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The effect of substituents R on the tautomerism and electronic absorption spectra of 1-hydroxy-x-R-9,10-anthraquinones and 9-hydroxy-x-R-1,10-anthraquinones was studied by quantum-chemical and correlation methods. The former compounds (x 2) are more sensitive to substituent effects than the latter compounds. Examination of the fine structure of long-wave absorption showed that the experimental spectra of 1-hydroxy-x-R-9,10-anthraquinones contain no bands assignable to ana-quinoid forms. 相似文献
23.
Quinalizarin and anions derived therefrom exist as equilibrium mixtures of different tautomers and conformers, whose structure depends on the conditions. Quinalizarin was shown to have 9,10-, 1,10-, 1,4-, 1,5-, 1,7-, and 2,9-quinoid structures, but not 1,2-quinoid structure; and its anions in ethanol media were identified as 9,10-, 1,10-, 2,9-, and 1,5-quinoid tautomers. Interactions with solvents and ionization could give rise to displacement of tautomeric and conformational equilibria, leading to considerable change in the number and position of π l ,π* bands in the electronic absorption spectra, which are responsible for the color. 相似文献
24.
Fain V. Ya. Avakyan V. G. Zaitsev B. E. Ryabov M. A. 《Russian Journal of Coordination Chemistry》2004,30(9):671-677
The character of the electronic absorption spectra of metal complexes with alizarin complexone AC is determined by the ionization degree of the ligand and the ratio between its excited states with different contributions of tautomeric 9,10-, 1,10-, 2,9-, and 1,2-anthraquinoid resonance structures. It was found by the spectrophotometric, quantum-chemical, and correlation methods that the ligand in metal complexes can exist in three forms, namely, neutral and two ionized forms (containing one or two deprotonated hydroxy groups). For each of the latter two forms, four excited states with the dominating contribution of the 9,10-, 1,10-, 2,9-, or 1,2-anthraquinoid resonance structures are possible. The formation of red monometallic complexes involves the peri- or ortho-hydroxycarbonyl group in anthraquinoid tautomers (mostly, 1,2- and 2,9-structures). The color of bimetallic complexes is determined by four anthraquinoid structures of the ligand (from red 9,10- to blue 1,10-anthraquinones). Fluorine-containing complexes exist only as 1,2- and 1,10-anthraquinoid structures, which are responsible for their blue color. The known metal complexes with Alizarin Complexone AS were classified by their structures. 相似文献
25.
According to the data of quantum-chemical calculations and correlation analysis, the experimental electronic absorption spectra of quinizarin and its substituted derivatives contain bands corresponding to 9,10-, 1,10-, and 1,4-anthraquinoid tautomers. Analysis of the absorption spectra revealed specific features of the tautomeric structure of substituted quinizarins. 相似文献
26.
A procedure was proposed for quantitative analysis of tautomeric equilibria of organic compounds. Purpurin was found to exist mainly as 9,10-, 1,4-, and 1,10-anthraquinoid tautomers, its monoanion, as 1,10-anthraquinoid tautomer, the dianion, as 1,10- and 2,9-anthraquinoid tautomers, and the trianion, as 1,10-, 1,4-, and 2,9-anthraquinoid tautomers. Tautomeric transformations occur both in the ground and in the excited states, and the corresponding changes of quantum-chemical parameters in these states are essentially different. The excited states are more sensitive to tautomeric transformations than the ground states.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 43–50.Original Russian Text Copyright © 2005 by Fain, Zaitsev, Ryabov. 相似文献
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28.
Ganesh Kamath Igor Kurnikov Boris Fain Igor Leontyev Alexey Illarionov Oleg Butin Michael Olevanov Leonid Pereyaslavets 《Journal of computer-aided molecular design》2016,30(11):977-988
We present the performance of blind predictions of water—cyclohexane distribution coefficients for 53 drug-like compounds in the SAMPL5 challenge by three methods currently in use within our group. Two of them utilize QMPFF3 and ARROW, polarizable force-fields of varying complexity, and the third uses the General Amber Force-Field (GAFF). The polarizable FF’s are implemented in an in-house MD package, Arbalest. We find that when we had time to parametrize the functional groups with care (batch 0), the polarizable force-fields outperformed the non-polarizable one. Conversely, on the full set of 53 compounds, GAFF performed better than both QMPFF3 and ARROW. We also describe the torsion-restrain method we used to improve sampling of molecular conformational space and thus the overall accuracy of prediction. The SAMPL5 challenge highlighted several drawbacks of our force-fields, such as our significant systematic over-estimation of hydrophobic interactions, specifically for alkanes and aromatic rings. 相似文献
29.
The products of reaction of α-hydroxyanthraquinones with boric acid are mixtures of 9,10-, 1,10 -, 1,4- and 1,5-quinoid tautomeric
complexes of boric acid and borate esters differing by the coordination bonds with carbonyl groups existing in the dynamic
equilibrium. The deepening of the reagents color in the presence of boron does not a result only of the complexation, but
in the accompanying shift of the tautomeric equilibria. 相似文献
30.
V. Ya. Fain B. E. Zaitsev M. A. Ryabov 《Russian Journal of Coordination Chemistry》2006,32(8):610-613
Reactions of metal salts with 1-hydroxyanthraquinone and its derivatives gave tautomeric 9,10-and 1,10-quinoid complexes and compounds containing no C=0 → M coordination bond. Each form is characterized by a single π1,π*-band. The absorption bands were assigned by using correlations with the σA-constants of the hydroxy and oxido groups for tautomeric anthraquinones. Complexes with nonionized ligands have particularly the 9,10-anthraquinoid structures; complexes with ionized ligands can form both 9,10-and 1,10-quinoid structures. 相似文献