13 research outputs found
Multiphotochromism in an Asymmetric Ruthenium Complex with Two Different Dithienylethenes
An asymmetric bisÂ(dithienylethene-acetylide)
rutheniumÂ(II) complex <i>trans</i>-RuÂ(dppe)<sub>2</sub>(L1o)Â(L2o)
(<b>1oo</b>) incorporating two different dithienylethene–acetylides
(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>-RuÂ(dppe)<sub>2</sub>(L1o)<sub>2</sub> (<b>2oo</b>) and <i>trans</i>-RuÂ(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> → <b>oc</b>/<b>co</b> → <b>cc</b> and <b>oo</b><sup><b>+</b></sup> → <b>oc</b><sup><b>+</b></sup>/<b>co</b><sup><b>+</b></sup> → <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 [RuÂ(BPI)Â(PPh<sub>3</sub>)<sub>2</sub>(Cî—¼CR)] (BPI = 1,3-bisÂ(2-pyridylimino)Âisoindolate;
R = −C<sub>6</sub>H<sub>5</sub> (<b>2</b>), −Cp<sub>2</sub>Fe (<b>3a</b>), −C<sub>6</sub>H<sub>4</sub>C<sub>6</sub>H<sub>4</sub>CCCp<sub>2</sub>Fe (<b>3b</b>))
and bisÂ(acetylide)-linked binuclear ruthenium complexes [{RuÂ(BPI)Â(PPh<sub>3</sub>)<sub>2</sub>}<sub>2</sub>(Cî—¼CRCî—¼C)] (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 UV–vis–near-IR spectroscopy, and
cyclic and differential pulse voltammetry. Oxidation of <b>3</b>–<b>7</b> with 1 equiv of ferrocenium perchlorate afforded
the corresponding one-electron-oxidized complexes <b>3</b><sup>+</sup>–<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 Ru–CC–Cp<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 RuCî—¼CC<sub>6</sub>H<sub>4</sub>C<sub>6</sub>H<sub>4</sub>Cî—¼CCp<sub>2</sub>Fe. For
bisÂ(acetylide)-linked binuclear ruthenium complexes <b>4</b>–<b>7</b>, electrochemical, UV–vis–near-IR
spectral and TD-DFT computational studies reveal that electronic delocalization
along the bridging RuCî—¼CRCî—¼CRu backbone is highly dependent
on the R spacer. It is demonstrated that with the gradual increase
of a π-conjugated system in aromatic R spacer, the electronic
delocalization shows progressive enhancement along the Ru–CCRCC–Ru
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>–<b>7</b><sup>+</sup> are on the borderline of electronic delocalization
Photophysical and Electroluminescent Properties of PtAg<sub>2</sub> Acetylide Complexes Supported with <i>meso</i>- and <i>rac</i>-Tetraphosphine
1,2-BisÂ[[(diphenylphosphino)Âmethyl]Â(phenyl)Âphosphino]Âethane
(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 PtÂ(PPh<sub>3</sub>)<sub>2</sub>(Cî—¼CR)<sub>2</sub> (R = aryl) with <i>rac</i>- or <i>meso</i>-dpmppe gives PtÂ(<i>rac</i>-dpmppe)Â(Cî—¼CR)<sub>2</sub> or PtÂ(<i>meso</i>-dpmppe)Â(Cî—¼CR)<sub>2</sub>, respectively.
Using PtÂ(<i>rac</i>-dpmppe)Â(Cî—¼CR)<sub>2</sub> or
PtÂ(<i>meso</i>-dpmppe)Â(Cî—¼CR)<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>–1</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
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
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
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
Modulating Stepwise Photochromism in Platinum(II) Complexes with Dual Dithienylethene–Acetylides by a Progressive Red Shift of Ring-Closure Absorption
To
modulate stepwise photochromism by shifting ring-closure absorption
of the dithienylethene (DTE) moiety, <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Cî—¼C-DTE)<sub>2</sub> [Cî—¼C-DTE
= L1o (<b>1oo</b>), L2o (<b>2oo</b>), L3o (<b>3oo</b>), and L4o (<b>4oo</b>)] and <i>cis</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(L4o)<sub>2</sub> (<b>5oo</b>) with two
identical DTE–acetylides were elaborately designed. With the
gradual red shift of ring-closure absorption for L1c (441 nm) →
L2c (510 nm) → L3c (556 nm) → L4c (602 nm), stepwise
photochromism is increasingly facilitated in <i>trans</i>-PtÂ(PEt<sub>3</sub>)<sub>2</sub>(Cî—¼C-DTE)<sub>2</sub> following <b>1oo</b> → <b>2oo</b> → <b>3oo</b> → <b>4oo</b>. The conversion percentage of singly ring-closed <b>2co</b>–<b>4co</b> to dually ring-closed <b>2cc</b>–<b>4cc</b> at the photostationary state is progressively
increased in the order <b>1cc</b> (0%) → <b>2cc</b> (18%) → <b>3cc</b> (67%) → <b>4cc</b> (100%).
