Field Desorption Spectra Research Articles

Field desorption mass spectrometry of organometallic complex salts

The field desorption spectra of [(L)M(CO) 3] +BF 4 − [M = Fe, L = cyclo-C 6H 7, cyclo-C 7H 9, cyclo-C 10H 11, 2-MeO-cyclo-C 6H 7; M = W, L = cyclo-C 7H 7], [(Ar)Fe(C 5H 5)] +PF 6 − [Ar = C 6H 6, CH 3C 6H 5, (CH 3) 3C 6H 3], [(cyclo-C 8H 11)Co(C 5H 5)] +BF 4 − and [(C 6H 6)Cr(CO) 3] have been obtained. In all cases molecular or quasi-molecular ions for the cations were present, usually as the base peaks in the spectra. Fragment ions corresponding to metal—ligand cleavages were also found in most cases.

Beneficial effect of macrocyclic ligands on field desorption mass spectra of samples containing alkali metal ions.

Addition of a macrocyclic ligand, such as a crown ether or cryptate, to the solution of an organic compound containing alkali metal ions prior to field desorption mass spectral analysis, has been shown to result in a reproducible, smooth field desorption process at low anode temperature. Crystalline dibenzo-18-crown-6 ether complexes of NaI and KI give field desorption spectra in which free and complexed ligands are of comparable intensity. Cryptate complexes retain the metal ion even more strongly, as illustrated by the fact that the complex of LiCl with [2.1.1]-cryptate yields almost exclusively the complexed lithium peak on field desorption. Alkali metal salts with organic anions also desorb more smoothly after complexation, although in the case of simple carboxylates the anion is found only in a cluster peak.