Imidazolium molecular motifs located on dicationic frameworks. Electrospray mass spectrometric observation of carbenes: imidazolylidenes.

Electrospray ionization mass spectral analysis of simple dicationic imidazolium prototypes (M.2X) is reported and direct observation was obtained for proton-mediated ion-molecule reactions in the gas phase. The comparative ESI-MS study with heterophanes 1a.2Cl and 3.2Br, the open chain system 5.2Br, and their regiospecific deuterated counterparts 2a.2Cl, 4.2Br and 6.2Br showed that the nature of the frameworks containing two imidazolium subunits modulates their electrospray ionization, changing the stability of the common characteristic peaks: the carbene specie [M - H](+) or [M - D](+) as well as [M](2+) and [M. X](+).Copyright 2000 John Wiley & Sons, Ltd.