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Chiroptical Spectroscopic Studies on Lanthanide Complexes with Valinamide Derivatives in Solution
Author(s) -
Hasegawa Miki,
Iwasawa Daichi,
Kawaguchi Takuma,
Koike Hikaru,
Saso Akira,
Ogata Shuhei,
Ishii Ayumi,
Ohmagari Hitomi,
Iwamura Munetaka,
Nozaki Koichi
Publication year - 2020
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201900692
Subject(s) - europium , luminescence , lanthanide , chemistry , ligand (biochemistry) , moiety , bipyridine , crystallography , quantum yield , photochemistry , acetonitrile , crystal structure , stereochemistry , fluorescence , ion , materials science , organic chemistry , biochemistry , receptor , optoelectronics , physics , quantum mechanics
Ligands based on 2,2’‐bipyridine and valinamide moieties induce circularly polarized luminescence in their europium complexes. Both the R and S enantiomers of the complexes were successfully obtained. Single‐crystal X‐ray analysis of the racemic crystal confirmed that the ligand is coordinated to the europium ion in a tetradentate fashion. The π‐electronic system of the ligand is co‐planar with the valinamide moiety, and acts as an efficient photoantenna to sensitize europium luminescence by UV excitation. The luminescence quantum yield (QY) of europium in the valinamide‐containing complex was 44 % in acetonitrile. The g lum value to evaluate the circularly polarized luminescence was relatively high at |0.13| estimated from their magnetic dipole transitions around 593 nm. For comparison, we prepared hexadentate europium complexes in the S ‐ and R ‐forms derived from two bipyridine moieties linked by ethylenediamines. The determined QYs were 18 % ( S ) and 16 % ( R ), and the g lum value |0.12| for the hexadentate complexes. The photophysical properties of the gadolinium complexes of the ligands were also evaluated.