A new hybrid material exhibiting room temperature spin-crossover and ferromagnetic cluster-glass behavior

Abstract

A new compound, [Fe(5–Cl-qsal)₂][Ni(α-tpdt)₂].CH₃CN, where α-tpdt = 2,3-thiophenedithiolate and H5–Cl-qsal = N-(8-quinolyl)-5-chlorosalicylaldimine, was prepared and structurally and magnetically characterized. The crystal structure is based on an arrangement of alternate layers of [Fe(5–Cl-qsal)₂]⁺ cations and [Ni(α-tpdt)₂]⁻ anions. The magnetic measurements and Mössbauer spectroscopy revealed hybrid behavior in this compound, where a ferromagnetic cluster-glass behavior, ascribed to the anions network, and a spin crossover (SCO) of the [Fe(5–Cl-qsal)₂]⁺ cations were observed. The glassy behavior, with a blocking temperature of ca. 7.5 K, results from the disorder in the anionic layer and the competition between ferro- and antiferromagnetic interactions in the anionic layers. The SCO process with T_1/2 = 298 K (high spin fraction = γ_HS = 0.5) is rather sluggish in the limits of the conversion (γ_HS ∼ 0 and γ_HS ∼ 1), which is attributed to the effect of the anions that seem to restrict somehow the structural distortions of the cations associated with the SCO process.