16 research outputs found
Structural Characterization and Luminescence Properties of a Triphosphine-Stabilized Ag<sub>16</sub>Cu<sub>9</sub> Heterometallic Alkynyl Cluster
A triphosphine-stabilized Ag<sub>16</sub>Cu<sub>9</sub> heterometallic
alkynyl cluster complex was prepared by the reaction of polymeric
silverÂ(I) (4-<i>tert</i>-butylphenyl)Âacetylide with a copperÂ(I)
dpepp (dpepp = bisÂ(2-(diphenylphosphino)Âethyl)Âphenylphosphine) complex
and characterized by X-ray crystallography. This Ag<sub>16</sub>Cu<sub>9</sub> heterometallic alkynyl complex exhibits an unprecedented
structural topology stabilized by three auxiliary triphosphine ligands.
The (4-<i>tert</i>-butylphenyl)Âacetylide exhibits five types
of asymmetric bonding modes,
including μ-η<sup>1</sup>, μ-η<sup>1</sup>(σ):η<sup>2</sup>(π), μ<sub>3</sub>-η<sup>1</sup>, μ<sub>3</sub>-η<sup>1</sup>(σ):η<sup>1</sup>(σ):η<sup>2</sup>(π), and η<sup>1</sup>-μ<sub>4</sub>. This Ag<sub>16</sub>Cu<sub>9</sub> complex
exhibits visible to near-infrared luminescence in both fluid CH<sub>2</sub>Cl<sub>2</sub> solution and the solid state
Zn<sup>2+</sup> Responsive Bimodal Magnetic Resonance Imaging and Fluorescent Imaging Probe Based on a Gadolinium(III) Complex
A Zn<sup>2+</sup>-responsive bimodal magnetic resonance
imaging (MRI) and luminescence imaging probe GdL was synthesized.
The relaxivity and luminescence properties were examined. In the presence
of 0.5 equiv of Zn<sup>2+</sup>, the longitudinal relaxivity is increased
from 3.8 mM<sup>–1</sup> s<sup>–1</sup> to 5.9 mM<sup>–1</sup> s<sup>–1</sup> at 23 MHz and 25 °C with
55% enhancement, whereas the fluorescence exhibits a 7-fold increase.
The Zn<sup>2+</sup> responsive imaging probe shows favorable selectivity
and tolerance over a variety of biologically relevant anions and metal
ions in physiological pH range for both relaxivity and luminescence.
In vitro phantom images and confocal fluorescence images in living
cells show that the bimodal Zn<sup>2+</sup> probe can effectively
enhance <i>T</i><sub>1</sub>-weighted imaging contrast and
luminescence imaging effect through Zn<sup>2+</sup> coordination with
excellent cellmembrane permeability and biocompatibility. Spectral
and electrospray ionization mass spectrometry (ESI-MS) studies indicate
that two different Zn<sup>2+</sup>-bound species, (GdL)<sub>2</sub>Zn and GdLZn, are formed when 0.5 and 1 equiv of Zn<sup>2+</sup> are
bound to GdL complex, respectively. Crystal structural determination
and dysprosium-induced <sup>17</sup>O NMR shift (DIS) experiment demonstrate
that the increased molecular weight and the improved molecular rigidity
upon complexation of Zn<sup>2+</sup> with GdL is the primary factor
for relaxivity enhancement. Significant enhancement of the luminescence
is due to a heavy atom effect and much increased molecular rigidity
upon Zn<sup>2+</sup> binding to 8-sulfonamidoquinoline chromophore
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 lanthanideÂ(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 erbiumÂ(III) and ytterbiumÂ(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
Vapochromic and Mechanochromic Phosphorescence Materials Based on a Platinum(II) Complex with 4-Trifluoromethylphenylacetylide
Planar platinumÂ(II) complex PtÂ(Me<sub>3</sub>SiCî—¼CbpyCî—¼CSiMe<sub>3</sub>)Â(Cî—¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub> (<b>6</b>) with 5,5′-bisÂ(trimethylsilylethynyl)-2,2′-bipyridine
and 4-trifluoromethylphenylacetylide exhibits remarkable luminescence
vapochromic and mechanochromic properties and a thermo-triggered luminescence
change. Solid-state <b>6</b> is selectively sensitive to vapors
of oxygen-containing volatile compounds such as tetrahydrofuran (THF),
dioxane, and tetrahydropyrane (THP) with phosphorescence vapochromic
response red shifts from 561
and 608 nm to 698 nm (THF), 689 nm (dioxane), and 715 nm (THP), respectively.
