Coordination Chemistry of Cyclohexane-1,2,4,5-tetracarboxylate (H4L). Synthesis, Structure, and Magnetic Properties of Metal-Organic Frameworks with Conformation-Flexible H4L Ligand

To study the conformations and coordination chemistry of cyclohexane-1,2,4,5-tetracarboxylic acid (H4L), we have obtained four new coordination polymers, [Mn2(μ4-LI)(H2O)6] (1), [Mn2(μ8-LI)(H2O)2] (2), [Mn2(μ7-LII)(H2O)3] (3), and [Ag4(LI)(4,4′-bpy)3]·10H2O (4), from the reactions of Mn(II) or Ag(I) salts with cyclohexane-1e,2a,4a,5e-tetracarboxylic acid (2e+2a, H4LI). A new conformation, cyclohexane-1e,2a,4e,5e-tetracarboxylate (3e+1a, LII), was derived from conformational conversions of LI and trapped in 3 upon coordination by controlling the hydrothermal reaction conditions. The stabilization and separation of different conformations of the flexible organic ligands in coordination structures may help us understand and utilize various interesting conformational transformations. Magnetic studies show that antiferromagnetic interaction occurs in both 1 and 2.