Quantitative evaluation of solvation and packing effects on the visible absorption of anthraquinone derivatives (original) (raw)
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Study of natural anthraquinone colorants by EPR and UV/vis spectroscopy
The spectroscopic study was performed on 9,10-anthraquinone derivatives (purpurin, alizarin, carminic acid, and 2-(hydroxymethyl)-9,10-anthraquinone) in dimethylsulfoxide in the presence of triethylamine to bring information on their protonation/deprotonation equilibria in aprotic solvent. An interesting deprotonation effect of 5,5-dimethyl-1-pyrroline N-oxide (a spin trapping agent used in the EPR experiments) was revealed. The quantum chemical calculations enabled the identification of the individual protonated/deprotonated tautomeric forms present in the experimental systems. The UV photoexcitation of hydroxyanthraquinones (HAQ) led to the generation of reactive radical species and singlet oxygen, detected by in situ EPR spectroscopy (spin trapping, nitroxide radical elimination, oxidation of sterically hindered amines). The changes in the electronic absorption spectra upon photoexcitation, linked with the ability of the studied HAQ to generate reactive oxygen species upon exposure, confirm a substantial effect of the substituent character and position on the overall photochemical behavior of the HAQ, significantly influenced by the actual experimental conditions (solvent, pH).
Analytica Chimica Acta, 1995
The solvatochromic studies on 9,10-anthraquinone (AQ), and its symmetric dihydroxy derivatives namely l,Sdihydroxyanthraquinone (1,5-DHAQ) and 2,6_dihydroxyanthraquinone (2,6-DHAQ) in aqueous solvent mixtures of methanol, acetonitrile, tetrahydrofuran and n-propanol are reported. Preferential solvation is detected in every case. However, a remarkable variation in the magnitude of the preferential solvation constant KAB is observed when the composition of the mixture is changed. This effect is attributed to the solvent-solvent interaction between components. Moreover, and although stronger dipolar interactions are to be expected between the solute and water, only preferential solvation by the organic solvent is detected in every case. These effects may be explained in terms of self association of water through hydrogen bonding and the "microheterogeneity" of the binary mixtures. Moreover, differences are observed in the solvatochromic behavior of the solutes. In the case of 2,6-DHAQ the so-called synergistic effect is observed and explained as a function of the strong hydrogen bond solute-solvents interactions. Reversed-phase liquid chromatographic (RPLC) studies of AQ and 2,6-DHAQ in aqueous mixtures of methanol, acetonitrile and tetrahydrofuran were also performed. The results were interpreted by the Kamlet-Taft solvatochromic comparison method showing that the solvatochromic results can be correlated with certain success with RPLC data.
DNA-binding study of anthraquinone derivatives using Chemometrics methods
European Journal of Medicinal Chemistry, 2011
This work presents the interaction of two anthraquinones including quinizarin (1, 4-dihydroxyanthraquinone) and danthron (1, 8-dihydroxyanthraquinone) with CT-DNA in a mixture of Brittone eRobinson buffer (pH ¼ 7) with 50% of ethanol by UVevis absorption, circular dichroism spectroscopic methods and viscosity measurements. The PCA and INDICES methods were used for predicting the number of light-absorbing components. Partially intercalative and hydrogen binding were found to be the dominant binding modes between anthraquinones and CT-DNA. The effect of ionic strength and pH on the behavior of the above system and also the interaction of anthraquinones with ds and ss-DNA were used to confirm the mentioned binding modes. The EQUISPEC software and nonlinear least-squares analysis were applied for binding constant determination.
Theoretical investigation of substituted anthraquinone dyes
The Journal of Chemical Physics, 2004
We have investigated with computational chemistry techniques the visible spectra of substituted anthraquinones. A wide panel of theoretical methods has been used, with various basis sets and density functional theory ͑DFT͒ functionals, in order to assess a level of theory that would lead to converged excitation energies. It turns out that the hybrid Becke-Lee-Yang-Parr and Perdew-Burke-Erzenrhof functionals with the 6-31G (d,p) atomic basis set provide reliable max when the solvent effects are included in the model. Combining the results of both DFT schemes allows the prediction of max with a standard deviation limited to 13 nm.
