Hole-transporting [3,3′]bicarbazolyl-based polymers and well-defined model compounds

Polymers containing bicarbazolyl moieties in the main chain have been synthesized by the modified Ullmann coupling reaction from 9H,9′H-[3,3′]bicarbazolyl and different dihalo derivatives. The number-average molecular weights of the polymers synthesized were in the range of 2500-6200 with a molecular weight distribution of 1.6-3.1. Well-defined model compounds for the polymers have been synthesized by stepwise reactions. All these compounds have been found to form glasses with glass transition temperatures in the range of 57-119 °C as characterised by differential scanning calorimetry. The electron photoemission spectra of the compounds have been recorded and the ionisation potentials of 5.35-5.4 eV have been established. Room temperature hole drift mobility of the synthesized compounds molecularly dispersed in a polymer host range from 10⁻⁶ to 3 × 10⁻⁵ cm²/V s at an electric field of 10⁶ V/cm at the room temperature.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

Aggregation-Enhanced Emission and Thermally Activated Delayed Fluorescence of Derivatives of 9-Phenyl-9H-Carbazole: Effects of Methoxy and tert-Butyl Substituents

Derivatives of 9-phenyl-9H-carbazole were synthesized as efficient emitters exhibiting both thermally activated delayed fluorescence and aggregation-induced emission enhancement. Effects of methoxy and tert-butyl substituents at the different positions of carbazolyl groups on the properties of the emitters were studied. Depending on the substitutions, photoluminescence quantum yields (PLQY) of non-doped solid films of the compounds ranged from 17 % to 53 % which were much higher than those observed for the solutions in low-polarity solvent toluene. Compounds substituted at C-3 and C-6 positions of carbazole moiety by methoxy- and tert-butyl- groups showed the highest solid-state PLQY. Ionization potentials of the studied derivatives in solid-state were found to be in the short range of 5.75–5.89 eV. Well-balanced hole and electron mobilities were detected for tert-butyl-substituted compound. They exceeded 10⁻⁴ cm² (V×s)⁻¹ at electric fields higher than 3×10⁵ V cm⁻¹. Two compounds with the highest solid-state PLQYs showed higher efficiencies in non-doped organic light-emitting diodes than in the doped devices. Maximum external quantum efficiency of 7.2 % and brightness of 15000 cd m⁻² were observed for the best device.     

奥尔堡PBL模式对提升有机波谱分析教学效果的启示

概述了有机波谱分析课程教学中存在的主要问题，介绍了奥尔堡PBL模式的主要特点和优势，分析了将奥尔堡PBL模式用于有机波谱分析课程教学的必要性和可行性，并从课时分配、教学内容、教学方式和考核方式等4方面提出了教学改革方案，旨在提高教学效果。     

Synthesis of heterocyclic thiosulfonates

[formula: see text] A simple synthesis of heterocyclic thiosulfonates containing indole, indoline, benzoimidazole, and quinoxaline rings is described. The synthesis of these thiosulfonates involves the preparation of the appropriately substituted thiols followed by sulfonylation to give thiosulfonates. The corresponding thiols were prepared in a simple and efficient manner by using a thiocyanation reaction either prior to heterocycle ring formation or after heterocycle ring formation. These thiosulfonates were coupled successfully to the 5,6-dihydropyran-2-one ring to give products that showed excellent HIV protease activity.     

Diastereoselective Strategies towards Thia[n]helicenes

In the present study, we have investigated different strategies for diastereoselective synthesis of thia[n]helicenes. We describe the introduction of different chiral auxiliaries at various positions and investigated their effect in the photocyclization reaction. Different chiral groups were placed at the sterically hindered position of the helical core and their interactions with various solvents and metals like copper were investigated. The use of Cu^I salts has led to high diastereoselectivity in the photocyclization process and we were successful in obtaining the thia[5]helicene in enantiomerically pure form in good yield. The single diastereomer obtained was characterized by X‐ray crystallography. From the study of the barrier of racemization of these thia[5]helicenes, the stability was found to be comparable to unsubstituted tetrathia[7]helicenes and substituted diazadithia[7]helicenes. This approach provides an easy access to enantiopure helicenes.     

