Organic Light-emitting Materials Research Articles

有機トランジスタおよび有機発光材料における分子パッキング制御

有機トランジスタおよび有機発光材料における分子パッキング制御

Synthesis of D-A Type Organic Molecules Based on Carbazole and Phenothiazine for Organic Light-Emitting Materials

Novel D-A type conjugated organic molecules composed of central carbazole and phenothiazine units and aldehyde terminal groups have been designed and constructed. Optical properties of the resulting compounds were examined by the mean of UV-vis and fluorescence spectroscopies. The fluorescence spectra of the molecule C2 based on central carbazole unit show strong emission peaks in the blue light regions, which are expected to be promising light-emitting materials for organic light-emitting diodes applications.

An organic molecule with asymmetric structure exhibiting aggregation-induced emission, delayed fluorescence, and mechanoluminescence.

Compounds displaying delayed fluorescence (DF), from severe concentration quenching, have limited applications as nondoped organic light-emitting diodes and material sciences. As a nondoped fluorescent emitter, aggregation-induced emission (AIE) materials show high emission efficiency in their aggregated states. Reported herein is an AIE-active, DF compound in which the molecular interaction is modulated, thereby promoting triplet harvesting in the solid state with a high photoluminescence quantum yield of 93.3%, which is the highest quantum yield, to the best of our knowledge, for long-lifetime emitters. Simultaneously, the compound with asymmetric molecular structure exhibited strong mechanoluminescence (ML) without pretreatment in the solid state, thus exploiting a design and synthetic strategy to integrate the features of DF, AIE, and ML into one compound.

Determination of dynamic surface tension and viscosity of non-Newtonian fluids from drop oscillations

The oscillations of free-falling drops with size range from pl to μl have been used to measure the transient shear viscosity and the dynamic surface tension of shear-thinning fluids on the timescale of 10−5–10−2 s. The method is first validated with Newtonian fluids. For a given surface tension, the lower and upper limits for accurate measurement of the viscosity are determined as a function of drop size. The dynamic properties of two types of shear-thinning fluids with varying viscoelasticity are reported: aqueous suspensions of the antifungal drug griseofulvin and of the organic light-emitting diode material poly(3,4-ethylenedioxythiophene): polystyrene-sulphonate. In both cases, the free-falling drop retains the high-shear viscosity.

Theoretical Investigation on Firefly Oxyluciferin Analogs Bearing an Amino Group Used as Organic Light-Emitting Diodes Materials

Firefly oxyluciferin has great potential application in organic light-emitting devices, because of the high efficiency and wide range of multicolor light from green to red. To gain an insight into the structure-property relationships, a set of firefly oxyluciferin analogs bearing an amino group with benzopyran, biphenyl, bipyridine, phenanthrene, phenanthroline, fluorine and coronene instead of benzothiazole ring were designed. In this study, a systematic investigation into them was carried out using the density functional theory and time-dependent density functional theory methods. The calculated values show that bipyridylaminooxyluciferin (BPAOL) and orthophenanthrolylaminooxyluciferin (PMAOL) with nitrogen atom have smaller the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, larger ionization potential (IP) and electron affinity (EA) values than biphenylaminooxyluciferin (BIAOL) and phenanthrylaminooxyluciferin (PHAOL) with carbon atom. Compound aminooxyluciferin (AOL), BIAOL, BPAOL, PHAOL, PMAOL, fluorenylaminooxyluciferin (FLAOL) and coronenylaminooxyluciferin (COAOL) can be used as electron-injection/transporting materials. AOL, PHAOL, FLAOL and COAOL can be used as blue light-emitting materials. These results indicate that the firefly Chinese Journal of Organic Chemistry ARTICLE Chin. J. Org. Chem. 2015, 35, 432~438 © 2015 Chinese Chemical Society & SIOC, CAS http://sioc-journal.cn/ 433 oxyluciferin analogs bearing an amino group have many interesting properties and are good candidates for optoelectronic application.

