Artiflcial photosynthetic reaction centers with porphyrins as primary electron acceptors
Artiflcial photosynthetic reaction centers with porphyrins as primary electron acceptors
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DOI：
10.1021/jp040143y
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发表时间：
2004-07-22
影响因子：
3.3
通讯作者：
Moore, AL
中科院分区：
文献类型：
--
作者：
Gould, SL;Kodis, G;Moore, AL
本文合成了一个由类胡萝卜素（C）、二均三甲苯基卟啉（P）和三（七氟丙基）卟啉（P-F）组成的三元组（C-P-P-F），并发现在卟啉部分之间发生快速的单重态-单重态能量转移，使它们的激发态处于平衡状态。来自P的第一激发单重态的光诱导电子转移或来自PF的第一激发单重态的空穴转移产生C-P。P-F（. -）。然后从C的电子转移产生最终的电荷分离态C。P-P-F（. -）室温下在四氢呋喃溶液中的量子产率为0.73，寿命为500 ns。最后的电荷分离态衰变，主要形成三重激发态，位于类胡萝卜素C-3-P-P-F上，而不是基态。还合成了其中P被金属化（P-Zn）的第二个三元组。在该体系中，卟啉的激发单重态不再处于平衡状态，电子从激发态P-Zn快速转移到P-F，形成C-P-Zn（.+）- P-F（. -）并且从P-Zn到P-F的快速能量转移与随后从P-F到P-Zn的空穴转移也收敛，得到相同的C-P-Zn（.+）。P-F（. -）物种，进化到C +- P-Zn-P-F（. -）量子产率为0.14。在四氢呋喃中，该态在室温下衰变为C-3-P-Zn-P-F，量子产率为0.06。电荷复合反应遵循C.+- P-P-F（. -）从室温到77 K，对于C.+- P-Zn-P-F（. -）低于250 K。在250 K以上，C.+-的复合反应为两步反应P-Zn-P-F（. -）除了直接重组机制之外。这种新的途径涉及到一个吸能步骤，以填充C-P-Zn（.+）- P-F（. -）具有类似于0.23eV的E-a。这些三元组的某些物理化学特征，特别是重组到三重态，让人想起那些人工反应中心与C-60作为主要的电子受体。
A triad consisting of a carotenoid (C), a dimesitylporphyrin (P), and a tris(heptafluoropropyl)porphyrin (P-F), C-P-P-F, has been synthesized and found to undergo rapid singlet-singlet energy transfer between the porphyrin moieties so that their excited states are in equilibrium. Photoinduced electron transfer from the first excited singlet state of P, or hole transfer from the first excited singlet state Of PF, yields C-P.+-P-F(.-). Electron transfer from C then yields the final charge-separated state C.+-P-P-F(.-) with a quantum yield of 0.73 and a lifetime of 500 ns in tetrahydrofuran solution at ambient temperature. The final charge-separated state decays to form primarily a triplet excited state localized on the carotenoid, C-3-P-P-F, rather than the ground state. A second triad in which P is metalated (P-Zn) has also been synthesized. In this system, the excited singlet states of the porphyrins are no longer in equilibrium; fast electron transfer from excited P-Zn to P-F to form C-P-Zn(.+)-P-F(.-) and also fast energy transfer from P-Zn to P-F with subsequent hole transfer from P-F to P-Zn converge to give the same C-P-Zn(.+)-P-F(.-) species, which evolves to C.+-P-Zn-P-F(.-) with a quantum yield of 0.14. This state decays to C-3-P-Zn-P-F with a quantum yield of 0.06 in tetrahydrofuran at room temperature. The charge recombination reaction follows a single-step mechanism for C.+-P-P-F(.-) from room temperature to 77 K and for C.+-P-Zn-P-F(.-) below 250 K. Above 250 K, a two-step pathway is accessed for the recombination reaction Of C.+-P-Zn-P-F(.-) in addition to the direct recombination mechanism. This new pathway involves an endergonic step to populate C-P-Zn(.+)-P-F(.-) having an E-a of similar to0.23 eV. Certain photophysical characteristics of these triads, in particular the recombination to the triplet state, are reminiscent of those of artificial reaction centers with C-60 as the primary electron acceptor.