Synthesis, optical, electrochemical, and thermal properties of conjugated α-fluorenyl oligothiophenes

A series of new α-fluorenyl oligothiophenes up to the pentamer have been synthesized using Suzuki cross-coupling and bromination reactions. The optical, electrochemical, and thermal properties of these materials can be tuned by varying the number of thiophene rings. The longer oligomers (n ? 4) were stable, crystalline, and unreactive to electrochemical oxidative dimerization.     

Preparation and properties of oxadiazole‐containing polyacetylenes as electron transport materials

A series of functional polyacetylenes (PAs) bearing diphenyl oxadiazole pendant groups ( P1 – P4 ) were prepared, and the resultant polymers are completely soluble in common organic solvents. Their structures and properties were characterized and evaluated by DSC, TGA, UV, PL, CV, and EL analyses. The results show that all the resulting polymers possesses low LUMO energy level and high thermal stability, and the resultant functional polyacetylenes without spacer group between the polyacetylene conjugated main chain and oxadiazole pendant groups ( P1 – P3 ) show lower LUMO energy level (～?3.87 eV) and higher thermal properties (T_g) than that ( P4 ) with a flexible spacer. The resultant polymer ( P2 ) was applied as an ETM in bilayer electroluminescent devices and effectively enhances external quantum efficiency and the brightness of device, and decreases turn‐on voltages of devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1406–1414, 2010     

Dispirofluorene-indenofluorene (DSFIF): synthesis, electrochemical, and optical properties of a promising new family of luminescent materials

[reaction: see text] A series of new dispiro[fluorene-9',6,9' ',12-indeno[1,2b]fluorenes] (DSFIFs) that combine indenofluorene (IF) and spirobifluorene (SBF) architectural specificities have been prepared. Their anodic oxidations lead to the formation of nonsoluble transparent polymers. The photophysical and electrochemical properties of these new molecules have been evaluated for further blue OLED applications.     

用于电子传输材料的含噻吩环噁二唑衍生物的合成

在有机电致发光器伯研究中,电子传输材料占有特殊重要的地位。但现存在的材料存在着不同的缺点。因噁二唑环的高的电子亲和性,噁二唑衍生物是常见的电子传输材料,如：2-(4-叔丁苯基)-5-联苯基噁二唑(PBD),但容易结晶和低的电子? 缀托韵拗屏怂挠τ谩Ｎ说玫叫碌挠行У牡缱哟洳牧希疚囊脏绶晕鹗挤从ξ锞獯Ⅳ人峄Ⅴセ苯獾炔街韬铣闪肃绶远ｋ拢偻ü绶远ｋ掠胂嘤Φ娜〈郊柞Ｂ人鹾稀⒐鼗返姆椒ń坏缱拥泥绶曰泛透叩缱忧缀托缘泥绶曰吠币耄铣闪巳中碌暮绶曰穱f二唑衍生物2,5-双[2,2'-双(5-取代苯基)-1,3,4-噁二唑]噻吩(R-OXDR=H,OCH~3,CH~3)。同时,采用循环伏安法对其电? 阅芙辛瞬舛āＵ馊只衔锒荚诟悍较虺鱿至艘欢钥赡娴难趸乖澹纱说玫狡涞缱忧缀褪?EA)分别为-3.10eV,-3.07eV和-3.08eV,其EA值都高于常用? 牡缱哟洳牧螾BD。R-OXD的高电子亲和势有利于电子从阴极注入。并且由时间渡? 椒?TOF)测得R-OXD的电子迁移率达到10^-^4cm^2/V.S(E=10^6V/cm)。所以R-OXD有可能是好的电子传输材料。     

Donor/acceptor-substituted anthradithiophene materials: synthesis, optical and electrochemical properties

The synthesis and characterization of two new anthradithiophene (ADT) derivatives bearing electron donating (triphenylamine) or accepting (5-formylthiophen-2-yl unit) moieties have been performed to assess their potential as materials for organic photovoltaics. Optical spectroscopy was used to evaluate the effect of electron rich/poor substituents on the visible absorption spectrum and on the stability towards photo-oxidation. The results are interpreted with the assistance of quantum-chemical calculations and cyclic voltammetry experiments.     

