“…The irreversibility on Pt is considered as no affinity of both the ligand and the complex onto the Pt surface. The improvement on GC is most likely due to the affinity of the ligand or the complex onto the GC surface or the affinity of the acetylacetone-like oxidized surface of the carbon electrode (Scheme ). 3 Cyclic voltammograms of Me 2 SO/0.1 M TBAP solution containing UO 2 (acac) 2 (a, d), UO 2 1 (b, e) and UO 2 2 (c, f) complexes at Pt (a−c) and GC (d−f) electrodes.…”
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)/U(V) and U(IV)/U(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.
“…The irreversibility on Pt is considered as no affinity of both the ligand and the complex onto the Pt surface. The improvement on GC is most likely due to the affinity of the ligand or the complex onto the GC surface or the affinity of the acetylacetone-like oxidized surface of the carbon electrode (Scheme ). 3 Cyclic voltammograms of Me 2 SO/0.1 M TBAP solution containing UO 2 (acac) 2 (a, d), UO 2 1 (b, e) and UO 2 2 (c, f) complexes at Pt (a−c) and GC (d−f) electrodes.…”
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)/U(V) and U(IV)/U(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.
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