Lightweight Ionic Networks Composed of Li or Mg 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 [Li (2,2-bpdc)(DMF) ] and [Mg(2,2-bpdc)(DMF) ] (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. [Li (3,5-pdc) (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. [Li (3,5-pdc) (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[Mg OH(2,2-bqdc) (DMF/H O) ]⋅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 μ -hydroxide ion serves as a 6-connecting, trigonal prismatic node within a 3 D network that has the point symbol, 4 6 . Solvent-filled intraframework spaces represent over 50 % of the crystal volume and are occupied by highly disordered solvent and Li ions. Immersion of Li[Mg OH(2,2-bqdc) (DMF/H O) ]⋅solvate in a solution of Fe(2,2-bipyridine) results in the incorporation of the Fe complex into the large channels of the anionic network.