15121-26-3Relevant articles and documents
Reactions of tris(oxalato)cobaltate(in) with two-electron reductants
Yang, Zhiyong,Gould, Edwin S.
, p. 3601 - 3603 (2004)
The tris(oxalato)cobaltate(in) complex [Co(C2O4) 3]3-, EoCoIII/II = +0.57 V) is readily reduced by the 2e- reagents, Sn(II) and Ge(ii), in contrast to (NH3)5CoCl2+ and (NH3) 5CoBr2+, which are unreactive toward these donors. Rates for the oxalato oxidant are only 10-3-10-2 as great as those for vitamin B12a (aquacob(III)alamin, Eo +0.35 V at pH 1), in accord with the suggestion that reductions of corrin-bound cobalt(III) by Sn(II) and Ge(II) occur predominantly through an additional path involving Co(I). Reductions of the oxalato complex by 2e- donors are taken to proceed by initial formation of odd-electron intermediates (e.g., Sn III and GeIII) which react rapidly with CoIII. Such a two-step sequence is in keeping with the observed behavior of the rare reductant, TiII, which is found to be oxidized by [Co(C 2O4)3]3- more slowly than (independently prepared) Ti(III) under comparable conditions.
Titrations with hypovanadous salts - Part I Standardization of hypovanadous solutions with ferric and cupric salts using visual indicators
Mittal,Tandon,Mehrotra
, p. 330 - 336 (1962)
In the present investigations, the standardization of vanadium(II) solution against ferric and cupric salts has been described and a few visual indicators have been shown to be applicable in the above titrations. When iron(III) solution is added to vanadium(II) solution neutral red marks the end point for VII to VIII change. This change is also noted when vanadium(II) solution is added to ferric solution in the presence of excess of concentrated hydrochloric acid at an elevated temperature and neutral red and phenosafranine as visual indicators. Under the same conditions, the end point with eupric solution also corresponds to this change. When vanadium(II) solution is added to ferric solution at an elevated temperature in the presence of methylene blue or gallocyanine as visual indicators, the end point marks VII to VIV change. A mixture of iron and copper has also been titrated successfully with the help of visual indicators.
Freed, S.
, p. 2456 - 2468 (1927)
Synergistic catalysis of sno2/reduced graphene oxide for vo2+/vo2+ and v2+/v3+ redox reactions
Liu, Yongguang,Jiang, Yingqiao,Lv, Yanrong,He, Zhangxing,Dai, Lei,Wang, Ling
, (2021/08/30)
In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO2/reduced graphene oxide (SnO2/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO2/rGO shows better electrochemical catalysis for both redox reactions of VO2+/VO2+ and V2+/V3+ couples as compared to SnO2 and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO2 has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO2/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm?2, the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions.
The nonadiabaticity question for europium(III/II): Outer-sphere reactivities of europium(III/II) cryptates
Yee, Edmund L.,Hupp, Joseph T.,Weaver, Michael J.
, p. 3465 - 3470 (2008/10/08)
The one-electron reduction kinetics of the europium cryptates Eu(2.2.1)3+ and Eu(2.2.2)3+ by the aquo ions Vaq2+ and Euaq2+ and the oxidation kinetics of Eu(2.2.1)2+ by Co(NH3)63+ have been studied by using a polarographic technique in order to examine the effects of encapsulating europium within cryptate cavities upon the reactivity of the Eu(III/II) couple. At 25°C and an ionic strength μ = 0.1, the second-order rate constants (M-1 s-1) for acid-independent pathways are as follows: Eu(2.2.1)3+-Vaq2+, 0.5; Eu(2.2.1)3+-Euaq2+, ca. 0.2; Eu(2.2.2)3+-Euaq2+, 1.5; Eu(2.2.2)3+-Euaq2+, 1.4; Co(NH3)63+-Eu(2.2.1)2+, 0.055. By comparison of these kinetic data with those for similar reactions involving the Euaq3+/2+ couple, the rate constant for Eu(III/II) self-exchange, kex, is estimated to increase by factors of ca. 1 × 107 and 2 × 104 upon encapsulation of europium in (2.2.1) and (2.2.2) cryptate cavities, respectively. Estimates of kex equal to ca. 10, 4 × 10-2, and 5 × 10-6 M-1 s-1 (μ = 0.1) for Eu(2.2.1)3+/2+, Eu(2.2.2)3+/2+, and Euaq3+/2+, respectively, are obtained from the Marcus cross relation. The increases in kex resulting from cryptate encapsulation suggest that nonadiabaticity is not primarily responsible for the extremely low reactivity of Euaq3+/2+. The values of kex are shown to be roughly consistent with the Franck-Condon barriers estimated from structural data.