Journal of Photochemistry and Photobiology A-chemistry, 1995
The photoinduced polymerization activities of six novel I-chloro4oxy substituted thioxanthones have been determined and compared to that of the Chydroxy and 4-n-propoxy derivatives in different monomers and prepolymers using RTIR and photocalorimetry methods. Absorption, fluorescence and phosphorescence analysis, as well as photoreduction studies have been undertaken on the compounds and the data is inter-related to their photopolymerization activities. In the case of the 4-propoxy derivative the I-chloro group has been replaced with a I-phenylthio substituent. Fluorescence and phosphorescence analysis indicates a high rate of intersystem crossing to the triplet state. The latter is essentially excited nn* in nature as indicated by the phosphorescence lifetime data. Compared with the I-chloro4hydroxy
Solvatochromism of anthraquinone and symmetrical dihydroxy derivatives. Local interactions
Spectrochimica Acta Part A: Molecular Spectroscopy, 1993
The solvent effects on the electronic absorption spectra of 9,10-anthraquinone (AQ) and its symmetric dihydroxy derivatives namely 1.5dihydroxyanthraquinone (1,SDHAQ) and 2,6dihydroxyanthraquinone (2,6-DHAQ) have been studied in pure solvents and some binary solvent mixtures. The frequencies of the absorption for AQ and 2,6-DHAQ are quite solvent sensitive while those for 15 DHAQ are not. Due to the intramolecular hydrogen bond between the C=O and OH groups, no influence of solvent hydrogen bond acceptors is observed in 1.5DHAQ. This hydrogen bond gives a stable six member cycle which is not broken even by the strongest hydrogen bond acceptor solvents used in this work, such as DMSO and DMF. The Taft and Kamlet's solvatochromic comparison method was applied for AQ and 2,6-DHAQ. Aromatic solvents and aliphatic amines were not included in the correlations since they strongly deviate suggesting another type of interactions. All the X+II * bands of AQ and 2,6-DHAQ show strong influence of n* despite the fact that their dipole moment is zero. Although it would be reasonable to expect that in the absence of a solute dipole moment there is not significant orientation of solvent molecules around the solute molecules, in this case dipolar interactions between solute and solvent due to local effects might be expected. AQ may be considered as formed by two carbonyl groups weakly interacting with the benzene rings; that means that the carbonyl group can behave as an isolated dipole and independently of the other. To detect possible specific interactions between the AQ and aliphatic amines and aromatic hydrocarbons, preferential solvation in mixed solvent was investigated. It is concluded that EDA interactions are important in the solvation of AQ with these compounds as solvents.
Journal of Chemical & Engineering Data, 1997
Dissociation equilibria of 4-(2-pyridylazo) resorcinol (PAR) in aqueous micellar solutions were determined spectrophotometrically at 25°C and at the constant ionic strength I = 0.1 M KNO 3 . For this purpose, the effect of nonionic (Brij-35, Triton X-100, Triton X-114, Triton X-405), and anionic (SDS) surfactants on the absorption spectra of PAR at different pH values was studied. Results show that the pK a values and pure spectra of each species of PAR are influenced by percentages of a neutral and an anionic surfactant such as Brij-35, Triton X-100, Triton X-114, Triton X-405 and SDS, respectively, added to the solution of this reagent. Ghasemi et al. . The pure spectra of different forms of PAR in (a) pure water, (b) 0.05% (w/v) Brij-35 to water, (c) 0.05% (w/v) Triton X-100 to water, (d) 0.05% (w/v) Triton X-114 to water, (e) 0.05% (w/v) Triton X-405 to water and (f) 0.05% (w/v) SDS to water.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2003
Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthraquinone (14DAAQ), 1,5-diamino-9,10-anthraquinone (15DAAQ), and 2,6-diamino-9,10-anthraquinone (26DAAQ) are investigated. Molecular geometries of the amino anthraquinones in the ground state are optimized using the semiempirical ZINDO/1 and AM1 methods without imposing any symmetry constraints. The ground state geometries of all the molecular systems are found to be planar. For interpretation of the spectra, ZINDO/S-CI and AM1-CI calculations employing singly excited configuration using the completely optimized geometry are carried out. Such calculations on the electronic spectra of amino anthraquinones are carried out for the first time. On the basis of these calculations, the assignment of the spectra are successfully made. #
Separation of 9,10-anthraquinone derivatives: Evaluation of C18 stationary phases
Journal of Chromatography A, 2011
A series of reversed phases bonded with several functional groups was investigated for separation of anthraquinone derivatives, following the previous work, dedicated to the selectivity of octadecyl silica bonded phases. Considering wide diversity of substitutions in hydrophobic anthraquinone skeleton, interactions like dipole-dipole,or H-bond acceptor/donor, as well as inclusion complexes formation can be employed to improve separation. In this study, several phases with grafts like cyano, nitro, aromatic, PEG, diol, calixarene and cyclodextrin were used with water-acetonitrile gradient for separation of thirty anthraquinoids' standards. The evaluation of performances was measured using the symmetry parameter and the number of critical pairs of peaks formed. The results point out the aromatic and calixarene bonded silica as the most interesting in terms of symmetry and critical pairs number. Finally we tested the performance of Caltrex Resorcinaren, Pursuit XRs DP and Luna Phenyl-Hexyl on real samples of anthraquinone natural dye extracted from a red thread taken from a 15th C. tapestry. We observed and compared the retention behaviour of some new anthraquinoids additional to our standards set and showing behaviour particular to substituted anthraquinone carboxylic acids.
Study of substitution effect of anthraquinone by SERS spectroscopy
Bull. Korean Chem …, 2004
In the present study, we carried out comparative research on the anthraquinones Raman spectrum and on the anthraquinones derivative 1, 4-diamino-anthraquinone focusing on change in its intermediate in terms of pH and change in the substituent. WE use the SERS ...