Electrospray ionization of neutral metal dithiocarbamate complexes using in-source oxidation

An electrospray ionization (ESI) mass spectral characterization of eight su bstituted tris(dithiocarbamato)iron(III) complexes (Fe(III)(dtc)(3)) and of the diethyldithiocarbamate (et(2)dtc)(-), complexes of Mn(III), Cu(II), Ni (II), and Co(III) is presented. Use is made of the inherent electrochemical potential of the ESI source to oxidize the neutral metal complexes and in- source collision-induced dissociation (CID) to characterize the resulting i ons. The mass spectra obtained at low source offset voltages all show molec ular ions of the oxidized complexes, in addition to ions due to the loss of a dithiocarbamate, (dtc)(-), ligand. Three of the Fe(III)(dtc)(3) complexe s also show ions due to fragmentation of the (dtc)(-) ligands. Ions corresp onding to the thiuram disulfide formed following the oxidation of excess (d tc)(-) in solution are also seen. In-source CID studies of the Fe(III), Mn( III), Cu(II), Ni(II) and Co(III) (et(2)dtc)(-) complexes all show [M(I)(et( 2)dtc)+H](+) ions attributed to proton transfer from a protonated solvent i on to a M(I)(et(2)dtc) neutral formed upon following CID in the high-pressu re region of the ion source. The results of the present in-source oxidation studies are compared with those obtained in previous ESI studies in which external oxidizing agents were added to the metal complex solutions prior t o analysis. Copyright (C) 1999 John Wiley & Sons, Ltd.