Synthesis, structure, and magnetic properties of manganese–organic frameworks of 2-methyl-4,4′-biphenyldicarboxylate with different auxiliary ligands

Three new metal–organic frameworks, [Mn(mbpdc)(phen)]n (1), [Mn(mbpdc)(4,4′-bipy)]n (2) and [Mn(mbpdc)(bpee)]n·nC2H5OH (3) (H2mbpdc = 2-methyl-4,4′-biphenyldicarboxylicacid, phen = 1,10-phenanthroline, and bpee = 1,2-Di(4-pyridyl)ethane), have been synthesized by the liquid phase diffusion method and characterized by single crystal X-ray determination and infrared spectra. Compounds 1 and 2 are characterized by elemental analysis, powder X-ray diffraction and thermogravimetric analysis. Compounds 1 and 2 both feature 1D [Mn(COO)2]n chains. In 1 the chains are connected by the dicarboxylate ligands into a 3D framework with the pts topology, which is reinforced by interchain zipper-like π–π stacking arrays of the phen ligands. Differently, the chains in 2 are connected by the dicarboxylate ligands into 2D networks, which are pillared by the 4,4′-bipy ligands to generate a 3D framework with the new topology (44 × 62)(44 × 610 × 8). Compound 3 features double carboxylate bridged dimanganese(II) SBUs, which are connected by single mbpdc linkers and double bpee ones to give threefold interpenetrated 3D frameworks with the pcu topology. Magnetic investigations suggested 1 and 2 both exhibit weak antiferromagnetic exchanges mediated through the bis(syn-skew-carboxylate) bridges.

The co-assembly of the title dicarboxylate ligand with Mn(II) and different pyridyl-based ligands afford three MOFs with different topologies; the compound with 4,4′-bipyridine demonstrates a new net topology; the compounds feature chains or binuclear units with bis(carboxylate) bridges, which always induce antiferromagnetic coupling between Mn(II) ions.Figure optionsDownload as PowerPoint slideHighlights
► Different pyridyl-based ligands afford three MOFs with different topologies.
► The compound with 4,4′-bipyridine demonstrates a new net topology.
► Bis(carboxylate) bridges between Mn(II)’s always induce antiferromagnetic coupling.