The aqueous reaction of mellitic acid (H(6)mell) with (PuBr3)-Pu-242 center dot nH(2)O forms two plutonium mellitates, Pu-242(2)(mell)-(H2O)(9)center dot H2O (Pu-1 alpha) and Pu-242(2)(mell)(H2O)(8) center dot 2H(2)O (Pu-1 beta). 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 Pu-1 alpha having two unique metal centers and Pu-1 beta having one. All plutonium metal centers exhibit ninecoordinate 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.