Favereau Ludovic, Makhal Abhinandan, Pellegrin Yann, Blart Errol, Petersson Jonas, Göransson Erik, Hammarström Leif, Odobel Fabrice
CEISAM, Chimie et Interdisciplinarité, Synthèse, Analyse, Modélisation, CNRS, UMR CNRS 6230, Université de Nantes , 2 rue de la Houssinière, BP 92208, Nantes 44322 Cedex 3, France.
Department of Chemistry-Ångström Laboratory, Uppsala University , Box 523, Uppsala, SE75120 Sweden.
J Am Chem Soc. 2016 Mar 23;138(11):3752-60. doi: 10.1021/jacs.5b12650. Epub 2016 Mar 14.
The oxygenic photosynthesis of green plants, green algae, and cyanobacteria is the major provider of energy-rich compounds in the biosphere. The so-called "Z-scheme" is at the heart of this "engine of life". Two photosystems (photosystem I and II) work in series to build up a higher redox ability than each photosystem alone can provide, which is necessary to drive water oxidation into oxygen and NADP(+) reduction into NADPH with visible light. Here we show a mimic of the Z-scheme with a molecular tetrad. The tetrad Bodipy-NDI-TAPD-Ru is composed of two different dyes-4,4-difluoro-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (Bodipy) and a Ru(II)(bipyridine)3 (Ru) derivative-which are connected to a naphthalene diimide (NDI) electron acceptor and tetraalkylphenyldiamine (TAPD) playing the role of electron donor. A strong laser pulse excitation of visible light where the two dye molecules (Ru and Bodipy) absorb with equal probability leads to the cooperative formation of a highly energetic charge-separated state composed of an oxidized Bodipy and a reduced Ru. The latter state cannot be reached by one single-photon absorption. The energy of the final charge-separated state (oxidized Bodipy/reduced Ru) in the tetrad lies higher than that in the reference dyads (Bodipy-NDI and TAPD-Ru), leading to the energy efficiency of the tetrad being 47% of the sum of the photon threshold energies. Its lifetime was increased by several orders of magnitude compared to that in the reference dyads Bodipy-NDI and TAPD-Ru, as it passes from about 3 ns in each dyad to 850 ns in the tetrad. The overall quantum yield formation of this extended charge-separated state is estimated to be 24%. Our proof-of-concept result demonstrates the capability to translate a crucial photosynthetic energy conversion principle into man-made molecular systems for solar fuel formation, to obtain products of higher energy content than those produced by a single photon absorption.
绿色植物、绿藻和蓝细菌的有氧光合作用是生物圈中富含能量化合物的主要提供者。所谓的“Z-方案”是这个“生命引擎”的核心。两个光系统（光系统I和II）串联工作，以建立比每个光系统单独提供的更高的氧化还原能力，这对于利用可见光将水氧化成氧气以及将NADP(+)还原成NADPH是必要的。在这里，我们展示了一种具有分子四联体的Z-方案模拟物。四联体Bodipy-NDI-TAPD-Ru由两种不同的染料——4,4-二氟-1,3,5,7-四甲基-2,6-二乙基-4-硼-3a,4a-二氮杂-s-茚（Bodipy）和Ru(II)(联吡啶)3（Ru）衍生物——组成，它们与萘二酰亚胺（NDI）电子受体和扮演电子供体角色的四烷基苯基二胺（TAPD）相连。在可见光的强激光脉冲激发下，两个染料分子（Ru和Bodipy）以相等的概率吸收，导致由氧化的Bodipy和还原的Ru组成的高能电荷分离态的协同形成。后一种状态不能通过单光子吸收达到。四联体中最终电荷分离态（氧化的Bodipy/还原的Ru）的能量高于参考二元体（Bodipy-NDI和TAPD-Ru）中的能量，导致四联体的能量效率为光子阈值能量总和的47%。与参考二元体Bodipy-NDI和TAPD-Ru相比，其寿命增加了几个数量级，从每个二元体中的约3 ns增加到四联体中的850 ns。这种扩展的电荷分离态的整体量子产率形成估计为24%。我们的概念验证结果证明了将关键的光合能量转换原理转化为人造分子系统以用于太阳能燃料形成的能力，从而获得比单光子吸收产生的能量含量更高的产物。
