Synthesis, Characterization, and X-ray Structure of Tetraaminoguanidinium Diuranyl Tetraoxalate Monohydrate (HAgun)4[(UO2)2(C2O4)4]·H2O

Abstract

A new uranyl oxalate complex containing aminoguanidinium cation was isolated from an aqueous solution containing uranyl nitrate hexahydrate, oxalic acid dihydrate, and aminoguanidinium bicarbonate in appropriate ratio. The compound was characterized by analytical, spectral (UV-Vis and IR), and thermal (TG-DTA) techniques. The X-ray crystallographic study shows that the complex has a polymeric structure with two types of coordination around the alternative uranyl ions. The oxalate ions exhibit tetradentate bridging and tri-dentate bridging modes. The aminoguanidinium cation is in the outer sphere, acting as charge-neutralizing species. An intense photoluminescence peak is observed at 519 run. The thermal decomposition of the complex yields U₃O₈. SEM photographs of U₃O₈ show the presence of irregularly shaped agglomerated particles of sub-micron size.