24 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
silverĀ(I) (4-<i>tert</i>-butylphenyl)Āacetylide with a copperĀ(I)
dpepp (dpepp = bisĀ(2-(diphenylphosphino)Āethyl)Āphenylphosphine) 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)Āacetylide exhibits five types
of asymmetric bonding modes,
including Ī¼-Ī·<sup>1</sup>, Ī¼-Ī·<sup>1</sup>(Ļ):Ī·<sup>2</sup>(Ļ), Ī¼<sub>3</sub>-Ī·<sup>1</sup>, Ī¼<sub>3</sub>-Ī·<sup>1</sup>(Ļ):Ī·<sup>1</sup>(Ļ):Ī·<sup>2</sup>(Ļ), and Ī·<sup>1</sup>-Ī¼<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
Tetranuclear Gadolinium(III) Porphyrin Complex as a Theranostic Agent for Multimodal Imaging and Photodynamic Therapy
We
describe herein the elaborate design of a GdĀ(III)āporphyrin
complex as a theranostic agent for multimodal imaging and photodynamic
therapy. Far-red-emitting (665 nm) and high relaxivity (14.1 mM<sup>ā1</sup> s<sup>ā1</sup>) with 107% increase upon binding to HSA (human
serum albumin) (29.2 mM<sup>ā1</sup> s<sup>ā1</sup>)
together with efficiently generating singlet oxygen upon exposure
to far-red light irradiation at 650 Ā± 20 nm demonstrate that
this GdĀ(III)āporphyrin complex with four GdĀ(III)āDTTA
units bound to tetraphenylporphyrin acts as a potentially theranostic
agent with excellent performance for magnetic resonance imaging, optical
imaging, and photodynamic therapy
Multiphotochromism in an Asymmetric Ruthenium Complex with Two Different Dithienylethenes
An asymmetric bisĀ(dithienylethene-acetylide)
rutheniumĀ(II) complex <i>trans</i>-RuĀ(dppe)<sub>2</sub>(L1o)Ā(L2o)
(<b>1oo</b>) incorporating two different dithienyletheneāacetylides
(L1o and L2o) was designed to modulate multistate photochromism in
view of the well separated ring-closing absorption bands between L1o
and L2o. Upon irradiation with appropriate wavelengths of light, complex <b>1</b> undergoes stepwise photocyclization and selective photocycloreversion
to afford four states (<b>1oo</b>, <b>1co</b>, <b>1oc</b>, and <b>1cc</b>). As a contrast, symmetric complexes <i>trans</i>-RuĀ(dppe)<sub>2</sub>(L1o)<sub>2</sub> (<b>2oo</b>) and <i>trans</i>-RuĀ(dppe)<sub>2</sub>(L2o)<sub>2</sub> (<b>3oo</b>) with two identical dithienylethene-acetylides
were synthesized, and the corresponding photochromic behavior was
investigated. The photochromic properties of the oxidized species
(<b>1oo</b><sup><b>+</b></sup>/<b>1co</b><sup><b>+</b></sup>/<b>1oc</b><sup><b>+</b></sup>/<b>1cc</b><sup><b>+</b></sup>, <b>2oo</b><sup><b>+</b></sup>/<b>2co</b><sup><b>+</b></sup>/<b>2cc</b><sup><b>+</b></sup>, and <b>3oo</b><sup><b>+</b></sup>/<b>3co</b><sup><b>+</b></sup>/<b>3cc</b><sup><b>+</b></sup>) were also investigated. The ring-closing absorption bands
of one-electron oxidized species <b>1oo</b><sup><b>+</b></sup>, <b>2oo</b><sup><b>+</b></sup>, and <b>3oo</b><sup><b>+</b></sup> show obvious blue shifts relative to those
of <b>1oo</b>, <b>2oo</b>, and <b>3oo</b>, respectively.
