3 research outputs found
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 [M(μ-L)(μ-OAc)Ln(NO<sub>3</sub>)<sub>2</sub>], one nitrate-diphenoxo triply bridged Ni<sup>II</sup>–Tb<sup>III</sup> complex, [Ni(μ-L)(μ-NO<sub>3</sub>)Tb(NO<sub>3</sub>)<sub>2</sub>]·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 [Ni(H<sub>2</sub>O)(μ-L)Ln(NO<sub>3</sub>)<sub>3</sub>]·2CH<sub>3</sub>OH have been prepared in
one pot reaction from the compartmental ligand <i>N</i>,<i>N</i>′,<i>N</i>″-trimethyl-<i>N</i>,<i>N</i>″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine
(H<sub>2</sub>L). Moreover, Ni<sup>II</sup>-Ln<sup>III</sup> complexes
bearing benzoate or 9-anthracenecarboxylate bridging groups of formula
[Ni(μ-L)(μ-BzO)Dy(NO<sub>3</sub>)<sub>2</sub>] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO<sub>3</sub>)<sub>2</sub>]·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 M(μ-O<sub>2</sub>)Ln bridging fragment of ∼22°,
whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly
bridged complexes exhibit more planar structures with hinge angles
of ∼13° and ∼2°, 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 M–(O)<sub>2</sub>–Gd bridging fragment and with
the increase of the Ni–O–Gd 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 ∼1.38 and ∼2.1 cm<sup>–1</sup> for the folded [Ni(μ-L)(μ-OAc)Gd(NO<sub>3</sub>)<sub>2</sub>] and planar [Ni(H<sub>2</sub>O)(μ-L)Gd(NO<sub>3</sub>)<sub>3</sub>]·2CH<sub>3</sub>OH complexes, respectively.
The Ni<sup>II</sup>Dy<sup>III</sup> complexes exhibit slow relaxation
of the magnetization with Δ/<i>k</i><sub>B</sub> energy
barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for
[Ni(μ-L)(μ-BzO)Dy(NO<sub>3</sub>)<sub>2</sub>] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO<sub>3</sub>)<sub>2</sub>]·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 [M(μ-L)(μ-OAc)Ln(NO<sub>3</sub>)<sub>2</sub>], one nitrate-diphenoxo triply bridged Ni<sup>II</sup>–Tb<sup>III</sup> complex, [Ni(μ-L)(μ-NO<sub>3</sub>)Tb(NO<sub>3</sub>)<sub>2</sub>]·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 [Ni(H<sub>2</sub>O)(μ-L)Ln(NO<sub>3</sub>)<sub>3</sub>]·2CH<sub>3</sub>OH have been prepared in
one pot reaction from the compartmental ligand <i>N</i>,<i>N</i>′,<i>N</i>″-trimethyl-<i>N</i>,<i>N</i>″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine
(H<sub>2</sub>L). Moreover, Ni<sup>II</sup>-Ln<sup>III</sup> complexes
bearing benzoate or 9-anthracenecarboxylate bridging groups of formula
[Ni(μ-L)(μ-BzO)Dy(NO<sub>3</sub>)<sub>2</sub>] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO<sub>3</sub>)<sub>2</sub>]·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 M(μ-O<sub>2</sub>)Ln bridging fragment of ∼22°,
whereas nitrate-diphenoxo doubly bridged complexes and diphenoxo-doubly
bridged complexes exhibit more planar structures with hinge angles
of ∼13° and ∼2°, 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 M–(O)<sub>2</sub>–Gd bridging fragment and with
the increase of the Ni–O–Gd 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 ∼1.38 and ∼2.1 cm<sup>–1</sup> for the folded [Ni(μ-L)(μ-OAc)Gd(NO<sub>3</sub>)<sub>2</sub>] and planar [Ni(H<sub>2</sub>O)(μ-L)Gd(NO<sub>3</sub>)<sub>3</sub>]·2CH<sub>3</sub>OH complexes, respectively.
The Ni<sup>II</sup>Dy<sup>III</sup> complexes exhibit slow relaxation
of the magnetization with Δ/<i>k</i><sub>B</sub> energy
barriers under 1000 Oe applied magnetic fields of 9.2 and 10.1 K for
[Ni(μ-L)(μ-BzO)Dy(NO<sub>3</sub>)<sub>2</sub>] and [Ni(μ-L)(μ-9-An)Dy(9-An)(NO<sub>3</sub>)<sub>2</sub>]·3CH<sub>3</sub>CN, respectively
Thermally Activated Delayed Fluorescence (TADF) and Enhancing Photoluminescence Quantum Yields of [Cu<sup>I</sup>(diimine)(diphosphine)]<sup>+</sup> ComplexesPhotophysical, Structural, and Computational Studies
The complexes [Cu(I)(POP)(dmbpy)][BF<sub>4</sub>] (<b>1</b>) and [Cu(I)(POP)(tmbpy)][BF<sub>4</sub>]
(<b>2</b>) (dmbpy = 4,4′-dimethyl-2,2′-bipyridyl;
tmbpy = 4,4′,6,6′-tetramethyl-2,2′-bipyridyl;
POP = bis[2-(diphenylphosphino)-phenyl]ether) have been studied in
a wide temperature range by steady-state and time-resolved emission
spectroscopy in fluid solution, frozen solution, and as solid powders.
Emission quantum yields of up to 74% were observed for <b>2</b> in a rigid matrix (powder), substantially higher than for <b>1</b> of around 9% under the same conditions. Importantly, it
was found that the emission of <b>2</b> at ambient temperature
represents a thermally activated delayed fluorescence (TADF) which
renders the compound to be a good candidate for singlet harvesting
in OLEDs. The role of steric constraints within the complexes, in
particular their influences on the emission quantum yields, were investigated
by hybrid-DFT calculations for the excited triplet state of <b>1</b> and <b>2</b> while manipulating the torsion angle
between the bipyridyl and POP ligands. Both complexes showed similar
flexibility within a ±10° range of the torsion angle; however, <b>2</b> appeared limited to this range, whereas <b>1</b> could
be further twisted with little energy demand. It is concluded that
a restricted flexibility leads to a reduction of nonradiative deactivation
and thus an increase of emission quantum yield