Synthesis and Properties of Novel Light-Emitting Materials Containing Triphenylamine, Olefinic Linkers and Bipyridine Units

Organic light-emitting materials D1~D3 containing triphenylamine donors, bipyridine acceptors and olefinic linkers were synthesized and characterized. The optical, electrochemical properties of materials were studied by UV-Vis spectra, fluorescence emission spectra and cyclic voltammetry method. The results show that the maximal absorption peaks of three compounds are in the range of 404nm~408nm and fluorescence emission peaks at the region of 534nm~557nm in dichloromethane solutions, respectively. Cyclic voltammetry measurement showed that these compounds had HOMO energy level in the range of-5.02eV~-5.16eV, which is proper for hole injection. The properties indicate that these compounds have potential for the application as light-emitting materials or hole-transporting materials.

Synthesis and Fluorescence Properties of a New Eu(III) Complexes with β-Diketone Ligand

A novel β-diketone 4-[4-(Dibenzylamino) phenyl]-2,4-dioxobutanoic (DPD) and its corresponding Eu3+ complex with 1,10-phenanthroline were synthesized. The structure, thermal behaviour and fluorescence property of the complex was characterized by Fourier Transform Infrared (FT-IR), thermal gravimetric analysis (TGA) and fluorescence spectrophotometer. The fluorescence characterization shown that the addition of β-diketone and 1,10-phenanthroline enhance the fluorescence intensity of the complex. Eu3+ complex was considered to be a valuable organic light-emitting material with bright red fluorescence because of its strong emission band. Furthermore, the thermal stability characterizarion shows that the obtained rare earth β-diketone complexes have good thermostability.

Synthesis of a Novel D-A Type Molecule Based on Carbazole Unit for Organic Light-Emitting Material Applications

A novel D-A type molecule based on carbazole central core and aldehyde terminal groups has been designed and synthesized. Optical properties of the resulting compounds were examined by means of UV-vis and fluorescence spectroscopies. It shows that, the absorption and fluorescence spectra of M2 are large red-shifted relative to M1 in both states, whereas the absorption maximum and emission maxima of M1 and M2 are small blue-shifted, from solution to the solid state. The fluorescence spectra exhibit that the emission maxima of the compounds which range from 419 nm to 472 nm belong to blue light region. As expected, the target compounds should be a promising pure blue light-emitting material for applications in organic light-emitting diodes (OLEDs).

Synthesis of a Novel Donor Unit for Organic Light-Emitting Materials: 10-octyl-3,7-Di(thiophen-2-yl)-10H-phenothiazine

A novel electron donor unit based on phenothiazine has been designed and constructed. The target compound 10-octyl-3,7-di (thiophen-2-yl)-10H-phenothiazine was easily synthesized in high yields with a milder and efficient route via the Suzuki coupling reaction. Optical spectra show that, from the solution to the solid state, both the absorption and fluorescence spectra of the target compound are small blue-shifted. Moreover, the fluorescence spectra exhibit the emission maxima of the target compound ranging from 485 nm to 496 nm, which belongs to blue-green light range. As expected, the target compound should be a promising donor to construct D-A type materials for applications in organic light-emitting diodes (OLEDs).

Optical and charge transport properties of N-butyl-1,8-naphthalimide derivatives as organic light-emitting materials: A theoretical study

A series of N-butyl-1,8-naphthalimide derivatives have been designed to explore their optical, electronic, and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes (OLEDs). The frontier molecular orbitals (FMOs) analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer (ICT). The calculated results show that the optical and electronic properties of N-butyl-1,8-naphthalimide derivatives are affected by the substituent groups in 4-position of 1,8-naphthalimide ring. Our results suggest that N-butyl-1,8-naphthalimide derivatives with biphenyl (1), 2-phenylthiophene (2), 2-(thiophen-2-yl)thiophene (3), 2,3-dihydrothieno[3,4-b][1,4]dioxine (4), 2-phenyl-1,3,4-oxadiazole (5), benzo[c][1,2,5]thiadiazole (6), benzo[c]thiophene (7), and benzo[d]thieno[3,2-b]thiophene (8) fragments are expected to be promising candidates for luminescent materials for OLEDs, particularly for 1–3 and 5. In addition, 7 and 8 can be used as promising hole transport materials for OLEDs.

