Interfacial assembly of a series of Cu(II)-coordinated Schiff bases complexes: Orderly nanostructures and supramolecular chirality

Four achiral Cu(II)-coordinated Schiff bases complexes containing aromatic structures were synthesized and their supramolecular assemblies at the air/water interface were investigated. All the compounds could be spread on water surface although they have no alkyl chains. The Schiff base complex molecules with naphthyl groups tended to form J-aggregate in the Langmuir-Blodgett (LB) films transferred from water surface. By investigation of atomic force microscopy, a multilayer film or three-dimensional structures were observed. It was interesting to note that the LB films of achiral compound Cu-NA with naphthyl segment and without methyl groups transferred from water surface showed chirality. The supramolecular chirality in the present LB films was suggested to be due to a cooperative stereoregular pi-pi stacking of the functional groups in a helical sense. This research work provides a helpful clue for regulating the nanostructures and supramolecular chiral assembly in organized films.