Development of Supramolecular Nanodevices Based on Photosynthetic Antennas

作为绿色光合细菌主要捕光天线系统(叶绿体)中的模型叶绿素，通过有机和生物合成方法对天然生成的叶绿素和合成的卟啉进行修饰，制备了具有空间受阻较小的羟基和氢键羰基的环状四吡咯的配位金属配合物(镁、锌和镉)。这里研究的各种模型化合物自聚集形成大的低聚物，就像天然的叶绿体叶绿素一样。合成分子的自聚集体吸收了从可见光到近红外区的光，比天然绿小体宽。为了阐明这些自聚集体的超分子结构，^&lt；18&gt；O标记的振动和^&lt；13&gt；C标记的幻角旋转核磁共振谱以及电子和圆二色吸收谱表明，3^1-羟基与中心金属的配位、13-羰基与配位的羟基的氢键以及环状四氢吡咯之间的π-π堆积形成了自聚集。亚微米级的自组装体与均匀体系中的自聚集体具有相同的光学性质。这些胶囊在水溶液和天然绿小体的表面都有负电荷，并吸附在任何带正电荷的表面。这种超分子体系在构建光活性纳米器件方面具有广阔的应用前景。

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.