Excited-state chiral discrimination of Tb(III) complexes of (S,S′)- and (R,R′)-ethylenediamine-N,N′-disuccinic acid in circularly polarized luminescence and luminescence decay profiles

Abstract

Total luminescence (TL), circularly polarized luminescence (CPL), and decay times are measured in solution to investigate excited-state chiral discrimination of Tb (III) complexes of (S,S′)- and (R,R′)-ethylenediamine-N,N′-disuccinic acid (EDDS), K [Tb (l, d-EDDS)]·2H 2O, in the presence of two different complexes: (a) transition metal complexes; (+) and (−) [Co(en) 3](ClO 4) 3·3H 2O (en=ethylendiamine) and (b) rare earth complexes; K[Nd (l,d-EDDS)]·2H 2O. The magnitude of the quenching of Tb(III) complexes being found to be almost linearly dependent on the concentration of the quencher, the pseudo-Stern–Volmer quenching constants in luminescence, decaytime and luminescence dissymmetry factors g lum are obtained for homochiral and heterochiral pair complexes. The quenching constants between homochiral pairs are found to be larger in magnitudes than those between heterochiral ones in the case of (a), but an opposite result is found in the case of (b). If we take account of ligand-exchange reactions between lanthanide complexes in solution, the experimental results are in agreement with the description that the dispersion energy discriminates between homochiral and heterochiral complex pairs, with the homochiral pair being stabilized relative to the heterochiral pair in the photo-excited states.