Synthesis, structure, and photophysical and electrochemical properties of a pi-stacked polymer

Dibenzofulvene (DBF) was polymerized using anionic initiators to afford a vinyl polymer. Oligo(DBF)s having from two to eight side-chain fluorene moieties bearing different chain-terminal groups were isolated by preparative size-exclusion chromatography. The structures of the isolated oligomers were revealed by single-crystal X-ray and (1)H NMR analyses. Both in solution and in crystal, the in-chain fluorene moieties stacked on top of each other, while the terminal conformation varied depending on the terminal group. These conformational characteristics were supported by molecular mechanics and dynamics calculations. The oligomers and polymers indicated hypochromism and red shift in UV absorption spectra and exclusive excimer emission in fluorescence spectra. In addition, reduced oxidation potentials were observed for the oligomers in electrochemical analyses, which suggests charge delocalization over the pi-stacked electron systems. The photophysical and electrochemical effects increased with the chain length of the oligomers and leveled off around the chain length of an oligomer consisting of five fluorene units.     

超支化聚芴的合成与性能研究

采用2,7-二(4-羟基苯基)-9,9-二烷基芴(A2)与四对甲基苯磺酸季戊四醇酯(B4)通过A2+B4型缩聚反应合成了一系列共轭型超支化聚合物.利用紫外和荧光谱对聚合物予以表征,结果表明,此类聚合物均可发出稳定、纯正的蓝光.DSC和TGA显示,4种聚合物在150℃以下没有明显的相态变化,300℃以内无明显的热分解现象,这表明此类聚合物具有良好的热稳定性,有利于材料的发光效率及发光稳定性.     

Synthesis,characterization, and optoelectronic properties of hyperbranched polyfluorenes containing pendant benzylether dendrons

Linear polyfluorenes with low generation of side benzylether dendrons ( PLG0 , PLG1 ) and hyperbranched polyfluorenes with 1,3,5‐benzene branch unit ( PHG0 and PHG1 ) were prepared by the Suzuki coupling reaction to investigate the structural effect on optoelectronic properties. Their optical properties, both in solution and film state, were investigated using absorption and photoluminescence (PL) spectra. The excimer emission of polyfluorene at about 530 nm, induced by thermal annealing, was completely suppressed by the hyperbranched structure, but the suppression was not obvious by the side benzylether dendrons. The optoelectronic performance of the EL devices (ITO/PEDOT:PSS/polymer/Ca/Al) was strongly dependent upon chemical structures of the emitting polyfluorenes. The hyperbranched PHG0 with zero generation of benzylether side groups revealed the best device performance, with maximal luminance and maximal luminance efficiency of 2350 cd/m² and 0.33 cd/A, respectively. The results suggest that incorporation of branch units with low generation of benzylether dendrons is an effective way to improve annealing stability and EL performance of the polyfluorenes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5945–5958, 2008     

Quantum-chemical evaluation of electron-donor properties of ordinary and modified carbon sorbents

The electron-donor properties of ordinary and modified activated carbons were compared on the basis of quantum-chemical calculations and electrochemical investigations. The mechanisms of the effect of heteroatoms and functional groups on the aromatic system of the carbon matrix were shown on the electronic level.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 723–727, November–December, 1989.     

Intermolecular interactions in pi-stacked conjugated molecules. Synthesis,structure, and spectral characterization of alkyl bithiazole oligomers

Syntheses are reported of new 4,4'-dialkyl-2,2'-bithiazole oligomers that have alkenoxy side chains that are capable of easy conversion to oligomers with functionalized side chains, e.g., terminally substituted hydroxy chains. The crystal structures of two representative oligomers (4,4',4' ',4' "-tetra-(2-propenoxymethyl)-2,2',5',5' ',2' ',2' "-quaterthiazole (3P2) and 4,4',4' ',4' "-tetra-(3-hydroxypropyloxymethyl)-2,2',5',5' ',2' ',2' "-quaterthiazole (3H2)) were determined; 3P2 crystallizes in a pi-stacked motif with two molecules per unit cell, whereas 3H2 forms pi-stacks that are linked with hydrogen bonds to form infinite two-dimensional sheets with one molecule per unit cell. A comparison of the UV-vis spectra of the compounds in solution and in the solid state provides unequivocal evidence for the presence of a Davydov splitting, W(D) approximately 0.2 eV, in solid 3P2. The spectra are interpreted in the framework of molecular exciton theory to extract a value of the intermolecular transfer integral, J approximately 0.2 eV, for a total exciton bandwidth of ca. 0.8 eV. Monte Carlo calculations were used to determine the density of states of the exciton band and the absorption and emission line shapes of the 0 <-- 0 transition. It is suggested that the "three-humped" absorption profile typical of partially crystalline, regioregular polymers is the "optical signature" of pi-stacking.     

