Hybrid open frameworks (MIL-n). Part 5 Synthesis and crystal structure of MIL-9: a new three-dimensional ferrimagnetic cobalt(II) carboxylate with a two-dimensional array of edge-sharing Co octahedra with 12-membered rings

Abstract

Co ₅ (OH) ₂ (C ₄ H ₄ O ₄ ) ₄ , a new cobalt(II) succinate with an open framework, was prepared hydrothermally (180°C, 72 h, autogenous pressure) from a 2:3:8:120 mixture of Co(II) chloride, succinic acid, potassium hydroxide and water. Its monoclinic structure was solved by single crystal X-ray diffraction [space group P2 ₁ /c (no. 14) with a=9.5631(2) Å, b=9.4538(2) Å, c=12.5554(2) Å, β=96.968(1)°, V=1126.72(4) Å ³ , Z=4] from 3077 unique reflections [I≥2σ(I)], R1=0.020 and wR2=0.054. The three-dimensional structure is built up from layers of edge sharing octahedra pillared by succinate ions. Within the layers, cobalt octahedra form 12-membered ring windows. Below 10 K, Co ₅ (OH) ₂ (C ₄ H ₄ O ₄ ) ₄ , exhibits ferrimagnetic behavior.