Hydrothermal synthesis, structure, and magnetic properties of a layered organically templated uranium aquofluoride: [C5H14N2][U2F10(H2O)]

Application of a compositional space diagram to the UO3/HF/homopiperazine ( C5H12N2) system at 180 degreesC in aqueous media has allowed for the isolat ion of a unique organically templated U(IV) aquofluoride, [C5H14N2]-[U2F10( H2O)] (AU2-3) that has been characterized by single-crystal X-ray diffracti on, elemental analysis, and magnetic susceptibility measurements. Crystallo graphic data: AU2-3, monoclinic, space soup P2(1)/m, a = 8.332-(4) Angstrom , b = 7.186(3) Angstrom, c = 10.812(9) Angstrom. beta = 95.07(6)degrees. Z = 2. The structure of AU2-3 consists of UF9 and UF8(H2O) tricapped trigonal prisms that share two edges to form (1)(infinity)[UF4F4/2(H2O)] and (1)(in finity)[UF5F4/2] chains extending along the b direction. These chains are t hen cross-linked by face-sharing of the tricapped trigonal prisms to yield (2)(infinity)[U2F10(H2O)](2-) layers. These layers contain small channels r unning down the a axis that are partially filled with coordinated water mol ecules. The layers are separated by diprotonated homopiperazine cations tha t form strong hydrogen-bonding networks. The magnetic susceptibility at tem peratures above 150 K reveals a theta value of -15 K and an effective momen t of 3.68 mu (B)/U(IV), while low-temperature measurements suggest the pres ence of a nonmagnetic ground state with a linear isothermal magnetization a t 2 K and a temperature-independent susceptibility of 0.088 emu/fu (fu form ula unit) below 8 K.