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Mixed Tb/Dy coordination ladders based on tetra(carboxymethyl)thiacalix[4]arene: a new avenue towards luminescent molecular nanomagnets
Ist Teil von
RSC advances, 2020-03, Vol.1 (2), p.11755-11765
Ort / Verlag
England: Royal Society of Chemistry
Erscheinungsjahr
2020
Quelle
EZB Free E-Journals
Beschreibungen/Notizen
The macrocyclic ligand calix[4]arene (
L1
) and its sulphur-containing analogue thia[4]calixarene (
L2
) are promising precursors for functional molecular materials as they offer rational functionalization with various organic groups. Here, we present the first example of lanthanide-based coordination polymers built from the macrocyclic thiacalix[4]arene backbone bearing four carboxylic moieties, namely, ligand
H
4
L3
. The combination of
H
4
L3
with the Tb
3+
and Dy
3+
cations led to the formation of 1D ladder-type coordination polymers with the formula [Ln
III
HL3
DMF
3
]·(DMF) (where DMF = dimethylformamide and Ln = Tb or Dy, denoted as
HL3-Tb
and
HL3-Dy
), which resulted from the coordination of the lanthanide cations with the partially deprotonated ligand
HL3
3−
that behaved as a T-shape connector. The coordination sphere around the metal was completed by the coordinated DMF solvent molecules. By combining both Tb
3+
and Dy
3+
cations, isostructural heterobimetallic solid solutions
HL3-Tb
1−
x
Dy
x
were also prepared.
HL3-Tb
and
HL3-Dy
showed visible light photoluminescence originating from the f-f electronic transitions of pale green emissive Tb
3+
and pale yellow emissive Dy
3+
with efficient sensitization by the functionalized thia[4]calixarene ligand
HL3
. In the
HL3-Tb
1−
x
Dy
x
solid solutions, the Tb/Dy ratio governed both the emission colour as well as the emission quantum yield, which reached even 28% at room temperature for
HL3-Tb
. Moreover,
HL3-Dy
exhibited a slow magnetic relaxation effect related to the magnetic anisotropy of the dodecahedral Dy
3+
complexes, which were well isolated in the crystal lattice by expanded organic spacers.
The single crystals of the two isostructural Tb
3+
- and Dy
3+
-based coordination polymers (
HL3-Tb
and
HL3-Dy
) were structurally characterized, and their photophysical properties were investigated, together with their corresponding solid solutions.