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.
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.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2000年第5期559-562,共4页
Acta Chimica Sinica
基金
国家自然科学基金(29805003)资助
关键词
镧叶绿素a
EXAFS
MCD
分子结构
La substituted Chlorophyll a, EXAFS, MCD, molecular structure
