Family of Carboxylate- and Nitrate-diphenoxo Triply Bridged Dinuclear NiIILnIII Complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): Synthesis, Experimental and Theoretical Magneto-Structural Studies, and Single-Molecule Magnet Behavior

摘要

Seven acetate-diphenoxo triply bridged MIILnIIIncomplexes (MII = NiII and LnIII = Gd, Tb, Ho, Er, and Y;nMII = ZnII and LnIII = HoIII and ErIII) of formula [M(μ-L)(μ-nOAc)Ln(NO3)2], one nitrate-diphenoxo triply bridged NiII−nTbIII complex, [Ni(μ-L)(μ-NO3)Tb(NO3)2]·2CH3OH, andntwo diphenoxo doubly bridged NiII-LnIII complexes (LnIII =nEu, Gd) of formula [Ni(H2O)(μ-L)Ln(NO3)3]·2CH3OH havenbeen prepared in one pot reaction from the compartmentalnligand N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-nmethylbenzyl)diethylenetriamine (H2L). Moreover, NiII-LnIIIncomplexes bearing benzoate or 9-anthracenecarboxylate bridging groups of formula [Ni(μ-L)(μ-BzO)Dy(NO3)2] and [Ni(μ-nL)(μ-9-An)Dy(9-An)(NO3)2]·3CH3CN have also been successfully synthesized. In acetate-diphenoxo triply bridged complexes,nthe acetate bridging group forces the structure to be folded with an average hinge angle in the M(μ-O2)Ln bridging fragment ofn∼22°, whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly bridged complexes exhibit more planarnstructures with hinge angles of ∼13° and ∼2°, respectively. All NiII-LnIII complexes exhibit ferromagnetic interactions betweennNiII and LnIII ions and, in the case of the GdIII complexes, the JNiGd coupling increases weakly but significantly with the planaritynof the M−(O)2−Gd bridging fragment and with the increase of the Ni−O−Gd angle. Density functional theory (DFT)ntheoretical calculations on the NiIIGdIII complexes and model compounds support these magneto-structural correlations as wellnas the experimental JNiGd values, which were found to be ∼1.38 and ∼2.1 cm−1 for the folded [Ni(μ-L)(μ-OAc)Gd(NO3)2] andnplanar [Ni(H2O)(μ-L)Gd(NO3)3]·2CH3OH complexes, respectively. The NiIIDyIII complexes exhibit slow relaxation of thenmagnetization with Δ/kB energy barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for [Ni(μ-L)(μ-nBzO)Dy(NO3)2] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO3)2]·3CH3CN, respectively.