3 research outputs found
Bifunctional Zn<sup>II</sup>Ln<sup>III</sup> Dinuclear Complexes Combining Field Induced SMM Behavior and Luminescence: Enhanced NIR Lanthanide Emission by 9āAnthracene Carboxylate Bridging Ligands
There
were new dinuclear Zn<sup>II</sup>āLn<sup>III</sup> complexes
of general formulas [ZnĀ(Ī¼-L)Ā(Ī¼-OAc)ĀLnĀ(NO<sub>3</sub>)<sub>2</sub>] (Ln<sup>III</sup> = Tb (<b>1</b>), Dy (<b>2</b>), Er (<b>3</b>), and Yb (<b>4</b>)), [ZnĀ(Ī¼-L)Ā(Ī¼-NO<sub>3</sub>)ĀErĀ(NO<sub>3</sub>)<sub>2</sub>] (<b>5</b>), [ZnĀ(H<sub>2</sub>O)Ā(Ī¼-L)ĀNdĀ(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>OH (<b>6</b>), [ZnĀ(Ī¼-L)Ā(Ī¼-9-An)ĀLnĀ(NO<sub>3</sub>)<sub>2</sub>]Ā·2CH<sub>3</sub>CN (Ln<sup>III</sup> =
Tb (<b>7</b>), Dy (<b>8</b>), Er (<b>9</b>), YbĀ(<b>10</b>)), [ZnĀ(Ī¼-L)Ā(Ī¼-9-An)ĀYbĀ(9-An)Ā(NO<sub>3</sub>)<sub>3</sub>]Ā·3CH<sub>3</sub>CN (<b>11</b>), [ZnĀ(Ī¼-L)Ā(Ī¼-9-An)ĀNdĀ(9-An)Ā(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>CNĀ·3H<sub>2</sub>O
(<b>12</b>), and [ZnĀ(Ī¼-L)Ā(Ī¼-9-An)ĀNdĀ(CH<sub>3</sub>OH)<sub>2</sub>(NO<sub>3</sub>)]ĀClO<sub>4</sub>Ā·2CH<sub>3</sub>OH (<b>13</b>) prepared from the reaction of the compartmental
ligand <i>N,N</i>ā²<i>,N</i>ā³-trimethyl-<i>N,N</i>ā³-bisĀ(2-hydroxy-3-methoxy-5-methylbenzyl)Ādiethylenetriamine
(H<sub>2</sub>L), with ZnX<sub>2</sub>Ā·<i>n</i>H<sub>2</sub>O (X = NO<sub>3</sub><sup>ā</sup> or OAc<sup>ā</sup>) salts, LnĀ(NO<sub>3</sub>)<sub>3</sub>Ā·<i>n</i>H<sub>2</sub>O, and, in some instances, 9-anthracenecarboxylate anion (9-An).
In all these complexes, the Zn<sup>II</sup> ions invariably occupy
the internal N<sub>3</sub>O<sub>2</sub> site whereas the Ln<sup>III</sup> ions show preference for the O<sub>4</sub> external site, giving
rise to a ZnĀ(Ī¼-diphenoxo)ĀLn bridging fragment. Depending on
the Zn<sup>II</sup> salt and solvent used in the reaction, a third
bridge can connect the Zn<sup>II</sup> and Ln<sup>III</sup> metal
ions, giving rise to triple-bridged diphenoxoacetate in complexes <b>1</b>ā<b>4</b>, diphenoxonitrate in complex <b>5</b>, and diphenoxoĀ(9-anthracenecarboxylate) in complexes <b>8</b>ā<b>13</b>. Dy<sup>III</sup> and Er<sup>III</sup> complexes <b>2</b>, <b>8</b> and <b>3</b>, <b>5</b>, respectively, exhibit field induced single molecule magnet
(SMM) behavior, with <i>U</i><sub>eff</sub> values ranging
from 11.7 (3) to 41(2) K. Additionally, the solid-state photophysical
properties of these complexes are presented showing that ligand L<sup>2ā</sup> is able to sensitize Tb<sup>III</sup>- and Dy<sup>III</sup>-based luminescence in the visible region through an energy
transfer process (antenna effect). The efficiency of this process
is much lower when NIR emitters such as Er<sup>III</sup>, Nd<sup>III</sup>, and Yb<sup>III</sup> are considered. When the luminophore 9-anthracene
carboxylate is incorporated into these complexes, the NIR luminescence
