Lightweight Ionic Networks Composed of Li+ or Mg2+ Centres Linked Together by Dicarboxylate Ligands.

The combination of lightweight metal cations with a range of dicarboxylate ligands has led to the generation of ionic network materials that possess channels occupied by solvent molecules. The compounds [Li2(2,2-bpdc)(DMF)2] and [Mg(2,2-bpdc)(DMF)2] (2,2-bpdc=2,2-dipyridyl-4,4-dicarboxylate) adopt a similar structure in which parallel metal-carboxylate chains are linked to four equivalent chains to generate a 3 D network in which DMF molecules occupy channels. [Li4(3,5-pdc)2(DMF)]⋅solvate (3,5-pdc=3,5-pyridine dicarboxylate) adopts a similar structure but the chains are more complex. As with the other structures, coordinated DMF molecules occupy network channels. [Li4(3,5-pdc)2(DMF)]⋅solvate is able to adsorb carbon dioxide at elevated pressures with the adsorption following a type V isotherm; hysteresis is apparent upon desorption. The final compound, Li[Mg3OH(2,2-bqdc)3(DMF/H2O)3]⋅solvate (2,2-bqdc=2,2-biquinoline-4,4-dicarboxylate) has a distinctly different structure in which a trio of magnesium centres bound to a central μ3-hydroxide ion serves as a 6-connecting, trigonal prismatic node within a 3 D network that has the point symbol, 4966. Solvent-filled intraframework spaces represent over 50 % of the crystal volume and are occupied by highly disordered solvent and Li+ ions. Immersion of Li[Mg3OH(2,2-bqdc)3(DMF/H2O)3]⋅solvate in a solution of Fe(2,2-bipyridine)32+ results in the incorporation of the FeII complex into the large channels of the anionic network. [ABSTRACT FROM AUTHOR]