| Abstract: | 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]?. |
