Ionothermal Synthesis of Uranyl Vanadate Nanoshell Heteropolyoxometalates.

ABSTRACT

Two uranyl vanadate heteropolyoxometalates (h-POMs) have been synthesized by ionothermal methods using the ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate (EMIm-Et2PO4). The hybrid actinide-transition metal shell structures have cores of (UO2)8(V6O22) and (UO2)6(V3O12), which we designate as {U8V6} and {U6V3}, respectively. The diethyl phosphate anions of the ionic liquids in some cases terminate the core structures to form actinyl oxide clusters, and in other cases the diethyl phosphate oxyanions link these cluster cores into extended structures. Three compounds exist for the {U8V6} cluster core {U8V6}-monomer, {U8V6}-dimer, and {U8V6}-chain. Tungsten atoms can partially substitute for vanadium in the {U6V3} cluster, which results in a chain-based structure designated as {U6V3}-W. Each of these compounds contains charge-balancing EMIm cations from the ionic liquid. These compounds were characterized crystallographically, spectroscopically, and by mass spectrometry.