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

Two examples of copper(II)-assisted self-assembly of bis-N, O-bidentate Sch iff base ligands L-55 and L-56 with an aromatic spacer group are described. Single-crystal X-ray analyses demonstrated clearly the formation of a tetr anuclear double-helical architecture for the L-55-Cu-II system and a dinucl ear non-helical U-shaped one for the L-56-Cu-II system. The self-assembly p rocess for these systems in solution has been deduced from UV-vis and ESI m ass spectral and analytical data. Aromatic pi...pi and CH...pi interactions between the spacer groups in L-55 and L-56 could stabilize these unprecede nted supramolecular motifs in solution and the solid state. Their crystal p ackings are also controlled by the aromatic interactions between two entiti es.