Dissociation of Diglycolamide Complexes of Ln3+ (Ln = La-Lu) and An3+ (An = Pu, Am, Cm): Redox Chemistry of 4f and 5f Elements in the Gas Phase Parallels Solution Behavior

Tripositive lanthanide and actinide ions, Ln(3+) (Ln = La-Lu) and An(3+) (An = Pu, Am, Cm), were transferred from solution to gas by electrospray ionization as Ln(L)(3)(3+) and An(L)(3)(3+) complexes, where L = tetramethyl-3-oxa-glutaramide (TMOGA). The fragmentation chemistry of the complexes was examined by collision-induced and electron transfer dissociation (CID and ETD). Protonated TMOGA, HL+, and Ln(L)(L-H)(2+) are the major products upon CID of La(L)(3)(3+), Ce(L)(3)(3+), and Pr(L)(3)(3+), while Ln(L)(2)(3+) is increasingly pronounced beyond Pr. A C-Oether bond cleavage product appears upon CID of all Ln(L)(3)(3+); only for Eu(L)(3)(3+) is the divalent complex, Eu(L)(2)((2+)), dominant. The CID patterns of Pu(L)(3)(3+), Am(L)(3)(3+), and Cm(L)(3)(3+) are similar to those of the Ln(L)(3)(3+) for the late Ln. A striking exception is the appearance of Pu(IV) products upon CID of Pu(L)(3)(3+), in accord with the relatively low Pu(IV)/Pu(III) reduction potential in solution. Minor divalent Ln(L)(2)(2+) and An(L)(2)(2+) were produced for all Ln and An; with the exception of Eu(L)(2)(2+) these complexes form adducts with O-2, presumably producing superoxides in which the trivalent oxidation state is recovered. ETD of Ln(L)(3)(3+) and An(L)(3)(3+) reveals behavior which parallels that of the Ln(3+) and An(3+) ions in solution. A C-Oether bond cleavage product, in which the trivalent oxidation state is preserved, appeared for all complexes; charge reduction products, Ln(L)(2)(2+) and Ln(L)(3)(2+), appear only for Sm, Eu, and Yb, which have stable divalent oxidation states. Both CID and ETD reveal chemistry that reflects the condensed-phase redox behavior of the 4f and 5f elements.