Compared with trans-arranged <b>4oo</b>, stepwise photochromism
in the corresponding cis-counterpart <b>5oo</b> is less pronounced,
ascribed to either direct conversion of <b>5oo</b> to <b>5cc</b> or rapid conversion of <b>5co</b> to <b>5cc</b>. The progressively facile stepwise photocyclization following <b>2oo</b> → <b>3oo</b> → <b>4oo</b> is
reasonably interpreted by gradually enhanced transition character
involving LUMO+1, which is the only unoccupied frontier orbital responsible
for further photocyclization of singly ring-closed <b>2co</b>–<b>4co</b>
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
Multistate Photochromism in a Ruthenium Complex with Dithienylethene–Acetylide
The
preparation, characterization, and photochromic properties
of the rutheniumÂ(II) vinylidene complex <b>1o</b> and the rutheniumÂ(II)
acetylide complex <b>2o</b> and its oxidized species <b>2o</b><sup>+</sup> with one dithienylethene (DTE) unit are described. Complexes <b>1o</b> and <b>2o</b> can be mutually transformed upon the
addition of base or acid due to the interconversion RuCCH–DTE
⇆ Ru–CC–DTE. <b>2o</b> and its
oxidized species <b>2o</b><sup>+</sup> can be interconverted
through a reversible redox process. It is found that the ring-closing
absorption band of DTE shows a progressive red shift in the order
628 nm (<b>1c</b>) → 641 nm (<b>2c</b><sup>+</sup>) → 692 nm (<b>2c</b>). The photocyclization/cycloreversion
quantum yields are in the order <b>1</b> (Φ<sub>o→c</sub> = 0.0066, Φ<sub>c→o</sub> = 0.001) < <b>2</b><sup>+</sup> (Φ<sub>o→c</sub> = 0.35, Φ<sub>c→o</sub> = 0.012) < <b>2</b> (Φ<sub>o→c</sub> = 0.58,
Φ<sub>c→o</sub> = 0.019), implying that the photochemical
reactivity exhibits the order <b>1</b> < <b>2</b><sup>+</sup> < <b>2</b>, coinciding well with the progressively
increased electronic density at the reactive carbon atoms. The interconversion
among six states is clearly demonstrated by NMR, UV–vis–near-IR,
and IR spectral, electrochemical, and computational studies
Synthesis and characterization of emissive mononuclear Cu(I) complexes with 5-<i>tert</i>-butyl-3-(pyrimidine-2-yl)-1<i>H</i>-1,2,4-triazole
<div><p>A new series of mononuclear copper(I) halide complexes possessing 5-<i>tert</i>-butyl-3-(pyrimidine-2-yl)-1<i>H</i>-1,2,4-triazole (bpmtzH) and PPh<sub>3</sub>, Cu(bpmtzH)(PPh<sub>3</sub>)X (X = I (<b>1</b>); Br (<b>2</b>); Cl (<b>3</b>)), have been synthesized and characterized. As revealed via X-ray crystallography, <b>1–3</b> show a chiral, distorted tetrahedral N<sub>2</sub>PX arrangement, in which bpmtzH is a neutral bidentate chelating ligand using the 4-N of the 1,2,4-triazolyl ring and one N donor from the 2-pyrimidyl ring, consistent with the computational results. A comparatively weak low-energy absorption tail is observed between 320 and 450 nm for CH<sub>2</sub>Cl<sub>2</sub> solutions of <b>1–3</b> at room temperature, ascribing to charge-transfer transitions with appreciable metal-to-ligand charge transfer (MLCT) character. Complexes <b>1–3</b> in the solid state have good luminescence at ambient temperature, although they are non-emissive in solution. The solid-state emission, most likely originating from both <sup>3</sup>MLCT and <sup>3</sup>XLCT transitions, can be modulated via alteration of the halide bound to {Cu(bpmtzH)(PPh<sub>3</sub>)} motif.</p></div