APPLICATION OF ELECTROSPRAY-IONIZATION TO THE OBSERVATION OF HIGHER FULLERENE ANIONS

Negative-ion electrospray mass spectrometry for the detection of higher fullerene anions is discussed. The fullerenes were reduced in dimethoxyethane/aromatic solvent using NaK amalgam and analyzed by electrospray ionization mass spectrometry using a double-focusing mass spectrometer. All the C(n)- ions (n = 2k, and k is an integer) could be detected up to n = 102 except for 60 < n < 70 and n = 72. The detection efficiency Of C76 is found to be considerably lower than that for C78, probably because the C76- ion reacts further in solution and is converted to undetectable reaction products. In addition to the fullerene anions, large peaks due to methoxy-substituted fullerene anions, C(n)(OCH3)m-, are observed. The intensities of these ions grow with time.