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叶绿素稀土配位结构的EXAFS研究——镧叶绿素a双层夹心分子结构的确认

Determination of Double Decker Sandwich Structured La - Substituted Chlorophyll a by EXAFS

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【作者】 魏正贵洪法水赵贵文陶冶胡天斗刘涛谢亚宁尹明李冰杨建虹

【Author】 WEI Zheng - Gui HONG Fa - Shui ZHAO Gui - Wen ( Department of Chemistry, University of Science and Technology of China , Hefei, 230026)TAO Ye HU Tian - Dou LIU Tao XIE Ya - Nin ( Synchrotron Radiation Laboratory, Institute of High Energy Physics , The Chinese Academy of Science, Beijing, 100039)YIN Ming LI Bin ( Institute of Rock and Mineral Analysis, Beijing, 100037 )YANG Jian - Hong ( Graduate School of Beijing, University of Science and Technology of China, Beijing, 100039)

【机构】 中国科学技术大学化学系中国科学院高能物理研究所同步辐射室地矿部岩矿测试技术研究所中国科学技术大学研究生院生物学部 合肥230026合肥230026北京100039北京100037北京100039

【摘要】 通过合成镧叶绿素a(La-Chla),研究稀土在叶绿素中的赋存状态.La-Chla的紫外可见光谱(UV-vis)、红外光谱(FT-IR)证实,镧离子已配位到叶绿素a的卟啉环上.其磁圆二色谱(MCD)在Soret带具有双层夹心卟啉结构的特征结构.通过扩展X射线吸收精细结构谱(EXAFS),采用双层夹心结构模型拟合,确定La周围的近邻结构,取得满意结果.表明合成镧叶绿素a具有双层夹心结构.La夹于两个卟啉环之间,与上下卟啉环上共八个N原子配位,La—N平均键长0.261nm.

【Abstract】 Double decker sandwich lanthanoid porphyrins have been synthesized and characterized systematically. Chlorophyll is a representative of natural porphyrin derivatives. It is therefore interesting to study the chemical form of lanthanide in chlorophyll. We synthesized Lanthanum ( Ⅲ) Chlorophyll a derivatives, whose UV - vis and IR spectra confirm the coordination of La(Ⅲ) to the porphyrin rings. MCD spectra show the special bands in Soret band region, which indicate a transition from sandwich structure porphyrin complexes. By extended X - ray absorption fine structure (EXAFS) method, it is found that the molecular structure of synthesized La - Chla can be well fitted by the double decker sandwich structure model that La is surrounded by eight nitrogen atoms from two porphyrin rings. The MCD and EXAFS results indicate that the La in chlorophyll a exist as a sandwich shaped complexes with an average La-N bond length of 0.261nm. To our best knowledge, this is the first example of La - Chla with a double decker sandwich molecular structure.

【关键词】 镧叶绿素aEXAFSMCD分子结构
【Key words】 La substituted Chlorophyll aEXAFSMCDmolecular structure
【基金】 国家自然科学基金(29805003)资助
  • 【文献出处】 化学学报 ,Acta Chimica Sinica , 编辑部邮箱 ,2000年05期
  • 【分类号】O641
  • 【被引频次】21
  • 【下载频次】193
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