Synthesis and characterization of pi-stacked phenothiazine-labeled oligodeoxynucleotides

[reaction: see text] A facile procedure for the incorporation of N-methyl phenothiazine as the terminal nucleoside in oligodeoxynucleotides is reported. The phenothiazine nucleoside analogue is synthesized and then incorporated into DNA using an automated DNA solid-phase synthesizer. Phenothiazine-labeled oligodeoxynucleotides form stable B-form duplexes with higher melting temperatures compared to unlabeled DNA duplexes.     

Synthesis and structural, electrochemical, and stacking properties of conical molecules possessing buckyferrocene on the apex

A series of conical molecules featuring a [60]fullerene/ferrocene hybrid and five aralkyl side chains (Fe[C60{C6H4-(OCO-C6H3-(OR)2-3,4)-4}5]Cp) have been synthesized and examined for their structural and electrochemical properties as well as their ability to form supramolecular structures in crystals and liquid crystals. When the R group on the side is a methyl group, the compound forms crystals in which the dipolar conical molecules are stacked head-to-tail to form a columnar structure. When the R group is as long as a C18H38 group, the compound forms liquid crystals. Oxidation of the liquid crystalline compound by an aminium salt [(4-BrC6H4)3N][SbCl6] produces the corresponding paramagnetic Fe(III) compound that also exhibits liquid crystalline properties.     

Synthesis and photophysical properties of polyfluorenes bearing silicon‐based functional groups

Five polyfluorenes bearing bulky trimethylsilyl (PTMS1 and PTMS2), tris(trimethylsilyl)silyl (PTTMS1), and silsesquioxane groups (PPOSS1 and PPOSS2) were synthesized through palladium‐catalyzed Suzuki coupling reactions. In the solution state, every polymer showed comparable ultraviolet–visible spectra, and they emitted blue light with high quantum efficiency. In the solid state, however, three trimethylsilyl‐functionalized polyfluorenes indicated redshifts of the fluorescence peak. In particular, PTMS1 and PTTMS1, having a hydrogen at the C‐9 position of fluorene, also showed green‐light emissions. After the annealing of the spin‐coated films, the blue‐emissive peak decreased and the green‐emissive peak became stronger in the photoluminescence spectra of three trimethylsilyl‐functionalized polyfluorenes. In contrast, PPOSS2 showed a pure blue‐light emission in the film state and even after the thermal treatment, which could be accomplished by the encapsulation of the polymer chains by the large polyhedral oligomeric silsesquioxane molecule. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2119–2127, 2005     

Synthesis and optoelectronic properties of silole‐containing polyfluorenes with binary structures

2,5‐Bis(2‐bromofluorene‐7‐yl)silole was prepared by a modified one‐pot synthesis with a reverse addition procedure, from which novel silole‐containing polyfluorenes with binary random and alternating structures (silole contents between 4.5 and 25% and high M_w up to 509 kDa were successfully synthesized. The well‐defined repeating unit of the alternating copolymer comprises a terfluorene and a silole ring. Optoelectronic properties including UV absorption, electrochemistry, photoluminescence (PL), and electroluminescence (EL) of the copolymers were examined. The different excitation energy transfers from fluorene to silole of the copolymers in solution and in the solid state were compared. The films of the copolymers showed silole‐dominant green emissions with high absolute PL quantum yields up to 83%. EL devices of the copolymers with a configuration of ITO/PEDOT/copolymer/Ba/Al displayed exclusive silole emissions peaked at around 543 nm and the highest EL efficiency was achieved with the alternating copolymer. Using the alternating copolymer and poly(9,9‐dioctylfluorene) as the blend‐type emissive layer, a maximum external quantum efficiency of 1.99% (four times to that of the neat film) was realized, which was a high efficiency so far reported for silole‐containing polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 756–767, 2007     

