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

This work reports (a) conglomerate and racemic crystal structures of [(Δ,Δ,Δ,Δ,Δ,Δ)- or/and (Λ,Λ,Λ,Λ,Λ,Λ)-Eu III 6 (TTP) 8 (OH 2 ) 6 Na 4 ] n coordination polymers, (b) racemic crystal structures of (Δ,Δ,Δ,Δ)-/(Λ,Λ,Λ,Λ)-Eu III 4 (TTP) 4 (bipy) 4 (MEK) 2 (OH 2 ) 2 tetrahedral clusters, and (c) the achiral crystal structure of the [Eu III 2 (BTP) 4 (OH 2 ) 2 Na 2 ] n coordination polymer (where BTP = dianionic bis-β-diketonate, TTP = trianionic tris- β -diketonate, and bipy = 2,2'-bipyridine). The screw coordination arrangement of the TTP ligand has led to the formation of homoconfigurational racemic Eu III products. The conglomerate crystallization of [Eu III 6 (TTP) 8 (OH 2 ) 6 Na 4 ] 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 ( 5 D 0 → 7 F J , J = 0-4) in solution or in the solid crystalline state. Circularly polarized luminescence (CPL) was observed in the chiral Eu III 6 (TTP) 8 (OH 2 ) 6 Na 4 ] n species, displaying a | g lum | value in the range of 0.15 to 0.68 at the 5 D 0 → 7 F 1 emission band. Subtle changes of the [Eu III 6 (TTP) 8 (OH 2 ) 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.