Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies

Abstract

Several lanthanide and actinide tetranitrate ions, M(III)(NO3)4(-), were produced by electrospray ionization and subjected to collision induced dissociation in quadrupole ion trap mass spectrometers. The nature of the MO(NO3)3(-) products that result from NO2 elimination was evaluated by measuring the relative hydrolysis rates under thermalized conditions. Based on the experimental results it is inferred that the hydrolysis rates relate to the intrinsic stability of the M(IV) oxidation states, which correlate with both the solution IV/III reduction potentials and the fourth ionization energies. Density functional theory computations of the energetics of hydrolysis and atoms-in-molecules bonding analysis of representative oxide and hydroxide nitrates substantiate the interpretations. The results allow differentiation between those MO(NO3)3(-) that comprise an O(2-) ligand with oxidation to M(IV) and those that comprise a radical O(-) ligand with retention of the M(III) oxidation state. In the particular cases of MO(NO3)3(-) for M = Pr, Nd and Tb it is proposed that the oxidation states are intermediate between M(III) and M(IV).

Redox behavior of gas phase Pu(IV)-monodentate ligand complexes: an investigation by electrospray ionization mass spectrometry

“…This is consistent with fragmentation studies of Pu(IV)(NO 3 ) 5 -reported by Maurice et al [48] which indicate the loss of two NO 2 or N 2 O 4 groups. Fragmentation studies on other metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) in the presence of nitrate have also reported the loss of NO 3 -, NO 2 , or NO molecules and oxidation of the metal [33,64]. Thus, it can be concluded that when nitrate is present in the inner coordination sphere of the metal, CID can lead to oxidation of the metal.…”

“…gas phase behavior [45,47,52,53], Pu(III) gas phase behavior [32,33,44], and Pu(IV) tetrapositive gas phase behavior [48,54]. Rios et al reported in 2011 the gas phase reduction of PuO 2 2? to Pu(V) and Pu(IV), followed by ESI-MS [47], demonstrating parallel rich redox chemistry for Pu in the gas phase and solution phase.…”

“…One advantage of this technique that lends it to be quite useful in actinide studies is its low detection level, as only small amounts of sample are required for analysis [30][31][32][33]. Actinide species have been studied by ESI-MS since the early 1990's where the use of electrospray mass spectrometry was utilized for the analysis of various elements, including UO 2 2?…”

Exploring the Coordination of Plutonium and Mixed Plutonyl–Uranyl Complexes of Imidodiphosphinates

“…This technique is known to be used in combination with traditional solution chemistry techniques to investigate metal-ligand interactions 45,46 . Actinide species have been studied by ESI-MS since the early 1990's where the use of electrospray mass spectrometry was utilized for the analysis of various elements including U(VI) 47,48 , Th(IV) 49,50,51,52,53,54,55,56,57 , Am(III) 34,58,59,60,61,62,63 , Np and Pu in different oxidation states 64,65,66,67,68,69,70 . The publications range from species identification to specific interest in the chemistry of the f-elements 59,50,71 through the investigation of competitive interactions 54 .…”

“…Additionally, a number of studies have included the use of ESI-MS to investigate the gas phase behavior of UO 2 + , UO 2 2+ , PuO 2 + and PuO 2 2+ 55,72, 65,66,67,73,74,75,76,77 Pu(III) 61,59,60 , Pu(IV) gas phase behavior 59,78 and Rios et al reported the gas phase reduction of PuO 2 2+ to Pu(V) and Pu(IV) followed by ESI-MS 67 . The ESI-MS spectra in positive ionisation mode of 1 after dissolution of some crystals in THF and 1/1000 th dilution in CH 3 CN are reported in the SI (Figure S4 and S5) .…”