is enhanced which proves the efficiency of this bridging ligand to
act as antenna group. Complexes <b>2</b>, <b>3</b>, <b>5</b>, and <b>8</b> can be considered as dual materials
as they combine SMM behavior and luminescent properties
Family of Carboxylate- and Nitrate-diphenoxo Triply Bridged Dinuclear Ni<sup>II</sup>Ln<sup>III</sup> Complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): Synthesis, Experimental and Theoretical Magneto-Structural Studies, and Single-Molecule Magnet Behavior
Seven acetate-diphenoxo triply bridged M<sup>II</sup>-Ln<sup>III</sup> complexes (M<sup>II</sup> = Ni<sup>II</sup> and
Ln<sup>III</sup> = Gd, Tb, Ho, Er, and Y; M<sup>II</sup> = Zn<sup>II</sup> and Ln<sup>III</sup> = Ho<sup>III</sup> and Er<sup>III</sup>) of formula [MĀ(Ī¼-L)Ā(Ī¼-OAc)ĀLnĀ(NO<sub>3</sub>)<sub>2</sub>], one nitrate-diphenoxo triply bridged Ni<sup>II</sup>āTb<sup>III</sup> complex, [NiĀ(Ī¼-L)Ā(Ī¼-NO<sub>3</sub>)ĀTbĀ(NO<sub>3</sub>)<sub>2</sub>]Ā·2CH<sub>3</sub>OH, and
two diphenoxo doubly bridged Ni<sup>II</sup>-Ln<sup>III</sup> complexes
(Ln<sup>III</sup> = Eu, Gd) of formula [NiĀ(H<sub>2</sub>O)Ā(Ī¼-L)ĀLnĀ(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>OH have been prepared in
one pot reaction from the compartmental ligand <i>N</i>,<i>N</i>ā²,<i>N</i>ā³-trimethyl-<i>N</i>,<i>N</i>ā³-bisĀ(2-hydroxy-3-methoxy-5-methylbenzyl)Ādiethylenetriamine
(H<sub>2</sub>L). Moreover, Ni<sup>II</sup>-Ln<sup>III</sup> complexes
bearing benzoate or 9-anthracenecarboxylate bridging groups of formula
[NiĀ(Ī¼-L)Ā(Ī¼-BzO)ĀDyĀ(NO<sub>3</sub>)<sub>2</sub>] and [NiĀ(Ī¼-L)Ā(Ī¼-9-An)ĀDyĀ(9-An)Ā(NO<sub>3</sub>)<sub>2</sub>]Ā·3CH<sub>3</sub>CN have also been successfully
synthesized. In acetate-diphenoxo triply bridged complexes, the acetate
bridging group forces the structure to be folded with an average hinge
angle in the MĀ(Ī¼-O<sub>2</sub>)ĀLn bridging fragment of ā¼22Ā°,
whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly
bridged complexes exhibit more planar structures with hinge angles
of ā¼13Ā° and ā¼2Ā°, respectively. All Ni<sup>II</sup>-Ln<sup>III</sup> complexes exhibit ferromagnetic interactions
between Ni<sup>II</sup> and Ln<sup>III</sup> ions and, in the case
of the Gd<sup>III</sup> complexes, the <i>J</i><sub>NiGd</sub> coupling increases weakly but significantly with the planarity of
the Mā(O)<sub>2</sub>āGd bridging fragment and with
the increase of the NiāOāGd angle. Density functional
theory (DFT) theoretical calculations on the Ni<sup>II</sup>Gd<sup>III</sup> complexes and model compounds support these magneto-structural
correlations as well as the experimental <i>J</i><sub>NiGd</sub> values, which were found to be ā¼1.38 and ā¼2.1 cm<sup>ā1</sup> for the folded [NiĀ(Ī¼-L)Ā(Ī¼-OAc)ĀGdĀ(NO<sub>3</sub>)<sub>2</sub>] and planar [NiĀ(H<sub>2</sub>O)Ā(Ī¼-L)ĀGdĀ(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>OH complexes, respectively.