Synthesis and photochromic properties of indolinospirochromenes with electron-donor substituents in the indoline part of the molecule

1,3,3-Trimethylspiro(indoline-2,2'-[2H]chromenes) with CH₃ and CH₃O groups in the 4–7 positions and NO₂ and CH₃O groups in the 6 and 8 positions were obtained by the reaction of 4,6-, 4,7-, 5,6-, and 6,7-dimethoxy- and 4-methyl-7-methoxy-2-methyleneindolines and 1,3,3,4,5,6,7-heptamethyl-2-methyleneindoline with 3- and 5-nitrosalicylaldehydes and their derivatives. Most of the compounds have photochromic properties. The introduction of electron-donor groups into the indoline fragment of the spirochromene molecules changes the rate of the dark reaction within the limits of one order of magnitude and has a small effect on the position of the long-wave absorption band of the photomerocyanine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1220–1224, September, 1982.     

Perfect polar stacking of parallel beloamphiphile layers. Synthesis, structure and solid-state optical properties of the unsymmetrical acetophenone azine DCA

Extraordinary high degrees of polar order can be achieved by a rational design that involves the polar stacking of parallel beloamphiphile monolayers (PBAM). This strategy is exemplified by the acetophenone azines MCA (4-methoxy-4'-chloroacetophenone azine) and DCA (4-decoxy-4'-chloroacetophenone azine). The beloamphiphile design aims to achieve strong lateral interactions by way of arene-arene, azine-azine, arene-azine and halogen-bonding interactions. Dipole-induced interactions and halogen bonding dominate interlayer interactions and halogen bonding is shown to effect the layer stacking. Crystals of DCA contain PBAMs with perfect polar order and perfect polar layer stacking, while crystals of MCA features perfect polar order only in one of two layers and layer stacking is polar but not entirely perfect. We report the synthesis of the beloamphiphile DCA, its crystal structure, and we present a comparative discussion of the structures and intermolecular interactions of MCA and DCA. Absorbance and photoluminescence measurements have been carried out for solutions of DCA and for DCA crystals. DCA exhibits a broad emission centered at 2.5 eV when excited with UV radiation. The nonlinear optical response was studied by measuring second harmonic generation (SHG). Strong SHG signals have been observed due to the polar alignment and the DCA crystal's NLO response is 34 times larger than that of urea. Optimization of the beloamphiphile and systematic SAR studies of the polar organic crystals, which are now possible for the very first time, will further improve the performance of this new class of functional organic materials. The materials are organic semiconductors and show promise as blue emitters, as nonlinear optical materials and as OLED materials.     

Synthesis,structure, and properties of N-quinoxalylformazans

The first representatives of the previously unknown N-quinoxalylformazans were synthesized. Their chemical properties were investigated, and their structure and chromaticity are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1705–1707, December, 1973.     

Synthesis and characterization of polyfluorenes containing bisphenazine units

Novel conjugated copolymers based on 9,9‐dioctylfluorene and bisphenazine (BP) were synthesized by Suzuki polymerization. Energy transfer from the conjugated main chain to the BP moieties was observed. Full energy transfer was achieved when the molar content of the bisphenazine was 20% (20BPPF) in toluene solution. The similar phenomena were observed even for 1% bisphenazine content copolymer (1BPPF) in film. The lowest occupied molecular orbital (LUMO) energy levels (?3.06 eV) of the copolymers were lower than that of the polyfluorene homopolymer (PFO; ?2.65 eV), indicating that the introduction of the BP unit was benefit to electron injection. Single‐layer electroluminescent devices (ITO/PEDOT:PSS/polymer/LiF/Al) were fabricated to investigate their electroluminescence (EL) performances. The maximum brightness and current efficiency of all BPPF copolymers surpassed the PFO homopolymer. The best single‐layer device was based on 5BPPF, with a maximum brightness of 1532 cd/m² and current efficiency of 1.09 cd/A. Much higher efficiency could be achieved for multilayer EL devices of 5BPPF (ITO/PEDOT:PSS/PVK/polymer/TPBI/LiF/Al), which showed a maximum current efficiency of 10.01 cd/A. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1990–1999, 2010     

