Switching on single-molecule magnet properties of homoleptic sandwich tris(pyrazolyl)borate dysprosium(iii) cations via intermolecular dipolar coupling

Abstract

Two new homoleptic Dy^III compounds [Dy(Tp^Me₂)₂][DyCl₃(Tp^Me₂)]·CH₂Cl₂ (1) and [Dy(Tp^Me₂)₂]I (3) as well as a heteroleptic (NMe₄)[DyCl₃(Tp^Me₂)] (2) (Tp^Me₂ = tris(3,5-dimethylpyrazolyl)borate) species are reported. Magnetic studies revealed that 1 is a single-molecule magnet (SMM) with an energy barrier of U_eff = 80.7 K with τ₀ = 6.2 × 10⁻⁷ s under a zero applied field. Compound 3 exhibits a U_eff of 13.5 K with τ₀ = 1.6 × 10⁻⁶ s under a 0.08 T applied field. Ab initio CASSCF + RASSI-SO calculations were performed to further investigate the magnetic behavior of complexes 1–3. The results support experimental magnetic data for 1 and 3 and indicate that an intermolecular dipolar interaction of (zJ = −0.1 cm⁻¹) is responsible for the SMM behavior of 1.