Gas phase derivatization of endohedral metallofullerenes R@C82 and R2@C80 (R = Nd, Ce)

Abstract

1 The interest in these species is driven by the expectation that a whole new series of materials may be created, with properties tailored by altering the encapsulated atom.2 Researches on metallofullerenes developed slowly until the K-H method was used to prepare samples in bulk.3 Subsequently most of the rare-earth elements have been encapsulated in fullerene cages successfully, 4 and the isolation and characterization of these rare-earth metallofullerenes has been extensively studied.2 Up to now, however, their chemical properties have been little studied due to the low yields and separation difficulties. Only recently have T. Akasaka et al. published the chemical derivatization of isolated La@C 82 and Gd@C 82 by 1,1,2,2-tetramesityl-1,2-disilirane. 5,6 Mirroring studies in the condensed phase, mass spectrometry provides a powerful tool for chemical property research by virtue of its advantages, viz. small quantity sample requirements, convenience and speed. Reactions of singly, doubly and triply charged fullerene ions have been studied systematically, 7,8 and the Freiser group has embarked upon an extensive study of reactions of exohedrally bound MC 60 + ions by using the FTICRMS technique. 9,10 In our previous studies, the gas phase ion/molecule reactions of neutral C 60 with ions derived from small organic compounds have been investigated, and the two-fold reactivities of C 60 , 'superalkenity' and 'superaromaticity', have been confirmed intensively. 11-13Herein we report the first gas phase chemical derivatization of endohedral metallofullerenes by ion/molecule reactions with the plasma from self-chemical ionization of vinyl acetate. The strong electron-donating character of endohedral metallofullerenes, in contrast to the empty fullerenes is demonstrated directly from these reactions. EXPERIMENTAL MaterialsMetallofullerenes were prepared by using the K-H method, 3 arc burning under a 160 Torr He atmosphere. The 6 mm diameter graphite rods were cored by a 4 mm drill, and filled with a mixture of graphite and rare earth oxides. These R 2 O 3 /graphite composite rods (1.0R/100C, R = Ce, Nd) were baked for 4 hr at 2000 K, using a high-frequency generator under vacuum, before arc discharging. The resulting metallofullerene soots were extracted by using a toluene-pyridine two-step extraction method, 14 in which they were Soxhlet extracted (8 hr) with toluene to first remove the C 60 and C 70 and further extracted with pyridine in a sealed stainless steel autoclave under 20 atm at 523 K to dissolve most of the metallofullerenes from the soots.Vinyl acetate is commercially available with analytical grade purity, and was used without further purification. EI-MSElectron impact (EI) mass spectra were acquired using a QUATTRO triple-quadrupole mass spectrometer (Micromass, Manchester, UK). Spectra were recorded by using a direct exposure probe (DEP). The pyridine extract of metallofullerenes was dropped onto the wire at the end of the probe and the solvent was blown off before insertion into the ion source. 1400 mA c...

Chemische, elektrochemische und Struktureigenschaften von endohedralen Metallofullerenen

“…Liu und Mitarbeiter berichteten 1997 über die Funktionalisierung von M‐EMFs (M=Nd, Ce) mit Vinylacetat in einem Elektronenstoß‐Massenspektrometer 80. Im Massenspektrometer bildet sich das elektrophile C 2 H 3 O + ( m / z 43), das sofort an den Kohlenstoffkäfig addiert 80. Neben den m / z ‐Signalen für M@C 80 und M@C 82 (M=Nd, Ce) wurden auch die höheren Signale der Additionsverbindungen (+43 m / z ) beobachtet.…”

Anisotropic Magnetic Behavior of Anionic Ce@C82 Carbene Adducts

“…11 To date, however, no article has reported the spin-spin interactions and anisotropic magnetism of chemically functionalized EMFs having paramagnetic carbon cage structures. Furthermore, there have been only a few studies of chemical modifications of Ce@C 82 , 18j, 21,22 and to the best of our knowledge, none of the reports achieved structural elucidations of the derivatives. In view of the promising potential applications of EMFs in the nanotechnology area, it is very interesting and important to clarify the influence of chemical modifications of EMFs on their magnetic properties.…”

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.…”

“…Ce 2 @C 80 was first reported over a decade ago, 38 but only a few follow-up studies have been reported. [38][39][40][41][42][43] The UV-Vis spectrum of Ce 2 @C 80 differs from the spectrum of the pristine C 80 cage, indicating that Ce 2 @C 80 has a different isomer than the empty cage (I h and D 2 , respectively), with the proposition that each Ce donates three electrons to the cage in Ce 2 @C 80 . 38,41 X-Ray photoemission spectroscopy confirms that Ce has the same +3 oxidation state in Ce 2 @C 80 and Ce@C 82 .…”