Two types of dimeric complexes [Ln
2(hfa)
6(
2-O(CH
2)
2NHMe
2)
2] and [Ln(thd)
2(
2,
2-O(CH
2)
2NMe
2)]
2 (Ln= Y
III, Eu
III, Gd
III, Tb
III, Tm
III, Lu
III; hfa
- = hexafluoroacetylacetonato, thd
- = dipi
valoylmethanato) areobtained by reacting [Ln(hfa)
3(H
2O)
2] and [Ln(thd)
3], respecti
vely, with
N,
N-dimethylaminoethanol in tolueneand are fully characterized. X-ray single crystal analysis performed for the Tb
III compounds confirms theirdimeric structure. The coordination mode of
N,
N-dimethylaminoethanol depends on the nature of the
![](/images/gifchars/beta2.gif)
-diketonate. In [Tb
2(hfa)
6(
2-O(CH
2)
2NHMe
2)
2], eight-coordinate Tb
III ions adopt distorted square antiprismaticcoordination en
vironments and are O-bridged by two zwitterionic
N,
N-dimethylaminoethanol ligands with aTb1···Tb2 separation of 3.684(1) Å. In [Tb(thd)
2(
2,
2-O(CH
2)
2NMe
2)]
2, the
N,
N-dimethylaminoethanol actsas chelating-bridging O,N-donor anion and the Tb
III ions are se
ven-coordinate; the Tb1···Tb1A separationamounts to 3.735(2) Å within centrosymmetric dimers. The dimeric complexes are thermally stable up to180
![](/images/entities/deg.gif)
C, as shown by thermogra
vimetric analysis, and their
volatility is sufficient for quantitati
ve sublimation under reduced pressure. The Eu
III and Tb
III dimers display metal-centered luminescence, particularly[Eu
2(hfa)
6(O(CH
2)
2NHMe
2)
2] (quantum yield
![](/isubscribe/journals/jpcafh/112/i16/eqn/jp711305ue10001.gif)
= 58%) and [Tb(thd)
2(O(CH
2)
2NMe
2)]
2 (32%). Consideration of energy migration paths within the dimers, based on the study of both pure and Eu
III- or Tb
III-doped(0.01-0.1 mol %) Lu
III analogues, leads to the conclusion that both the
![](/images/gifchars/beta2.gif)
-diketone and
N,
N-dimethylaminoethanol ligands contribute significantly to the sensitization process of the Eu
III luminescence. The ancillaryligand increases considerably the luminescence of [Eu
2(hfa)
6(O(CH
2)
2NHMe
2)
2], compared to [Ln(hfa)
3(H
2O)
2],through the formation of intra-ligand states while it is detrimental to Tb
III luminescence in both
![](/images/gifchars/beta2.gif)
-diketonates.Thin films of the most luminescent compound [Eu
2(hfa)
6(O(CH
2)
2NHMe
2)
2] obtained by
vacuum sublimationdisplay photophysical properties analogous to those of the solid-state sample, thus opening perspecti
ves forapplications in electroluminescent de
vices.