Circular dichroism enhancement by the coordination of different metal ions with a pair of chiral tripodal ligands.

The coordination of metal ions with a pair of chiral tripodal ligands ( R or S )-2-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenoxy)- N -(1-phenylethyl)acetamide ( R - or S - L ) results in the circular dichroism (CD) enhancement distinctly, giving fingerprint information among different metals. Specifically, the CD signals show more obvious magnification upon coordination with Ln 3 + compared with Zn 2 + and other metals. Structural analyses show that in Eu-complex ( 1 ), the Eu 3 + metal center is surrounded in a 10-coordinating geometry and the ligand takes fan-like configuration, while in Zn-complex ( 2 ), Zn 2 + is surrounded in a 7-coordinating geometry and the ligand takes pincer-like configuration. These differences in the coordination structure as well as intramolecular packing effects are responsible for the variation in CD signal responses of different metal-coordinated systems. [ABSTRACT FROM AUTHOR]