Synthesis and studies on luminescent biphenyl compounds

Hohnholz, Dirk; Schweikart, Karl-Heinz; Subramanian, L. R.; Wedel, Armin; Wischert, W.; Hanack, Michael

doi:10.1016/s0379-6779(99)00291-x

Cited by 42 publications

(14 citation statements)

References 13 publications

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“…The strongest peak in the electronic spectrum of complex XI was computed at 296.4 nm with a shoulder at 316.6 nm, which matches with the experimental bands at 283 nm with the small peak at 337 nm in the similar compound 3,3'-bis(2-phenylvinyl)-4,4'-dihexyloxy-1,1'-biphenyl. 10 …”

Section: Electronic Absorption Spectramentioning

confidence: 99%

“…On the other hand, a novel similar compound to PPV containing the biphenyl and stilbene structures has been obtained, and its characteristics in the solid state have been studied. 9 According to the Hohnholz's experiments on the PPV derivatives, 10 the computational models for a series of similar PPV derivatives were formed. The characters of the derivatives, such as HOMO-LUMO energy gap, ionization potential, electron affinity, absolute electron negativity, and the other spectra were studied in this paper.…”

Section: Introductionmentioning

confidence: 99%

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Electronic Structures and Spectroscopy of Luminescent para‐Phenylenevinylene Oligomers

Ding

Teng³

et al. 2008

Chin. J. Chem.

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The computational models for a series of PPV (para-phenylenevinylene) oligomers were formed based on the biphenyl and stilbene structures. These oligomers were optimized using DFT at B3LYP/6-31G (d) level. On the basis of the optimized geometries, the electronic spectra and 13 C NMR spectra were calculated by the INDO/CIS and B3LYP/6-31G(d) methods, respectively. It indicates that the main absorptions in the electronic spectra are red-shifted when the oligomer length is increased. The main absorptions in the electronic spectra and the 13 C chemical shifts are altered obviously when the substituents on the matrix are changed.

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Section: Electronic Absorption Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic Structures and Spectroscopy of Luminescent para‐Phenylenevinylene Oligomers

Ding

Teng³

et al. 2008

Chin. J. Chem.

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“…According to the data in [11], substituted biphenyls have a low tendency to crystallize and are convenient for studying low-molecular weight analogs of PPV. Owing to high emissivity in the solid state and good electron transport properties, TVD films of benzoxazole derivatives of biphenyl are also promising for use in electroluminescent devices [12].…”

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confidence: 99%

Effect of substituents in benzoxazole derivatives of biphenyl on the optical properties and photostability of their thin films

et al. 2009

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established that fluorine atoms in the biphenyl moiety of the benzoxasole derivatives significantly improve the stability of the TVD films relative to oxidative aging compared with hexyloxy substituents. Irradiation with UV light stimulates quenching of luminescence and structuring of the TVD film of the difluoro-substituted derivative.Introduction. The spectral properties of poly(phenylene vinylenes) (PPVs), used as thin-film electroluminescent materials, depend considerably on the nature of the substituents on the PPV backbone and side chains [1-3]. Thus the electroluminescence turn-on voltage for diodes containing thin films of poly[2-(2-ethylhexyloxyl)-5-(4-trifluoromethylphenyl)-1,4-phenylene vinylene] and poly[2-(2-ethylhexyloxy)-5-(3,5-bis(trifluoromethyl)phenyl)-1,4-phenylene vinylene] as emitting layers is 4.0 V and 3.3 V respectively [4], and 18 V for poly[2-(2-ethylhexyloxy)-5-phenyl)-1,4-phenylene vinylene] not containing electron-acceptor trifluoromethylphenyl substituents [5]. Very high photoluminescence efficiency (>60%) is observed for PPV films containing alkylsilyl substituents [6].The position of the substituents also affects the photoluminescent properties of PPV, and this effect is especially important in sold samples in which the major role is played by the steric factor and intermolecular interaction. For a poly(2,3-dibutoxy)-1,4-phenylene vinylene film, not only a hypsochromic shift has been observed but also a significant increase in the photoluminescence efficiency (~40%) [7] relative to a poly(2-methoxy-5-ethylhexyloxy)-1,4-phenylene vinylene film (~15%-20%) [8,9].We should point out that introducing bulky oxyalkyl side substituents is a widely used method for improving the stability of PPV films relative to crystallization. However, it has been established [10] that in TVD films of model low-molecular weight octyloxy-substituted phenylene vinylenes, the crystal phase content is higher than in octyl-substituted analogs.According to the data in [11], substituted biphenyls have a low tendency to crystallize and are convenient for studying low-molecular weight analogs of PPV. Owing to high emissivity in the solid state and good electron transport properties, TVD films of benzoxazole derivatives of biphenyl are also promising for use in electroluminescent devices [12].We showed earlier in [13] that 2,2′-oxyhexyl substituents in the biphenyl moiety of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl-1,1′-biphenyl (BP) reduce the photostability and promote aggregation of hexyloxy-substituted TVD films of biphenyl on storage, while a TVD film of unsubstituted biphenyl is stable relative to irradiation and oxidative aging.

