Long-lived MLCT states for Ru(ii) complexes of ferrocene-appended 2,2′-bipyridines

Abstract

In this study, we present two ruthenium(II) diimine complexes appended with ferrocene which show metal to ligand charge transfer ³MLCT emission lifetimes around 630 ns. We also present a similar complex with two ferrocene units which has decreased emission. These complexes have been studied by electrochemical, electronic absorption, and Raman, resonance Raman and transient resonance Raman means, coupled with density functional theoretical approaches. For these systems, the optical spectra are dominated by a low energy ruthenium(II) MLCT transition; which can be modulated by the presence of pendant ferrocene units and the extent of conjugation of the ferrocenyl bipyridine backbone. Tuning of the lowest energy transition in terms of intensity (4 to 18 × 10⁻³ M⁻¹ cm⁻¹) and energy (535 to 563 nm) was achieved by these means.