Université de Nantes, CNRS, Chimie et Interdisciplinarité: Synthèse, Analyse, Modélisation (CEISAM), UMR CNRS No. 6230, Nantes, France.
J Phys Chem A. 2011 May 26;115(20):5069-80. doi: 10.1021/jp2012182. Epub 2011 May 2.
A series of multiporphyrin clusters has been synthesized and characterized in which there exists a logical gradient for either energy or electron transfer between the porphyrins. A central free-base porphyrin (FbP), for example, is equipped with peripheral zinc(II) porphyrins (ZnP) which act as ancillary light harvesters and transfer excitation energy to the FbP under visible light illumination. Additional energy-transfer steps occur at the triplet level, and the series is expanded by including magnesium(II) porphyrins and/or tin(IV) porphyrins as chromophores. Light-induced electron transfer is made possible by incorporating a gold(III) porphyrin (AuP(+)) into the array. Although interesting by themselves, these clusters serve as control compounds by which to understand the photophysical processes occurring within a three-stage dendrimer comprising an AuP(+) core, a second layer formed from four FbP units, and an outer layer containing 12 ZnP residues. Here, illumination into a peripheral ZnP leads to highly efficient electronic energy transfer to FbP, followed by charge transfer to the central AuP(+). Charge recombination within the resultant charge-shift state is intercepted by secondary hole transfer to the ZnP, which occurs with a quantum yield of around 20%. The final charge-shift state survives for some microseconds in fluid solution at room temperature.
已经合成并表征了一系列多卟啉簇，其中卟啉之间存在能量或电子转移的逻辑梯度。例如，一个中心的自由碱基卟啉（FbP）配备了外围的锌（II）卟啉（ZnP），它们作为辅助光收集器，并在可见光照射下将激发能量转移到 FbP。在三重态水平上还会发生额外的能量转移步骤，并且通过将镁（II）卟啉和/或锡（IV）卟啉作为发色团来扩展该系列。通过将金（III）卟啉（AuP(+)）纳入该阵列，可以实现光诱导电子转移。虽然这些簇本身很有趣，但它们作为对照化合物，可以帮助我们理解包含金（III）卟啉（AuP(+)）核心、由四个 FbP 单元组成的第二层和包含 12 个 ZnP 残基的外层的三级树状大分子内发生的光物理过程。在这里，外围 ZnP 的照射导致高效的电子能量转移到 FbP，然后转移到中心的 AuP(+)。在所得电荷转移态内的电荷复合被次级空穴转移到 ZnP 所拦截，其量子产率约为 20%。在室温下的流体溶液中，最终的电荷转移态可以存活几微秒。
