Low-dimensional organically templated uranium fluorides (C5H14N2)2U2F12•2H2O and (C2H10N2)U2F10:: Hydrothermal syntheses, structures, and magnetic properties

Two new organically templated U(IV) fluorides, (C5H14N2)(2)U2F12. 2H(2)O (AU1-1) and (C2H10N2)U2F10 (AU2-1), have been prepared from the reaction of UO3 with HF and homopiperazine (C5H12N2) at 200 degreesC in aqueous media. These compounds have been characterized by single-crystal X-ray diffraction, elemental analysis, and magnetic susceptibility measurements. Crystallographic data: AU1-1, monoclinic, space group P2(1)/c, a = 9.272(4) Angstrom, b = 12.314(4) Angstrom, c = 18.475(7) Angstrom, beta = 90.32(3)degrees, Z = 4; AU2-1, monoclinic, space group C2/c, a = 16.038(8) Angstrom, b = 7.131(3) Angstrom, c = 8.782(4) Angstrom, beta = 91.75(4)degrees, Z = 4. AU1-1 consists of face-sharing UF9 tricapped trigonal prisms that form one-dimensional chains that further hydrogen-bond with diprotonated homopiperazine and water molecules. AU2-1 forms, in part, from the cleavage of homopiperazine to yield diprotonated ethylenediamine, which serves to template the formation of uranium fluoride layers. These layers consist of edge- and corner-sharing UF9 tricapped trigonal prisms. The variable-temperature magnetic susceptibility of AU1-1 is consistent with antiferromagnetic interactions between U(IV) centers, with mu (eff)(300 K) = 4.37 mu (B)/f.u. and theta = -1.3 K. The magnetization of AU1-1 at 2 K displays an irreversible metamagnetic-like transition at H-c = 3.60 T. The magnetic susceptibility for AU2-1 (mu (eff)(300 K) = 4.58 mu (B)/f.u.) with theta = +21 K suggests the presence of weak ferromagnetic interactions within the [U2F10](2-) layers.