Single Crystal Synthesis Methods Dedicated to Structural Investigations of Very Low Solubility Mixed-Actinide Oxalate Coordination Polymers

Abstract

Two crystal growth methods dedicated to very low solubility actinide coordination polymers have been developed and applied to the synthesis of mixed actinide-(IV)−actinide(IV) or actinide(IV)−actinide(III) oxalate single crystals of a size (typically 100−300 μm) suitable for isolating them and examining their crystal structure. These methods have been optimized on mixed systems composed of U(IV) and lanthanide (surrogate of trivalent actinides) and then assessed on U(IV)−Am(III), Pu(IV)−Am(III), and U(IV)−Pu(IV) mixtures. Three types of single crystals characterized by different structures have been obtained according to the synthesis and the chemical conditions. This is the first time that these well-known or recently discovered key compounds are formed by crystal growth methods specifically developed for actinide crystal handling (i.e., in glove boxes), thus enabling direct structural studies on transuranium element systems and acquisition of basic data. Characterization by X-ray diffraction, UV−visible solid spectroscopy, thermal ionization mass spectroscopy (TIMS), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) demonstrates the potentialities and complementarity of the two crystal growth methods for obtaining the targeted mixed oxalates (actinide oxidation state and presence of both metallic ions in the crystal). More generally, this development opens broad prospects for single crystal synthesis of novel actinide organic frameworks and their structural description.

Structural study of (N2H5,H)2.9U1.1Ce0.9(C2O4)5·10H2O from a conventional X-ray diffraction diagram obtained on a powder synthesized by a fast vortex process

“…Different mechanisms could explain growth of hollow crystals. Tamain [7] proposed that the hole appearing is due to the ionic reagent flow through the membrane pore by the diffusion gradients, whereas PerezHernandez [8] suggested that a mechanism with water-induced 'dissolution" and "recrystallization" processes occur simultaneously at variable rates far exceeding the net crystal growth rate.…”

Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7·H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates

“…The technique used for the synthesis of hydrated CPP single crystals consists of the diffusion of separate calcium and pyrophosphate solutions into a silica gel, leading to a sufficiently high supersaturation in the gel to initiate homogeneous nucleation and slow growth of calcium pyrophosphate crystals. The gel method of crystal growth is often used for singlecrystal synthesis because of its simplicity and the quality of the crystals produced, which are suitable for single-crystal characterization (Tamain et al, 2012).…”

Structural Variations of 2D and 3D Lanthanide Oxalate Frameworks Hydrothermally Synthesized in the Presence of Hydrazinium Ions

“…Similar two-dimensional lanthanide oxalate arrangement has been reported with various monovalent cations, including (NH 4 )­[ Ln (H 2 O)­(C 2 O 4 ) 2 ] with Ln = Eu–Yb, (H 5 O 2 )­[ Ln (H 2 O)­(C 2 O 4 ) 2 ] with Ln = Er and Y, , (CN 3 H 6 )­[La­(H 2 O)­(C 2 O 4 ) 2 ], (CN 3 H 6 ) 0.5 (NH 4 ) 0.5 [Nd­(H 2 O)­(C 2 O 4 ) 2 ], Na­[Yb­(H 2 O)­(C 2 O 4 ) 2 ]·3H 2 O, and the yttrium compounds A [Y­(H 2 O)­(C 2 O 4 ) 2 ] with A = Cs, NH 4 , and Na­[Y­(H 2 O)­(C 2 O 4 ) 2 ]·3H 2 O . Surprisingly, this structure had not been achieved until now for lanthanide oxalates with hydrazinium as a monovalent cation, whereas it is observed in mixed actinide III and IV oxalates (N 2 H 5 ,H 3 O) 1–x [ An 1– x III An ′ x IV (C 2 O 4 ) 2 (H 2 O)]·4H 2 O precipitated from solutions , or isolated as single crystals , in which the two actinides are disordered on the lanthanide site.…”

“…42 The N−N distance within the N 2 H 5 + ion, 1.429(8) Å and 1.449(4) for 3-Tb and 3-Ho, respectively, is in agreement with values generally observed for noncoordinated hydrazinium ions. 44 33,34 or isolated as single crystals 54,55 in which the two actinides are disordered on the lanthanide site.…”