Gas-phase plutonium nitrate anion complexes were produced by electrospray ionization (ESI) of a plutonium nitrate solution. The ESI mass spectrum included species with all four of the common oxidation states of plutonium: Pu(III), Pu(IV), Pu(V) and Pu(VI). Plutonium nitrate complexes were isolated in a quadrupole ion trap and subjected to collision induced dissociation (CID). CID of complexes of the general formula PuO_x(NO₃)_y⁻ resulted in the elimination of NO₂ to produce PuO_x+1(NO₃)_y−1⁻, which in most cases corresponds to an increase in the oxidation state of plutonium. Plutonyl species, Pu^VO₂(NO₃)₂⁻ and Pu^VIO₂(NO₃)₃⁻, were produced from Pu^III(NO₃)₄⁻ and Pu^IV(NO₃)₅⁻, respectively, by the elimination of two NO₂ molecules. CID of Pu^VIO₂(NO₃)₃⁻ resulted in NO₂ elimination to yield PuO₃(NO₃)₂⁻, in which the oxidation state of plutonium could be VII, a known oxidation state in condensed phase but not yet in the gas phase. Density functional theory confirmed the nature of Pu^VO₂(NO₃)₂⁻ and Pu^VIO₂(NO₃)₃⁻ as plutonyl(V/VI) cores coordinated by bidentate equatorial nitrate ligands. The computed structure of PuO₃(NO₃)₂⁻ is essentially a plutonyl(VI) core, Pu^VIO₂²⁺, coordinated in the equatorial plane by two nitrate ligands and one radical oxygen atom. The computations indicate that in the ground spin-orbit free state of PuO₃(NO₃)₂⁻, the unpaired electron of the oxygen atom is antiferromagnetically coupled to the spin-triplet state of the plutonyl core. The results indicate that Pu(VII) is not a readily accessible oxidation state in the gas phase, despite that it is stable in solution and solids, but rather that a Pu(VI)-O• bonding configuration is favored, in which an oxygen radical is involved.