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Borisevich, N. A.; Kazakov, Sergey M.; Кухто, А. В.; Murtazaliev, D. V.; Khristoforov, O. V.

doi:10.1023/a:1016124815652

Cited by 9 publications

(10 citation statements)

References 5 publications

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“…From the EEL spectrum we see that the cross section of the long-wavelength transition with maximum at 3.9 eV, corresponding to the energy of the lowest unoccupied molecular orbital (LUMO), is considerably greater than the cross section of the intense shorter wavelength 6.6 eV transition even for electron energy 50 eV, which indicates that the studied compound is promising for use in OLED's. Such behavior occurs for many oxazoles and oxadiazoles [12], perylene and naphthalimide [13]. We should note that for low electron energy (17.5 eV), a low-intensity triplet transition is observed at 2.3 eV, which is close to the calculated value of 2.2 eV.…”

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confidence: 83%

Electroluminescent properties of dibenzoxazolyl biphenyl molecules

et al. 2007

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We have measured the energy loss spectra of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2-n-hexyloxy biphenyl for interaction with electrons with energies 17.5 eV and 50 eV. We used time-dependent density functional theory to calculate spectra of the singlet transitions, which match the experimental data well. We have shown that the cross section for the long-wavelength transitions is greater than the cross section for the short-wave transitions, which is attractive for efficient excitation by low-energy electrons. Electroluminescence was achieved for the studied compound. The threshold voltage was 3.5 V. Introducing an additional layer of copper phthalocyanine increases the brightness of the luminescence several-fold.Introduction. Electroluminescent devices based on organic compounds (organic electroluminescent diodes, also called organic light-emitting diodes (OLEDs)) have attracted tremendous attention from researchers because of their many applications, in particular in flat color displays [1,2]. They are distinguished by low operating voltage, high brightness of the luminescence, a broad range of organic compounds that can be used (emitting in different regions of the spectrum), easy fabrication and low cost. Despite the large number of proposed compounds, the search for them is always continuing, with the aim of achieving better operating characteristics. Only a small number of stable and efficient compounds are known that emit in the blue region of the spectrum. On the other hand, in order to improve the emission characteristics, a very promising approach is to use electroluminescent compounds with a large cross section for the long-wavelength transition that is greater than the cross section for the short-wavelength transitions. Generally for most compounds, the cross section for the long-wavelength transition is several times smaller than for the shortwavelength transition. It is convenient to use electron energy loss spectroscopy [3] to search for compounds satisfying the necessary conditions for the blue region of the spectrum. This method gives the position of the transition bands over a broad spectral region and the transition cross sections, and also other characteristics of electron-molecule collisions occurring in OLEDs.In this work, we have studied the electron energy loss (EEL) spectra of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2-n-hexyloxy biphenyl (dibenzoxazolyl biphenyl for short, or DBB):

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confidence: 83%

Electroluminescent properties of dibenzoxazolyl biphenyl molecules

et al. 2007

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“…The higher value of the maximum of the band of the formyl molecule seems to be associated with the conjugation of the C=O group with the indole ring. In the electron energy loss spectra of indole, formyl, and N-acetyl-L-tryptophan, just as of a number of earlier studied molecules [1][2][3][4], there are highfrequency bands of 8.3, 9.8, and 9.6 eV, respectively, which are assigned to superexcited states.…”

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confidence: 89%

“…The Stokesian shift of the fluorescence spectra relative to the low-frequency singlet bands of the electron energy loss spectra is +3000 cm -1 , which corresponds to complex organic molecules. In [1][2][3][4], it is shown that with increase in the energy of electrons E 0 (up to ,50 eV) the probability of excitation of molecules to higher singlet levels increases, but even at its very high values (E 0 + 100 eV) the electrons interacting with the molecule do not transfer to them an energy higher than 8-12 eV, which is needed to excite superexcited states. The bands in the electron energy loss spectra related to superexcited states have a very low intensity as compared to the S 0 -S 3 bands (6 eV) and S 0 -S 4 bands (7 eV); therefore the observed change in the fluorescence spectra of the studied compounds at E 0 should be related to dissociation of the molecules excited to the S 3 and S 4 levels.…”

