7 research outputs found
Synthesis and Properties of Nitrogen-Introduced Phenylazomethine Dendrimer
<div><p></p><p>The pyridine ring–introduced phenylazomethine dendrimer (PyDPA) was synthesized by a dehydration reaction using titanium(IV) chloride. The ultraviolet–visible absorption and the electrochemical study showed that the introduction of the pyridine ring produces a smaller band gap by increasing the highest occupied molecular orbital level and decreasing the lowest unoccupied molecular orbital level. A crystal of a PyDPA-PdCl<sub>2</sub> complex was also prepared. Traditional phenylazomethine dendrimers cannot form a complex with palladium, indicating that PyDPA can potentially coordinate with various metal salts such as Co, Ni, Ru, and Mn and can be used for catalytic or electronic applications.</p>
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Synthesis, Properties, and Polymerization of Spiro[(dipyridinogermole)(dithienogermole)]
Compounds
with spiro-condensed dithienogermole (DTG) and dipyridinogermole
(DPyG) units were synthesized, and their optical and electrochemical
properties were investigated. The reaction of tetrachlorogermane and
3,3′-dilithio-5,5′-bis(trimethylsilyl)bithiophene, followed
by treatment of the resulting mixture containing 1,1-dichlorodithienogermole
with 3,3′-dilithio-4,4′-bipyridyl, gave spiro{(dipyridinogermole)
[bis(trimethylsilyl)dithienogermole]} (<b>sDPyDTG1</b>). The
UV–vis spectrum of <b>sDPyDTG1</b> showed absorption
bands that were due to both electronically isolated DTG and DPyG units.
In contrast, the photoluminescence (PL) spectrum showed only the band
ascribed to the DTG unit even when the DPyG unit was irradiated, indicating
intramolecular photoenergy transfer. It was also suggested that photoinduced
electron transfer from DTG to DPyG occurred to suppress the PL quantum
yield. Bromination of <b>sDPyDTG1</b> with NBS provided the
dibromide, and the subsequent Stille coupling of the resulting dibromide
with distannylbithiophenes produced the corresponding conjugated oligomer
and polymer. The oligomer and the polymer also showed different optical
properties, suggesting intramolecular photoenergy and electron transfer,
depending on the substituent
Synthesis, Properties, and Polymerization of Spiro[(dipyridinogermole)(dithienogermole)]
Compounds
with spiro-condensed dithienogermole (DTG) and dipyridinogermole
(DPyG) units were synthesized, and their optical and electrochemical
properties were investigated. The reaction of tetrachlorogermane and
3,3′-dilithio-5,5′-bis(trimethylsilyl)bithiophene, followed
by treatment of the resulting mixture containing 1,1-dichlorodithienogermole
with 3,3′-dilithio-4,4′-bipyridyl, gave spiro{(dipyridinogermole)
[bis(trimethylsilyl)dithienogermole]} (<b>sDPyDTG1</b>). The
UV–vis spectrum of <b>sDPyDTG1</b> showed absorption
bands that were due to both electronically isolated DTG and DPyG units.
In contrast, the photoluminescence (PL) spectrum showed only the band
ascribed to the DTG unit even when the DPyG unit was irradiated, indicating
intramolecular photoenergy transfer. It was also suggested that photoinduced
electron transfer from DTG to DPyG occurred to suppress the PL quantum
yield. Bromination of <b>sDPyDTG1</b> with NBS provided the
dibromide, and the subsequent Stille coupling of the resulting dibromide
with distannylbithiophenes produced the corresponding conjugated oligomer
and polymer. The oligomer and the polymer also showed different optical
properties, suggesting intramolecular photoenergy and electron transfer,
depending on the substituent
Synthesis of π-Conjugated Polymers Containing Fluorinated Arylene Units via Direct Arylation: Efficient Synthetic Method of Materials for OLEDs
Polycondensation via direct arylation of tetrafluorobenzene
or
octafluorobiphenyl was investigated for the synthesis of π-conjugated
polymers consisting of fluorinated arylene units. The optimization
of reaction conditions revealed that a combination of Pd(OAc)<sub>2</sub> and P<sup><i>t</i></sup>Bu<sub>2</sub>Me-HBF<sub>4</sub> is the most efficient catalytic system for the polycondensation
reactions. The polycondensation reactions produced four types of π-conjugated
polymers having low highest occupied molecular orbital (HOMO) levels
due to the strong electron-withdrawing nature of the fluorine substituents.
