ELECTRON-AFFINITIES AND C-60 ANION CLUSTERS OF CERTAIN BOWL-SHAPED POLYCYCLIC AROMATIC-HYDROCARBONS

The kinetic method is applied to the determination of the electron aff inities (EAs) of the bowl-shaped polycyclic aromatic hydrocarbons (PAH s) dibenzo [a,g]corannulene (C28H14) 1 and dinndenochrysene (C26H12) 2 using electron attachment desorption chemical ionization mass spectro metry (DCI-MS) and triple-quadrupole tandem mass spectrometry. The est imated EAs of 1 and 2 are 1.00+/-0.20 and 1.16+/-0.20 eV respectively. In an analogous experiment, loosely bound dimeric radical anions comp rising C-60 with 1 and C-60 with 2 were generated in the gas phase by electron attachment desorption chemical ionization. The collision-indu ced dissociation of each of these cluster ions yields both the monomer ic radical anions as products and yields calculated electron affinitie s of C-60 of 1.20+/-0.20 eV (C-60/1 dimer) and 1.24+/-0.20 eV (C-60/2 dimer). These values are significantly different from the known electr on affinity of C-60 (2.65 eV) and support previous studies on electron -bound dimers comprising C-60 and coronene [G., Chen, R. G. Cooks, E. Corpuz and L. T. Scott, J. Am. Sec. Mass Spectrom. 7, 619 (1996)] in s howing that the dissociation of electron-bound dimers comprising C-60 and reference PAHs is controlled by the electron affinity of a portion of the C-60 surface, i.e. that a 'local' electron affinity of C-60 is measured. The 'local' electron affinity value corresponds approximate ly to the electron affinity of the reference PAHs, C-60 exhibiting an affinity for the 'extra' electron in the cluster which approximately m atches that of its PAH partner. (C) 1997 by John Wiley & Sons, Ltd.