Synthesis,physical properties,and structure of TIPS-difuranoacenes

The synthesis, physical properties, and structure of triisopropylsilylethynyltetracenodifuran (2) and pentacenodifuran (3) derivatives were reported. There showed high stability in solution in the dark, yet decomposed under light. Single crystal of pentacenodifuran was analyzed by X-ray diffraction analysis, and showed one dimensional packing array along the c-axis. The molecules were stacked with a 3.30 Å interlayer distance. The crystals exhibited a high thermal stability under an ambient condition.     

Synthesis,structure, and properties of isomeric polyaminoacetophenones

In terms of the ability for electrochemical transformations in acidic medium, the reactivity decreases in the order o-aminoacetophenone > p-aminoacetophenone > m-aminoacetophenone > aniline. The products of electrochemical polycondensation of the ortho and para isomers are conductors. Oxidative polycondensation of o-aminoacetophenone forms emeraldin hydrosulfate, and with p- and m-aminoacetophenones, emeraldin and leucoemeraldin are formed. In terms of thermal stability, polyacetoaminophenones can be ranked in the order poly-o-aminoacetophenone > poly-m-aminoacetophenone > poly-p-aminoacetophenone.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 2012–2018.Original Russian Text Copyright © 2004 by Stratan, Kovalchuk, Blazejowski.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis,structure, and properties of aromatic polysulfides

Polycondensation of haloaromatics and sodium sulfide has been studied. An increase in reactivity of functional groups, a change of the composition of the elementary polymeric unit with a change of the relative amounts of the monomers, and a key role of side-reactions, i.e. intra(molecular) and macrocyclisation, have been revealed. Low-melting isomeric poly(phenylene sulfides), as well as their derivatives, reactive telechelic oligomers, have been prepared. New methods of preparation of poly(arene sulfides) by transarylation of diphenyl sulfide, polymerisation of cyclic aromatic sulfides, or by direct polycondensation of arenes with sulfur under the action of AlCl₃, as well as by polycondensation of aniline with sulfur in the absence of catalysts have been suggested. Structures and properties of newly prepared polymers have been studied.     

Synthesis, structure, and properties of branched polymethacrylates

The methacrylate: branching agent: chain growth regulator optimal ratios that allow the synthesis of branched polymethacrylates via the crosslinking free-radical copolymerization under the regime of conventional or catalytic chain transfer have been estimated. Relationships between the molecular-mass characteristics of the copolymers, their content of intact C=C bonds, the composition of the starting monomer mixture, and the structure of the branching agent and polymer chain growth regulator have been established. The rheological properties of the branched MMA-based copolymers have been studied. It has been shown that the copolymers are characterized by a weaker dependence of reduced viscosity on the polymer concentration in solution than that for the linear PMMA. The diffusion-sorption behavior of the branched polymethacrylates is determined by the content of the branching agent in them.     

Synthesis,structure, and properties of LaSrCuGaO5

The new brownmillerite-related compound, LaSrCuGaO₅, has been synthesized and characterized. It crystallizes in the orthorhombic non-centrosymmetric space group Ima2. The unit cell dimensions are a = 16.383(1) Å, b = 5.5293(7) Å, c = 5.3275(6) Å. The structure is related to perovskite but contains ordered oxygen vacancies within the two-dimensional gallium oxygen layers resulting in tetrahedral coordination of the gallium cations. Other important structural features include buckled copper-oxygen planes, and disorder of the lanthanum and strontium cations over the A-site. Accurate lattice constant measurements reveal an a-axis expansion of 0.17 Å when doped with strontium La_1–xSr_1+xCuGaO₅ (x_max = 0.13). Magnetic susceptibility measurements demonstrate that the compound remains paramagnetic to 4 K.