Syntheses, Crystal Structure and Magnetic Properties of an Unprecedented One-Dimensional Coordination Polymer Derived from an {(NiL)2Ln} Node and a Pyrazine Spacer (H2 L=N,N’-Bis(salicylidene)-1,3-propanediamine, Ln=Gd, Tb and Dy)

摘要

In order to investigate the coordinative interaction of the [NiIIL] metalloligand with lanthanides (H2L =N,N’-bis(salicylidene)-1,3- propanediamine or H2salpn) and the building block potential of the resultant unstable {(Ni~(II)L)2Ln~(III)} (Ln~(III)=Lanthanides) complex with a short spacer pyrazine (pyz), three heterometallic coordination polymers of formulae [{(NiL)2Ln(NO3)3}pyz]n·1.5nH2O [Ln=Gd (1), Tb (2) and Dy (3)] have been synthesized. In these compounds the central LnIII ion is connected to two terminal [NiL] metalloligands through m1,1-diphenoxido bridges to form the trinuclear node with three nitrato coligands (LnO9 monocapped square-antiprism). The coordinative preference of pyrazine ligand towards the NiII-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 μB 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.