Peculiarities of the Supramolecular Assembly of Tetraethylammonium and 3‑Bromopropionate Ions in Uranyl, Neptunyl, and Plutonyl Coordination Compounds

Synthesis and X-ray diffraction studies of {N­(C2H5)4}­[AnO2(C2H4BrCOO)3] [An = U (I), Np (II), or Pu (III)] and C2H4BrCOOH (IV), where C2H4BrCOO– is an anion of the 3-bromopropionic acid, are reported. The isostructural coordination compounds I–III contain mononuclear anionic complexes [AnO2(C2H4BrCOO)3]− belonging to the crystal chemical group AB01 3 (A = AnO2 2+; B01 = C2H4BrCOO–). In the crystal structure of IV, the C2H4BrCOOH molecules are hydrogen bonded into centrosymmetric dimers R2 2(8). Using the method of molecular Voronoi–Dirichlet (VD) polyhedra, the features of intermolecular interactions in crystals of I–IV are discussed in support of the results of IR and UV spectroscopy experiments. Actinide contraction in I–III manifests itself in a regular reduction of the average length of the axial and equatorial bonds in hexagonal bipyramids AnO8, in an increase in νas(AnO2 2+) wavenumbers, and in a simultaneous decrease in the volume and sphericity degree of VD polyhedra of An atoms in the U–Np–Pu series. The title compounds represent an interesting architecture, where 3-bromopropionate ions penetrate through the square 44 net of tetraethylammonium ions and thus bind adjacent nets via the “locking effect”.