1 research outputs found
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)-EuIII6(TTP)8(OH2)6Na4]n coordination polymers,
(b) racemic crystal structures of (Δ,Δ,Δ,Δ)-/(Λ,Λ,Λ,Λ)-EuIII4(TTP)4(bipy)4(MEK)2(OH2)2 tetrahedral clusters, and (c)
the achiral crystal structure of the [EuIII2(BTP)4(OH2)2Na2]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 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 EuIII 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 EuIII6(TTP)8(OH2)6Na4]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 [EuIII6(TTP)8(OH2)6Na4]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