Graduate School of Science and Engineering, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577, Japan.
J Phys Chem B. 2010 Nov 18;114(45):14717-28. doi: 10.1021/jp102966x. Epub 2010 Jun 7.
Free base and zinc porphyrins are linked with fullerene (C(60)) through β,β'-pyrrolic positions rather than meso-positions by Diels-Alder reaction of monoanthraporphyrins (H(2)P-mA and ZnP-mA) and C(60) to afford a π-expanded free base porphyrin-fullerene dyad (H(2)P-C(60)) and its zinc porphyrin-fullerene dyad (ZnP-C(60)) in 86 and 51% yield, respectively. The X-ray crystallographic analysis of ZnP-C(60) showed two comma-shaped swirls-like structure in a unit cell. The intramolecular center-to-center and edge-to-edge distances between the porphyrin and fullerene moieties were 11.5 and 2.5 Å, respectively. The porphyrins and fullerenes were packed in layer-by-layer structure and the porphyrins lied down in parallel. The intermolecular center-to-center distances between the neighboring fullerenes were 10.252, 10.028, and 10.129 Å, which were less than typical van der Waals distance and the π-π interaction spread two-dimensionally. The energy of the charge-separated (CS) state of ZnP-C(60) (1.11 eV) determined by differential-pulse voltammetry measurements in benzonitrile is significantly lower than those of zinc porphyrin-C(60) dyads linked at meso positions because of the low oxidation potential of the π-expanded ZnP moiety. The CS energy of ZnP-C(60) in a nonpolar solvent such as toluene (1.40 V) is lower than the triplet excited state of C(60) ((3)C(60)*), enabling us to attain a long lived triplet CS state (8.1 μs) in toluene, detected by nanosecond laser flash photolysis experiments. The distance between unpaired electrons in the triplet CS state was determined by the EPR spectrum to be 9.1 Å, which agreed with the distance between a zinc atom of the porphyrin and a carbon edge of C(60) in the crystal structure of ZnP-C(60). The rate constants of photoinduced electron transfer and back electron transfer of H(2)P-C(60) and ZnP-C(60), which were determined by femtosecond and nanosecond laser flash photolysis measurements, were analyzed in light of the Marcus theory of electron transfer.
通过单蒽卟啉（H2P-mA 和 ZnP-mA）与 C60 之间的 Diels-Alder 反应，自由碱卟啉和锌卟啉与富勒烯（C60）通过β，β'-吡咯位置而不是中位连接，得到π扩展的自由碱卟啉-富勒烯偶联物（H2P-C60）及其锌卟啉-富勒烯偶联物（ZnP-C60），产率分别为 86%和 51%。ZnP-C60 的 X 射线晶体学分析表明，在一个单元中存在两个逗号形的漩涡状结构。卟啉和富勒烯部分之间的分子内中心到中心和边缘到边缘距离分别为 11.5 和 2.5 Å。卟啉和富勒烯以层状结构包装，卟啉平行排列。相邻富勒烯之间的分子间中心到中心距离为 10.252、10.028 和 10.129 Å，小于典型的范德华距离，π-π 相互作用在二维上扩展。通过在苯腈中的差分脉冲伏安法测量确定 ZnP-C60 的电荷分离（CS）态的能量（1.11 eV）显著低于通过中位连接的锌卟啉-C60 二联体，因为π扩展的 ZnP 部分的氧化电位较低。ZnP-C60 的 CS 能量在非极性溶剂（如甲苯）中（1.40 V）低于富勒烯的三重激发态（3C60*），使我们能够在甲苯中获得长寿命的三重态 CS 态（8.1 μs），通过纳秒激光闪光光解实验检测到。通过 EPR 光谱确定三重态 CS 态中未配对电子之间的距离为 9.1 Å，与 ZnP-C60 晶体结构中卟啉的锌原子和富勒烯 C（60）的碳边缘之间的距离一致。通过飞秒和纳秒激光闪光光解测量确定的 H2P-C60 和 ZnP-C60 的光诱导电子转移和反向电子转移的速率常数，根据电子转移的 Marcus 理论进行了分析。
