Formation of a Long-Lived Photoinduced Electron-Transfer State in an Electron Acceptor-Donor-Acceptor Porphyrin Triad Connected by Coordination Bonds
Formation of a Long-Lived Photoinduced Electron-Transfer State in an Electron Acceptor-Donor-Acceptor Porphyrin Triad Connected by Coordination Bonds
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DOI：
10.1021/jp105116y
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发表时间：
2010-08-26
影响因子：
3.7
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Honda, Tatsuhiko;Nakanishi, Tatsuaki;Fukuzumi, Shunichi
Sn（DPP）（OH）（2）（DPP 2- = 2，3，5，7，8，10，12，13，15，17，18，20-十二苯基卟啉二价阴离子）与H2 F16 DPPCOOH（2，3，7，8，12，13，17，18-八（3，5-二氟苯基）-5-（4-羧基苯基）-10，15，20-三苯基卟啉）得到卟啉三联体Sn（DPP）（H2 F16 DPPCOO）（2）（1），其中Sn（DPP）单元与两个H2 F16 DPPCOO-单元通过强配位键连接。Sn（DPP）（H，F16 DPPCCOO）2的H2 F16 DPPC 00-单元通过与三氟乙酸（CF 3C 001 -1）反应而双质子化，以提供稳健的电子受体供体受体卟啉三联体Sn（DPP）I（H4 F16 DPPCOO）（CF 3COO）212（2），其中Sn（DPP）单元和H4 F16 DPP 2 +COO-（H4 F16 DPPCOO+）单元分别充当电子供体和受体。1的光动力学研究通过飞秒激光闪光光解测量在PhCN中，揭示能量转移发生从单重激发态的Sn（DPP）单元的H2 F16 DPPC 00-单元，以产生单重激发态的H2 F16 DPPCOO-。与1的情况相反，通过飞秒激光闪光光解观察到的含有双质子化形式（H4 FI 6DPPC 00+）的2的瞬态吸收光谱清楚地表明发生了从Sn（DPP）单元的单重激发态到H4 F16，DPPCOO+单元的快速电子转移。由Sn（1）1313 r和Sn（DPP）（H2 F16 DPPCOO）（2）组成的单重电子转移（ET）态以1.4 × 1010 s的速率常数衰减到基态，与三重ET态的产生竞争，这也通过纳秒瞬态吸收光谱检测到。由于背电子转移过程的自旋禁戒特性，三重态的寿命（50 its）比单重态的寿命（71 ps）长得多。
The reaction of Sn(DPP)(OH)(2) (DPP2- = 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin dianion) with H2F16DPPCOOH (2,3,7,8,12,13,17,18-octakis(3,5-difluorophenyl)-5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin) afforded a porphyrin triad, Sn(DPP)(H2F16DPPCOO)(2) (1), in which the Sn(DPP) unit is linked with the two H2F16DPPCOO- units by strong coordination bonds. The H2F16DPPC00- unit of Sn(DPP)(H,F16DPPCOO)2 was diprotonated by the reaction with trifluoroacetic acid (CF3C001-1) to afford a robust electron acceptor donor acceptor porphyrin triad, Sn(DPP)I(H4F16DPPCOO)(CF3COO)212 (2), in which the Sn(DPP) unit and the H4F16DPP2+COO- (H4F16DPPCOO+) unit act as an electron donor and an acceptor, respectively. The photodynamics of 1 was examined by femtosecord laser flash photolysis measurements in PhCN to reveal that the energy transfer occurs from the singlet excited state of the Sn(DPP) unit to the H2F16DPPC00- unit to generate the singlet excited state of H2F16DPPCOO-. In contrast to the case of 1, the transient absorption spectra of 2 that contains the diprotonated form (H4FI6DPPC00+), observed by femtosecond laser flash photolysis, clearly indicated the occurrence of fast electron transfer from the singlet excited state of the Sn(DPP) unit to the H4F16,DPPCOO+ unit. The resulting singlet electron-transfer (ET) state composed of Sn(1)1313r and Sn(DPP)(H2F16DPPCOO)(2) decays to the ground state with the rate constant of 1.4 x 1010 s in competition with generation of the triplet ET state, which was also detected by the nanosecond transient absorption spectroscopy. The lifetime of the triplet ET state (50 its) was much longer than that of the singlet ET state (71 ps) due to the spin-forbidden character of the back electron-transfer process.