The Ni<sup>II</sup>Dy<sup>III</sup> complexes exhibit slow relaxation
of the magnetization with Ī/<i>k</i><sub>B</sub> energy
barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for
[NiĀ(Ī¼-L)Ā(Ī¼-BzO)ĀDyĀ(NO<sub>3</sub>)<sub>2</sub>] and [NiĀ(Ī¼-L)Ā(Ī¼-9-An)ĀDyĀ(9-An)Ā(NO<sub>3</sub>)<sub>2</sub>]Ā·3CH<sub>3</sub>CN, respectively
Family of Carboxylate- and Nitrate-diphenoxo Triply Bridged Dinuclear Ni<sup>II</sup>Ln<sup>III</sup> Complexes (Ln = Eu, Gd, Tb, Ho, Er, Y): Synthesis, Experimental and Theoretical Magneto-Structural Studies, and Single-Molecule Magnet Behavior
Seven acetate-diphenoxo triply bridged M<sup>II</sup>-Ln<sup>III</sup> complexes (M<sup>II</sup> = Ni<sup>II</sup> and
Ln<sup>III</sup> = Gd, Tb, Ho, Er, and Y; M<sup>II</sup> = Zn<sup>II</sup> and Ln<sup>III</sup> = Ho<sup>III</sup> and Er<sup>III</sup>) of formula [MĀ(Ī¼-L)Ā(Ī¼-OAc)ĀLnĀ(NO<sub>3</sub>)<sub>2</sub>], one nitrate-diphenoxo triply bridged Ni<sup>II</sup>āTb<sup>III</sup> complex, [NiĀ(Ī¼-L)Ā(Ī¼-NO<sub>3</sub>)ĀTbĀ(NO<sub>3</sub>)<sub>2</sub>]Ā·2CH<sub>3</sub>OH, and
two diphenoxo doubly bridged Ni<sup>II</sup>-Ln<sup>III</sup> complexes
(Ln<sup>III</sup> = Eu, Gd) of formula [NiĀ(H<sub>2</sub>O)Ā(Ī¼-L)ĀLnĀ(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>OH have been prepared in
one pot reaction from the compartmental ligand <i>N</i>,<i>N</i>ā²,<i>N</i>ā³-trimethyl-<i>N</i>,<i>N</i>ā³-bisĀ(2-hydroxy-3-methoxy-5-methylbenzyl)Ādiethylenetriamine
(H<sub>2</sub>L). Moreover, Ni<sup>II</sup>-Ln<sup>III</sup> complexes
bearing benzoate or 9-anthracenecarboxylate bridging groups of formula
[NiĀ(Ī¼-L)Ā(Ī¼-BzO)ĀDyĀ(NO<sub>3</sub>)<sub>2</sub>] and [NiĀ(Ī¼-L)Ā(Ī¼-9-An)ĀDyĀ(9-An)Ā(NO<sub>3</sub>)<sub>2</sub>]Ā·3CH<sub>3</sub>CN have also been successfully
synthesized. In acetate-diphenoxo triply bridged complexes, the acetate
bridging group forces the structure to be folded with an average hinge
angle in the MĀ(Ī¼-O<sub>2</sub>)ĀLn bridging fragment of ā¼22Ā°,
whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly
bridged complexes exhibit more planar structures with hinge angles
of ā¼13Ā° and ā¼2Ā°, respectively. All Ni<sup>II</sup>-Ln<sup>III</sup> complexes exhibit ferromagnetic interactions
between Ni<sup>II</sup> and Ln<sup>III</sup> ions and, in the case
of the Gd<sup>III</sup> complexes, the <i>J</i><sub>NiGd</sub> coupling increases weakly but significantly with the planarity of
the Mā(O)<sub>2</sub>āGd bridging fragment and with
the increase of the NiāOāGd angle. Density functional
theory (DFT) theoretical calculations on the Ni<sup>II</sup>Gd<sup>III</sup> complexes and model compounds support these magneto-structural
correlations as well as the experimental <i>J</i><sub>NiGd</sub> values, which were found to be ā¼1.38 and ā¼2.1 cm<sup>ā1</sup> for the folded [NiĀ(Ī¼-L)Ā(Ī¼-OAc)ĀGdĀ(NO<sub>3</sub>)<sub>2</sub>] and planar [NiĀ(H<sub>2</sub>O)Ā(Ī¼-L)ĀGdĀ(NO<sub>3</sub>)<sub>3</sub>]Ā·2CH<sub>3</sub>OH complexes, respectively.
The Ni<sup>II</sup>Dy<sup>III</sup> complexes exhibit slow relaxation
of the magnetization with Ī/<i>k</i><sub>B</sub> energy
barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for
[NiĀ(Ī¼-L)Ā(Ī¼-BzO)ĀDyĀ(NO<sub>3</sub>)<sub>2</sub>] and [NiĀ(Ī¼-L)Ā(Ī¼-9-An)ĀDyĀ(9-An)Ā(NO<sub>3</sub>)<sub>2</sub>]Ā·3CH<sub>3</sub>CN, respectively