Thermal and photochemical reduction of aqueous chlorine by ruthenium(II) polypyridyl complexes.
Thermal and photochemical reduction of aqueous chlorine by ruthenium(II) polypyridyl complexes.
复制标题
钌(II)聚吡啶络合物对氯水的热和光化学还原。
DOI：
10.1021/ic9910920
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发表时间：
2000
影响因子：
4.6
通讯作者：
D. Stanbury
中科院分区：
文献类型：
--
作者：
Basudeb Saha;D. Stanbury
研究了一系列取代惰性单电子金属络合物与氯水的反应，包括[Ru(Bpy)3]2+、[Ru(4，4‘-Me2bpy)3]2+、[Ru(4，7-Me2phen)3]2+、[Ru(Terpy)2]2+和[Fe(3，4，7，8-Me4phen)3]2+。用分光光度法研究了该反应在25℃、Mu=0.3M的酸性氯化物介质中的反应。通常，该反应具有化学计量比2[ML3]2++Cl2-->；2[ML3]3++2Cl2-。在[Ru(Bpy)3]2+的情况下，反应是非常光敏的；热反应是如此缓慢，以至于几乎无法测量。[Ru(4，4‘-Me_2bpy)_3]~(2+)和[Ru(4，7-Me2phen)_3]~(2+)的反应也具有很高的光敏性，给出了依赖于停流仪中单色器狭缝宽度的准一级速率常数；然而，热速率足够快，可以由Kobs外推到零狭缝宽度。[Ru(Terpy)2]2+和[Fe(3，4，7，8-Me4phen)3]2+的反应没有明显的光敏性，可以直接测定它们的热速率规律。从pH、[Cl2]Tot和[Cl2-]的动力学效应可以看出，所有的热速率定律都与[ML3]2+和[Cl2]有一级依赖关系。二阶速率常数随着络合物EO的增加而减小，这与Marcus理论对外球电子转移机制的预言一致。[Ru(4，4‘-Me2bpy)3]2+和[Ru(4，7-Me2phen)3]2+的反应在460 nm处的量子产率超过0.1，并与[Cl2]有关，表明*Ru的自发衰变、Cl2的非反应猝灭和Cl2的反应猝灭之间存在竞争关系。
Studies are reported on the reactions of aqueous chlorine with a series of substitution-inert, one-electron metal-complex reductants, which includes [Ru(bpy)3]2+, [Ru(4,4'-Me2bpy)3]2+, [Ru(4,7-Me2phen)3]2+, [Ru(terpy)2]2+, and [Fe(3,4,7,8-Me4phen)3]2+. The reactions were studied by spectrophotometry at 25 degrees C in acidic chloride media at mu = 0.3 M. In general the reactions have the stoichiometry 2[ML3]2+ + Cl2-->2[ML3]3+ + 2Cl-. In the case of [Ru(bpy)3]2+, the reaction is quite photosensitive; the thermal reaction is so slow as to be practically immeasurable. The reactions of [Ru(4,4'-Me2bpy)3]2+ and [Ru(4,7-Me2phen)3]2+ are also highly photosensitive, giving pseudo-first-order rate constants that depend on the monochromator slit width in a stopped-flow instrument; however, the thermal rates are fast enough that they can be obtained by extrapolation of kobs to zero slit width. The reactions of [Ru(terpy)2]2+ and [Fe(3,4,7,8-Me4phen)3]2+ show no appreciable photosensitivity, allowing direct determination of their thermal rate laws. From the kinetic effects of pH, [Cl2]tot, and [Cl-] it is evident that all of the thermal rate laws have a first-order dependence on [ML3]2+ and on [Cl2]. The second-order rate constants decrease as Eo for the complex increases, consistent with the predictions of Marcus theory for an outer-sphere electron-transfer mechanism. Quantum yields at 460 nm for the reactions of [Ru(4,4'-Me2bpy)3]2+ and [Ru(4,7-Me2phen)3]2+ exceed 0.1 and show a dependence on [Cl2] indicative of competition among spontaneous decay of *Ru, nonreactive quenching by Cl2, and reactive quenching by Cl2.