Enhancements in the electron-transfer kinetics of uranium-based redox couples induced by tetraketone ligands with potential chelate effect

Tomoo Yamamura, Kenji Shirasaki, Hironori Sato, Yoshiyuki Nakamura, Hiroshi Tomiyasu, Isamu Satoh, Yoshinobu Shiokawa

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Acetylacetone shows dissociative electron transfer when it is complexed with metal ions. In an effort to improve the kinetics of electron transfer of uranium-based complexes for application to a redox-flow battery, improvement by dimerization of acetylacetone into tetraketones with potential chelate effect is examined and discussed quantitatively. For the monomer acetylacetone, electron transfer of uranium complexes reveals an ECE mechanism and an inner-sphere reaction on the electrode surface. By using tetraketones, 8-oxo-2,4,-12,14- tetraoxapentadecane and m-bis(2,4-dioxo-1-pentyl)benzene, the electron transfer of tetraketones with U(VI)ZU(V) and U(IV)ZU(III) shows rapid kinetics based on the E mechanism. In clear contrast to U(acac)4, the electrochemically reduced species of the U(IV) complex with tetraketone is stable during potential cycling. These results are also supported by NMR of tetraketones with U(VI) and U(IV); each acetylacetone site to uranium atom is stable at -40 ∼ +40°C. The results demonstrate a remarkable enhancement of the stability of the reduced form of the metal center and thereby an improvement of the redox kinetics by the chelate effect. The tetraketones are eminently suitable for use in the active materials of a high-efficiency redox-flow battery.

Original languageEnglish
Pages (from-to)18812-18820
Number of pages9
JournalJournal of Physical Chemistry C
Volume111
Issue number50
DOIs
Publication statusPublished - 2007 Dec 20

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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