The ring-closing absorption bands in both neutral and oxidized species
grow progressively following <b>oo</b> ā <b>oc</b>/<b>co</b> ā <b>cc</b> and <b>oo</b><sup><b>+</b></sup> ā <b>oc</b><sup><b>+</b></sup>/<b>co</b><sup><b>+</b></sup> ā <b>cc</b><sup><b>+</b></sup>. As revealed by spectroscopic, electrochemical,
and computational studies, complex <b>1</b> displays eight switchable
states through stepwise photocyclization, selective cycloreversion,
and a reversible redox process
Electrochemical, Spectroscopic, and Theoretical Studies on Diethynyl Ligand Bridged Ruthenium Complexes with 1,3-Bis(2-pyridylimino)isoindolate
A series
of ruthenium acetylide complexes [RuĀ(BPI)Ā(PPh<sub>3</sub>)<sub>2</sub>(Cī¼CR)] (BPI = 1,3-bisĀ(2-pyridylimino)Āisoindolate;
R = āC<sub>6</sub>H<sub>5</sub> (<b>2</b>), āCp<sub>2</sub>Fe (<b>3a</b>), āC<sub>6</sub>H<sub>4</sub>C<sub>6</sub>H<sub>4</sub>Cī¼CCp<sub>2</sub>Fe (<b>3b</b>))
and bisĀ(acetylide)-linked binuclear ruthenium complexes [{RuĀ(BPI)Ā(PPh<sub>3</sub>)<sub>2</sub>}<sub>2</sub>(Cī¼CRCī¼C)] (R = none
(<b>4</b>), 1,4-benzenediyl (<b>5</b>), 1,4-naphthalenediyl
(<b>6</b>), 9,10-anthracenediyl (<b>7</b>)) were synthesized
and characterized by ESI-MS spectrometry, IR, <sup>1</sup>H and <sup>31</sup>P NMR, and UVāvisānear-IR spectroscopy, and
cyclic and differential pulse voltammetry. Oxidation of <b>3</b>ā<b>7</b> with 1 equiv of ferrocenium perchlorate afforded
the corresponding one-electron-oxidized complexes <b>3</b><sup>+</sup>ā<b>7</b><sup>+</sup>. In contrast to the case
for <b>3a</b><sup><b>+</b></sup>, where spin density is
localized at the Fe center due to moderate electronic communication
between Ru<sup>II</sup> and Fe<sup>III</sup> centers along the RuāCī¼CāCp<sub>2</sub>Fe backbone, the spin density is primarily populated on Ru
for <b>3b</b><sup><b>+</b></sup> without an appreciable
electronic interaction between Ru<sup>III</sup> and Fe<sup>II</sup> across the quite long bridging system RuCī¼CC<sub>6</sub>H<sub>4</sub>C<sub>6</sub>H<sub>4</sub>Cī¼CCp<sub>2</sub>Fe. For
bisĀ(acetylide)-linked binuclear ruthenium complexes <b>4</b>ā<b>7</b>, electrochemical, UVāvisānear-IR
spectral and TD-DFT computational studies reveal that electronic delocalization
along the bridging RuCī¼CRCī¼CRu backbone is highly dependent
on the R spacer. It is demonstrated that with the gradual increase
of a Ļ-conjugated system in aromatic R spacer, the electronic
delocalization shows progressive enhancement along the RuāCī¼CRCī¼CāRu
backbone due to an increasing participation of the bridging ligand. <b>4</b><sup>+</sup> displays highly electronically delocalized behavior,
whereas <b>5</b><sup>+</sup>ā<b>7</b><sup>+</sup> are on the borderline of electronic delocalization
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
Photophysical and Electroluminescent Properties of PtAg<sub>2</sub> Acetylide Complexes Supported with <i>meso</i>- and <i>rac</i>-Tetraphosphine
1,2-BisĀ[[(diphenylphosphino)Āmethyl]Ā(phenyl)Āphosphino]Āethane
(dpmppe) was prepared as a new tetraphosphine, and the corresponding <i>rac</i> and <i>meso</i> stereoisomers were successfully
separated in view of their solubility difference in acetone. The substitution
of PPh<sub>3</sub> into PtĀ(PPh<sub>3</sub>)<sub>2</sub>(Cī¼CR)<sub>2</sub> (R = aryl) with <i>rac</i>- or <i>meso</i>-dpmppe gives PtĀ(<i>rac</i>-dpmppe)Ā(Cī¼CR)<sub>2</sub> or PtĀ(<i>meso</i>-dpmppe)Ā(Cī¼CR)<sub>2</sub>, respectively.
Using PtĀ(<i>rac</i>-dpmppe)Ā(Cī¼CR)<sub>2</sub> or
PtĀ(<i>meso</i>-dpmppe)Ā(Cī¼CR)<sub>2</sub> as a precursor,
PtAg<sub>2</sub> heterotrinuclear cluster complexes were synthesized
and characterized by X-ray crystallography. Depending on the conformations
of tetraphosphine, the structures of PtAg<sub>2</sub> complexes supported
with <i>rac</i>- and <i>meso</i>-dpmppe are quite
different. The higher molecular rigidity of <i>rac</i>-dpmppe-supported
PtAg<sub>2</sub> complexes results in stronger phosphorescent emission
than that of PtAg<sub>2</sub> species with <i>meso</i>-dpmppe.
