Structural and Spectroscopic Investigation of Two Plutonium Mellitates.

The aqueous reaction of mellitic acid (Hmell) with PuBr·HO forms two plutonium mellitates, Pu(mell)(HO)·HO () and Pu(mell)(HO)·2HO (). These compounds are compared to the isomorphous lanthanide mellitates with similar ionic radii via bond length analysis. Both plutonium compounds form three-dimensional metal-organic frameworks, with having two unique metal centers and having one. All plutonium metal centers exhibit nine-coordinate geometries. Our results show metal-oxygen bond lengths for plutonium significantly shorter than those of the previously reported lanthanum and herein reported cerium analogues, consistent with the nine-coordinate ionic radii. Clear Laporte-forbidden 5f → 5f transitions are observed in the ultraviolet-visible-near-infrared spectra and are assigned to trivalent plutonium. However, there is a distinct color difference between the two plutonium compounds.