Multi-triphenylamine-substituted porphyrin-fullerene conjugates as charge stabilizing "Antenna-Reaction center" mimics
Multi-triphenylamine-substituted porphyrin-fullerene conjugates as charge stabilizing "Antenna-Reaction center" mimics
复制标题
DOI：
10.1021/jp073121v
复制
发表时间：
2007-09-06
影响因子：
2.9
通讯作者：
Ito, Osamu
中科院分区：
文献类型：
--
作者：
D'Souza, Francis;Gadde, Suresh;Ito, Osamu
本文报道了一种新的电荷稳定概念，即在一个相对简单的带有给体-受体的多模块共轭物中，π-阳离子自由基在给体大环取代基上离域。新合成的多模块系统由三个共价连接的三苯胺实体在卟啉环的中位和一个富勒烯吡咯烷在第四个中位。预期三苯胺实体充当能量转移天线单元，并增强这些五单元组的游离碱和锌（II）卟啉衍生物的供电子能力。观察到meso取代的三苯胺实体和卟啉，π-系统之间的明显的电子相互作用，因此，这些部分一起作为电子供体，而富勒烯部分作为电子受体在多模块缀合物中。与光谱和电化学结果一致，通过DFT B3 LYP/3- 21 G（*）方法进行的计算研究显示，除了卟啉大环之外，三苯胺实体的前线最高占据分子轨道（HOMO）也发生了离域。自由能计算表明，在所研究的多模共轭物中，卟啉单重激发态的光诱导过程是放热的。光诱导电荷分离和电荷复合过程的发生，证实了时间分辨荧光和纳秒瞬态吸收光谱测量相结合。电荷分离状态，在几微秒的顺序上，观察到作为离域的结果，π-阳离子自由基物种的卟啉大环和中位取代的三苯胺实体。本研究成功地证明了一种新的方法，在供体-受体多模块缀合物的电荷稳定。
A new concept of charge stabilization via delocalization of the,pi-cation radical species over the donor macrocycle substituents in a relatively simple donor-acceptor bearing multimodular conjugates is reported. The newly synthesized multimodular systems were composed of three covalently linked triphenylamine entities at the meso position of the porphyrin ring and one fulleropyrrolidine at the fourth meso position. The triphenylamine entities were expected to act as energy transferring antenna units and to enhance the electron donating ability of both free-base and zinc(II) porphyrin derivatives of these pentads. Appreciable electronic interactions between the meso-substituted triphenylamine entities and the porphyrin,pi-system were observed, and as a consequence, these moieties acted together as an electron-donor while the fullerene moiety acted as an electron-acceptor in the multimodular conjugates. In agreement with the spectral and electrochemical results, the computational studies performed by the DFT B3LYP/3-21G(*) method revealed delocalization of the frontier highest occupied molecular orbital (HOMO) over the triphenylamine entities in addition to the porphyrin macrocycle. Free-energy calculations suggested that the light-induced processes from the singlet excited state of porphyrins are exothermic in the investigated multimodular conjugates. The occurrence of photoinduced charge-separation and charge-recombination processes was confirmed by the combination of time-resolved fluorescence and nanosecond transient absorption spectral measurements. Charge-separated states, on the order of a few microseconds, were observed as a result of the delocalization of the,pi-cation radical species over the porphyrin macrocycle and the meso-substituted triphenylamine entities. The present study successfully demonstrates a novel approach of charge-stabilization in donor-acceptor multimodular conjugates.