Low molecular weight and polymeric heterocyclics as electron transport/hole-blocking materials in organic light-emitting diodes

The use of low molecular weight, oligomeric and polymeric heterocyclics as electron transport/hole-blocking layers in organic light-emitting diodes is reviewed. The most widely applied materials are π-electron deficient heterocyclics carrying imine nitrogen atoms in the aromatic ring, such as 1,3,4-oxadiazoles, 1,2,4-triazoles, 1,3,5-triazines, and 1,4-quinoxalines. Properties such as redox potentials, ionization potential, electron affinity and charge transport mobility of the materials, if known, are taken into consideration to support the electron injection/transport and hole-blocking effectiveness. It can be generalized that heterocyclic moieties with high reduction potential reduce the interface barriers caused by the band offset between organic material and cathode and are most suitable materials for electron injection in organic electroluminescent devices. These materials are generally characterized by high ionization potential values that contribute towards the hole-blocking property. A general comparison of devices and materials is only possible with limitations owing to the variations in device structure, fabrication, electrode materials, emitter materials, etc. © 1998 John Wiley & Sons, Ltd.     

New small-molecular benzimidazole derivatives for photovoltaics: Synthesis,optical and electrochemical properties and application in perovskite solar cells

New small molecule photovoltaic materials containing benzimidazole fragment were prepared by cross-coupling of the corresponding 1-bromo-4-(imidazol-2-yl)benzenes with multiborylated/stannylated polycyclic (het)arenes. Energies of HOMO/LUMO levels were calculated from cyclic voltammetry and UV/VIS spectroscopy data and are within the ranges –5.27... –5.73 and –2.33...–2.89 eV, respectively. Solar cells based on three different perovskites as light absorbing layers and compound SM7 as electron transporting material demonstrated power conversion efficiency values up to 10.78% without doping additives or perovskite engineering.     

Use of Wittig reaction for the synthesis of conjugated Aza-BODIPYs and their spectral and electrochemical properties

The 2-formyl 1,3,5,7-tetraaryl aza-BODIPY and 2-formyl-6-bromo 1,3,5,7-tetraaryl aza-BODIPY were subjected to Wittig reaction with three different ylides under simple reaction conditions and afforded the conjugated aza-BODIPYs in high yields. The aza-BODIPYconjugates resulted from 2-formyl-6-bromo aza-BODIPYs were reacted further with 4-anisyl boronic acid under mild Pd(0) coupling conditions and afforded 1,2,3,5,7-pentaaryl aza-BODIPYconjugates. The method works efficiently and allows to introduce different substituents at the aza-BODIPY core. All compounds were characterized by HRMS, 1D, 2D NMR, absorption, fluorescence and electrochemical techniques. The spectral and electrochemical studies indicated that the introduction of conjugated substituents at the aza-BODIPY core alter the electronic properties significantly.     

微波作用下2,3,5-三取代噻吩的合成及光电性质的研究

含硫芳香化合物可用于有机半导体、电致发光器件,电致变色器件和场效应管。噻吩是一种富电子的五元芳杂环,电子的流动性大,有望成为较好的电子注入／传输材料。我们利用微波辐射在噻吩环的2,3,5位引入了芳基,产物的结构经元素分析、质谱、^1H NMR表征,采     

New mesogenic materials bearing 1,2,4-oxadiazole moiety: Synthesis,characterization and investigation their mesomorphic behaviors

In this work, two series containing a 1,2,4-oxadiazole ring as a central core were synthesized and characterized by common spectroscopic techniques, including FT-IR, ¹H-NMR, and elemental analysis. The first series was 3-(4-alkoxyphenyl)-5-(p-methylphenyl)-1,2,4-oxadiazole (C_n), which consisted of alkoxy group in the terminal arm and a methyl group in the other, while, the oxidation reaction of methyl group in a series (C_n) to the carboxy group was the method used to synthesize the second series in this work, 4-(3-(4-alkoxyphenyl)-1,2,4-oxadiazol-5-yl)benzoic acid (D_n). The mesophase behaviors of these two series were studied by optical polarized microscopy (OPM) and differential scanning calorimetry (DSC). The liquid crystalline investigations of the compounds (C_n and D_n) show that the last six homologeus of the series (C_n), (C₆–C₁₁), have a monotropic nematic phase, while only the intermediate compounds in the series (D_n), (D₃–D₉), displayed monotropic nematic phase, also, the liquid crystalline properties in the first and last two compounds in this series (D₁, D₂, D₁₀, and D₁₁) had disappeared. The differences in liquid crystalline properties between the two series, (C_n and D_n), were discussed through the influences of the different terminal groups (–CH₃ and –COOH) in addition to the effect of the 1,2,4-oxadiazole ring and the length of the terminal alkyl chain.     

