CRYSTAL-STRUCTURE AND ELECTRONIC ABSORPTION-SPECTRUM OF NEPTUNYL(V) PERCHLORATE NPO2CLO4-CENTER-DOT-4H(2)O

Crystal structure of NpO2ClO4 . 4H(2)O has been determined using a CAD 4 autodiffractometer and MoKalpha radiation. Crystal data: space group P2(1), a = 8.252(3), b = 5.736(2), c = 9.786(3) Angstrom, beta = 108. 25(3)degrees, d(calc) = 3.20 g cm(-3), R = 0.029, and R(omega) = 0.038 . The crystal structure consists of alternating cation layers with the composition [NpO2 . 4H(2)O](n+)(n) and anion layers formed by outer-s phere perchlorate ions. Each NpO2 group is a monodentate ligand for ne ighboring NpO2 group; as a result, zigzag neptunyl(V) chains are forme d. Coordinated water molecules complete the coordination sphere of Np atom; the coordination polyhedron of Np atom is pentagonal bipyramid ( coordination number 7). Effect of structural features on electronic ab sorption spectra is discussed.