Heterometallic Pentanuclear [Ni4Ln] (LnIII = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions

Abstract

AbstractThe reaction of 6‐formyl‐2‐(hydroxymethyl)‐4‐methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square‐antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxygen atoms. The magnetic properties of 1–4 were investigated in the temperature range 2–300 K. The magnetic properties of 1 were fitted by using a Hamiltonian containing isotropic exchange, NiII local zero‐field‐splitting, and Zeeman effects (Ĥ = Ĥexchange + Ĥzfs + Ĥzeeman). The molecular structures of 1–4 reveal that the Ni–O–Ln angle is around 89° whereas the Ni–O–Ni angle is about 96°. Because of this accidental orthogonality, ferromagnetic interactions between the nearest‐neighbor NiII ions and between NiII and LnIII ions have been observed. The observed J values are 0.34 and 1.88 cm–1 between GdIII–NiII and NiII–NiII, respectively.