Substituents dependent capability of bis(ruthenium-dioxolene-terpyridine) complexes toward water oxidation
Substituents dependent capability of bis(ruthenium-dioxolene-terpyridine) complexes toward water oxidation
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DOI：
10.1039/c0dt00977f
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发表时间：
2011-01-01
影响因子：
4
通讯作者：
Tanaka, Koji
中科院分区：
文献类型：
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作者：
Wada, Tohru;Muckerman, James T.;Tanaka, Koji
在Pd(PPh_3)(4)(5摩尔%)存在下，由1，8-苯基-1，8-二硼酸和4‘-三氟基-2，2’-三联吡啶通过Miyaura-Suzuki交叉偶联反应合成了桥联配体1，8-双(2，2‘：6’，2‘-三吡啶-4’基)菲(Btpyan)，产率为68%。以邻苯二酚[Ru2Cl6(Btpyan)](0)与3，6-二叔丁基-1，2-苯并半喹酮([1](0))、3，5-二氯-1，2-苯并半喹酮([2](0))和4-硝基-1，2-苯并二喹酮([3](0))为原料，合成了三个Ru-2(OH)(2)(二氧戊烯)(2)(Btpyan)(0)(0)(二氧二氧戊烯=3，6-二叔丁基-1，2-苯并半喹酮([1](0)。[1](0)的电子结构近似为[Ru-2(II)(OH)(2)(Sq)(2)(Btpyan)](0)(sq=半奎尼托)。另一方面，[2](0)和[3](0)的电子态接近于[Ru-2(III)(OH)(2)(CAT)(2)(Btpyan)](0)(cat=儿茶酚)，表明具有吸电子基团的二羟基苯作为共振异构体稳定[Ru-2(III)(OH)(2)(Cat)(2)(Btpyan)](0)而不是[Ru-2(Ii)(OH)(2)(Sq)(Btpyan)](0)。在t-BuOLi和HClO4的处理中，没有发现[1](0)的羟基脱质子的迹象，而[2](0)和[3](0)的处理显示了酸碱平衡。此外，控制电位电解沉积在ITO电极上的[1](0)催化H2O的四电子氧化放出O-2，在pH为4.0时的电位大于+1.6V(vs.SCE)。另一方面，在类似条件下，沉积在ITO电极上的[2](0)和[3](0)的电解对水氧化没有表现出催化活性。[1](0)，[2](0)和[3](0)之间的反应性差异归因于[Ru-2(II)(OH)(2)(Sq)(2)(Btpyan)](0)和[Ru-2(III)(OH)(2)(Cat)(2)(Btpyan)](0)之间的共振平衡的移动。
The bridging ligand, 1,8-bis(2,2':6',2 ''-terpyrid-4'-yl)anthracene (btpyan) was synthesized by the Miyaura-Suzuki cross coupling reaction of anthracenyl-1,8-diboronic acid and 4'-triflyl-2,2': 6'-2 ''-terpyridine in the presence of Pd(PPh3)(4) (5 mol%) with 68% in yield. Three ruthenium-dioxolene dimers, [Ru-2(OH)(2)(dioxolene)(2)(btpyan)](0) (dioxolene = 3,6-di-tert-butyl-1,2-benzosemiquinone ([1](0)), 3,5-dichloro-1,2-benzosemiquinone ([2](0)) and 4-nitro-1,2-benzosemiquinone ([3](0))) were prepared by the reaction of [Ru2Cl6(btpyan)](0) with the corresponding catechol. The electronic structure of [1](0) is approximated by [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) (sq = semiquinonato). On the other hand, the electronic states of [2](0) and [3](0) are close to [Ru-2(III)(OH)(2) (cat)(2)(btpyan)](0) (cat = catecholato), indicating that a dioxolene having electron-withdrawing groups stabilizes [Ru-2(III)(OH)(2)(cat)(2)(btpyan)](0) rather than [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) as resonance isomers. No sign was found of deprotonation of the hydroxo groups of [1](0), whereas [2](0) and [3](0) showed an acid-base equilibrium in treatments with t-BuOLi followed by HClO4. Furthermore, controlled potential electrolysis of [1](0) deposited on an ITO (indium-tin oxide) electrode catalyzed the four-electron oxidation of H2O to evolve O-2 at potentials more positive than +1.6 V (vs. SCE) at pH 4.0. On the other hand, the electrolysis of [2](0) and [3](0) deposited on ITO electrodes did not show catalytic activity for water oxidation under similar conditions. Such a difference in the reactivity among [1](0), [2](0) and [3](0) is ascribed to the shift of the resonance equilibrium between [Ru-2(II)(OH)(2)(sq)(2)(btpyan)](0) and [Ru-2(III)(OH)(2)(cat)(2)(btpyan)](0).