Ha Jeong-Hyon, Cho Hyun Sun, Song Jae Kyu, Kim Dongho, Aratani Naoki, Osuka Atsuhiro
Center for Ultrafast Optical Characteristics Control, Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
Chemphyschem. 2004 Jan 23;5(1):57-67. doi: 10.1002/cphc.200300758.
Excitation-energy transport (EET) phenomena in meso-meso directly linked Zn(II)porphyrin arrays in the singlet and triplet excited states were investigated with a view to electronic coupling strength and coherence length by steady-state and time-resolved spectroscopic measurements. To investigate energy transfer in the triplet states, we modified the Zn(II)porphyrin arrays with bromo substituents at both ends. The coupling strength of the Soret bands of the arrays was estimated to be about 2200 cm-1, and that of the Q bands is about 570 cm-1. The coherence length in the S1 state of the Zn(II)porphyrin arrays was determined to be 4-5 porphyrin units, which is comparable to that of the well-ordered two-dimensional circular structure B850 in the peripheral light-harvesting antenna (LH2) in photosynthetic purple bacteria. This indicates that the Zn(II)porphyrin arrays are well suited for mimicking natural light-harvesting antenna complexes. On the other hand, the rate of energy transfer in the triplet state is estimated to be on the order of 100 microseconds-1, and the very weak coupling between the triplet states (ca. 0.003 cm-1), indicates that the triplet excitation energy is essentially localized on a single porphyrin moiety.
通过稳态和时间分辨光谱测量，研究了处于单重态和三重态激发态的中-中直接相连的锌（II）卟啉阵列中的激发能转移（EET）现象，以考察电子耦合强度和相干长度。为了研究三重态中的能量转移，我们在两端用溴取代基修饰了锌（II）卟啉阵列。阵列的Soret带的耦合强度估计约为2200 cm-1，Q带的耦合强度约为570 cm-1。锌（II）卟啉阵列S1态的相干长度确定为4-5个卟啉单元，这与光合紫色细菌外周光捕获天线（LH2）中有序的二维圆形结构B850的相干长度相当。这表明锌（II）卟啉阵列非常适合模拟天然光捕获天线复合物。另一方面，三重态中的能量转移速率估计约为100微秒-1，并且三重态之间非常弱的耦合（约0.003 cm-1）表明三重态激发能基本上局限于单个卟啉部分。
