Development of Supramolecular Nanodevices Based on Photosynthetic Antennas

作为绿色光合细菌主要捕光天线系统（叶绿素体）的模型叶绿素，通过有机和生物合成方法对天然叶绿素和合成卟啉进行修饰，制备了具有空间位阻较小的羟基和氢键羰基的环状四吡咯金属配合物（Mg，Zn和Cd）.各种各样的模型化合物在这里检查自我聚集，形成大的低聚物，以及天然的chlorosomal叶绿素。合成分子的自聚集体吸收的光范围从可见光到近红外，比天然叶绿体宽，为了阐明自聚集体的超分子结构，用~ 1 <18>O-标记的振动和~ 1C<13>-标记的魔角自旋核磁共振谱以及电子和圆二色吸收谱进行了研究，表明3^1-羟基与中心金属的配位，通过13位羰基与OH的氢键作用以及四吡咯环之间的π-π堆积作用，形成了自组装体。亚微米尺度的自组装体具有与均匀体系中的自聚集体相同的光学性质。胶囊在水溶液中的表面上具有负电荷，以及天然绿小体，并且吸附在任何带正电荷的表面上。这样的超分子体系是有希望的光活性纳米器件的建设。

As model chlorophylls in main light-harvesting antenna systems (chlorosomes) of green photosynthetic bacteria, coordinatable metal complexes (Mg, Zn and Cd) of cyclic tetrapyrroles possessing sterically less hindered hydroxy and hydrogen-bonded carbonyl groups were prepared by modifying naturally occurring chlorophylls and synthetic porphyrins using organic and bio-synthetic procedures. A variety of model compounds examined here self-aggregated to form large oligomers as well as natural chlorosomal chlorophylls did. The self-aggregates of synthetic molecules absorbed lights from visible to near-infrared region, which are wider than natural chlorosomes.To elucidate the supramolecular structures of the self-aggregates, ^<18>O-labeled vibrational and ^<13>C-labeled magic angle spinning nuclear magnetic spectroscopies were examined as well as electronic and circular dichroism absorption ones, indicating that coordination of 3^1-hydroxy group to central metal, hydrogen bond of 13-carbonyl group to the coordinated OH and π-π stacking among cyclic tetrapyrroles made the self-aggregates.Chemically and mechanically stable self-assemblies of synthetic chlorophylls were prepared using condensation of silanols (sol-gel method). The submicrometer-sized self-assemblies had the same optical properties as the self-aggregates in a homogeneous system. The capsules had negative charges on their surface in an aqueous solution as well as natural chlorosomes, and adsorbed on any positive charged surfaces. Such supramolecular systems are promising for construction of photoactive nanodevices.