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“…Generally introducing bulky side substituents into the PPV backbone increases its solubility and reduces the tendency toward crystallization in the thin-film state [3,4]. In order to study the effect of substituents on the optical properties of PPV and also the use of PPV as emission layers in light-emitting diodes, its low-molecular weight analogs can certainly be of interest: polyconjugated derivatives of biphenyl [5]. Depending on the electrondonor or electron-acceptor character and steric factors, substituents in these model derivatives affect their electrophysical and optical characteristics [6].…”

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confidence: 99%

“…Consequently, by controlling the number of side substituents in the biphenyl moiety, we can successively change the color of the fluorescence of TVD films of benzoxazole derivatives of biphenyls from yellow to green. We know [5] that oxyhexyl substituents in the 2,2′ position increase the angle of deviation of the linked 1,1′-biphenyl moieties from the unstrained state and this steric effect is most pronounced in the solid state, where molecular motions are hindered. As we see from Table 1 The optical density (Figs.…”

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confidence: 99%

Morphology and spectral properties of thin films of benzoxazole derivatives of biphenyl

et al. 2007

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We have studied the spectral properties and morphology of thin films (TVD films) formed by thermal vacuum deposition of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-1,1′-biphenyl and its substituted derivatives. We have shown that introducing bulky 2,2′-oxyhexyl substituents into the biphenyl units leads to a shift of the fluorescence maximum for the TVD films toward shorter wavelengths, a decrease in their photostability, and aggregation of the films during storage.Introduction. Polyphenylenevinylene (PPV) and its derivatives have been widely used in designing electroluminescent thin-film materials used as components of electronic devices for various purposes [1,2]. However, the low solubility of PPV limits its use, since in making electroluminescent cells the polymer layer is usually formed from solutions by centrifuging. Generally introducing bulky side substituents into the PPV backbone increases its solubility and reduces the tendency toward crystallization in the thin-film state [3,4]. In order to study the effect of substituents on the optical properties of PPV and also the use of PPV as emission layers in light-emitting diodes, its low-molecular weight analogs can certainly be of interest: polyconjugated derivatives of biphenyl [5]. Depending on the electrondonor or electron-acceptor character and steric factors, substituents in these model derivatives affect their electrophysical and optical characteristics [6]. A very important property of biphenyls is also their ability to form thin films by both the liquid method and the thermal vacuum deposition (TVD) method.The aim of this work was to establish the effect of the substituents in benzoxazole derivatives of biphenyl on the spectral characteristics and morphology of their TVD films. Benzoxazole derivatives have, along with electroluminescent properties, good electronic conductivity and can be used as one of the layers in making photoluminescent and electroluminescent devices [7].The Experiment. Substituted biphenyls having trans-trans stereochemistry of the double bonds were synthesized by reaction of the corresponding biphenyl dicarbaldehydes with 2-methylbenzoxazoles [8]:

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Synthesis and studies on luminescent biphenyl compounds

Cited by 42 publications

References 13 publications

Electronic Structures and Spectroscopy of Luminescent para‐Phenylenevinylene Oligomers

Electronic Structures and Spectroscopy of Luminescent para‐Phenylenevinylene Oligomers

Effect of substituents in benzoxazole derivatives of biphenyl on the optical properties and photostability of their thin films

Morphology and spectral properties of thin films of benzoxazole derivatives of biphenyl

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