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  • Title: Generation and dissociation pathways of singly and doubly protonated bisguanidines in the gas phase.
    Author: Tintaru A, Roithová J, Schröder D, Charles L, Jusinski I, Glasovac Z, Eckert-Maksić M.
    Journal: J Phys Chem A; 2008 Nov 27; 112(47):12097-103. PubMed ID: 18983132.
    Abstract:
    Para-bisguanidinyl benzene 1 and its N-permethylated derivative 2 are both sufficiently strong bases to afford not only the monocations [1+H]+ and [2+H]+, but also the doubly protonated ions, [1+2H]2+ and [2+2H]2+, in the gas phase. The title ions generated via electrospray ionization are probed by collision-induced dissociation experiments which inter alia reveal that the dicationic species [1+2H]2+ and [2+2H]2+ can even undergo fragmentation reactions with maintenance of the 2-fold charge. Complementary results from density functional theory predict PAs above 1000 kJ mol(-1) for the neutral compounds, i.e., PA(1) = 1025 kJ mol(-1) and PA(2) = 1067 kJ mol(-1). Due to the stabilization of the positive charge in the guanidinium ions and the para-phenylene spacer separating the basic sites, even the monocations bear sizable proton affinities, i.e., PA([1+H]+) = 740 kJ mol(-1) and PA([2+H]+) = 816 kJ mol(-1).
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