 ppm [15,16] ), consistent with the large size of methane.Correlation of Dd with the van der Waals radius of the enclosed species has been described for the inert gas@C 60 series. [49] The 1 Hspin-lattice relaxation time constant of 12 CH 4 @C 60 was found to be T 1 = 1.4904 AE 0.0005 sat295 K. Measurement of T 1 as afunction of temperature indicates aclear increase in relaxation rate constant (T 1 À1 )w ith increasing temperature. This is indicative of asignificant spin-rotation contribution to the relaxation, and is consistent with 1 Hr elaxation of methane in the gas phase [51] (Figure 5a).…”

Section: Angewandte Chemiementioning

confidence: 97%

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First Synthesis and Characterization of CH₄@C₆₀

et al. 2019

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The endohedral fullerene CH 4 @C 60 ,i nw hich each C 60 fullerene cage encapsulates asingle methane molecule,has been synthesized for the first time.Methane is the first organic molecule,a swella st he largest, to have been encapsulated in C 60 to date.T he key orifice contraction step,aphotochemical desulfinylation of an open fullerene,w as completed, even though it is inhibited by the endohedral molecule.T he crystal structure of the nickel(II) octaethylporphyrin/ benzenesolvate shows no significant distortion of the carbon cage,r elative to the C 60 analogue,and shows the methane hydrogens as ashell of electron density around the central carbon, indicative of the quantum nature of the methane.The 1 Hspin-lattice relaxation times (T 1 )f or endohedral methane are similar to those observed in the gas phase,i ndicating that methane is freely rotating inside the C 60 cage.T he synthesis of CH 4 @C 60 opens ar oute to endofullerenes incorporating large guest molecules and atoms.Soon after the discovery of C 60 in 1985, [1] came recognition that its approximately spherical 3.7 diameter cavity provides aunique environment in which to isolate single atoms. [2] Since then endohedral fullerenes,that is,compounds denoted A@C 60 in which molecules or atoms are enclosed within the fullerene cage,have been the focus of substantial experimental and theoretical efforts. [3][4][5] Endohedral fullerenes may be synthesized by forming the fullerene in the presence of the endohedral species (particularly successful for metallofullerenes), [3,5] by high temperature and pressure treatment of the fullerene with the endohedral species (inert gas@C 60 ), [6,7] or by ion bombardment of the fullerene (N@C 60 ), [8] but all give very low incorporation and require extensive purification. Furthermore,t hese methods are not applicable to the incorporation of small organic molecules.Them acroscopic-scale preparation of endohedral fullerenes by multi-step "molecular surgery" [9][10][11][12] involves chemically opening an orifice in the fullerene,o fas ize suitable to allow entry of the single molecule.S uturing of this orifice to restore the pristine carbon cage was pioneered by Komatsu [13,14] and Murata [15] who reported the first syntheses of H 2 @C 60 and H 2 O@C 60 following insertion of H 2 or H 2 O under high-pressure,i nto open-cage fullerenes 1 and 2, respectively.O ptimized procedures for the synthesis of H 2 @C 60 and H 2 O@C 60 have subsequently been reported by ourselves, [16] based on Murataso pen-cage C 60 derivative 2, and also applied to the synthesis of HF@C 60 (Figure 1). [17,18] Them acroscopic quantities of endohedral fullerenes provided by molecular surgery have allowed detailed investigation of physical properties,i ncluding by neutron scattering, infrared spectroscopy,a nd NMR spectroscopy. [19] These methods have shown that, as ar esult of the inert and highly symmetrical environment of the cavity,a ne ntrapped molecule behaves much as would be expected in the very lowpressure gas state, [17,[19][20][21][22][23] displ...

