Solvent-assisted control of the oxidation state in a dinuclear cobalt(II) complex with slow relaxation of the magnetization

Abstract

The use of the reduced compartmental N₂O₄-donor ligand, H₂L^r (= 2,2-dimethyl-1,3-propanediyl-bis(iminomethylene)-bis(6-ethoxyphenol)), containing an inner N₂O₂ and an outer O₂O′₂ cavity, with Co^II in dimethylsulfoxide (dmso) gives rise to a p-nitrobenzoic −bridged cobalt(II) dimer: [(dmso)Co^IIL^r(μ-RCO₂)Co^II(NCS)] (1) (RCO₂H = p-nitrobenzoic acid). The reducing environment of the solvent dmso plays a crucial role in stabilizing cobalt(II) in the complex 1. The dimeric complex has been structurally characterized by single-crystal X-ray diffraction and various spectroscopic techniques. Magnetic DC and AC susceptibility measurements show very weak ferromagnetic interactions in the complex and a field-induced slow magnetization relaxation (SMR) at relatively low temperatures. For an applied DC field of 100 mT, the complex shows a slow relaxation process that follows Direct and Orbach mechanisms with A = 1.47(5) × 10⁴ s⁻¹ K⁻¹, τ₀ = 4.0(4) × 10⁻⁸ s and U_eff = 18(2) K.