Metallo-supramolecular libraries: triangles, polymers and double-helicates assembled by copper(I) coordination to directly linked bis-pyridylimine ligands

Copper(I) coordination is investigated for three pyridine-azine ligands, in which two pyridylimine binding units are linked directly through the imine nitrogen atoms. Substituents on the imine units of the ligands influence the metallo-supramolecular architecture adopted. X-Ray analysis confirms the solid state structures for a dinuclear double-helicate, a trinuclear circular-helicate and a polymeric array. In each structure the copper(I) centre is four-coordinate. In acetone solution a library of architectures is observed. For the unsubstituted and methyl substituted ligands dinuclear (double-helical) and trinuclear (circular helical) structures dominate. With phenyl substituents only the double-helical species is present in solution. The work casts further light on the use of multiple competing interactions ('frustration') to design libraries of supramolecular architectures.