Impact of intramolecular twisting and exciton migration on emission efficiency of multifunctional fluorene-benzothiadiazole-carbazole compounds

Novel donor-acceptor compounds consisting of singly bonded fluorene (Fl), benzothiadiazole (BT), and carbazole (Cz) functional units in the same molecule were investigated. Analysis of the optical spectra and fluorescence transients of the compounds revealed the domination of intramolecular charge transfer (ICT) states with high fluorescence quantum yield (72%-85%). A similar Cz-Fl-Cz compound exhibiting 100% fluorescence quantum yield and no ICT character was also studied as a reference to reveal the impact of electron-accepting BT groups. Thorough examination of the optical properties of the compounds in different media, i.e., dilute solution and polymer matrix, indicated their twisted conformations due to steric hindrance in the ground state and flattened geometry in the excited state for both reference and ICT compounds. Remarkable fluorescence efficiency losses (amounting to 70%) observed upon casting the molecular solutions into neat films were determined to originate from the low-fluorescent twisted conformers and migration-facilitated exciton quenching. The majority of emission efficiency losses (over 70%) were caused by the twisted conformers, whereas only less than 30% by exciton-migration-induced nonradiative deactivation.     

Cationic photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether

An absorbance probe method was used for the investigation of photolysis of cationic photoinitiators. The rates of the photolysis of diphenyliodonium hexafluorophosphate (DPIH), diphenyliodonium tetrafluoroborate (DPIB), di(tert-butylphenyl)iodonium tetrafluoroborate (DTIB), di(tert-butylphenyl)iodonium bromate (DTIBr), triphenylsulfonium hexafluorophosphate (TPS) and cyclopropyldiphenylsulfonium tetrafluoroborate (CPS) were studied in the presence of acid indicator quinaldine red (QR) in acetonitrile. Diphenyliodonium hexafluorophosphate and triphenylsulfonium hexafluorophosphate showed the highest photolysis rate. Photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether (DCPGE) initiated with the iodonium and sulfonium salts in bulk and in solution was studied. It was established that the highest initial rate of polymerization is characteristic of DCPGE photopolymerization initiated with DPIH and TPS in bulk. The oligomers of DCPGE of number average molecular weight ( [`(M<sub>n</sub>)]\overline{M_n} ) ranging from 710 to 1220 were obtained in these reactions in bulk and those with [`(M_n)]\overline{M_n} ranging from 1300 to 1600 were obtained in solution.     

Cationic photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether

An absorbance probe method was used for the investigation of photolysis of cationic photoinitiators. The rates of the photolysis of diphenyliodonium hexafluorophosphate (DPIH), diphenyliodonium tetrafluoroborate (DPIB), di(tert-butylphenyl)iodonium tetrafluoroborate (DTIB), di(tert-butylphenyl)iodonium bromate (DTIBr), triphenylsulfonium hexafluorophosphate (TPS) and cyclopropyldiphenylsulfonium tetrafluoroborate (CPS) were studied in the presence of acid indicator quinaldine red (QR) in acetonitrile. Diphenyliodonium hexafluorophosphate and triphenylsulfonium hexafluorophosphate showed the highest photolysis rate. Photopolymerization of 1,3-di(9-carbazolyl)-2-propanol glycidyl ether (DCPGE) initiated with the iodonium and sulfonium salts in bulk and in solution was studied. It was established that the highest initial rate of polymerization is characteristic of DCPGE photopolymerization initiated with DPIH and TPS in bulk. The oligomers of DCPGE of number average molecular weight ( ) ranging from 710 to 1220 were obtained in these reactions in bulk and those with ranging from 1300 to 1600 were obtained in solution. Correspondence: Ruta Lazauskaite, Juozas V. Grazulevicius, Department of Organic Technology, Kaunas University of Technology, Radvilenu plentas 19, LT-50254 Kaunas, Lithuania.     

A Continuous-Wave Ho：YA103 Laser with Output 8.5 W Pumped by a 1.91μm Laser at Room Temperature

A cw high efficient Ho：YAI03 laser pumped by 1.91 μm diode-pumped Tm：YLF laser at room temperature is realized. The maximum output power reaches 8.5 W when the incident pump power is 15.6 W. The slope efficiency is 63.7%, and the Tm：YLF to Ho：YAP optical conversion efficiency is 54.5%. The laser wavelength is 2118.3nm when the transmission of output coupler is 30%. The beam quality factor is M2 -1.39 measured by the traveling knife-edge method.