The nature of the bands in the electronic absorption spectrum of trans-chalcone

Sukhorukov, Andrey A.; Zadorozhnyi, B. A.; Lavrushin, V. F.

doi:10.1007/bf00530061

Cited by 7 publications

(6 citation statements)

References 13 publications

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“…In addition to their significant biological activities, chalcones, and aurones display attracting spectroscopic properties and potential application . Thus, the UV–Vis spectra of chalcones and aurones have been the subject of experimental and theoretical investigation. To the best of our knowledge, however, no experimental data about the UV–Vis spectra are available for all the studied compounds except for CH4 .…”

Section: Resultsmentioning

confidence: 99%

Antioxidant and spectral properties of chalcones and analogous aurones: Theoretical insights

Xue

Liu

Zhang

et al. 2018

Int J of Quantum Chemistry

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Density functional theory (DFT) and time-dependent DFT (TD-DFT) have been employed to elucidate the radical scavenging capacity and the UV-Vis spectral property of several chalcones and analogous aurones. Three main antioxidant mechanisms, hydrogen atom transfer (HAT), electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were investigated. The results indicate that all the studied compounds adopt a fully planar conformation in their neutral, radical, cationic as well as anionic forms. 2 0 -OH plays important role in the stabilization of phenolic radicals due to the formation of intramolecular hydrogen bonds (IHBs). Introduction of electron-donating substituent on B-ring is helpful for improving the activity. For the considered compounds, HAT is proposed as the thermodynamically favored mechanism in gas phase and nonpolar environment, while SPLET is preferred in polar media. The results confirmed the crucial role of hydroxyl group on A-ring, especially on position 5 0 /5, in terms of the radical scavenging ability. The absorption spectra of title compounds were successfully simulated and the lowest energy transitions predominantly correspond to the π-π* transitions from HOMO to LUMO with charge transfer (CT) character. K E Y W O R D Saurones, chalcones, density functional theory, mechanism, radical scavenging activity

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Section: Resultsmentioning

confidence: 99%

Antioxidant and spectral properties of chalcones and analogous aurones: Theoretical insights

Xue

Liu

Zhang

et al. 2018

Int J of Quantum Chemistry

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“…This π-π* transition is caused by the intramolecular charge transfer from the dimethylamino group acting as a donor to the electron acceptor fragment, carbonyl group. [10][11][12][13] Control experiments demonstrated that DMAC mol ecules do not form dimers at the concentrations used (50 µmol L -1 and lower): in a range of DMAC concen trations in hexane from 230 to 0.6 µmol L -1 , the station ary absorbance of the solution remains proportional to the DMAC concentration, and the shape of the absorp tion spectrum remains unchanged.…”

Section: Resultsmentioning

confidence: 99%

4-Dimethylaminochalcone as fluorescent probe: effect of the medium polarity on relaxation processes in the excited state

