کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1232817 1495245 2014 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Spectroscopic and quantum chemical investigations of substituent effects on the azo-hydrazone tautomerism and acid–base properties of arylazo pyridone dyes
ترجمه فارسی عنوان
بررسی های شیمیایی اسپکتروسکوپی و کوانتومی اثرات جایگزین بر تودومریزه آزو هیدرازون و خواص پایه آکاسیا رنگ آریلا زوپیریدون
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
چکیده انگلیسی


• A good linear correlation between bond length and Hammett σp constants was observed.
• Difference in λmax between hydrazone and anionic forms correlates well with σp.
• The pKa values showed good correlations with σI constants.
• N3C5 bond length is the most sensitive to the electronic effects of substituents.

A series of 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone dyes was synthesized and the structure of the dyes was confirmed by UV–Vis, FT-IR, 1H NMR and 13C NMR spectroscopic techniques. The azo-hydrazone tautomeric equilibrium was found to depend on the substituents as well as on the acidity and basicity of the media. Ionization constant, pKa, of the dyes was determined by UV–Vis spectroscopy and correlated with the Hammett substituent constants, σp and σI. The interpretation of the effect of different substituent in phenyl ring of arylazo pyridone dyes on their spectroscopic and structural properties was based on quantum chemical calculations performed by the density functional theory (DFT/M06-2X) method. The DFT calculations confirmed the existence of two forms in water solution: hydrazone form in acidic and neutral media and anionic form in basic media. The different contribution of azo and hydrazone canonical forms of anionic form is observed for dyes with electron-donating and dyes with electron-withdrawing groups. The dependence of absorption spectra and determined pKa values to the substituent type seems to be mostly due to azo/hydrazone canonical structure ratio in their anionic form.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy - Volume 123, 5 April 2014, Pages 37–45
نویسندگان
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