Owing to the low HOMO levels, the synthesized polymers served as an
efficient hole-blocking layer (HBL) in OLEDs
Synthesis, Optical Properties, and Crystal Structures of Dithienostannoles
Reactions of dichlorodiphenylstannane
with 3,3′-dilithio-5,5′-bis(trimethylsilyl)-2,2′-bithiophene
and 3,3′-dilithio-2,2′-di(benzo[<i>b</i>]thiophene)
gave 1,1-diphenyl-3,6-bis(trimethylsilyl)dithienostannole (<b>DTSn1</b>) and di(benzo[<i>b</i>]thieno)-1,1-diphenylstannole (<b>DTSn2</b>), respectively. Optical properties of the dithienostannoles
and the results of DFT calculations on a model suggested an in-phase
interaction between Sn σ* and bithiophene π* orbitals,
stabilizing the LUMO. Interestingly, <b>DTSn1</b> showed crystallization-enhanced
emission and the photoluminescence (PL) quantum yield of the crystals
was determined to be higher by about 20 times than that in the amorphous
and solution phase, while <b>DTSn2</b> exhibited moderate PL
efficiency both as crystals and in solution. Crystal structures of
the dithienostannoles were determined by X-ray diffraction studies,
which showed the differences in the molecular packing between <b>DTSn1</b> and <b>DTSn2</b>, being responsible for their
different PL properties in the crystal state
Visible-Light-Promoted Photocatalytic Hydrogen Production by Using an Amino-Functionalized Ti(IV) Metal–Organic Framework
The present article describes the hydrogen production
from an aqueous
medium over amino-functionalized Ti(IV) metal–organic framework
(Ti-MOF-NH<sub>2</sub>) under visible-light irradiation. Ti-MOF-NH<sub>2</sub>, which employs 2-amino-benzenedicarboxylic acid as an organic
linker, has been synthesized by a facile solvothermal method. Pt nanoparticles
as cocatalysts are then deposited onto Ti-MOF-NH<sub>2</sub> via a
photodeposition process (Pt/Ti-MOF-NH<sub>2</sub>). The XRD and N<sub>2</sub> adsorption measurements reveal the successful formation of
a MOF framework structure and its remaining structure after deposition
of Pt nanoparticles. The observable visible-light absorption up to
∼500 nm can be seen in the DRUV–vis spectrum of Ti-MOF-NH<sub>2</sub>, which is associated with the chromophore in the organic
linker. Ti-MOF-NH<sub>2</sub> and Pt/Ti-MOF-NH<sub>2</sub> exhibit
efficient photocatalytic activities for hydrogen production from an
aqueous solution containing triethanolamine as a sacrificial electron
donor under visible-light irradiation. The longest wavelength available
for the reaction is 500 nm. The results obtained from wavelength-dependent
photocatalytic tests and photocurrent measurements as well as in situ
ESR measurements demonstrate that the reaction proceeds through the
light absorption by its organic linker and the following electron
transfer to the catalytically active titanium-oxo cluster
Synthesis of Group 14 Dipyridinometalloles with Enhanced Electron-Deficient Properties and Solid-State Phosphorescence
Silicon- and germanium-bridged bipyridyls
were prepared, and their
optical and electrochemical properties were investigated. It was found
that they exhibited enhanced electron deficiency and phosphorescence
properties in comparison to parent bipyridyl. The single-crystal structure
of a dipyridinosilole and results of DFT calculations on models are
also described