Synthesis, crystal structure and magnetic properties of dinuclear NiIILnIII complexes based on a flexible polydentate ligand

The synthesis and characterization of three isomorphous complexes [Ni-II(L)Ln(III)(DBM)(3)] (Ln = Gd (1.2.5CH(3)CN center dot 0.5H(2)O), Tb (2.2CH(3)CN center dot 0.5MeOH), and Dy (3.2CH(3)CN center dot 0.5MeOH center dot 0.5H(2)O)) are reported (H2L = N,N'-dimethyl-N,N'-(2-hydroxy-3-methoxy-5-methylbenzyl)ethylenediamine, DBM- = anion of 1,3-diphenylpropane-1,3-dione). The flexible ligand L2- contains an N2O2-inner and an O-4-outer coordination site. There are diphenoxo bridges between NiII and LnIII ions in these complexes. The remaining coordination sites are occupied by DBM-anions. Direct current (dc) magnetic susceptibility measurements indicate the presence of intramolecular ferromagnetic interactions in desolvated complexes 1-3. The magnetic coupling constant J(NiGd) in complex 1 is estimated to be 1.11 cm(-1) (H = -2/NiGdSNiSGd). Alternating current (ac) magnetic susceptibility studies reveal that complexes 2 and 3 show frequency-dependent out-of-phase signals, which indicate that they exhibit SMM behavior. The energy barriers for complexes 2 and 3 under a 2 kOe applied direct current (dc) magnetic field are estimated from Arrhenius plots to be 14.4 and 11.3 K, respectively.