et al. 2004

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Relaxation processes in a 4 dimethylaminochalcone molecule after excitation with a light pulse of duration 70 fs were studied. During 0.4-1 ps after excitation, an absorbance of an excited state S 1 with a maximum at ~460 nm is formed in both polar and nonpolar media. Subsequent relaxation processes depend on the polarity of the medium. In nonpolar hexane, the 4 dimethylaminochalcone molecule transits to the triplet state having an absorption maxi mum at 570 nm (lifetime longer than 600 ps) for 20 ps. In polar aprotic acetonitrile, the absorbance at 460 nm decreases slowly (during hundreds of picoseconds), indicating that the molecules return to the ground state. The induced emission from the level S 1 in a region of 520-550 nm and fluorescence from the same level with a maximum at 537 nm are also observed in acetonitrile. Thus, a reason for a sharp decrease in the fluorescence yield on going from polar to nonpolar media was found. The mechanism of fluorescence quenching of 4 dimethylaminochalcone in nonpolar media is confirmed by the data on phosphorescence. The phosphorescence of 4 dimethylaminochalcone is observed at -196 °C in nonpolar sol vents, indicating a triplet excited state, while no phosphorescence is revealed in polar solvents.Key words: fluorescent probe, 4 dimethylaminochalcone, femtosecond dynamics, polarity of medium, triplet state.4 Dimethylaminochalcone (DMAC) as a fluorescent probe is used for studying biological membranes and lipo proteins. 1-6 It is poorly soluble in water and, hence, binds to lipids in the presence of mem branes or lipoproteins. 1 In polar solvents, the quantum yield of fluores cence can reach 0.26; however, the fluorescence of DMAC in water is almost completely quenched due to the forma tion of a hydrogen bond (other protic solvents quench DMAC flluorescence in the same manner). 3,4 When bind ing to proteins or lipids, a DMAC molecule is shielded from water, and the fluorescence yield can increase to 0.1 and higher. However, if the molecule has "drown" in the lipid depth and got into a nonpolar environment, the yield decreases to 0.01 and lower. Thus, it seems clearly why polar protic solvents quench fluorescence, while rea sons for fluorescence quenching in nonpolar media are unknown. In this work, we attempted to elucidate this problem. Experimental4 Dimethylaminochalcone was synthesized and kindly pre sented by B. M. Krasovitskii (Institute for Single Crystals, Na tional Academy of Sciences, Kharkov, Ukraine). 7 Acetonitrile, 95% EtOH, methylcyclohexane, and hexane (Aldrich) were used.The femtosecond dynamics of transient absorption spectra of DMAC was studied on an experimental system based on a femtosecond CPM dye laser designed at the N. N. Semenov Institute of Chemical Physics of the Russian Academy of Sci ences. 8 The "pump-probe" spectroscopy technique was used. The second harmonic from the main sequence of pulses gener ated by the system was used as pump pulses. The bearing wave length of a pump pulse was 308 nm, and the duration was 70 fs. Probe pulses were carr...

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“…That is why GS -1 (n, p*) transition intensity is weak, but it is distinguishable on DMAC absorption spectra in non-polar solvents. 31 Geometry optimization of 1 (n, p*), 1 (p, p*) and 3 (p, p*) states allowed to obtain the relaxed structures of excited states of the DMAC. The main parameters of optimized geometry of these states are shown in Table 4 (for atom numbering see Fig.…”

Section: The Nature and Properties Of Dmac Lower Excited Statesmentioning

confidence: 99%

Electronically excited states of membrane fluorescent probe 4-dimethylaminochalcone. Results of quantum chemical calculations

Romanov¹,

Gularyan

Polyak

et al. 2011

Phys. Chem. Chem. Phys.

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Quantum-chemical calculations of ground and excited states for membrane fluorescent probe 4-dimethylaminochalcone (DMAC) in vacuum were performed. Optimized geometries and dipole moments for lowest-lying singlet and triplet states were obtained. The nature of these electronic transitions and the relaxation path in the excited states were determined; changes in geometry and charge distribution were assessed. It was shown that in vacuum the lowest existed level is of (n, π*) nature, and the closest to it is the level of (π, π*) nature; the energy gap between them is narrow. This led to an effective (1)(π, π*) →(1)(n, π*) relaxation. After photoexcitation the molecule undergoes significant transformations, including changes in bond orders, pyramidalization angle of the dimethylamino group, and planarity of the molecule. Its dipole moment rises from 5.5 Debye in the ground state to 17.1 Debye in the (1)(π, π*) state, and then falls to 2 Debye in the (1)(n, π*) state. The excited (1)(n, π*) state is a short living state; it has a high probability of intersystem crossing into the (3)(π, π*) triplet state. This relaxation path explains the low quantum yield of DMAC fluorescence in non-polar media. It is possible that (3)(π, π*) is responsible for observed DMAC phosphorescence.

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The nature of the bands in the electronic absorption spectrum of trans-chalcone

Cited by 7 publications

References 13 publications

Antioxidant and spectral properties of chalcones and analogous aurones: Theoretical insights

Antioxidant and spectral properties of chalcones and analogous aurones: Theoretical insights

4-Dimethylaminochalcone as fluorescent probe: effect of the medium polarity on relaxation processes in the excited state

Electronically excited states of membrane fluorescent probe 4-dimethylaminochalcone. Results of quantum chemical calculations

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