关键词: 稀土, 镧络合物, 叶绿素, 分子结构, 夹心化合物, 卟啉, 扩展X射线吸收谱法, 结构谱

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.

Key words: RARE EARTH, LANTHANUM COMPLEX, CHLOROPHYLL, MOLECULAR STRUCTURE, SANDWICH COMPOUNDS, PORPHYRIN, STRUCTURE SPECTROSCOPY