Mass Spectral Study of Extractable La- and Lu-Containing Fullerenes

Abstract

Mass spectra of La x C 2n (x = 1,2), well known endohedral metallofullerenes, and Lu 2 C 2n (2n = 76-112), new members of extractable metallofullerenes, were studied. Positive-ion laser desorption/ionization (LDI) and electron impact (EI) mass spectra indicated that lutetium is a special lanthanide that prefers to form dilutetium fullerenes by the arc-burning method. However, the signals for Lu 2 C 2n become very weak in negative-ion LDI-MS, this is different from La 2 @C 80 , which has close relative abundances in positive-and negative-ion MS. The distinction between Lu 2 C 2n and La 2 @C 80 in the negative-ion LDI mass spectra may be due to the different structures of La-and Lu-containing fullerenes. © 1997 by John Wiley & Sons, Ltd. Received 23 December 1996; Accepted 7 February 1997 Rapid Commun. Mass Spectrom. 11, 000-000 (1997 Since the first macroscopic preparation of metallofullerenes by Chai et al. 1 in 1991, these compounds have attracted considerable interest and have become one of the most interesting branches of fullerene study owing to their novel electronic and structural properties and potential applications as superconductors, organic ferromagnets, laser and ferroelectric materials and so on.2 Mass spectrometry provided the crucial evidence that led to the discovery of metallofullerenes in 1985 3 and has always played a key role in the identification and characterization of metallofullerenes from then on.4-6 Now, most lanthanides, including La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er, have been encapsulated in fullerene cages and extracted successfully. 7 In this paper, we report a mass spectral study of La x C 2n (x = 1, 2), well known endohedral metallofullerenes, and Lu 2 C 2n , new members of extractable metallofullerenes prepared by arc-burning of metal/ graphite composite rods in a low-pressure helium environment. EXPERIMENTAL MaterialsThe metal-containing fullerenes were prepared by arcburning of 6 mm diameter spectrograde graphite rods which were core-drilled and packed with M 2 o 3 (99.99%)/graphite powder, giving an M/C total atomic ratio of 1:100 (M = La, Lu). These composite rods were baked at 2000 K for 3 h under vacuum (10 -3 Torr) first and an arc between them and a graphite rod was sparked at 80 A DC under a 160 Torr static He atmosphere. The resulting soot was collected and Soxhlet extracted with toluene for 12 h, then further treated in a sealed stainless-steel autoclave under about 20-atm pressure and at 523 K with toluene and pyridine, respectively. Laser desorption/ionization mass spectrometry (LDI-MS)The LDI-MS measurements were performed on an LDI-1700 mass spectrometer (Linear Scientific, Reno, NV, USA). About 0.5 µL of extract was applied to the probe tip and dried under vacuum for crystallization (no matrix was used). A nitrogen laser (337 nm) was focused on the coated probe for desorption and ionization; the power was kept at 3-6 µJ to avoid ion fragmentation. The vacuum of the flight tube was 10 -6Torr. All spectra were obtained with the accumulation of 50 single las...

Explanation of the different preferential binding sites for Ce and La in M2@C80 (M = Ce, La)—a density functional theory prediction

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23] Two encapsulated metal atoms are frequently found in the C 80 -I h fullerene as this unstable isomer [24][25][26] is stabilised by forming M 2 @C 80 (M ¼ La, Ce, etc.) [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] These metallofullerenes have been adapted for further usage by specific cage functionalization. [29][30][31] The motion of the dopants within the cage has also been shown to be manipulated with functional groups.…”

A study ofaconitum alkaloids from aconite roots inAconitum carmichaeli Debx using matrix-assisted laser desorption/ionization mass spectrometry

“…16 The alkaloids (or extract) and matrix (DHB, a saturated solution in 1:1 acetonitrile and water) were mixed together in the ratio of 10:1. About 0.5 mL of the resulting solution was applied to the probe tip and dried under vacuum for crystallization.…”