Prolonged Luminescence Lifetime of a Dual Emissive Ruthenium Dipyridophenazine-Type Complex in Aprotic and Protic Solvents.

A recently reported ruthenium(II) complex bearing an extended dipyridophenazine ligand exhibits unusual long-lived dual emission at room temperature. In this study, the effect of the introduction of a methyl protecting group to the imidazole moiety of this ligand (, 11-methyl-11-imidazo[4,5-]dipyrido[3,2-:2',3'-]phenazine) on the photophysics of the respective ruthenium(II) complex [(tbbpy)Ru()] () is demonstrated by means of electrochemistry, UV/vis absorption and emission spectroscopy, as well as emission lifetime measurements, and transient absorption spectroscopy on the nanosecond time scale. At room temperature, shows dual emission both in aprotic and in protic solvents with time constants of 1.

Influence of the Protonation State on the Excited-State Dynamics of Ruthenium(II) Complexes with Imidazole π-Extended Dipyridophenazine Ligands.

Ruthenium(II) complexes, like [(tbbpy)Ru(dppz)] (; tbbpy = 4,4'-di--butyl-2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine), have emerged as suitable photosensitizers in photoredox catalysis. Since then, there has been ongoing interest in the design of π-extended systems with red-shifted visible absorption maxima and sufficiently long-lived excited states independent of the solvent or pH value. Herein, we explore the photophysical properties of protonation isomers of the linearly π-extended [(tbbpy)Ru()]-type complexes bearing a dppz ligand with directly fused imidazole () and methyl-imidazole units () as .

Two Emissive Long-Lived Excited States of an Imidazole-Functionalized Ruthenium Dipyridophenazine Complex.

A ruthenium(II) polypyridine-type complex based on the dipyridophenazine ligand with a directly fused imidazole unit (, dipyrido[3,2-:2',3'-]phenazine-10,11-imidazole) has been synthesized, and its electrochemical and photophysical properties have been studied. The cyclic voltammogram of [Ru(tbbpy)()] () (tbbpy is 4,4'--butyl-2,2'-bipyridine) shows a cathodic shift of the phenazine-based reduction process compared to similar molecules, while the first detected reduction wave (-1.34 V vs Fc/Fc) is assigned to the imidazole unit within the molecule.