Homochiral, Supramolecular Frameworks Built from a Zinc(II) Tetramer or Cadmium(II) Dimer Containing Enantiopure Carboxylate Ligands Functionalized with a Strong π···π Stacking Synthon



The enantiopure ligand (S)-2-(1,8-naphthalimido)propanoate (Lala) forms a tetrameric zinc(II) complex [Zn4(Lala)6(OH)2(MeOH)4]·3(CH2Cl2)·2(MeOH) (1) and a dimeric cadmium(II) complex [Cd2(Lala)4(DMF)3(MeOH)] (2). Bridging κ2-carboxylate and hydroxide ligands link the four zinc centers in 1. The strong π···π-stacking 1,8-naphthalimide supramolecular synthons organize the tetramers into a 3D architecture that contains linked, homochiral helical chains. In the structure, each chain is connected to four other chains by the π···π-stacking interactions of the naphthalimide rings. The structure is open with two types of channels filled with ordered and disordered solvent molecules. The two cadmium centers in 2 are linked by two κ2-carboxylate ligands. The π···π-stacking interactions of the naphthalimide rings organize the structure into 2D sheets, which lack complex chiral features. The naphthalimide rings in these d10 metal complexes promote blue (1) and green (2) emission in the solid state.