Darstellung, Isolierung und Charakterisierung von Ba@C74

Abstract

Professor Rolf Appel zum 80. Geburtstag gewidmet Inhaltsu È bersicht. Aus einem Gemisch von im Hochfrequenzofen hergestellten Fullerenen und endohedralen Bariumfullerenen wurde Ba@C 74 erstmalig isoliert. Die Trennung erfolgte nach einer zweistufigen Sublimation des Rohruûes mittels Hochleistungs-Flu È ssigchromatographie (HPLC) an einer Buckyprep-Sa È ule. Der Kapazita È tsfaktor fu È r Ba@C 74 betra È gt 6,0. Der endohedrale Charakter der Titelverbindung wurde u È ber das Fragmentierungsverhalten in der Flugzeitmassenspektroskopie nachgewiesen und ihre Identita È t durch den Vergleich von berechnetem und gemessenem Isotopenmuster belegt. Weitere Charakterisierungen erfolgten mit VIS/NIR-Absorptionsspektroskopie und Elektronen-Spinresonanz-Spektroskopie (ESR). Preparation, Isolation, and Characterization of Ba@C 74Abstract. For the first time Ba@C 74 has been isolated in pure form. The title compound has been isolated from a raw material, produced in a radio-frequency-furnace, consisting of a mixture of fullerenes and endohedral Bariumfullerenes. Ba@C 74 was separated by two stage sublimation and subsequent high-performance liquid chromatography (HPLC) using a Buckyprep column. The capacity factor for Ba@C 74 is 6.0. Its endohedral character has been deduced from the fragmentation pattern obtained by time-of-flight mass spec-troscopy while the composition has been confirmed by comparison of calculated and measured isotopic pattern of the parent peak. Further characterization was performed by VIS/NIR-spectroscopy and electron-paramagnetic-resonance spectroscopy (EPR).

The Structure of Ba@C74

“…Preparation of Ba@C 74 . Endohedral barium fullerenes were synthesized using the RF method. , Details of the experimental setup as well as the isolation by means of multistep HPLC of Ba@C 74 are reported elsewhere. , …”

“…Upon exohedral reduction, i.e., by means of electrochemical methods, the resulting dianion, C 74 2- , is a stable closed shell molecule. Analogously, endohedral reduction by an incorporated divalent metal atom, i.e., the formation of M II @C 74 , leads to stable compounds, which have been isolated and investigated by means of spectroscopic methods. − Furthermore, mono-, di-, and trimetallo endohedral fullerenes of trivalent metals have been reported. − …”

Endohedral Fullerenes

“…Absorption spectroscopy thus can be used for the structure determination of the new EMFs, when the structures of homologues with different metals are determined. In addition to the aforementioned M@C 82 series, the M II @C 74 (M = Ca, Sr, Ba, , Sm, Eu, Yb , ) family can be mentioned as another illustrative example. Likewise, the first structure elucidation of the sulfide clusterfullerenes M 2 S@C 82 - C 3 v (8) (M = Sc, Dy, Lu) and Sc 2 S@C 82 - C s (6) isomers was based on the close correspondence of their absorption spectra to those of Sc 2 C 2 @C 82 isomers, , and was later confirmed by single-crystal X-ray diffraction study .…”

23 Fullerenes

“…39 Ba@C 74 has been produced for the first time using a radiofrequency furnace. 40 The single crystal X-ray structure of a trimetallic nitride unit encapsulated in [78]fullerene, Sc 3 N@C 78 , has been obtained. 41 Similarly a scandium carbide endohedral metallofullerene, (Sc 2 C 2 )@C 84 , has been obtained and characterised using 13 C NMR spectroscopy.…”