Synthesis of three series of ruthenium tris-diimine complexes containing acridine-based π-extended ligands using an efficient “chemistry on the complex” approach

Abstract

The preparation and characterization of three series of novel ruthenium(II) complexes are reported, each series differing by the nature of the ancillary ligands (2,2′-bipyridine – bpy, 1,10-phenanthroline – phen or 1,4,5,8-tetraazaphenanthrene – TAP). The third ligand was either the heptacyclic heterocycle dipyrido[3,2-a:2′,3′-c]quinolino[3,2-h]phenazine (dpqp) substituted at position 12 by an hydroxyl (oxo), 2,2-dimethoxyethylamine (DMEA) or halogeno (Cl or Br) substituent, or the octacyclic dipyrido[3,2-a:2′,3′-c]pyrido[2,3,4-de]quinolino[3,2-h]phenazine (dppqp), prepared by a multi-step “chemistry on the complex” strategy from [RuL₂(oxo-dpqp)](PF₆)₂. The three steps, halogenation, substitution by a dimethoxyethylamino group and cyclization in trifluoroacetic acid, were performed in reasonable to high yields depending on the nature of the ancillary ligands. Isolation and purification processes were facilitated by the ability to switch the solubility of the complex from aqueous to organic solvents, depending on the counter-ion. All new complexes were fully characterized; in particular their absorption properties were compared by UV-vis spectroscopy. Finally, π-stacking properties induced by these extended ligands were studied by ¹H NMR studies and quantum chemical calculations.