Odobel Fabrice, Séverac Marjorie, Pellegrin Yann, Blart Errol, Fosse Céline, Cannizzo Caroline, Mayer Cédric R, Elliott Kristopher J, Harriman Anthony
University of Nantes, CEISAM, Chimie Et Interdisciplinarité, Synthèse, Analyse, Modélisation, Faculté des Sciences et des Techniques, 2, rue de la Houssinière, BP 92208, 44322 Nantes Cedex, France.
Chemistry. 2009;15(13):3130-8. doi: 10.1002/chem.200801880.
Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide.
对于通过共价连接苝单酰亚胺发色团功能化的多金属氧酸盐，各种分子内电子转移反应很明显，但这些反应仅限于单电子事件。（et = 电子转移，cr = 电荷复合，csr = 电荷转移反应，PER = 苝，POM = 多金属氧酸盐）。引入了一种新策略，允许将有机发色团共价连接到多金属氧酸盐（POM）簇上。报道了两个例子，它们根据锚定基团的性质和连接体的灵活性而有所不同。两种POM都用苝单酰亚胺单元功能化，这些单元充当光子收集器，并在光照下形成相对长寿命的电荷转移态。它们通过电解被还原为稳定的π-自由基阴离子，或在三乙醇胺水溶液存在下光解时被还原为质子化二价阴离子。POM的存在开辟了一条分子内电子转移途径，通过该途径电荷转移态使POM还原。这个过程的速率取决于分子构象，似乎涉及空间相互作用。POM的预先还原导致有效的荧光猝灭，同样是由于分子内电子转移。在大多数情况下，由于在封闭构象内发生相对快速的反向电荷转移，很难解析电子转移产物。尽管POM可以存储多个电子，但由于从单电子还原的POM到苝单酰亚胺激发单重态的有效电子转移，尚未证明可以将这些系统用作分子尺度的电容器。
