Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane

Bloodworth, Sally; Gräsvik, John; Alom, Shamim; Kouřil, Karel; Elliott, Stuart J.; Wells, Neil J.; Horsewill, A.J.; Mamone, Salvatore; Jiménez‐Ruiz, Mónica; Rols, S.; Nagel, U.; Rõõm, T.; Levitt, Malcolm H.; Whitby, Richard J.

doi:10.1002/cphc.201701212

“…Open‐cage fullerene 3 was obtained from bis(hemiketal) 4 according to the published method . We have previously shown the 17‐membered orifice of 3 to be suitable for entry of a single molecule of methane, achieving 65 % encapsulation by heating 3 at 200 °C under 153 atm of methane . Upon increasing the pressure of methane above 1500 atm, we obtained CH 4 @ 3 with more than 95 % encapsulation of methane (estimated from the 1 H NMR spectrum) after 22 h at 190 °C.…”

Section: Figurementioning

confidence: 99%

First Synthesis and Characterization of CH₄@C₆₀

Bloodworth

¹

,

Sitinova

²

,

Alom

³

et al. 2019

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The endohedral fullerene CH 4 @C 60 , in which each C 60 fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C 60 to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/ benzene solvate shows no significant distortion of the carbon cage, relative to the C 60 analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The 1 H spin‐lattice relaxation times ( T 1 ) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C 60 cage. The synthesis of CH 4 @C 60 opens a route to endofullerenes incorporating large guest molecules and atoms.

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“…The key reaction in most of the reported open‐cage method is the addition of singlet oxygen to form a dioxetane ring followed by ring‐opening rearrangement . Some of the open‐cage molecules have a orifice large enough to encapsulate small molecules such as CH 4 , CO 2 , HCCH and MeOH . We have reported the synthesis of several fullerene‐mixed peroxides .…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Open‐Cage [60]Fullerenes with Five Carbonyl Groups on the Rim of the 15‐Membered Orifice

Xu

¹

,

Yang

²

,

Su

³

et al. 2019

ChemPlusChem

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A new type of open‐cage [60]fullerene was prepared starting from our previously reported open‐cage [60]fullerenes containing hydroxy and tert‐butylperoxo groups, and an iminofuranone moiety on the rim of the orifice. The key reactions are alcoholysis with MeOH/PCl5 and reductive aromatization with SnCl2 or HI (aq). The resulting open‐cage compound contains two ketone carbonyls, two amide carbonyls, and one ester carbonyl group. The X‐ray crystal structure of the precursor compound shows that the 18‐membered orifice is almost completely blocked because of the presence of the amide group directly above the orifice.

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“…[25] We have previously shown the 17-membered orifice of 3 to be suitable for entry of as ingle molecule of methane,achieving 65 %encapsulation by heating 3 at 200 8 8C under 153 atm of methane. [28] Upon increasing the pressure of methane above 1500 atm, we obtained CH 4 @3 with more than 95 %encapsulation of methane (estimated from the 1 HNMR spectrum) after 22 ha t1 90 8 8C. Oxidation with dimethyldioxirane [37] gave the sulfoxide CH 4 @5 cleanly.P hotochemical removal of the sulfinyl group (SO) has been reported for ringcontraction of the sulfoxide derivative of open-cage fullerene 1,u sing visible-light irradiation.…”

mentioning

confidence: 87%

“…Open-cage fullerene 3 was obtained from bis(hemiketal) 4 [15] according to the published method. [28] Upon increasing the pressure of methane above 1500 atm, we obtained CH 4 @3 with more than 95 %encapsulation of methane (estimated from the 1 HNMR spectrum) after 22 ha t1 90 8 8C. [28] Upon increasing the pressure of methane above 1500 atm, we obtained CH 4 @3 with more than 95 %encapsulation of methane (estimated from the 1 HNMR spectrum) after 22 ha t1 90 8 8C.…”

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confidence: 99%

“…[19][20][21][22][23][24] The16-membered orifice of 2 is too small to allow entry of bigger guests,b ut these can be accommodated by the larger (17-membered) opening of fullerene 3. [25] Insertion of N 2 and CO 2 , [26] CH 3 OH and H 2 CO, [27] CH 4 and NH 3 , [28] NO, [29] and O 2 , [30] into 3 have all been recently described, but aprocedure for suturing the opening of A@3 to give A@C 60 has not yet been reported. In this article,w ed escribe the successful closure of A@3 to give A@C 60 .Thee ndohedral fullerenes H 2 @C 60 and H 2 O@C 60 are exceptional platforms for the study of nuclear spin isomer-Figure 1.…”

mentioning

confidence: 99%

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First Synthesis and Characterization of CH₄@C₆₀

Bloodworth

¹

,

Sitinova

²

,

Alom

³

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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Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane

Cited by 27 publications

References 75 publications

First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀

Synthesis of Open‐Cage [60]Fullerenes with Five Carbonyl Groups on the Rim of the 15‐Membered Orifice

First Synthesis and Characterization of CH₄@C₆₀

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Synthesis and Properties of Open Fullerenes Encapsulating Ammonia and Methane

Cited by 27 publications

References 75 publications

First Synthesis and Characterization of CH4@C60

First Synthesis and Characterization of CH4@C60

Synthesis of Open‐Cage [60]Fullerenes with Five Carbonyl Groups on the Rim of the 15‐Membered Orifice

First Synthesis and Characterization of CH4@C60

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First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