Four Honeycomb Metal–Organic Frameworks with a Flexible Tripodal Polyaromatic Acid

Reaction of 4,4′,4″-{[(2,4,6-trimethylbenzene-1,3,5-triyl)­tris­(methylene)]­tris­(oxy)}­tribenzoic acid (H3TCM) with Mn2+, Cu2+, and Co2+ salts afforded four interesting metal–organic frameworks (MOFs), [Mn2(TCM)­Cl­(H2O)3]·3DMF·3CH3OH (1), [Mn4(TCM)2(CH3COO)2(DMF)5]·4CH3OH (2), [Cu2(TCM)­(CH3COO)­(DMF)­(H2O)]·2DMF·3CH3OH (3) and [Co3(TCM)2(H2O)5]·5DMF·3CH3OH (4). Single crystal X-ray diffraction analysis revealed that the four structures based on the flexible TCM tripod consist of honeycomb lattices with different metal–ligand macrocycles. The assembly of the metal–ligand macrocycles and framework topologies is dependent on the coordination geometries of transition metal cations. The two-dimensional coordination network of 1 was further connected by an auxiliary acetate ligand to give rise to a three-dimensional honeycomb network of 2. The TCM ligand centered photoluminescences of these compounds are very sensitive to the coordination modes of the TCM ligands, the metal secondary building units (SBUs), and their microstructures. These MOFs also present interesting magnetic behaviors, as revealed by the study of the magnetic susceptibilities.