General trends in dissociations of medium-sized hydrocarbon dications

This study aims towards a rationalization and generalization of the fragmentation patterns of medium-sized hydrocarbon dications by tandem mass spectrometry. Phenanthrene (C14H10) serves as a precursor for the generation of CmHn2+ dications with m = 9–14 and n = 1–10. Four characteristic channels occur in the metastable-ion spectra: loss of a hydrogen atom, elimination of molecular hydrogen, loss of acetylene, and charge-separation fragmentation (Coulomb explosion). The first two channels dominate the spectra and their relative intensities show some regularities for ions with an even number of carbon atoms. Further, parent ions with an odd number of hydrogen atoms exhibit loss of atomic hydrogen, whereas loss of molecular hydrogen is preferred for dications with an even number of hydrogen atoms. The ions with odd number of carbon atoms do not show any evident regularity for the H and H2 losses. The channels involving CC bond cleavages occur for larger dications with m > 9, but only for some combinations of m and n without an apparent regularity.