Effect of diamagnetic Zn(ii) ions on the SMM properties of a series of trinuclear ZnDy2 and tetranuclear Zn2Dy2 (LnIII = Dy, Tb, Gd) complexes: combined experimental and theoretical studies

Abstract

To study the effect of diamagnetic ions on magnetic interactions, utilizing a compartmental ligand (Z)-2-(hydroxymethyl)-4-methyl-6-((quinolin-8-ylimino)methyl)phenol (LH₂), two different series of Zn^II–Ln^III complexes, namely the trinuclear series of [DyZn₂(L)₂(μ₂-OAc)₂(CH₃OH)₂]·NO₃·MeOH (1), [TbZn₂(L)₂(μ₂-OAc)₂(CH₃OH)₂]·NO₃·5MeOH·H₂O (2), and [GdZn₂(L)₂(μ₂-OAc)₂(CH₃OH)₂]·NO₃·MeOH·CHCl₃ (3) and the tetranuclear series of [Dy₂Zn₂(LH)₄(NO₃)₄(μ₂OAc)]·NO₃·MeOH·H₂O (4), [Tb₂Zn₂(LH)₄(NO₃)₄(μ₂-OAc)]·NO₃·MeOH·2H₂O (5), and [Gd₂Zn₂(LH)₄(NO₃)₄(μ₂-OAc)]·NO₃·MeOH·2H₂O (6), were synthesized. Trinuclear Zn^II–Ln^III complexes 1–3 consist of one Ln^III ion sandwiched between two peripheral Zn^II ions forming a bent type Zn^II–Dy^III–Zn^II array with an angle of 110.64°. Tetranuclear Zn^II–Ln^III complexes 4–6 are basically a combination of two dinuclear moieties of [LnZn(LH)₂(NO₃)₂]⁺ connected by one bidentate bridging acetate ion in μ₂-OAc coordination mode. The detailed magnetic analysis reveals that complexes 1 and 4 are single molecule magnets having energy barriers of 34.98 K and 46.71 K with relaxation times (τ₀) of 5.05 × 10⁻⁴ s and 5.24 × 10⁻⁴ s, respectively. Ab initio calculations were employed to analyze the magnetic anisotropy and magnetic exchange interaction between the Zn^II and Ln^III centers with the aim of gaining better insights into the magnetic dynamics of complexes 1–6.