Rational Design of Star-Shaped Molecules with Benzene Core and Naphthalimides Derivatives End Groups as Organic Light-emitting Materials

A series of star-shaped molecules with benzene core and naphthalimides derivatives end groups have been designed to explore their optical, electronic, and charge transport properties as charge transport and/or luminescent materials for organic light-emitting diodes (OLEDs). The frontier molecular orbitals (FMOs) analysis has turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer (ICT). The calculated results show that the optical and electronic properties of star-shaped molecules are affected by the substituent groups in N-position of 1,8-naphthalimide ring. Our results suggest that star-shaped molecules with n-butyl (1), Benzene (2), Thiophene (3), thiophene S’,S’-dioxide (4), benzo[c][1,2,5]thiadiazole (5), and 2,7a-dihydrobenzo[d] thiazole (6) fragments are expected to be promising candidates for luminescent and electron transport materials for OLEDs. This study should be helpful in further theoretical investigations on such kind of systems and also to the experimental study for charge transport and/or luminescent materials for OLEDs.

Time-Resolved EPR Study on the Photoexcited Triplet State of the Electron–Donor–Acceptor Complex Formed in the System of fac-Tris[2-(4-octyl-phenyl) pyridine] Iridium(III) and Tetracene

The physical properties of the phosphorescent organic light-emitting diode material fac-tris(phenylpyridine) iridium(III), Ir(ppy)3, have been reported with experimental and theoretical studies. Here, the photochemical properties of the excited triplet state of partially modified fac-tris[2-(4-octyl-phenyl) pyridine] iridium(III), Ir(C8ppy)3, were investigated using time-resolved electron paramagnetic resonance (tr-EPR) and optical methods by adding tetracene in the toluene solution. The tr-EPR observation at 77 K revealed the following two species: the excited triplet state of tetracene and another triplet species with zero field splitting parameters of |D| = 0.088 cm(-1) and |E| = 0.018 cm(-1) with characteristic spin polarization. The latter species was assigned to the electron-donor-acceptor (EDA) complex formed between Ir(C8ppy)3 and tetracene. The mechanism of formation and the properties of this EDA complex, including the information on the principal axes of (3)Ir(C8ppy)3*, are discussed.

Theoretical study on optical and electronic properties of bipolar molecules with 1,8-naphthalimide and triphenylamine moieties as organic light-emitting materials

A series of D–π–A bipolar molecules with triphenylamine (TPA) fragments as donors, 1,8-naphthalimide (NI) fragments as acceptors, and different π-conjugated bridges (CB) as π-conjugated bridges have been designed to explore their optical, electronic, and charge transport properties as charge transport and luminescent materials for organic light-emitting diodes (OLEDs). The frontier molecular orbitals (FMOs), natural population analysis (NPA), and local density of states analysis have turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer (ICT). The calculated results show that their optical and electronic properties are affected by the π-conjugated bridges in bipolar molecules. The electron-donating (-withdrawing) π-conjugated bridges serve as donors (acceptors) for the compounds under investigation. Our results suggest that these bipolar molecules are expected to be promising candidates for holes transport and luminescent materials for OLEDs. The results presented show that varying the π-conjugated bridges of bipolar molecules is a highly promising approach to develop this series of materials for OLEDs applications.

Highly efficient and stable solid-state luminescent nanohybrids: Precise architecture and enhancement mechanism

Abstract

Synthesis, fine structure of 19F NMR and fluorescence of novel amorphous TPA derivatives having perfluorinated cyclopentenyl and benzo[b]thiophene unit

Three novel triphenylamine (TPA) derivatives having perfluorinated cyclopentenyl and benzo[b]thiophene unit are obtained from 4-bromo-N,N-diphenyl-2-methylbenzo[b]thiophen-5-amine. The new compounds are expected to find their use in thin film devices as charge transport materials and host organic light-emitting materials. It is found that the new compounds show relatively strong fluorescence either in solution or in solid state, and are amorphous due to a special conformation which is elucidated by the fine structure of 19F NMR. Molecular structure and properties of these compounds is characterized by 1H NMR, 13C NMR (broadband decoupled), ESI–HRMS, elemental analysis and thermal analysis (DSC). Fluorescent quantum yield in solution is measured using 9,10-diphenylanthrancene (DPA) as standard fluorescent substance.

