Synthesis and Solvatochromism of Substituted 4-(Nitrostyryl)phenolate Dyes
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- 作者：Rafaela I. Stock ; Leandro G. Nandi ; Celso R. Nicoleti ; Adriana D. S. Schramm ; Sheila L. Meller ; Renata S. Heying ; Daniel F. Coimbra ; Karla F. Andriani ; Giovanni F. Caramori ; Adailton J. Bortoluzzi ; Vanderlei G. Machado
- 刊名：Journal of Organic Chemistry
- 出版年：2015
- 出版时间：August 21, 2015
- 年：2015
- 卷：80
- 期：16
- 页码：7971-7983
- 全文大小：841K
- ISSN：1520-6904
文摘
4-(Nitrostyryl)phenols 2a鈥?b>9a were synthesized, and by deprotonation in solution, the solvatochromic phenolates 2b鈥?b>9b were formed. Their absorption bands in the vis region of the spectra are due to 蟺鈥撓€* electronic transitions, of an intramolecular charge-transfer nature, from the electron-donor phenolate toward the electron-acceptor nitroarene moiety. The frontier molecular orbitals and natural bond orbitals were analyzed for the protonated and deprotonated forms. The calculated geometries are in agreement with X-ray structures observed for 4a, 6a, and 8a. The HOMO鈥揕UMO energy gaps suggest that, after their deprotonation, an increase in the electron delocalization is observed. In the protonated compounds, the HOMO is primarily localized over the phenol ring and the C鈺怌 bridge. After deprotonation, it extends toward the entire molecule, including the NO2 groups. The solvatochromism of each dye was studied in 28 organic solvents, and it was found that all compounds exhibit a reversal in solvatochromism, which is interpreted in terms of the ability of the media to stabilize their electronic ground and excited states to different extents. The Catal谩n multiparameter equation is used in the interpretation of the solvatochromic data, revealing that the most important contribution to the solute/solvent interaction is the hydrogen-bond donor acidity of the solvent.