Design and Synthesis of Molecules which act as a catalyst for the Conversion of Solar Energy

自然界将太阳能转化为有用能量的光合作用一直是有机化学家的终极目标。光合作用初期的关键事件是稳定的电荷分离，这是由嵌入在蛋白质基质中的几种发色团实现的。负责稳定电荷分离的有效的正向和低效的反向电子转移高度依赖于发色团的结构因素。了解这些因素并为构建人工光合催化剂提供信息的最佳策略之一是合成合适的模型化合物。我们沿着这条路线进行了研究，得到了以下结果。1. 我们通过多步电子转移过程将模型化合物固定在脂质双分子层中，并观察辐照过程中穿过脂质双分子层的光电流。这表明这种分子确实是太阳能转化的催化剂。2. 制备了一种长烷基链的（卟啉）-(CH_2)_3-（醌）化合物，并将其固定在牛血清白蛋白中。不幸的是，我们无法确定蛋白质对电子转移的影响，因为蛋白质中的卟啉发色团不显示荧光。3. 我们已经合成了模型化合物，其中只有卟啉和醌的取向不同，并得出光诱导电子转移相当依赖于发色团的取向的结论。

Photosynthesis, in which Nature converts the solar energy into useful energy, has been an ultimate goal for organic chemists. The critical event in the early stage of photosynthesis is the stable charge separation which is achieved by the several kinds of chromophores embedded in the protein matrix. The efficient forward- and inefficient back-electron transfers, responsible for the stable charge separation, are highly dependent upon the structural factors of the chromophores. One of the best strategy to understand these factors and to get information for the construction of artificial photosynthetic catalysts is to synthesize suitable model compounds. We have carried out our study along this line and got the following results. 1. We fixed our model compound with multistep electron transfer process into lipid bilayer and observed the photocurrent across the layer during irradiation. This indicates that the molecule really act as a catalyst for solar energy conversion. 2. We have prepared a (porphyrin)-(CH_2)_3-(quinone) compound with a long alkyl chain and fixed it into bovine serum alubumin. Unfortunately, we could not determine the effect of protein upon electron transfer since the porphyrin chromophore in protein did not show fluorescence. 3. We have synthesized model compounds, in which only the orientation of a porphyrin and a quinone is different and concluded that photoinduced electron transfer is fairly dependent upon the orientation of chromophores.