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