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Section: Angewandte Chemiesupporting

confidence: 79%

Section: Angewandte Chemiementioning

confidence: 97%

First Synthesis and Characterization of CH₄@C₆₀

et al. 2019

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“…Endofullerenes of open-shell atoms, on the other hand, may also have interesting applied relevance [19]. At a rather exotic level, N@C 60 exhibited uniquely long spin relaxation times driven by the confinement [20], P@C 60 displayed an enhancement in hyperfine coupling of the phosphorous' unpaired electrons with its nucleus [21], and muonium@C 60 indicated a diminution of the hyperfine interaction between the positivelycharged muon and the unpaired electrons [22].…”

Section: Introductionmentioning

confidence: 99%

Electron vacancy-level dependent hybrid photoionization of the F⁻@ C60+ molecule: a novel effect

Ali¹,

Taylor²,

Dennis³

et al. 2022

J. Phys. B: At. Mol. Opt. Phys.

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Our previous studies [J. Phys. B 53, 125101 (2020); Euro. Phys. J. D 74, 191 (2020)] have predicted that the atom-fullerene hybrid photoionization properties for X = Cl, Br and I endohedrally conﬁned in C60 are diﬀerent before and after an electron transfers from C60 to the halogen. It was further found as a rule that the ionization dynamics is insensitive to the C60level the electron originates from to produce X−@C60+ . In the current study, we report an exception to this rule in F@C60. It is found that when the electron vacancy is situated in the C60level that participates in the hybridization in F−@C60+, the mixing becomes dramatically large leading to strong modiﬁcations in the photoionization of the hybrid levels. This novel eﬀect is fundamentally based on a level-crossing phenomenon driven by the electron transfer in F@C60. But when the vacancy is at any other pure level of C60, the level-invariance is retained showing weak hybridization. Even though this case of F@C60 is an exception in the halogen@C60 series, the phenomenon can be more general and can occur with compounds of other atoms caged in a variety of fullerenes. Possible experimental studies are suggested to benchmark the present results.

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“…Endofullerenes confining open-shell atoms have potential applied interests of rather exotic nature [13]. For instance, N@C 60 has attracted interest due to its uniquely long spin relaxation times driven by the confinement [14].…”

Section: Introductionmentioning

confidence: 99%

Photoemission from hybrid states of Cl@C₆₀ before and after a stabilizing charge transfer

Shields

Madjet

et al. 2020

J. Phys. B: At. Mol. Opt. Phys.

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Photoionization calculations of the endofullerene molecule Cl@C60 with an open-shell chlorine atom are performed in the time-dependent local density approximation (TDLDA) based on a spherical jellium model. Cross sections for atom-fullerene hybrid photoemission studied show the effects of the hybridization symmetry, the giant plasmon and the molecular cavity. Comparisons with the results of Ar@C60 provide insights in the role of a shell-closing electron and its influence on the dynamics. The results for Cl@C60 are further compared with those of a more stable, lower energy configuration that results after a C60 electron transfers to Cl forming Cl − @C60 + . This comparison reveals noticeable differences in the ionization properties of the antibonding hybrid state while the bonding hybrid remains nearly unaltered showing a magnification covering the entire giant plasmon energy range.

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Nonmetallic Endofullerenes and the Endohedral Environment: Structure, Dynamics, and Spin Chemistry

Cited by 10 publications

References 145 publications

First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀

Electron vacancy-level dependent hybrid photoionization of the F⁻@ C60+ molecule: a novel effect

Photoemission from hybrid states of Cl@C₆₀ before and after a stabilizing charge transfer

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Nonmetallic Endofullerenes and the Endohedral Environment: Structure, Dynamics, and Spin Chemistry

Cited by 10 publications

References 145 publications

First Synthesis and Characterization of CH4@C60

First Synthesis and Characterization of CH4@C60

Electron vacancy-level dependent hybrid photoionization of the F−@ C60+ molecule: a novel effect

Photoemission from hybrid states of Cl@C60 before and after a stabilizing charge transfer

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Product

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First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀

Electron vacancy-level dependent hybrid photoionization of the F⁻@ C60+ molecule: a novel effect

Photoemission from hybrid states of Cl@C₆₀ before and after a stabilizing charge transfer