Incorporation of helium, neon, argon, krypton, and xenon into fullerenes using high pressure

Abstract

In their first paper on Buckminsterfullerene,1 Kroto and Smalley et al. proposed a hollow structure. Interest in theinclusion of atoms into the cavity to form "endohedral complexesn has continued. Early work concentrated on incorporating metals? but noble gas atoms were obvious possibilities. Several studies reported that collisions of fullerene cation radicals with helium and neon in a mass spectrometer led to addition of the mass of the noble gas atoms to the ions.S7 Many theoretical studiesB-15 have appeared with estimates of the energies of fullerenes containing noble gas atoms, the dynamics of motion inside the cavity, and spectroscopic properties, even though none of these substances has been prepared in quantity.We have recently shown16 that fullerene prepared in the standard manner (a graphite arc in a low pressure of helium17) contains helium in about one in a million molecules. Heating fullerenes in several atmospheres of 3He or neon at 600 "C led to inclusion of these atoms at similar levels. We proposed that (1) Kroto, H. W.; Heath, J. R.; OBrien, S. C.; Curl, R. F.; Smalley, R. E. Nature 1985, 318, 162-163. (2) Heath, J. R.; OBrien, S. C.; Zhang, Q.; Liu, Y.; Curl, R. F.; Kroto, H. W.; Smalley, R. E. J. Am. Chem. Soc. 1985,107,7779-7780. (3) Weiske, T.; Bdhme, D. K.; HruUk, J.; KrHtchmer, K.; Schwarz, H. Angew. Chem., Int. Ed. Engl. 1991, 30, 884-886. (4) Schwarz, H.; Weiskc, T.; Bdhme, D. K.; HruUk, J. In Euckminrterfullerenes; Billups, W. E., Ciufolini, M. A,, Eds.; VCH Publishers: New (5) Ross, M. M.; Callahan, J. H. (7) Caldwcll, K. A.; Giblin, D. E.; Hsu, C. S.; Cox, D.; Gross, M. L. J. Am. (8) Breton, J.; Gonzalez-Platas, J.; Girardet, G. (IS) Cardini, 0.; Procacci, P.; Salvi, P. R.; Schettino, V. Chem. Phys. (16) Saunders, M.; JimCnez-Vhzqucz. H. A,; Cross, R. J.; Poreda, R. J. (17) KrHtchmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman, D. R. 3734. 8362. 8741. 1864-7869.this process takes place by the reversible breaking of one or more bonds, opening a "window" large enough for entry of atoms. The noble gases were detected by heating samples in the modified mass spectrometer operated by one of us (R.J.P.). 16 We have now incorporated krypton using -15 atm at 600 OC for 2 h. An 18.5-mg sample of the resulting fullerene yielded 1.6 X 1 V cm3 of 84Kr on heating (1 atom in 410 OOO molecules), with a release pattern similar to that reported for helium and neon. Since several theoretical papers predicted that krypton and xenon would not fit into CM, we wanted to try to incorporate xenon.To investigate the spectroscopic and other properties of these interesting noble gas compounds, it is necessary to increase the fraction of fullerene molecules occupied. We have done this by carrying out the incorporation step at high pressures of the gas. One of us (S.M.) operates a facility with high-pressure steel vessels that can be heated behind appropriate shielding. Usually, a pump is employed to compress the gas into the vessel. Using expensive gases (e.g., 3He), this is a disadvantage since large amounts o...

Direct detection and quantitation of He@C60 by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry

“…The results also demonstrate the feasibility of determining the extent of He incorporation from the FT-ICR mass spectral peak heights. The present measurements are in agreement with those obtained by the pyrolysis method [1][2][3]. Although limited in sensitivity, the mass spectral method is faster and easier than pyrolysis.…”

“…Neutral C 60 samples containing approximately 1% 3 He@C 60 and 4 He@C 60 were prepared by the labeling method, in the presence of KCN [1][2][3]23]. For comparison, C 60 (99.5% purity) was purchased from Aldrich (Milwaukee, WI).…”

“…Another technique for the preparation of endohedral fullerene compounds is that of ion implantation (the endohedral species is neutralized on implantation). Endohedral species containing lithium and other alkali metals [15][16][17], the noble gases, He and Ne [18], and nitrogen [19] have been produced by that method.Endohedral compounds of all the noble gases can be prepared by heating fullerenes under high noble gas pressure [1][2][3]20]. Initially, yields of incorporation were approximately 0.1% for He, Ne, Ar and Kr and 0.03% for Xe.…”

“…In the above studies, the noble gases were detected and quantified by pyrolyzing the material to release the gas, which was detected in either a quadrupole mass spectrometer [1,3,25] or a linear time-of-flight mass spectrometer [24]. It is possible, with sufficient labeling, for the larger noble gas endohedral fullerenes to be detected in standard mass spectra [2]. However, that method is not suitable…”

“…Endohedral compounds of all the noble gases can be prepared by heating fullerenes under high noble gas pressure [1][2][3]20]. Initially, yields of incorporation were approximately 0.1% for He, Ne, Ar and Kr and 0.03% for Xe.…”