Determination of double decker sandwich structure of praseodymium-chlorophyll a molecule

The Pr(III) complex of Chlorophyll a was synthesized and characterized. The results of UV-Vis and IR spectra indicate the coordination of Pr(III) to t he porphyrin rings. The special bands in Soret band region in MCD spectra s hown a transition type of the sandwich structure porphyrin complexes, By ex tended X-ray Absorption Fine Structure (XAFS) method, a double decker sandw ich structure was well fitted, in which Pr is surrounded by eight nitrogen atoms from two porphyrin rings. Combining the MCD with EXAFS results, it is believed that the binding mode of Pr ion in chlorophyll a is a sandwich st ructure with the Pr-N bond length of average 0.242 nm.