2 research outputs found
Structural and Photophysical Studies on Geometric (Er<sub>2</sub>Yb<sub>2</sub>/Yb<sub>2</sub>Er<sub>2</sub>) and Configurational (EuTb<sub>3</sub>/Eu<sub>3</sub>Tb) Isomers of Heterotetranuclear Lanthanide(III) Complexes
Heterotetranuclear geometrical (Er<sub>2</sub>Yb<sub>2</sub>/Yb<sub>2</sub>Er<sub>2</sub>) and configuational (EuTb<sub>3</sub>/Eu<sub>3</sub>Tb) isomeric lanthanideĀ(III) complexes have
been synthesized
and characterized by spectroscopy as well as X-ray crystallography.
The geometric Er<sub>2</sub>Yb<sub>2</sub>/Yb<sub>2</sub>Er<sub>2</sub> isomers exhibit dual emissions from both erbiumĀ(III) and ytterbiumĀ(III)
ions. For the EuTb<sub>3</sub>/Eu<sub>3</sub>Tb configurational isomers,
the Tb<sup>III</sup> subunits transfer energy to the Eu<sup>III</sup> centers in the EuTb<sub>3</sub> complex, whereas the Tb<sup>III</sup> ion in the TbEu<sub>3</sub> complex serves mainly as a structural
stabilizer
Hierarchical Assembly and Aggregation-Induced Enhanced Emission of a Pair of Isostructural Zn<sub>14</sub> Clusters
Information of solid-state and solution
structures is crucial in the characterization of molecular clusters
and in advancing the understanding of their diverse properties. [Et<sub>3</sub>NH]<sub>2</sub>[Zn<sub>14</sub>(hmq)<sub>8</sub>(OH)<sub>4</sub>X<sub>10</sub>] [X = Cl and Br; H<sub>2</sub>hmq = 2-(hydroxymethyl)Āquinolin-8-ol]
consist of a peanut-shaped Zn<sub>10</sub>O<sub>12</sub> core, in
which the Zn atoms occupy the faces and corners of an octahedron and
are protected by bonded halogen atoms and bulky organic ligands. Observation
of the [Zn<sub>14</sub>(hmq)<sub>8</sub>(OH)<sub>4</sub>X<sub>10</sub>]<sup>2ā</sup> fragment in electrospray ionization mass spectrometry
(ESI-MS) suggests that the cluster is stable in solution. ESI-MS analyses
from dissolved crystals and mother liquors reveal that ZnĀ(hmq) self-assembles
to Zn<sub>5</sub>(hmq)<sub>4</sub>Cl, then dimerizes through four
[OH]<sup>ā</sup> bridges to Zn<sub>10</sub>(hmq)<sub>8</sub>(OH)<sub>4</sub>Cl<sub>2</sub>, and progressively captures four ZnCl<sub>2</sub> one-by-one to [Zn<sub>14</sub>(hmq)<sub>8</sub>(OH)<sub>4</sub>Cl<sub>10</sub>]<sup>2ā</sup>. Because the supramolecular
interactions between the anion and cation in the solid suppress the
rotation/vibration of the halogen atoms and confine the movable organic
ligands on the rigid ZnāO core, both crystal phases exhibit
intense photoluminescence, much stronger than that in solution. This
is the first coordination cluster to exhibit āaggregation-induced
enhanced emissionā. In addition, preliminary tests indicate
that these coordination clusters are promising for organic-light-emitting-diode
applications