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 D-2d 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 g(lum) 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)](-).