Porphyrin boxes constructed by homochiral self-sorting assembly: Optical separation, exciton coupling, and efficient excitation energy migration
Porphyrin boxes constructed by homochiral self-sorting assembly: Optical separation, exciton coupling, and efficient excitation energy migration
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DOI：
10.1021/ja046241e
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发表时间：
2004-12-15
影响因子：
15
通讯作者：
Kim, D
中科院分区：
文献类型：
--
作者：
Hwang, IW;Kamada, T;Kim, D
meso-Pyridine-added锌（II）卟啉Mn和它们的meso-meso-linked二聚体Dn在非配位溶剂如CHCl 3中自发地组装成四聚体卟啉正方形Sn和卟啉盒Bn。有趣的是，从Dn形成Bn通过纯手性自分选组装进行，这已经通过B1和B2的光学分离得到验证。光学纯的对映体B1和B2显示出强烈的Cotton效应的CID光谱，这反映了吡啶臂的长度，从而提供了证据的激子耦合之间的非共价相邻的卟啉环。激发能量迁移过程中Bn已被调查的稳态和时间分辨光谱方法结合偏振各向异性测量。泵浦功率对飞秒瞬态吸收和瞬态吸收各向异性衰减曲线的依赖性都与Bn盒内的激发能量迁移过程直接相关，其中，激子-激子湮灭时间和偏振各向异性上升时间根据福斯特型非相干跳能模型通过假设N = 1的跳变位点的数量来很好地描述。4和激子相干长度L = 2。因此，锌（II）双卟啉单元之间的激发能跳跃率已被估计为B1（48 ps）（-1），B2（98 +/- 3 ps）（-1），和133（361 6 ps）-1。总的来说，自组装卟啉盒Bn用作光捕获复合物的明确定义的三维模型。
meso-Pyridine-appended zinc(II) porphyrins Mn and their meso-meso-linked dimers Dn assemble spontaneously, in noncoordinating solvents such as CHCl3, into tetrameric porphyrin squares Sn and porphyrin boxes Bn, respectively. Interestingly, formation of Bn from Dn proceeds via homochiral self-sorting assembly, which has been verified by optical separations of B1 and B2. Optically pure enantiomers of B1 and B2 display strong Cotton effects in the CID spectra, which reflect the length of the pyridyl arm, thus providing evidence for the exciton coupling between the noncovalent neighboring porphyrin rings. Excitation energy migration processes within Bn have been investigated by steady-state and time-resolved spectroscopic methods in conjunction with polarization anisotropy measurements. Both the pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly associated with the excitation energy migration process within the Bn boxes, where the exciton-exciton annihilation time and the polarization anisotropy rise time are well described in terms of the Forster-type incoherent energy hopping model by assuming a number of hopping sites of N = 4 and an exciton coherence length of L = 2. Consequently, the excitation energy hopping rates between the zinc(II) diporphyrin units have been estimated for B1 (48 ps)(-1), B2 (98 +/- 3 ps)(-1), and 133 (361 6 ps)-1. Overall, the self-assembled porphyrin boxes Bn serve as a well-defined three-dimensional model for the light-harvesting complex.