Experimental and Computational Studies of Structure and Bonding in Parent and Reduced Forms of the Azo Dye Orange II
| Autor: | Stephen Norman Batchelor, Laurence C. Abbott, Bruce C. Gilbert, John Oakes, Adrian C. Whitwood, John R. Lindsay Smith, John N. Moore |
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| Rok vydání: | 2005 |
| Předmět: |
Models
Molecular Magnetic Resonance Spectroscopy Free Radicals Spectrophotometry Infrared Hydrazone Electrons Protonation Crystal structure Spectrum Analysis Raman Photochemistry Vibration law.invention chemistry.chemical_compound symbols.namesake law Polymer chemistry Computer Simulation Physical and Theoretical Chemistry Electron paramagnetic resonance chemistry.chemical_classification Aqueous solution Molecular Structure Benzenesulfonates Carbon-13 NMR Sulfonate chemistry symbols Raman spectroscopy Azo Compounds Oxidation-Reduction |
| Zdroj: | The Journal of Physical Chemistry A. 109:2894-2905 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/jp045216s |
| Popis: | The structure and bonding of the azo dye Orange II (Acid Orange 7) in parent and reduced forms have been studied using NMR, infrared, Raman, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, allied with density functional theory (DFT) calculations on three hydrazone models (no sulfonate, anionic sulfonate, and protonated sulfonate) and one azo model (protonated sulfonate). The calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group (Solvent Yellow 14) closely matches its reported crystal structure. The 1H and 13C NMR resonances of Orange II, assigned directly from 1D and 2D experimental data, indicate that it is present asor = 95% hydrazone in aqueous solution, and as a ca. 70:30 hydrazone:azo mixture in dimethyl sulfoxide at 300 K. Overall, the experimental data from Orange II are matched well by calculations on the hydrazone model with a protonated sulfonate group; the IR, Raman, and UV-visible spectra of Orange II are assigned to specific vibrational modes and electronic transitions calculated for this model. The EPR spectrum obtained on one-electron reduction of Orange II by the 2-hydroxy-2-propyl radical (*CMe2OH) at pH 4 is attributed to the hydrazyl radical produced on protonation of the radical anion. Calculations on reduced forms of the model dyes support this assignment, with electron spin density on the two nitrogen atoms and the naphthyl ring; in addition, they provide estimates of the structures, vibrational spectra, and electronic transitions of the radicals. |
| Databáze: | OpenAIRE |
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