Time-resolved spectroscopy of the metal-to-metal charge transfer excited state in dinuclear cyano-bridged mixed-valence complexes.
Visible pump-probe spectroscopy has been used to identify and characterize short-lived metal-to-metal charge transfer (MMCT) excited states in a group of cyano-bridged mixed-valence complexes of the formula [LCo(III)NCM(II)(CN)(5)](-), where L is a pentadentate macrocyclic pentaamine (L(14)) or triamine-dithiaether (L(14S)) and M is Fe or Ru. Nanosecond pump-probe spectroscopy on frozen solutions of [L(14)Co(III)NCFe(II)(CN)(5)](-) and [L(14S)Co(III)NCFe(II)(CN)(5)](-) at 11 K enabled the construction of difference transient absorption spectra that featured a rise in absorbance in the region of 350-400 nm consistent with the generation of the ferricyanide chromophore of the photoexcited complex. The MMCT excited state of the Ru analogue [L(14)Co(III)NCRu(II)(CN)(5)](-) was too short-lived to allow its detection. Femtosecond pump-probe spectroscopy on aqueous solutions of [L(14)Co(III)NCFe(II)(CN)(5)](-) and [L(14S)Co(III)NCFe(II)(CN)(5)](-) at room temperature enabled the lifetimes of their Co(II)-Fe(III) MMCT excited states to be determined as 0.8 and 1.3 ps, respectively.
Macpherson
Brendan P
BP
Department of Chemistry, University of Queensland, Brisbane, Queensland 4072, Australia.
Bernhardt
Paul V
PV
Hauser
Andreas
A
Pagès
Stéphane
S
Vauthey
Eric
E
D019216:Metals, Heavy / Q000737:chemistry*; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013816:Thermodynamics; D013997:Time Factors
D019216:Metals, Heavy; D009570:Nitriles; D009942:Organometallic Compounds