Crystal Structures of Molecular Adducts between Uranyl Nitrate and 2,2′ : 6′,2′′-Terpyridine or 2,2′-Bipyridyl

Complexes of uranyl nitrate with aromatic molecular ligands : [UO2Terpy(NO3)2] and (H2Terpy)2[UO2(NO3)2(H2O)2](NO3)4 · 4H2O (Terpy 2,2′:6′,2′′-terpyridine), (Hbipy)[UO2(NO3)3] and [(UO2)2(Bipy)2O2(NO3)2] (Bipy—2,2′-bipyridyl) and (HPy)4[(UO2)2(NO3)4(OH)2](NO3)2 (Py—pyridine) were characterized by X-ray diffraction analysis. In all these compounds, the U(VI) atom has the hexagonal bipyramidal environment. The U–O bond lengths in the UO22+ have close values. In the equatorial planes, the U–N bond lengths with the Bipy and Terpy ligands are identical, whereas the U–O bond lengths depend on the type of the ligand. The lengths of the equatorial bonds increase in the sequence U–N > U–Onitr > U–Ohydr > U–Operox. The geometric characteristics of the coordinated and solvate Terpy and Bipy molecules are different. The lengths of the N–O bonds in the NO3– groups depend on the participation of the O atom in the coordination of the central atom, the coordination mode, and the formation of hydrogen bonds.