Upon being mechanically ground, desolvated <b>6</b>, <b>6</b>·CH<sub>2</sub>Cl<sub>2</sub>, and <b>6</b>·<sup>1</sup>/<sub>2</sub>CH<sub>2</sub>ClCH<sub>2</sub>Cl exhibit significant
mechanoluminescence red shifts from 561 and 608 nm to 730 nm, while
vapochromic crystalline species <b>6</b>·THF, <b>6</b>·dioxane, or <b>6</b>·THP affords a mechanoluminescence
blue shift from 698 nm (THF), 689 nm (dioxane), or 715 nm (THP) to
645 nm, respectively. When the compounds are heated, a thermo-triggered
luminescence change occurs, in which bright yellow luminescence at
561 and 608 nm turns to red luminescence at 667 nm with a drastic
red shift. The multi-stimulus-responsive luminescence switches have
been monitored by the changes in emission spectra and X-ray diffraction
patterns. Both X-ray crystallographic and density functional theory
studies suggest that the variation in the intermolecular Pt–Pt
interaction is the key factor in inducing an intriguing luminescence
switch
Zn<sup>2+</sup> Responsive Bimodal Magnetic Resonance Imaging and Fluorescent Imaging Probe Based on a Gadolinium(III) Complex
A Zn<sup>2+</sup>-responsive bimodal magnetic resonance
imaging (MRI) and luminescence imaging probe GdL was synthesized.
The relaxivity and luminescence properties were examined. In the presence
of 0.5 equiv of Zn<sup>2+</sup>, the longitudinal relaxivity is increased
from 3.8 mM<sup>–1</sup> s<sup>–1</sup> to 5.9 mM<sup>–1</sup> s<sup>–1</sup> at 23 MHz and 25 °C with
55% enhancement, whereas the fluorescence exhibits a 7-fold increase.
The Zn<sup>2+</sup> responsive imaging probe shows favorable selectivity
and tolerance over a variety of biologically relevant anions and metal
ions in physiological pH range for both relaxivity and luminescence.
In vitro phantom images and confocal fluorescence images in living
cells show that the bimodal Zn<sup>2+</sup> probe can effectively
enhance <i>T</i><sub>1</sub>-weighted imaging contrast and
luminescence imaging effect through Zn<sup>2+</sup> coordination with
excellent cellmembrane permeability and biocompatibility. Spectral
and electrospray ionization mass spectrometry (ESI-MS) studies indicate
that two different Zn<sup>2+</sup>-bound species, (GdL)<sub>2</sub>Zn and GdLZn, are formed when 0.5 and 1 equiv of Zn<sup>2+</sup> are
bound to GdL complex, respectively. Crystal structural determination
and dysprosium-induced <sup>17</sup>O NMR shift (DIS) experiment demonstrate
that the increased molecular weight and the improved molecular rigidity
upon complexation of Zn<sup>2+</sup> with GdL is the primary factor
for relaxivity enhancement. Significant enhancement of the luminescence
is due to a heavy atom effect and much increased molecular rigidity
upon Zn<sup>2+</sup> binding to 8-sulfonamidoquinoline chromophore
Spectroscopic and Phosphorescent Modulation in Triphosphine-Supported PtAg<sub>2</sub> Heterotrinuclear Alkynyl Complexes
A series of highly phosphorescent
PtAg<sub>2</sub> heterotrinuclear alkynyl complexes with bisÂ(diphenylphosphinomethyl)Âphenylphosphine
(dpmp) were prepared and characterized structurally. The solution