Preparation and property of a novel soluble electron transport POSS-based hybrid material

A novel POSS-based organic/inorganic hybrid covalently attached at molecular level, 2-（4-（allyloxy）phenyl）-5-（4-（octyloxy）phenyl）-1,3,4-oxadiazole-POSS （6） （abbreviated as oxadiazole-POSS） was synthesized by Pt（dcp） catalyst. The hybrid was soluble in common organic solvents such as CHCl3, toluene, C2H4Cl2, and THF. Its structures and properties were characterized and evaluated with FTIR, 1^H NMR, 13^C NMR,29^Si NMR, EA, TGA, DSC, GPC, and CV, respectively. The results show that the novel hybrid possesses high thermal stability and good electron injection ability.     

Density functional theory study on electron and hole transport properties of organic pentacene derivatives with electron-withdrawing substituent

Attaching electron-withdrawing substituent to organic conjugated molecules is considered as an effective method to produce n-type and ambipolar transport materials. In this work, we use density functional theory calculations to investigate the electron and hole transport properties of pentacene (PENT) derivatives after substituent and simulate the angular resolution anisotropic mobility for both electron and hole transport. Our results show that adding electron-withdrawing substituents can lower the energy level of lowest unoccupied molecular orbital (LUMO) and increase electron affinity, which are beneficial to the electron injection and ambient stability of the material. Also the LUMO electronic couplings for electron transport in these pentacene derivatives can achieve up to a hundred meV which promises good electron transport mobility, although adding electron-withdrawing groups will introduce the increase of electron transfer reorganization energy. The final results of our angular resolution anisotropic mobility simulations show that the electron mobility of these pentacene derivatives can get to several cm(2) V(-1) s(-1), but it is important to control the orientation of the organic material relative to the device channel to obtain the highest electron mobility. Our investigation provide detailed information to assist in the design of n-type and ambipolar organic electronic materials with high mobility performance.     

Donor-acceptor amphiphilic 2,2′-bipyridine chromophores: synthesis, linear optical, and thermal properties

Two symmetrical and one unsymmetrical ‘push-pull’ amphiphilic 2,2′-bipyridine chromophores have been synthesized through Horner-Wordsworth-Emmons and Knoevenagel reaction mechanized synthetic protocols and characterized by spectroscopy. Linear optical properties and thermal stability of the synthesized chromophores have been investigated.     

Synthesis, optical characterization, and electrochemical properties of isomeric tetraphenylbenzodifurans containing electron acceptor groups

Isomeric tetraphenylbenzodifuran systems, benzo[1,2-b:5,4]difuran and benzo[1,2-b:4,5]difuran, containing electron acceptor groups (CF(3), CN, and NO(2)) have been synthesized and studied. Their electronic absorption, fluorescence, two-photon absorption cross sections, and electrochemical properties were investigated. The absorption and emission maxima are red-shifted for the linear-conjugated systems in comparison with the corresponding isomer. Dual fluorescence was observed and the existence of a twisted intramolecular charge transfer state was confirmed by low-temperature emission experiments. Wide HOMO-LUMO energy gaps were obtained ranging from 2.53 to 3.28 eV. HOMO levels were found in the energy range of -6.03 to -6.63 eV while LUMO are within -2.55 to -3.52 eV.     

Synthesis, ionisation potentials and electron affinities of hexaazatrinaphthylene derivatives

Several hexaazatrinaphthylene derivatives and a tris(thieno)hexaazatriphenylene derivative have been synthesised by reaction of the appropriate diamines with hexaketocyclohexane. The crystal structure of 2,3,8,9,14,15-hexachloro-5,6,11,12,17,18-hexaazatrinaphthylene has been determined by X-ray diffraction; this reveals a molecular structure in good agreement with that predicted by density functional theory (DFT) calculations and pi-stacking with an average spacing between adjacent molecular planes of 3.18 A. Solid-state ionisation potentials have been measured by using UV photoelectron spectroscopy and fall in the range of 5.99 to 7.76 eV, whereas solid-state electron affinities, measured using inverse photoelectron spectroscopy, vary in the range -2.65 to -4.59 eV. The most easily reduced example is a tris(thieno)hexaazatriphenylene substituted with bis(trifluoromethyl)phenyl groups; DFT calculations suggest that the highly exothermic electron affinity is due both to the replacement of the outermost phenylene rings of hexaazatrinaphthylene with thieno groups and to the presence of electron-withdrawing bis(trifluoromethyl)phenyl groups. The rather exothermic electron affinities, the potential for adopting pi-stacked structures and the low intramolecular reorganisation energies obtained by DFT calculations suggest that some of these molecules may be useful electron-transport materials.     

