Solvents influence on sizes of channels in three fry topological Mn(ii)-MOFs based on metal–carboxylate chains: syntheses, structures and magnetic properties

Abstract

Three new 3D Mn(II)-MOFs have been synthesized via solvothermal reaction with MnCl₂·4H₂O and [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylic acid (H₄tptc) in three different solvents [N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF)], namely, [Mn₂(tptc)(H₂O)(NMP)]·NMP (1), [Mn₂(tptc)(H₂O)(DMA)]·DMA (2) and Mn₂(tptc)(DMF)₂ (3), all of which were fully characterized. In 1 and 2, the 1D uniform Mn–carboxylate chains with the (μ-EO-H₂O/NMP/DMA)(μ-COO)₂ triple bridges (EO = end-on) are extended by the tptc linkers to form a 3D (3,4)-connected fry net with 1D irregular quadrangular channels. Interestingly, 3 possess two kinds of Mn–carboxylate chains and can also be simplified as a fry net. The self-assembly synthesis system responds to small carbonyl solvents (NMP, DMA and DMF) with very high sensitivity and selectivity, but products using hydroxy solvents (methanol, alcohol and isopropanol) were not identified. The various pore frameworks of 1–3 are filled by different coordinated and latticed solvent molecules in their channels. The sizes of the channels [3 (33.11 Ų) < 2 (35.17 Ų) < 1 (35.37 Ų)] are induced by the sizes of the solvent molecules (DMF < DMA < NMP). The good chemical stabilities of 1–3 were observed. Magnetic studies demonstrate that the magnetic coupling through the mixed carboxylate bridges in all compounds is antiferromagnetic.