Synthesis and properties of a redox active starburst ligand with three bispicorylamino groups and its trinuclear complexes

A starburst-shaped ligand, 4,4′4″-tris[N,N-bis(2-pyridylmethyl) aminomethyl] triphenylamine, and its palladium and copper trinuclear complexes were designed and prepared. NMR techniques, COSY and ROESY, were applied to the palladium complex to examine its conformation in solution. The palladium complex was found to prefer a folded conformation even at 75 °C, indicating the occurrence of strong intramolecular stacking interaction. CV measurements of the palladium complex showed reversible TTA/TTA⁺ redox couples. ETSF measurements showed that the corresponding radical pendant complex is very unstable. Molecular design rules for triarylamine-based spin bearing ligands are discussed.