Luminescent Electropolymerizable Ruthenium Complexes and Corresponding Conducting Metallopolymers

Tris(2,2′-bipyridyl)ruthenium(II) dichloride [Ru(bpy)₃Cl₂] and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties as well as their excited-state lifetimes. Conducting polymers with similar ruthenium groups have also been investigated for various applications. In this study, syntheses of four ruthenium complexes with a polymerizable tridentate ligand, bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine (EDOT₂NNN), and with bidentate ligands, two of which were anionic (hfac: 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; dbm: dibenzoylmethane) and two of which were neutral (bpy: 2,2′-bipyridyl; phen: 1,10-phenanthroline), were achieved for potential OLED/PLED applications. Saturated CH₂Cl₂ solutions of monomers were oxidatively and electrochemically polymerized, and the scan rate dependences of the polymers were measured. UV-vis spectroscopic characterizations of the complexes and the EDOT-functionalized ligand were obtained. [Ru(EDOT₂NNN)(phen)(Cl)](PF₆) was electropolymerized on an ITO (indium tin oxide)-coated glass surface to obtain the solid-state absorption spectrum of the corresponding polymer. Photophysical data for each complex, i.e., excitation and emission spectra at 77 K and RT, in EtOH/MeOH (4:1) and in 2-MeTHF (dry, air-free, and aerated), quantum yield, and luminescence lifetime have been measured. The radiative and nonradiative decay constants as well as the oxygen quenching rate coefficient for each complex were calculated. [Ru(EDOT₂NNN)(phen)(Cl)](PF₆), having the highest quantum yield of phosphorescence and the longest lifetime, was electropolymerized on an ITO-coated glass surface to obtain the solid-state excitation and emission spectra of the corresponding polymer. Luminescence studies of the polymer had promising results for photoluminescence.