Three porous metal–organic frameworks based on an azobenzenetricarboxylate ligand: synthesis, structures, and magnetic properties

Abstract

Three porous metal–organic frameworks (MOFs) of {[Cd(HABTC)(H₂O)₂]·3H₂O}_n (1), {[Cd₃(ABTC)₂(H₂O)₉]·CH₃OH·DMF·2H₂O}_n (2), and {[Mn₃(ABTC)₂(H₂O)₄]·9.5H₂O}_n (3) have been constructed using azobenzene-3,5,4′-tricarboxylic acid (H₃ABTC) and Cd(NO₃)₂·4H₂O/MnCl₂·4H₂O as building blocks. The results of single-crystal X-ray diffraction analysis indicate that 1 is a 2D layer structure with 1D open channels. 2 is a rare 3D porous structure constructed from polycatenated 2D layers. 3 also shows a 3D porous structure with 1D carboxylate bridged Mn–(COO)–Mn chains. The result of magnetic susceptibility measurements indicates that the Mn(II) ions in 3 exhibit antiferromagnetic interactions.