Ligand mediated structural diversity and role of different weak interactions in molecular self-assembly of a series of copper(II)–sodium(I) Schiff-base heterometallic complexes

We report three new Cu–Na heterometallic complexes namely [Cu(L12−)Na(NO3)(CH3OH)] (1), [Cu(L22−)Na(NO3) (CH3OH)] (2) and [Cu Na (L33−)]n (3) where the topology of the synthon is directly governed by the π–π interaction involving the Cu-Schiff base chelate rings. The crystal structure analysis also reveals how the systematic variation in the ligand framework influences the supramolecular assembly and the mutual cooperation of different π-forces and the hydrogen bonding forces in the supramolecular assembly. The π-forces are more important than the hydrogen bonding forces in such compounds is evident from the supramolecular assembly of compound 3. Most interesting revelation of the studies are the presence of relatively uncommon π-forces such as chelate ring⋯chelate ring and metal–π interactions in the supramolecular architecture of the complexes. The analysis of the supramolecular assembly of the complexes 1–3 reveals that metal-chelate rings play prominent role in the organization of the molecular complexes and should seriously consider along with other π-stacking forces.