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摘要
Specific interactions of the I-/I-3(-) redox mediators with the reduced and oxidized dye, Ru(4,4'-dicarboxy2,2'-bipyridyl)(2)(NCS)(2), referred to as N3 or Ru(dcbpy)(2)(NCS)(2), have been studied by means of density functional theory (DFT) with the focus on the charge transfer process involving {dye(+) I-} adducts; computations had been performed with a series of density functionals (gradient-corrected density functional BP86, and the hybrid density functionals B3LYP, MPW1K, B3PW1K, and MPW1PW91). Different pathways leading to (dye(+) I-) adducts have been studied. First, mechanistic insights into the interaction of I- with Ru-III (dcbpy)(2)(NCS)(2) via an SCN- ligand directly giving rise to Ru-II(dcbpy)(2)(NCS)(2)I](0) have been obtained with the distinctive S-I bonding. Second, the binding of I- to the N3 dye cation via I(-)dcbpy interactions has been analyzed. We also report experimental and computational evidence that sheds light on the interaction of the redox mediator with bipyridyl moieties. Evidence for a charge transfer process in the presence of only one I- anion in the outer coordination sphere of the ruthenium center has been identified. Finally, geometries and electronic structures of plausible intermediates have been computationally analyzed based on an innersphere interaction between the metal center and the redox mediator, including a two-step regeneration reaction: Ru-III (dcbPy)(2)(NCS)(2)](+) + I- -> Ru-III(dcbpy)(2)(NCS)I](+) + SCN-, followed by the interaction of a second I- with the intermediate Ru-III(dcbpy)(2)(NCS)I](+) complex. Conclusive evidence of a charge-transfer process that gives rise to the regenerated Ru-II complex, where I- interacts with the intermediate Ru-III (dcbpy)(2)(NCS)I](+) complex has been identified.
- 出版日期2009-1-15
