Syntheses, Crystal Structure and Magnetic Properties of an Unprecedented One-Dimensional Coordination Polymer Derived from an {(NiL)(2)Ln} Node and a Pyrazine Spacer (H-2 L = N, N '-Bis(salicylidene)-1,3-propanediamine, Ln = Gd, Tb and Dy)

摘要

In order to investigate the coordinative interaction of the (NiL)-L-II metalloligand with lanthanides (H2L = N, N'-bis(salicylidene)-1,3-propanediamine or H2salpn) and the building block potential of the resultant unstable {((NiL)-L-II)(2)Ln(III)} (Ln(III) = Lanthanides) complex with a short spacer pyrazine (pyz), three heterometallic coordination polymers of formulae {(NiL)(2)Ln(NO3)(3)}pyz(n) center dot 1.5nH(2)O Ln= Gd (1), Tb (2) and Dy (3) have been synthesized. In these compounds the central Ln(III) ion is connected to two terminal NiL metalloligands through mu(1,1)-diphenoxido bridges to form the trinuclear node with three nitrato coligands (LnO(9) monocapped square-antiprism). The coordinative preference of pyrazine ligand towards the Ni-II-centre of the trinuclear units leads to the formation of these tailored 1D-zigzag coordination polymers with transoidtrinuclear nodes. The magnetization at 1.8 K for 1 (10.4 mu(B) at 7 T) indicates the presence of Gd - Ni ferromagnetic coupling through the phenoxido bridges. The exchange parameter was determined to be + 0.179(4) K from the magnetic susceptibility measurement. Both in-phase and outof- phase ac magnetic measurements under an applied dc magnetic field reveal temperature dependence of the susceptibility at different frequencies below 5 K for compound 3, characteristic of single molecule magnets (SMMs) or polymeric aggregates of SMMs.