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Interaction of Electrons with Indole, Tryptophan, and their Derivatives in the Gas Phase

et al. 2005

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UDC 535.376The electron energy loss spectra (EELS) of indole, 3-indolyl propionic acid, 3-indolealdehyde, 3-dimethylaminomethylindole, tryptophan, and N-acetyl-L-tryptophan in the gas phase upon excitation by monokinetic electrons with an energy of E 0 = 11-50 eV are obtained. The structure of EELS is determined in the main by the indole chromophore; the side groups, except for the C=O group of 3-indolealdehyde, exert an insignificant influence. The energy of the lower triplet level 3 L a is 3.3 eV for indole and its derivatives and 3.2 eV for tryptophan and N-acetyl-L-tryptophan. Four singlet transitions in the region of 4.4-7.2 eV have been identified. The molecules studied, except for tryptophan, fluoresce in the gas phase on excitation by electrons. At low values of E 0 (10-25 eV), the fluorescence spectra are similar and are due to the indole fluorophore. Just as in the case of optical excitation, fluorescence on excitation by electrons is associated with the 1 L b -S 0 transitions. An increase in the energy E 0 up to 60-80 eV leads to dissociation of a portion of the indole molecules and to the appearance of additional bands in the fluorescence spectrum. Keywords: electron, electron energy loss spectrum, fluorescence spectrum, triplet and singlet energy levels. Introduction. The processes of transformation of the energy of electrons by molecules are of great interest in physics, chemistry, and biology. In recent years, interactions of the molecules of a number of classes of organic compounds (polyphenyls and polyacenes [1], carbazole and furans [2], oxazoles and oxadiazoles [3], and fluorine and fluorenones [4]) with electrons have been studied.The present work is devoted to the investigation of interactions, with a monokinetic beam of electrons, of free biologically active molecules of indole, 3-indolylpropionic acid, 3-indolealdehyde (formyl), 3-dimethylaminomethylindole (gramine), tryptophan, and N-acetyl-L-tryptophan, which manifest themselves in electron energy loss and fluorescence spectra. Tryptophan -the most intensely fluorescing amino acid -is widely applied as a fluorescing mark in studying peptides and proteins, and it also serves as the main center used in investigating intracellular inclusions and the cells themselves. The electronic spectra of these molecules on optical excitation in condensed media were widely used and reflected in [5,8].Experimental. To measure electron energy loss spectra in interaction of electrons with the molecules studied, an electron spectrometer [9] with an energy resolution of 0.3 eV was used. The vapor pressure of the above-indicated compounds in the chamber did not exceed 10 -3 Torr, which ensured a single collision of molecules with electrons. The electrons scattered at an angle of 90 o relative to the incident monokinetic beam were analyzed by a HughesRozhanskii 127-deg electrostatic analyzer. The current of an electron beam was not higher than 10 µA. The optical absorption spectra were measured on an SP-700A spectrophotometer (Great Britain), and fluorescence ...

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“…15 Hence, gas-phase studies may offer insight into fundamental processes, which are not attainable when those molecules are embedded in their natural environment. For low-energy electron interactions with tryptophan, we note studies on electron transmission mapping the low-lying temporary anion states by Aflatooni et al 16 and an electron energy loss study by Borisevich et al 17 Furthermore, a number of electron attachment studies have been reported on tryptophan, 18−20 its methyl ester, 19 and N-acetyl tryptophan. 21 Also, electron stimulated desorption (ESD), from condensed films of tryptophan, has been reported for the electron energy range of 0 to 12 eV.…”

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confidence: 93%

Electron-Transfer-Induced Side-Chain Cleavage in Tryptophan Facilitated through Potassium-Induced Transition-State Stabilization in the Gas Phase

et al. 2021

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Fragmentation of transient negative ions of tryptophan molecules formed through electron transfer in collisions with potassium atoms is presented for the first time in the laboratory collision energy range of 20 up to 100 eV. In the unimolecular decomposition process, the dominating side-chain fragmentation channel is assigned to the dehydrogenated indoline anion, in contrast to dissociative electron attachment of free low-energy electrons to tryptophan. The role of the collision complex formed by the potassium cation and tryptophan negative ion in the electron transfer process is significant for the mechanisms that operate at lower collision energies. At those collision times, on the order of a few tens of fs, the collision complex may not only influence the lifetime of the anion but also stabilize specific transition states and thus alter the fragmentation patterns considerably. DFT calculations, at the BHandHLYP/6-311++G(3df,2pd) level of theory, are used to explore potential reaction pathways and the evolvement of the charge distribution along those.

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Cited by 9 publications

References 5 publications

Electroluminescent properties of dibenzoxazolyl biphenyl molecules

Electroluminescent properties of dibenzoxazolyl biphenyl molecules

Interaction of Electrons with Indole, Tryptophan, and their Derivatives in the Gas Phase

Electron-Transfer-Induced Side-Chain Cleavage in Tryptophan Facilitated through Potassium-Induced Transition-State Stabilization in the Gas Phase

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