Conjugated metallorganic macrocycles: opportunities for coordination-driven planarization of bidentate, pyridine-based ligands

Abstract

Two conjugated systems that can be constrained to planarity via metal coordination have been generated and their metal complexes studied. The potential for these architectures to be incorporated into metal-sensing arylene ethynylene/vinylene oligomers and polymers was probed by verifying that these ligands (1) bind strongly to Ag(I) and Pd(II) cations, and (2) that this event leads to complexes that are planar. Single crystal structures confirm that introduction of Ag(I) or Pd(II) cations enforces planarity in the newly formed macrocycles. Likewise, ¹H-NMR titration studies reveal stoichiometric binding of Pd(II) and strong binding of Ag(I) (K_{a (Ligand 1)} = 1.3 × 10² M⁻¹; K_{a (Ligand 2)} = 5.4 × 10² M⁻¹) for each conjugated ligand.