phosphorescence with various emitting colors is systematically modulated
by modifying substituents as well as π-conjugated systems in
aromatic acetylides. The crystals, powders, or films exhibit reversible
stimuli-responsive phosphorescence changes upon exposure to vapor
of MeCN, pyridine, DMF, etc., resulting from perturbation of d<sup>8</sup>-d<sup>10</sup> metallophilic interaction in the excited states
as a consequence of the formation/disruption of Ag–solvent
bonds. Both experimental and time-dependent density functional theory
(TD-DFT) studies demonstrate that d<sup>8</sup>-d<sup>10</sup> metallophilic
interaction exerts a crucial role on phosphorescent characteristics
due to the PtAg<sub>2</sub> cluster-based <sup>3</sup>[d →
p] state. This study affords a paradigm for phosphorescence modulation
in d<sup>8</sup>–d<sup>10</sup> heteronuclear complexes
Structures and Phosphorescence Properties of Triphosphine-Supported Au<sub>2</sub>Ag<sub>2</sub> and Au<sub>8</sub>Ag<sub>4</sub> Alkynyl Cluster Complexes
The synthesis, structure, and phosphorescence properties of two
families of triphosphine-supported AuÂ(I)–AgÂ(I) heteronuclear
alkynyl cluster complexes with unprecedented Au<sub>2</sub>Ag<sub>2</sub> and Au<sub>8</sub>Ag<sub>4</sub> cluster structures are described.
The phosphorescence emission over the whole visible light region was
systematically tuned through modification of the electronic effects
in aromatic acetylide ligands to attain bright phosphorescence with
different luminescent colors. Introduction of electron-withdrawing
CF<sub>3</sub> to phenylacetylides results in the emission spectral
blue-shift, while it shows progressive red-shift upon introducing
electron-donating Bu<sup>t</sup>, OMe, or NMe<sub>2</sub>. As demonstrated
from both experimental and theoretical studies, the phosphorescence
arises primarily from <sup>3</sup>LLCT/<sup>3</sup>IL and Au<sub>2</sub>Ag<sub>2</sub>/Au<sub>8</sub>Ag<sub>4</sub> cluster-centered <sup>3</sup>[d→p] transitions
Metal Complexes with a Hexadentate Macrocyclic Diamine-Tetracarbene Ligand
A hexadentate macrocyclic
N-heterocyclic carbene (NHC) ligand precursor (H<sub>4</sub>L)Â(PF<sub>6</sub>)<sub>4</sub> containing four benzimidazolium and two secondary
amine groups, has been synthesized and characterized. Coordination
chemistry of this new macrocyclic diamine-tetracarbene ligand has
been studied by the synthesis of its AgÂ(I), AuÂ(I), NiÂ(II), and PdÂ(II)
complexes. Reactions of (H<sub>4</sub>L)Â(PF<sub>6</sub>)<sub>4</sub> with different equiv of Ag<sub>2</sub>O result in AgÂ(I) complexes
[AgÂ(H<sub>2</sub>L)]Â(PF<sub>6</sub>)<sub>3</sub> (<b>1</b>)
and [Ag<sub>2</sub>(H<sub>2</sub>L)]Â(PF<sub>6</sub>)<sub>4</sub> (<b>2</b>). A mononuclear AuÂ(I) complex [AuÂ(H<sub>2</sub>L)]Â(PF<sub>6</sub>)<sub>3</sub> (<b>3</b>) and a trinuclear AuÂ(I) complex
[Au<sub>3</sub>(H<sub>2</sub>L)Â(Cl)<sub>2</sub>]Â(PF<sub>6</sub>) (<b>4</b>) are obtained by transmetalation of <b>1</b> and <b>2</b> with AuClÂ(SMe<sub>2</sub>), respectively. Reactions of (H<sub>4</sub>L)Â(PF<sub>6</sub>)<sub>4</sub> with NiÂ(OAc)<sub>2</sub> and
