Robust anionic building blocks [M(malonate)2(H2O)2]2− for crystal engineering of inorganic–organic hybrid materials

One-pot reactions of transition metal (CuII, NiII, CoII, or CdII) salt with malonic acid (H2mal) in the presence of mesocyclic diamine generate three supramolecular complexes and a coordination polymer. [Cu(mal)2(H2O)2](H2O)2(H2DACH) (1) and [M(mal)2(H2O)2](H2DACO) (M = Ni for 2, and Co for 3) are ion-pair products and managed by charge-assistant noncovalent interactions (DACO = 1,5-diazacyclooctane, and DACH = 1,4-diazacycloheptane). In these structures, the similar mononuclear [M(mal)2(H2O)2]2− building blocks are connected by hydrogen bonds to form 2D networks (with the aid of one lattice water in the case of 1), which are further extended by the cationic diamine components to yield 3D pillar-layered solids. While [Cd(mal)(H2O)2]n (4) is a neutral polymeric complex, in which the similar [Cd(mal)2(H2O)2]2− subunits are propagated by additional Cd–O coordinative forces to result in the final 2D layer.

Graphical abstractThis work demonstrates that the mononuclear anionic [M(malonate)2(H2O)2]2− entities are reliable building blocks for the rational design of inorganic–organic hybrid crystalline materials via charge-assistant hydrogen bonding.Figure optionsDownload full-size imageDownload as PowerPoint slide