STABILITY AND ELECTRONIC-SPECTRA OF C70X2 (X=H,F,CL)

The structures and stability of the four isomers of C70H2 have been in vestigated by INDO methods. It is indicated that the most stable isome rs are 1,9-C70H2 and 7,8-C70H2, and energy of the former is lower than that of the latter by 16.3 kJ.mol(-1), which is in good agreement wit h the experimental value and the calculated result of an ab initio met hod. The electronic spectra of C70H2 have been studied,of which the ch aracteristic absorptions are consistent with the experimental results. The stability and spectra of C70F2 and C70Cl2 have also been studied based on C70H2. It is shown that the sequence of stability for C70F2 i s the same as that of C70H2 but different from that of C70Cl2, for whi ch 21,42-isomer is the most stable one in which two Cl atoms are added to the equatorial belt of C-70 by 1,4-addition. The electronic spectr a of C70F2 and C70Cl2 are similar to that of C70H2 except the little d ifference beyond 500nm.