Temperature dependence of the carbon-13 proton spin-spin coupling constant in gaseous methane

Bennett, Brian R.; Raynes, W.T.

doi:10.1080/00268978700101891

Cited by 19 publications

(8 citation statements)

References 16 publications

(20 reference statements)

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“…a From ref. 20,115,116 The calculated 1 H and 13 C NMR chemical shifts as well as the 1 H− 13 C spin-spin couplings presented in Table 7 revealed a very good agreement with experimental data. For protons in the CH 4 molecule, the change in chemical shift (∆δ ) upon encapsulation in C 60 was predicted to be −7.54 ppm, which compared very well to −7.88 ppm observed in an experiment.…”

Section: Nmr Properties Of the Ch 4 @C 60supporting

confidence: 65%

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

Jaworski

Hedin²

2021

Preprint

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Methane has been successfully encapsulated within cages of C60 fullerene, and it is an appropriate model system to study confinement effects. Its chemistry and physics is also relevant for theoretical model descriptions. Here we provided insights into intermolecular interactions and predicted spectroscopic responses of the CH4@C60 complex and compared with results from other methods and with literature data. Local energy decomposition analysis (LED) within the domain-based local pair natural orbital coupled cluster singles, doubles, and perturbative triples (DLPNO-CCSD(T)) framework was used, and an efficient protocol for studies of endohedral complexes of fullerenes is proposed. This approach allowed us to assess energies in relation to electronic and geometric preparation, electrostatics, exchange, and London dispersion for the CH4@C60 endohedral complex. The calculated stabilization energy of CH4 inside the C60 fullerene was −13.5 kcal/mol and its magnitude was significantly larger than the latent heat of evaporation of CH4. Evaluation of vibrational frequencies and polarizabilities of the CH4@C60 complex revealed that the infrared (IR) and Raman bands of the endohedral CH4 were essentially “silent” due to dielectric screening effect of the C60, which acted as a molecular Faraday cage. Absorption spectra in the UV-Vis domain and ionization potentials of the C60 and CH4@C60 were predicted. They were almost identical. The calculated 1H/13C NMR shifts and spin-spin coupling constants were in very good agreement with experimental data. In addition, reference DLPNO-CCSD(T) interaction energies for complexes with noble gases (Ng@C60 ; Ng = He, Ne, Ar, Kr) were calculated. The values were compared with those derived from supermolecular MP2/SCS-MP2 calculations and estimates with London-type formulas by Pyykkö and coworkers [Phys. Chem. Chem. Phys., 2010, 12, 6187-6203], and with values derived from DFT-based symmetry-adapted perturbation theory (DFT SAPT) by Hesselmann & Korona [Phys. Chem. Chem. Phys., 2011, 13, 732-743]. Selected points at the potential energy surface of the endohedral He2@C60 trimer were considered. In contrast to previous theoretical attempts with the DFT/MP2/SCS-MP2/DFT-SAPT methods, our calculations at the DLPNO-CCSD(T) level of theory predicted the He2@C60 trimer to be thermodynamically stable, which is in agreement with experimental observations.

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Section: Nmr Properties Of the Ch 4 @C 60supporting

confidence: 65%

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

Jaworski

Hedin²

2021

Preprint

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“…The 1 H NMR spectrum in 1,2‐dichlorobenzene‐ d 4 displays a singlet at δ H =−5.71 ppm, where the shift results from the shielding effect of the C 60 cage, compared with 12 CH 4 in the gas phase, which has a chemical shift of δ H =2.166±0.002 ppm . From the natural abundance 13 CH 4 @C 60 , the measured coupling is 1 J HC =124.3±0.2 Hz (at 295 K), in comparison with 1 J HC =125.3 Hz (at 292 K) measured in the gas phase . The liquid state 13 C{ 1 H} NMR spectrum reports a sharp singlet for endohedral methane at δ C =−13.63 ppm in 1,2‐dichlorobenzene‐ d 4 , again shielded in comparison with the reported shift of δ C =−8.648±0.001 ppm measured in the gas phase (Figure a,b).…”

Section: Figurementioning

confidence: 96%

First Synthesis and Characterization of CH₄@C₆₀

et al. 2019

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“…[47] Theliquid state 13 C{ 1 H} NMR spectrum reports asharp singlet for endohedral methane at d C = À13.63 ppm in 1,2-dichlorobenzene-d 4 ,a gain shielded in comparison with the reported shift of d C = À8.648 AE 0.001 ppm measured in the gas phase [46] (Figure 4a,b). [47] Theliquid state 13 C{ 1 H} NMR spectrum reports asharp singlet for endohedral methane at d C = À13.63 ppm in 1,2-dichlorobenzene-d 4 ,a gain shielded in comparison with the reported shift of d C = À8.648 AE 0.001 ppm measured in the gas phase [46] (Figure 4a,b).…”

Section: Angewandte Chemiementioning

confidence: 86%

“…Zuschriften gas phase. [47] Theliquid state 13 C{ 1 H} NMR spectrum reports asharp singlet for endohedral methane at d C = À13.63 ppm in 1,2-dichlorobenzene-d 4 ,a gain shielded in comparison with the reported shift of d C = À8.648 AE 0.001 ppm measured in the gas phase [46] (Figure 4a,b). Figure 4c,d shows the relevant section of the INEPT NMR spectrum of 13 CH 4 @C 60 ,a longside experimental and simulated proton-coupled 13 CNMR spectra.…”

Section: Angewandte Chemiementioning

confidence: 99%

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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Temperature dependence of the carbon-13 proton spin-spin coupling constant in gaseous methane

Cited by 19 publications

References 16 publications

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

First Synthesis and Characterization of CH₄@C₆₀

First Synthesis and Characterization of CH₄@C₆₀

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Temperature dependence of the carbon-13 proton spin-spin coupling constant in gaseous methane

Cited by 19 publications

References 16 publications

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

Local Energy Decomposition Analysis and Molecular Properties of Encapsulated Methane in Fullerene (CH4@C60)

First Synthesis and Characterization of CH4@C60

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