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-PdCl₂ 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> </div

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)₂ and P^<i>t</i>Bu₂Me-HBF₄ 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-NH₂) under visible-light irradiation. Ti-MOF-NH₂, 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-NH₂ via a photodeposition process (Pt/Ti-MOF-NH₂). The XRD and N₂ 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-NH₂, which is associated with the chromophore in the organic linker. Ti-MOF-NH₂ and Pt/Ti-MOF-NH₂ 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