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 (4 ⁴ × 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.