Syntheses, Structures, and Magnetic Properties of Acetato- and Diphenolato-Bridged 3d–4f Binuclear Complexes [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (M = ZnII, CuII, NiII, CoII; Ln = LaIII, GdIII, TbIII, DyIII; 3-MeOsaltn = N,N′-Bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato; ac = Acetato; hfac = Hexafluoroacetylacetonato; x = 0 or 1)

摘要

ABSTRACT: A series of 3d−4f binuclear complexes, [M(3-nMeOsaltn)(MeOH)x(ac)Ln(hfac)2] (x = 0 for M = CuII, ZnII;nx = 1 for M = CoII, NiII; Ln = GdIII, TbIII, DyIII, LaIII), have beennsynthesized and characterized, where 3-MeOsaltn, ac, and hfacndenote N,N′-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato,nacetato, and hexafluoroacetylacetonato, respectively.nThe X-ray analyses demonstrated that all the complexes havenan acetato- and diphenolato-bridged MII−LnIII binuclear structure.nThe CuII−LnIII and ZnII−LnIII complexes are crystallized in annisomorphous triclinic space group P1̅, where the CuII or ZnIInion has square pyramidal coordination geometry with N2O2ndonor atoms of 3-MeOsaltn at the equatorial coordination sitesnand one oxygen atom of the bridging acetato ion at the axial site. The CoII−LnIII and NiII−LnIII complexes are crystallized in annisomorphous monoclinic space group P21/c, where the CoII or NiII ion at the high-spin state has an octahedral coordinationnenvironment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and anmethanol oxygen atom at the two axial sites. Each LnIII ion for all the complexes is coordinated by four oxygen atoms of twonphenolato and two methoxy oxygen atoms of “ligand-complex” M(3-MeOsaltn), four oxygen atoms of two hfac−, and one oxygennatom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilitiesnfrom 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbitalncontributions of the LnIII (TbIII, DyIII) and to a lesser extent the MII (NiII, CoII) components, the magnetic interaction betweennMII and LnIII ions were investigated by an empirical approach based on a comparison of the magnetic properties of the MII−LnIII,nZnII−LnIII, and MII−LaIII complexes. The differences of χMT and M(H) values for the MII−LnIII, ZnII−LnIII and thosenfor the MII−LaIII complexes, that is, Δ(T) = (χMT)MLn − (χMT)ZnLn − (χMT)MLa = JMLn(T) and Δ(H) = MMLn(H) − MZnLn(H) −nMMLa(H) = JMLn(H), give the information of 3d−4f magnetic interaction. The magnetic interactions are ferromagnetic if MII =n(CuII, NiII, and CoII) and Ln = (GdIII, TbIII, and DyIII). The magnitudes of the ferromagnetic interaction, JMLn(T) and JMLn(H), arenin the order CuII−GdIII > CuII−DyIII > CuII−TbIII, while those are in the order of MII−GdIII ≈ MII−TbIII > MII−DyIII for MII = NiIInand CoII. Alternating current (ac) susceptibility measurements demonstrated that the NiII−TbIII and CoII−TbIII complexes showednout-of-phase signal with frequency-dependence and the NiII−DyIII and CoII−DyIII complexes showed small frequency-dependence.nThe energy barrier for the spin flipping was estimated from the Arrhenius plot to be 14.9(6) and 17.0(4) K for the NiII−TbIII andnCoII−TbIII complexes, respectively, under a dc bias field of 1000 Oe.