Cation-Cation Interaction in Np(V) Perchlorates and Their Electronic Absorption Spectra.

Four new Np(V) perchlorate complexes of the composition [NpO(HO)]ClO (orthorhombic) (), [(NpO)(ClO)(HO)]ClO·HO (), (NpO)(UO)(HO) (), and [(NpO)Cl(HO)]ClO·2HO () have been synthesized and structurally characterized. The structure of previously known monoclinic modification of NpOClO·4HO () has been determined at 100 K. The coordination environment of Np and U atoms in compounds - is pentagonal bipyramids. A cation-cation (CC) interaction was found in structures -, in which the NpO ion manifests itself as a monodentate (, ) or bidentate (-) ligand. CC bonds play a fundamental role in the crystal structures of compounds , , and . They are the main structure-forming bonds that form the crystal package as a whole. The spectra of all compounds in the visible-near-IR range were measured.