Americium Oxalate: An Experimental and Computational Investigation of Metal–Ligand Bonding

Abstract

A novel actinide-containing coordination polymer, [Am(C2O4)(H2O)3Cl] (Am-1), has been synthesized and structurally characterized. The crystallographic analysis reveals that the structure is two-dimensional and comprised of pseudo-dimeric Am3+ nodes that are bridged by oxalate ligands to form sheets. Each metal center is nine-coordinate, forming a distorted capped square antiprism geometry with a C 1 symmetry, and features bound oxalate, aqua, and chloro ligands. The Am3+–ligand bonds were probed computationally using the quantum theory of atoms in molecules nd natural localized molecular orbital approaches to investigate the underlying mechanisms and hybrid atomic orbital contributions therein. The analyses indicate that the bonds within Am-1 are predominantly ionic and the 5f shell of the Am3+ metal centers does not add a significant covalent contribution to the bonds. Our bonding assessment is supported by measurements on the optical properties of Am-1 using diffuse reflectance and photoluminescence spectroscopies. The position of the principal absorption band at 507 nm (5L6′ ← 7F0′) is notable because it is consistent with previously reported americium oxalate complexes in solution, indicating similarities in the electronic structure and ionic bonding. Compound Am-1 is an active phosphor, featuring strong bright-blue oxalate-based luminescence with no evidence of metal-centered emission.

Chemical Kinetics for the Oxidation of Californium(III) Ions with Select Radiation-Induced Inorganic Radicals (Cl2•– and SO4•–)

“…Actinide chlorides are one of the most common starting materials used in fundamental actinide studies, − and as such, the chloride anion (Cl – ) is often present in either the inner or outer coordination sphere of many reported actinide crystal structures, − including californium . Furthermore, hydrochloric acid (HCl) and chlorinated hydrocarbons such as dichloromethane (DCM) are widely used for the purification and recycling of transuranic elements and as solvents in subsequent studies. − Consequently, there are many scenarios in which Cl – ions and chlorinated compounds may be exposed to ionizing radiation fields arising from the radioactive decay of the actinides and their radioactive daughter nuclides.…”

Insight into the Structural and Emissive Behavior of a Three‐Dimensional Americium(III) Formate Coordination Polymer

“…This assignment separates Am1 as the only nine coordinate Am 3+ with C 3v symmetry for which emission is reported. Emission of seven‐coordinate [17] (C 1 ), eight‐coordinate [7,12,99] (C 1 and C 2v ), and nine‐coordinate [98] (C 1 ) are known and do not display a dominant 5 D 1′ → 7 F 0′ emission band. As such, we postulate that the peculiar optical behavior is a direct result of the unique symmetry of the metal site.…”

“…To date only a few reported emissive Am 3 + containing compounds are known from single crystals. [7,12,17,98,99] The compound Am1 is an emissive material and as such. we have measured the luminescence spectrum, Figure 8.…”

Understanding the Complexation Behavior of Carbamoylphosphine Oxide Ligands with Representative f-Block Elements

“…In earlier investigations, density functional theory (DFT) methods were employed to deduce geometric configurations, and their effectiveness in elucidating experimental observations has been proven. − In this context, geometries of all of the complexes in the present study were optimized in the gas phase at the DFT level using the BP86 , density functional in conjunction with the def2-TVZP basis set. , For the heavy elements, an effective core potential (ECP) generated for a neutral atom with quasi-relativistic methods , was used to replace the inner-shell electrons (28 and 60 electrons for lanthanides and actinides, respectively). The rest of the electrons were explicitly treated using the standard def2-TZVP basis set.…”