In
this work, we report a systematic search of metastable C6H
n
2+ (n =
1–6) dications from electron impact time-of-flight measurements
of several benzene derivatives in combination with global minimum
search based on the genetic algorithm. Our theoretical calculations
reveal that the C6H
n
2+ (n < 6) global minimum structures are completely
different from that of the benzene dication, featuring linear carbon
chains and/or cyclopropenylium moieties. Experimentally, the doubly
charged species were investigated for a wide range of electron impact
energies, from 20 to 2000 eV, for benzene and several monosubstituted
compounds containing either electron-withdrawing or -donating groups.
Furthermore, the C6H
n
2+ production, evaluated from the yields of the dications with respect
to that of the parent ion (or parent dication), was compared to those
obtained from charge exchange in the doubly charged 2E spectra and
electron impact experiments available in the literature. The yields
of the long-lived benzene dications were contrasted to those analogues
formed in chlorobenzene. Moreover, the formation of C6H
n
2+ species is strongly dependent
on the nature of substituent groups, with electron-withdrawing ones
favoring the dication formation.