Theoretical study of the optical and charge transport properties of star-shaped molecules with 1,3,5-triazine-core derivatives as organic light-emitting and organic solar cells materials

A series of D–π–A star-shaped molecules has been investigated theoretically by using density functional theory (DFT) to reveal their optical, electronic, and charge transport properties for applications in organic light-emitting diodes (OLEDs) and organic solar cells (OSCs). The calculated results show that their optical, electronic, and charge transport properties are affected by the different end groups and π-bridges. Our results reveal that the molecules under investigation can serve as OSCs donor materials and/or luminescent materials for OLEDs. In addition, all molecules are expected to be promising candidates for hole- and electron-transport materials. On the basis of the obtained results, we propose a rational way for the design of multifunctional materials for OLEDs and OSCs applications.     

Derivatization of valproic acid using ferrocene derivatives: Synthesis,characterization and investigation of optical and electrochemical properties

New ferrocenyl‐based valproic acid (VPA) ester derivatives were designed and synthesized according to the reaction of appropriate haloalkylferrocene derivatives with VPA in the presence of K₂CO₃ and a catalytic amount of 18‐crown‐6 ether. Elemental analyses and Fourier transform infrared, ¹H NMR, ¹³C NMR and mass spectra all well confirmed the predicted molecular structure. This is the first report in which ferrocene has been applied in derivatization of VPA as a chromogenic group. The electrochemical properties of the synthesized compounds were studied using cyclic voltammetry measurements, and energies of the frontier molecular orbitals were determined. In addition, the solubilities of the final compounds were studied in distilled water, phosphate buffer (pH = 7.4) and 0.9% (w/v) NaCl solution.     

Poly(p‐phenylene vinylene) derivatives containing triazole or oxadiazole segments: Connector effect in optical,electrochemical, and electroluminescent properties

To study the effect of connector structure between hole‐ and electron‐transporting segments, we synthesized and characterized new electroluminescent polymers P 1 – P 7 consisting of hole‐transporting 1,4‐bis(hexyloxy)‐2,5‐distyrylbenzene (DSB: P 1 and P 2 ) and electron‐transporting 4‐(4‐(hexyloxy)phenyl)‐3,5‐diphenyl‐4H‐1,2,4‐triazole (TAZ: P 3 and P 4 ) or 2‐(2,5‐bis(hexyloxy)‐4‐(5‐phenyl‐1,3,4‐oxadiazol)phenyl)‐5‐phenyl‐1,3,4‐oxadiazole (DIOXD: P 5 – P 7 ) segments linked by different connectors. The connectors between hole‐ and electron‐transporting segments are (1) 1,4‐phenylene in P 3 and P 5 , (2) 1,4‐divinylbenzene in P 4 and P 6 , and (3) 4,4′‐biphenyl in P 7 . Three corresponding end‐capped model polymers P 1‐M , P 2‐M , and P 3‐M were also synthesized to evaluate the effect of end groups. From optimized semiempirical MNDO calculations, the adjacent benzene rings between DSB and TAZ or DIOXD chromophores in P 3 , P 5 , and P 7 twist about 81°–89°. The effect of twisted architectures and connectors in optical and electrochemical properties for P 1 – P 7 have been discussed by comparing with copolymers P 1 and P 2 , which possess single bond or ether spacer as connectors. From cyclic voltammograms, the torsion in P 3 , P 5 , and P 7 confines electron delocalization and leads to simultaneously enhanced hole and electron affinity as compared to those of P 1 and P 2 . Furthermore, double‐layer light‐emitting diodes with a configuration of ITO/PEDOT:PSS/ P 1 – P 7 /Al all reveal green–yellow electroluminescence with maximum luminance at 8–320 cd/m² and their performances are greatly influenced by the connector's structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4514–4531, 2006