The New Synthesis of Organic Light-Emitting Material BHBT Monomer by Stille Coupling

Heterocyclic monomer based on 2,1,3-benzothiadiazole bearing solubilizing side chains have been synthesized in high yields over three steps from readily available starting materials. The alkyl side chain in the 4-position of both thiophene rings gives the material mononer a good solubility.

Electron spin resonance of thin films of organic light-emitting material tris(8-hydroxyquinoline) aluminum doped by magnesium

We have successfully observed electron spin resonance (ESR) signals of radical anions in thin films of tris(8-hydroxyquinoline) aluminum (Alq3), a compound widely used as electron transporting and luminescent layers in organic light-emitting diodes. To obtain definitely defined radical-anion states in Alq3, we doped Alq3 with Mg by co-evaporating these materials. The obtained g value and peak-to-peak ESR linewidth ΔHpp of Alq3 radical anions are 2.0030 and 2.19mT, respectively. Theoretical g value and hyperfine interactions were calculated by density functional theory method, which are in good agreement with the experimental results. A quantitative evaluation of doping concentration was performed. We confirmed that doped charges are localized at deep trapping sites by the lineshape analysis and temperature dependence of the ESR signals. Morphological investigation using transmission electron microscopy clarified that the co-evaporated Mg atoms form clusters.

Synthesis and Characterization of Un-doped Deep-Blue Organic Light-Emitting Materials Containing Spirofluorene and Biphenyl or Substituted Biphenyl

A series of novel blue light-emitting materials, spirofluorene derivatives, DBSF, 3DBSF, and 5DBSF, based on 2′,7′-dibromospiro- [benzo[c]fluorene-7,9′-fluorene] (DBrSPFF) were successfully synthesized and identified by IR, 1H-NMR, and13C-NMR, MS. Optical properties were examined by UV-Vis absorption spectra and photoluminescence (PL) emission spectra. They performed great blue light characteristics. PL quantum yield was calculated by using quinine sulphate in 0.1M H2SO4 as standard. Electro-chemical behavior was examined through cyclic voltammeter measurement. They may be potential promising blue light-emitting materials for OLED.

Efficient, Scalable, and Solvent-free Mechanochemical Synthesis of the OLED Material Alq3 (q = 8-Hydroxyquinolinate)

The aluminum complex Alq3 (q = 8-hydroxyquinolinate), which has important applications in organic light-emitting diode materials, is shown to be readily synthesized as a pure phase under solvent-free mechanochemical conditions from Al(OAc)2OH and 8-hydroxyquinoline by ball milling. The initial product of the mechanochemical synthesis is a novel acetic acid solvate of Alq3, and the α polymorph of Alq3 is obtained on subsequent heating/desolvation of this phase. The structure of the mechanochemically prepared acetic acid solvate of Alq3 has been determined directly from powder X-ray diffraction data and is shown to be a different polymorph from the corresponding acetic acid solvate prepared by solution-state crystallization of Alq3 from acetic acid. Significantly, the mechanochemical synthesis of Alq3 is shown to be fully scalable across two orders of magnitude from 0.5 to 50 g scale. The Alq3 sample obtained from the solvent-free mechanochemical synthesis is analytically pure and exhibits identical photoluminescence behavior to that of a sample prepared by the conventional synthetic route.

The New Synthesis of Novel Organic Light-Emitting Material Spirobifluorene by Ullman Coupling

A mide, simple and efficient synthetic procedure for the preparation of 2,7-dibromo-2′,3′,6′,7′-tetra(2-methylbutyloxy)spirobifluorene and key intermediates, tetra(2-methlbutyloxy)biphenyl ，2-bromo-4,5,3′,4′-tetra(2-methylbutyloxy)biphenyl, 2,7-Dibromo-2′,6,3′,7′--tetra(2-methylbutyloxy)biphenyl-9-Fluorenol, has been developed. The procedure described herein offers several advantages, including high product yields, easy purification, and large scale production. Ether protected 2,7-dibromo-9,9′-spirobifluorene has good solubility in organic aolvents to permit an appropriate coating process, ability to achieve various colors so as to make full color display elements possible.