Synthesis and structural examination of complexes of Am(IV) and other tetravalent actinides with lacunary heteropolyanion alpha2-P2W17O61(10-).

This study concerns the formation of complexes with actinides at oxidation state +IV, from Th to Am, through a lacunary heteropolyanion ligand P(2)W(17)O(61)(10-). The preparation of original single crystals of complexes with 1:2 stoichiometry provided structural data through single-crystal X-ray diffraction for the entire An(IV) series. An(IV) atoms in these complexes have a coordination number of 8, and their coordination polyhedron is a distorted square antiprism. The data were used to compute a mean (An-O) interatomic distance for each actinide. When the interatomic distance is plotted versus the inverse ionic radius of these tetravalent actinides, it appears that the simple electrostatic model is not suitable for Am(IV) and Pu(IV), although this trend must be confirmed by further investigation with other examples from the An(IV) series.

Interaction of transuranium elements with biologically important molecules: structural and spectroscopic study of NP(V) complexes with imidazole.

New Np(V) complexes with imidazole, [NpO(2)(CH(3)COO)(Im)(2)(H(2)O)], [(NpO(2))(2)(C(2)O(4))(Im)(6)] x 5 Im x H(2)O, and [NpO(2)(NO(2))(Im)(4)], were synthesized. Their crystal structures were determined using X-ray single-crystal diffractometry. The crystal structures are confirmed by IR and UV-vis spectroscopic data. In all three complexes, neptunium coordinates the imidazole molecule through the nitrogen atom. These complexes are the first example of direct bonding of the imidazole molecule to the actinide atom. These results suggest that coordination of histidine residue in proteins or other imidazole-containing biologically important molecules could occur under usual biological conditions.

First structural evidence of actinide-nitrite coordination.

The first nitrite complex of actinide metal, {C(NH 2)3}2[NpO 2(NO 2)(Pic)2], was synthesized, and its crystal structure was determined using X-ray diffractometry and confirmed by NIR and IR spectroscopies. Main crystallographic data: space group P1, triclinic, a = 8.9329(1) A, b = 11.6669(2) A, c = 11.6698(2) A, alpha = 68.080(1) degrees, beta = 88.213(1) degrees, gamma = 73.254(1) degrees, V = 1076.45(3) A (3), and Z = 2.