Antimony-and bismuth-bridged bipyridyls (dipyridinostibole and dipyridinobismole; DPySb and DPyBi) were prepared by the reactions of dilithiobipyridyl with dibromophenylstibine and diiodophenylbismuthine. Xray diffraction studies of the crystal structures revealed a high planarity of the heterole ring. Cyclic voltammograms obtained in acetonitrile indicated enhanced electron affinity in comparison to a bridge-free bipyridyl. These compounds showed weak fluorescence at room temperature and visible phosphorescence at 77 K with emission maxima and lifetimes of λ max = 453 nm and τ = 1.03 ms for DPySb and λ max = 454 nm and τ = 0.26 ms for DPyBi, respectively. Solid-state phosphorescence was also observed from these dipyridinoheteroles at 77 K. Their copper complexes were prepared by interaction with Cu 2 I 2 (PPh 3 ) 3 , which produced red phosphorescence in the solid state at room temperature.
Catechol dyes (CAT-PET) possessing PET (photo-induced electron transfer) characteristics, which make it possible to retard the back-electron transfer rate, are an efficient dye sensitizer for type-II DSSCs.
Disilane‐ and disiloxane‐bridged bipyridyls (DSBPy and DSOBPy) were prepared and their optical properties were investigated in comparison with those of previously reported monosilane‐ and monogermane‐bridged counterparts. The UV–visible absorption and photoluminescence bands of DSBPy and DSOBPy were blue‐shifted as a result of elongation of the bridging units from monosilane and monogermane to disilane and disiloxane, likely due to the enhanced twisting of the bipyridyl units. Phosphorescent complexes DSBPy–Cu and DSOBPy–Cu were prepared by the interaction of DSBPy and DSOBPy with Cu2I2(PPh3)2. X‐ray diffraction studies of their single‐crystal structures revealed polymeric structures composed of repeat units of DSBPy or DSOBPy and [CuII(PPh3)]2. Organic light‐emitting diodes with the ITO/PEDOT:PSS/DSBPy–Cu or DSOBPy–Cu:PCTSQ/TAZ/Al structure were fabricated to examine the applications of the complexes as electroluminescent materials. The devices emitted yellow light with emission maxima at approximately 600 nm, and maximal luminance reached 120 and 190 cd m−2 for devices based on DSBPy–Cu and DSOBPy–Cu, respectively. The performance of the DSOBPy–Cu‐based device was improved by using TAZ as the dopant of the emissive layer, and luminance was increased to 390 cd m−2.
The introduction of unconventional elements into π‐conjugated systems has been studied to manipulate the electronic states and properties of compounds. Herein, boron‐ and germanium‐containing hybrid macrocycles, as a new class of element‐hybrid conjugated systems, have been synthesized. The palladium‐catalyzed Stille cross coupling of bis(bromothienyl)borane and bis(trimethylstannylthienyl)‐ or bis(trimethylstannylphenyl)‐substituted dithienogermoles as the boron‐ and germanium‐containing building blocks, respectively, produced a mixture of several macrocyclic compounds. Single‐crystal X‐ray analysis of the 2:2 coupling product revealed a planar structure with a cavity inside the macrocycle. The optical properties of the macrocyclic products indicated rather small electronic interactions between the building units. However, intramolecular photoenergy transfer from the dithienogermole unit to the boron unit was clearly observed with respect to the fluorescence spectra.
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