PdÂ(OAc)<sub>2</sub> in the presence of NaOAc yield [NiÂ(L)]Â(PF<sub>6</sub>)<sub>2</sub> (<b>5</b>) and [PdÂ(L)]Â(PF<sub>6</sub>)<sub>2</sub> (<b>6</b>), respectively, containing one NiÂ(II) and
PdÂ(II) ion with distorted square-planar geometry. Using more NaOAc
results in the formation of unusual dinuclear complexes [Ni<sub>2</sub>(L–2H)]Â(PF<sub>6</sub>)<sub>2</sub> (<b>7</b>) and [Pd<sub>2</sub>(L–2H)]Â(PF<sub>6</sub>)<sub>2</sub> (<b>8</b>) (L–2H = deprotonated ligand after removing two H<sup>+</sup> ions from two secondary amine groups in L), respectively, featuring
a rare M<sub>2</sub>N<sub>2</sub> core formed by two bridging amides. <b>7</b> is also formed by the reaction of <b>5</b> with 1.0
equiv of NiÂ(OAc)<sub>2</sub>·4H<sub>2</sub>O in the presence
of NaOAc. Transmetalation of <b>2</b> with 2.0 equiv of NiÂ(PPh<sub>3</sub>)<sub>2</sub>Cl<sub>2</sub> gives [Ni<sub>2</sub>(L)Â(μ-O)]Â(PF<sub>6</sub>)<sub>2</sub> (<b>9</b>), the first example of a dinuclear
NiÂ(II) complex with a singly bridging oxo group. <b>9</b> is
converted to <b>7</b> in good yield through the treatment with
NaOAc
Phosphorescent PtAu<sub>2</sub> Complexes with Differently Positioned Carbazole–Acetylide Ligands for Solution-Processed Organic Light-Emitting Diodes with External Quantum Efficiencies of over 20%
The utilization of
phosphorescent metal cluster complexes as new
types of emitting materials in organic light-emitting diodes (OLEDs)
is becoming an alternative and viable approach for achieving high-efficiency
electroluminescence. We report herein the design of cationic PtAu<sub>2</sub> cluster complexes with differently positioned 9-phenylcarbazole–acetylides
to serve as phosphorescent emitters in OLEDs. The rigid structures
of PtAu<sub>2</sub> complexes cause intense phosphorescence with quantum
yields of over 85%, which originates from <sup>3</sup>[Ï€Â(phenylcarbazole–acetylide)
→ Ï€*Â(dpmp)] ligand-to-ligand and <sup>3</sup>[Ï€Â(phenylcarbazole–acetylide)
→ p/sÂ(PtAu<sub>2</sub>)] ligand-to-metal charge-transfer triplet
excited states. When 8 wt % PtAu<sub>2</sub> is doped to blended host
materials of TCTA and OXD-7 (2:1 weight ratio) as light-emitting layers,
solution-processed OLEDs give a current efficiency of 78.2 cd A<sup>–1</sup> and an external quantum efficiency (EQE) of 21.5%
at a practical luminance of 1029 cd m<sup>–2</sup> with a slow
efficiency roll-off upon increasing luminance. This represents the
best device performance and the highest efficiency recorded at practical
luminance for solution-processed OLEDs
<i>RBMS3</i> arrests cell cycle at the G1/S checkpoint.
<p>(<b>A</b>) Representative and summary of DNA content detected by flow cytometry showed that the percentage of cells in the S phase was lower while the percentage of cells in the G1 phase was higher in SUNE1-RBMS3 cells than that in SUNE1-V1 cells. (* p<0.05, Student’s <i>t</i>-test). Values were expressed as mean ± SD of three independent experiments. (<b>B</b>) Protein expressions of cyclin D1, cyclin E, CDK2, p53, p21, Rb and Rb (Ser780) were compared between <i>RBMS3</i>- and empty vector-transfected NPC cells. β-actin was used as a loading control.</p