Bidentate ligands that contain pyrrole in place of pyridine

Article abstract of DOI:10.1021/ic990445s

A series of ligands are prepared that are analogues of benzo-fused derivatives of 2,2'-bipyridine (bpy), in which pyrrole has been substituted for a pyridine ring. These ligands include 2-(2'-pyridyl)-indole, 2-(2'-pyrrolyl)-quinoline, and pyrrolo[3,2-h]quinoline. A novel reductive cyclization approach to the latter species is presented. All these ligands react with [Ru(bpy-d₈)₂Cl₂], undergoing cyclometalation with concurrent deprotonation, to form complexes of the type [Ru(L)(bpy-d₈)₂]⁺ where L binds as a monoanionic ligand. The complexes are readily characterized by their ¹H NMR spectra. Changes in the redox potentials and the electronic absorption spectra of both the ligands and the complexes are interpreted in terms of charge delocalization on the ligand.