Series of octanuclear clusters of Ni(II)/Co(II) with tunable structures and magnetism supported by thiacalix[4]arenes

In this study, five thiacalix[4]arene (TC4A)-based octanuclear homometallic or heterometallic clusters, namely, {[Ni₈(TC4A)₂(μ₆-CO₃)₂(μ₂-CH₃CO₂)₃(μ₂-CO₃)(DMA)₄]}∙(CH₃CN)₂ (1) (DMA = N,N-dimethylamine), {[Ni_5.81Co_2.19(TC4A)₂(μ₆-CO₃)₂(μ₂-HCO₂)₂(μ₂-Cl)₂(DMA)₄]}∙2DMF∙2CH₃CN (2) (DMF = N,N-dimethylformamide), {[Ni_4.06Co_3.94(TC4A)₂(μ₆-CO₃)₂(μ₂-HCO₂)₂(μ₂-Cl)₂(DMA)₄]}∙2DMF∙2CH₃CN (3), {[Ni₂Co₆(TC4A)₂(μ₆-CO₃)₂(μ₂-HCO₂)₂(μ₂-Cl)₂(DMA)₄]}∙2DMF∙2CH₃CN (4), and {[Co₈(TC4A)₂(μ₆-CO₃)₂(μ₂-HCO₂)₃(μ₂-CO₃)₂(DMA)₄]}∙4DMF (5), are synthesized using a solvothermal method. Single-crystal X-ray diffraction analysis reveals that all synthesized compounds comprise two badminton-like secondary building units (SBUs) [M₄(TC4A)] (M = Co, Ni, Co/Ni) linked by two μ₆-CO₃²⁻ anions in a tail-to-tail manner, forming a chair-like octanuclear metal cluster. Their structures were also characterized using Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, etc. Magnetism studies indicate an antiferromagnetic interaction between the metal ions of compounds 1–5, and their magnetic susceptibility χ_MT increases as the cobalt content increases in the range of 50–300 K. The structures and magnetic properties of the Co(II)/Ni(II) cluster supported by TC4A can be conveniently tuned by varying the Ni(II):Co(II) molar ratio, providing a straightforward approach for fabricating TC4A-based heterometallic clusters.