A low-energy CAD study of the ions MOH(H2O)+ (M = Mn, Co, Ni, Cu, Zn) and [M(H2,O2)]+ (M = Cr, Fe, La, Pr)

The ions [MOH(H2O)](+) (M = divalent Mn, Co, Ni, Cu, Zn)and [M,O-2,H-2](+) (M = trivalent Cr, Fe, La, Pr) have been formed using an electrospray technique from aqueous solutions of metal salts. Their low-energy, collisionally activated dissociations have been studied in a triple sector instrument. At the lowest collision energies, [MOH(H2O)](+) (M = Co, Mn, Ni,) dissociates by loss of water, but with increasing energy loss of OH and formation of [M(H2O)](+) becomes the major reaction. This behavior correlates more with M+OH than with M+-OH2 bond energies. [ZnOH(H2O)](+) dissociates only to [ZnOH](+) at all available collision energies, which is inconsistent with published relative bond, energies. [CuOH(H2O)](+) dissociates to [Cu(H2O)](+) and OH at low collision energy, but [CuOH](+) becomes slightly greater in yield at high energy, implying that, in [CuOH(H2O)](+), D(Cu+-OH) is less than D(Cu+-OH2). The dissociation spectra of [M,O-2,H-2](+) (M = Cr, Fe), which may be [M(OH)(2)](+), show only loss of water at low collision energy, yielding MO+, but with increasing collision energy simple bond scission yields [MOH](+) as the major product. [M,O-2,H-2](+) (M = La, Pr) shows the same behavior, but the threshold energy for the appearance of MOH+ is much higher, consistent with the considerably higher M+-O bond energy. (Int J Mass Spectrom 202 (2000) 251-259) (C) 2000 Elsevier Science B.V.