Porous Coordination Polymers Based on {Mn₆} Single-Molecule Magnets

In this paper, three isostructural porous coordination polymers, namely, [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L¹)_2/3]·4DMF·2H₂O·2CH₃OH (<b>1</b>), [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L²)_2/3]·4DMF·2H₂O·2CH₃OH (<b>2</b>), and [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L³)_2/3]·4DMF·4H₂O·2CH₃OH (<b>3</b>) (DMF = dimethylformamide, H₂sao = salicylaldoxime, H₃L¹ = benzene-1,3,5-trisbenzoic acid, H₃L² = 4,4′,4″-<i>s</i>-triazine-2,4,6-triyltribenzoic acid, and H₃L³ = 2,4,6-tris­(4-carboxyphenoxy)-1,3,5-<i>s</i>-triazine), based on the oximato-bridged {Mn₆} single-molecule magnet (SMM) and tricarboxylic acid ligands, were designed and synthesized. X-ray structural analysis shows that they possess a two-dimensional layered structure, where the {Mn₆} moieties are linked by the corresponding (L^<i>x</i>)^3– carboxylate ligands (<i>x</i> = 1, 2, 3) forming a huge honeycomb layer. These compounds not only show the SMM behavior as confirmed by alternative current susceptibility measurements but also show selectivity for CO₂ over N₂ at 273 K. On the basis of the magnetic fitting to the magnetic susceptibilities and the field dependence of magnetization for complexes <b>1</b>–<b>3</b>, the spin ground states are <i>S</i> = 4. Compared with isolated {Mn₆} SMMs with <i>S</i> = 4, the out-of-phase susceptibilities of <b>1</b>–<b>3</b> show obvious peaks only under the external direct-current field of 2 kOe. However, no peaks in χ_m″ are observed in the partially desolvated sample of compound <b>1