Interaction of neptunium(V) with picolinic, nicotinic and isonicotinic acids

Abstract

Summary The interaction of Np(V) with all isomers of pyridinemonocarboxylic acid has been investigated, stability constants have been calculated using NIR spectroscopy. Single crystals of [NpO 2 (Pic)(H 2 O) 2 ] ( 1 ), Cs[NpO 2 (Pic) 2 (HPic)]·3H 2 O ( 2 ), [NpO 2 (Nic)(H 2 O)] ( 3 ), and [NpO 2 (iso-Nic)(H 2 O)] ( 4 ) have been synthesized. Compound 1 contains infinite chains; compound 2 consists of isolated Cs + , [NpO 2 (Pic) 2 (HPic)] - groups and water molecules. In both 3 and 4 neptunoyl-ion NpO 2 acts as monodentate ligand with one of the O atoms of NpO 2 group entering in coordination polyhedron of the adjacent Np atom. Compounds 3 and 4 have layered and three-dimensional topologies, respectively. Crystallographic data: [NpO 2 (Pic)(H 2 O) 2 ], space group P ¯1, triclinic, a = 6.380(2), b = 7.733(2), c = 10.700(4) Å, α = 96.49(3), β = 106.78(3), γ = 103.83(3)°, and Z = 2 ( 1 ); Cs[NpO 2 (Pic) 2 (HPic)]·3H 2 O, space group P ¯1, triclinic, a = 8.707(2), b = 9.777(2), c = 14.640(3) Å, α = 76.633(15), β = 78.75(2), γ = 86.55(2)°, and Z = 2 ( 2 ); [NpO 2 (Nic)(H 2 O)], space group P 2 1 / n , monoclinic, a = 11.901(4), b = 5.5628(15), c = 12.124(3) Å, β = 101.05(2)°, and Z = 4 ( 3 ); [NpO 2 (iso-Nic)(H 2 O)], space group P 2 1 2 1 2 1 , orthorhombic, a = 5.742(3), b = 8.550(5), c = 18.512(10) Å, and Z = 4 ( 4 ). Electron and IR spectra of solid compounds have been measured.