Supramolecular motifs in metal complexes of Schiff bases. Part 6. Topology of two types of self-assembly of bis-N,O-bidentate Schiff baseligands by copper(II) ions

Abstract

Two examples of copper(II)-assisted self-assembly of bis-N,O-bidentate Schiff base ligands L⁵⁵ and L⁵⁶ with an aromatic spacer group are described. Single-crystal X-ray analyses demonstrated clearly the formation of a tetranuclear double-helical architecture for the L⁵⁵–Cu^II system and a dinuclear non-helical U-shaped one for the L⁵⁶–Cu^II system. The self-assembly process for these systems in solution has been deduced from UV-vis and ESI mass spectral and analytical data. Aromatic π⋯π and CH⋯π interactions between the spacer groups in L⁵⁵ and L⁵⁶ could stabilize these unprecedented supramolecular motifs in solution and the solid state. Their crystal packings are also controlled by the aromatic interactions between two entities.