Chiral Sensing Using Circularly Polarized Luminescence of Bis(phenanthroline dicarboxylic acid) EuIII Complex Induced by Allosteric-type Interaction with Amino Acid Molecules.

[Eu(pda)2 ]- and [Eu(bda)2 ]- (pda=1,10-phenanthroline-2, 9-dicarboxylic acid; bda=2,2' bipyridine 5,5'-dicarboxylic acid) have an achiral D2d structure in crystals. These complexes exhibit circularly polarized luminescence (CPL) in water containing chiral amino acids. In this work, induced CPL of [Eu(pda)2 ]- and [Eu(bda)2 ]- in water solutions containing a mixture of d- and l- amino acids were examined. Plots of glum values of the induced CPL as a function of mol-fraction of l- and d- arginine reveal that [Eu(pda)2 ]- favors homo-association ([Eu(pda)2 ]- -(l-arginine)2 or [Eu(pda)2 ]- -(d-arginine)2 ) over hetero-association {[Eu(pda)2 ]- -(l-arginine)⋅(d-arginine)}. This suggests that association of an arginine molecule induces a structural change in [Eu(pda)2 ]- to promote chiral selective association to another arginine, i.e., homo-allosteric association. On the other hand, the system of [Eu(pda)2 ]- with histidine favors hetero-allosteric association over homo-association. No allosteric effect is recognized in CPL from [Eu(bda)2 ]- .