Conglomerate, Racemate, and Achiral Crystals of Polymetallic Europium(III) Compounds of Bis- or Tris--diketonate Ligands and Circularly Polarized Luminescence Study

This work reports (a) conglomerate and racemic crystal structures of [(Lambda,Lambda,Lambda,Lambda,Lambda,Lambda)- or/and (Delta,Delta,Delta,Delta,Delta,Delta)Eu-6(III)(TTP)(8)(OH2)(6)Na-4] n coordination polymers, (b) racemic c r y s t a l s t r u c t u r e s o f (Delta,Delta,Delta,Delta,) - / ( Lambda,Lambda,Lambda,Lambda) Eu-4(III)(TTP)(4)(bipy)(4)(MEK)(2)(OH2) (2) tetrahedral clusters, and (c) the achiral crystal structure of the [Eu-2(III)(BTP)(4)(OH2)(2)Na-2] n coordination polymer (where BTP = dianionic bis-ss-diketonate, TTP = trianionic tris-ss-diketonate, and bipy = 2,2'-bipyridine). The screw coordination arrangement of the TTP ligand has led to the formation of homoconfigurational racemic EuIII products. The conglomerate crystallization of [EuIII6(TTP)8(OH2)6Na4] n appears to be caused by the presence of the sodium, Na+ counterions, and interactions between oxygen atoms and the trifluoromethyl unit of the TTP ligand and Na+ ions. All the Eu-III compounds exhibit characteristic red luminescence (5D0. 7FJ, J = 0-4) in solution or in the solid crystalline state. Circularly polarized luminescence (CPL) was observed in the chiral Eu-6(III)(TTP)(8)(OH2)(6)Na-4] n species, displaying a |glum| value in the range of 0.15 to 0.68 at the 5D0. 7F1 emission band. Subtle changes of the [Eu-6(III)(TTP)(8)(OH2)(6)Na-4] n structure which may be due to selection of twinned crystals or crystals that do not correspond to a perfect spontaneous resolution, are considered to be responsible for the variation in the observed CPL values.