The Excited‐State Creutz–Taube Ion

Abstract

The excited-state version of the Creutz-Taube ion was prepared via visible light excitation of [(NH 3 ) 5 Ru II (μ-pz)Ru II (NH 3 ) 5 ] 4 + . The resulting excited state is a mixed valence {Ru III-δ (μ-pz *À )Ru II + δ } transient species, which was characterized using femtosecond transient absorption spectroscopy with vis-NIR detection. Very intense photoinduced intervalence charge transfers were observed at 7500 cm À 1 , revealing an excited-state electronic coupling element H DA = 3750 cm À 1 . DFT calculations confirm a strongly delocalized excited state. A notable consequence of strong electron delocalization is the nanosecond excited state lifetime, which was exploited in a proof-of-concept intermolecular electron transfer. The excited-state Creutz-Taube ion is established as a reference, and demonstrates that electron delocalization in the excited state can be leveraged for artificial photosynthesis or other photocatalytic schemes based on electron transfer chemistry.