Construction of the Lanthanide Diphosphonates via a Template-Synthesis Strategy: Structures, Proton Conduction, and Magnetic Behavior

Two series of lanthanide phosphonates, [H(4)BAPEN](1.5)center dot[Ln(2)(HEDP)(3)]center dot 5H(2)O [Ln = Gd3+ (1-Gd), Tb3+ (1-Tb), Dy3+ (1-Dy)] and [H(4)BAPEN](0.5)center dot[LnLi-(HHEDP)(2)(H2O)(2)]center dot 2H(2)O [Ln = Gd3+ (2-Gd), Tb3+ (2-Tb), Dy3+ (2-Dy)] (HEDP = 1-hydroxyethylidenediphosphonate) displaying diverse structures have been successfully constructed templated by a protonated aliphatic organic amine 1,2-bis(3-aminopropylamino)ethane (BAPEN). The connection of Ln(III) ions and the diphosphonate ligand generates the one-dimensional (1D) chains for both series 1 and 2. Interestingly, 2D layered heterometallic diphosphonate networks were fabricated in series 2 wherein the adjacent Ln-HHEDP chains are joined together through the linkage of Li+. Notably, the compounds feature interesting proton conduction behavior. The conductivity increases smoothly with rising temperature, indicating that these compounds could act as promising candidates for temperature sensing. Moreover, the magnetic properties of them have been investigated.