Synthesis and characterization of mixed ligand Ru(II) complexes with dipyrido(2,3-a:3′,2′-j)phenazine (dpop′)

The synthesis of mixed ligand [Ru(NH3)3(dpop′)]2+ and [Ru(tpy)(dpop′)]2+ (dpop′=dipyrido(2,3-a:3′,2′-j)phenazine; tpy=2,2′:6′,2″-terpyridine) complexes is described. Absorption, emission, electrochemistry and stability of the series of [Ru(L)1,3(dpop′)]2+ (L=dpop′, tpy and NH3) complexes is evaluated. Absorption spectra show the Ru(dπ)→dpop′(π*) CT transition energies increase when the ancillary ligands are varied in the order NH3, tpy and dpop′, consistent with increased Ru2+/3+ oxidation potentials in the same order. The [Ru(tpy)(dpop′)]2+ ion is emissive in room temperature de-oxygenated CH3CN with λem=748 nm. At 77 K, the [Ru(tpy)(dpop′)]2+ ion displays emissions at λem=600; 645(sh) and λem=735 nm attributed to [Ru(tpy*)(dpop′)]2+ and [Ru(tpy)(dpop′*)]2+3CT excited state relaxations. Spectro-electrochemistry shows the bis-tridentate [Ru(tpy)(dpop′)]2+ complex is reversible upon oxidation and reduction, while [Ru(NH3)3(dpop′)]2+ is irreversible.