The high phosphorescent quantum yields (as high as 90.5%) in doping
films warrant these PtAg<sub>2</sub> complexes as excellent phosphorescent
dopants in organic light-emitting diodes (OLEDs). The peak current
and external quantum efficiencies in solution-processed OLEDs are
61.0 cd A<sup>ā1</sup> and 18.1%, respectively. Electroluminescence
was elaborately modulated by modifying the substituent in aromatic
acetylide and the conformations in tetraphosphine so as to achieve
cyan, green, green-yellow, yellow, and orange-red emission
Luminescent Vapochromism Due to a Change of the Ligand Field in a One-Dimensional Manganese(II) Coordination Polymer
The
reactions of MnBr<sub>2</sub> and ethane-1,2-diylbisĀ(diphenylphosphine
oxide) (dppeO<sub>2</sub>) in dichloromethaneāmethanol solutions
gave colorless crystals with the general chemical formulas [MnBr<sub>2</sub>(dppeO<sub>2</sub>)]<sub><i>n</i></sub> (<b>1</b>), [MnBr<sub>2</sub>(dppeO<sub>2</sub>)Ā(DMF)]<sub><i>n</i></sub> (<b>1a</b>), [MnĀ(dppeO<sub>2</sub>)<sub>3</sub>]Ā[MnBr<sub>4</sub>] (<b>2</b>), and Mn<sub>2</sub>Br<sub>4</sub>(dppeO<sub>2</sub>)<sub>2</sub> (<b>3</b>) depending on the crystallization
conditions. Compounds <b>1</b> and <b>1a</b> display one-dimensional
chain structures composed of MnĀ(II) ions linked by bridging dppeO<sub>2</sub> to exhibit tetrahedral (<b>1</b>) or trigonal-bipyramidal
(<b>1a</b>) coordination geometry, whereas <b>3</b> exhibits
a cyclic dinuclear structure with two MnĀ(II) centers bridged by double
dppeO<sub>2</sub> to adopt tetrahedral geometry. Compound <b>2</b> consists of octahedrally coordinated cation [MnĀ(dppeO<sub>2</sub>)<sub>3</sub>]<sup>2+</sup> and tetrahedrally arranged anion [MnBr<sub>4</sub>]<sup>2ā</sup>. While <b>1</b> and <b>3</b> in crystalline and powder states are highly luminescent with green
emission bands centered at ca. 510 nm, <b>2</b> shows intense
orange luminescence peaking at 594 nm. Upon exposure of <b>1</b> to <i>N</i>,<i>N</i>-dimethylformamide vapor,
the green emission centered at 510 nm is converted to red luminescence
peaking at 630 nm, ascribed to the formation of DMF-coordinated compound <b>1a</b> with a trigonal-bipyramidal ligand field, as demonstrated
by X-ray crystallography. Red-emitting <b>1a</b> could be reverted
to the original green-emitting <b>1</b> with a tetrahedral ligand
field upon heat at 160 Ā°C, and such a reversible conversion could
be perfectly repeated for several cycles. A new mechanism of luminescent
vapochromism is thus proposed because of the reversible conversion
of ligand fields in manganeseĀ(II) complexes
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>ā1</sup> s<sup>ā1</sup> to 5.9 mM<sup>ā1</sup> s<sup>ā1</sup> at 23 MHz and 25 Ā°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
Vapochromic and Mechanochromic Phosphorescence Materials Based on a Platinum(II) Complex with 4-Trifluoromethylphenylacetylide
Planar platinumĀ(II) complex PtĀ(Me<sub>3</sub>SiCī¼CbpyCī¼CSiMe<sub>3</sub>)Ā(Cī¼CC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4)<sub>2</sub> (<b>6</b>) with 5,5ā²-bisĀ(trimethylsilylethynyl)-2,2ā²-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>Ā·CH<sub>2</sub>Cl<sub>2</sub>, and <b>6</b>Ā·<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>Ā·THF, <b>6</b>Ā·dioxane, or <b>6</b>Ā·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 PtāPt
interaction is the key factor in inducing an intriguing luminescence
switch
Gold(I)-Coordination Triggered Multistep and Multiple Photochromic Reactions in Multi-Dithienylethene (DTE) Systems
The preparation, characterization, and photochromic properties
of a mononuclear goldĀ(I) complex (<b>1oo</b>) with two identical
DTE-acetylides and a dinuclear goldĀ(I) complex (<b>2ooo</b>)
with both DTE-acetylide and DTE-diphosphine are described. Both goldĀ(I)
complexes exhibit multistep and multiple photocyclization/cycloreversion
reactions. Particularly, four-state and four-color photochromic switch
is successfully achieved for the dinuclear goldĀ(I) complex upon irradiation
with appropriate wavelengths of light. In contrast, fully ring-closed
form is unattained through multiple photocyclization for the two corresponding
model organic compounds coupling with the same DTE units as goldĀ(I)
complexes but without goldĀ(I)-participation. It is demonstrated that
coordination of goldĀ(I) ion to DTE-acetylides exerts indeed a crucial
role in achieving stepwise and selective photocyclization and cycloreversion
reactions for both goldĀ(I) complexes, in which the coordinated goldĀ(I)
atom acts as an effective ābarrierā to prohibit intramolecular
energy transfer between multi-DTE moieties