Papers by Yuliya Zhuravleva
Advanced Functional Materials, 2021
Linearly conjugated oligomers attract ever‐growing attention as promising systems for organic opt... more Linearly conjugated oligomers attract ever‐growing attention as promising systems for organic optoelectronics because of their inherent lucky combination of high charge mobility and bright luminescence. Among them, furan‐phenylene co‐oligomers (FPCOs) are distinguished by outstanding solubility, very bright luminescence, and good hole‐transport properties; however, furan‐containing organic semiconductors generally lack electron transport, which makes it impossible to utilize them in efficient light‐emitting electronic devices, specifically, ambipolar light‐emitting transistors. In this work, 1,4‐bis(5‐phenylfuran‐2‐yl)benzene (FP5) derivatives are synthesized with the fully/partially fluorinated central and edge phenyl rings. It is shown that the selective fluorination of FPCOs lowers the energies of frontier molecular orbitals, maintaining the bandgap, solubility, and bright luminescence, dramatically improves the photostability, tunes the π‐π stacked packing, and allows the first realization of electron transport in FPCOs. It is found that selectively fluorinated 2,2′‐(2,3,5,6‐tetrafluoro‐1,4‐phenylene)bis[5‐(3,5‐difluorophenyl)furan] demonstrates well‐balanced ambipolar charge transport and efficient electroluminescence in an organic light‐emitting transistor (OLET) with external quantum and luminous efficiencies as high as 0.63% and 5 cdA−1, respectively, which are among the best reported for OLETs. The findings show that “smart” fluorination is a powerful tool to fine‐tune the stability and performance of linearly conjugated small molecules for organic optoelectronics.
Free Radical Biology and Medicine, 2021
In the human eye lens the endogenous chromophores of UV-A light (315-400 nm) are able to sensitiz... more In the human eye lens the endogenous chromophores of UV-A light (315-400 nm) are able to sensitize radical reactions leading to protein modifications during normal aging and the cataract progression. Kynurenic acid (KNA-) is the most photochemically active dye of the human eye lens reported to date with pKa(KNAH2•) 5.5 for its radical form. Cataract is thought to develop under oxidative stress which could be accompanied by acidosis, an acidification of the intracellular environment. Protonation of kynurenyl radicals at mildly acidic conditions may change the outcome of radical reactions leading to additional damage to proteins. In this work we investigated the influence of pH on the degradation of initial reagents and the formation of products in photoinduced radical reactions between KNA- and amino acids tryptophan (Trp) and tyrosine (Tyr) in free states. Our results have shown that pH variation has minor influence on kinetics of reagent decay and accumulation of products in reactions between tyrosyl and kynurenic acid radicals. However in the case of Trp a two-fold decrease of the reagent degradation without visible changes in the composition of formed products was observed with pH decrease from 7 to 3. Time-resolved measurements have shown similar acidification-induced two-fold acceleration of decay of kynurenyl and tryptophanyl radicals via Back Electron Transfer (BET) with the restoration of initial reagents. Experiments with tryptophan derivatives with different pKa values for their radical forms point out the protonation of tryptophanyl radical as the driving force for BET acceleration at low pH. Our results demonstrate that the protonation of kynurenyl radical does not change its reactivity towards amino acids radicals but the total yield of radical photodamage decreases with the protonation of tryptophanyl radicals. It could be expected that radical induced damage to proteins will depend on the pKa of tryptophanyl radicals within a protein globule.
Journal of Photochemistry and Photobiology A: Chemistry, 2020
Proton-coupled electron transfer as the mechanism of reaction between triplet state of kynurenic ... more Proton-coupled electron transfer as the mechanism of reaction between triplet state of kynurenic acid and tryptophan Yuliya S. Zhuravleva (Investigation) (Validation) (Visualization), Olga B. Morozova (Methodology) (Writing-review and editing), Yuri P. Tsentalovich (Writing-review and editing), Peter S. Sherin (Conceptualization) (Methodology) (Supervision) (Writing-original draft) (Writing-review and editing)
Journal of Photochemistry and Photobiology A: Chemistry, 2018
Kynurenic acid (KNA), a degradation product of endogenous UV filter of the human lens kynurenine,... more Kynurenic acid (KNA), a degradation product of endogenous UV filter of the human lens kynurenine, is a convenient model compound for studying reactions of photoexcited chromophores with amino acids, peptides and proteins. In this work, transient absorption spectra of triplet KNA (T KNA) and KNA radical (KNA% −) were obtained for aqueous solutions with different pH's, and the dissociation constants for T KNA (pKa = 3.7) and KNA% − (pKa = 5.5) have been determined. The quenching of T KNA by oxygen, tryptophan and ascorbate proceeds with nearly diffusion rate constants, weakly dependent on the charge on T KNA and on quencher. The quenching by tyrosine and histidine are much slower, and the quenching rate constants depend on solution pH's. The most pronounced pH-dependence was found for T KNA quenching by thiols cysteine and glutathione, which can be attributed to the switch of the quenching mechanism from the electron transfer in alkaline solutions to the hydrogen atom transfer under neutral and acidic conditions.
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Papers by Yuliya Zhuravleva