Experimental and Theoretical Study of O-Substituent Effect on the Fluorescence of 8-Hydroxyquinoline

• Main Authors: Mohie E. M. Zayed, Reda M. El-Shishtawy, Shaaban A. Elroby, Abdullah Y. Obaid, Zahra M. Al-amshany
• Format: Article
• Language: English
• Published: MDPI AG 2015-02-01
• Series: International Journal of Molecular Sciences
• Subjects: ether and ester derivatives; 8-hydroxyquinoline (8-HQ); UV-visible and fluorescence spectra; TD-DFT calculations; electronic absorption; natural transition orbital (NTO)
• Online Access: http://www.mdpi.com/1422-0067/16/2/3804

The synthesis and characterization of different ether and ester derivatives of 8-hydroxyquinoline have been made. UV-visible and fluorescence spectra of these compounds have revealed spectral dependence on both solvent and O-substituent. The fluorescence intensity of ether derivatives revealed higher intensity for 8-octyloxyquinoline compared with 8-methoxyquinoline, whereas those of ester derivatives had less fluorescence than 8-hydroxyquinoline. Theoretical calculations based on Time-dependent density functional theory (TD-DFT) were carried out for the quinolin-8-yl benzoate (8-OateQ) compound to understand the effect of O-substituent on the electronic absorption of 8-hydroxyquinaline (8-HQ). The calculations revealed comparable results with those obtained from the experimental data. Optimized geometrical structure was calculated with DFT at B3LYP/6-311++G** level of theory. The results indicated that 8-OateQ is not a coplanar structure. The absorption spectra of the compound were computed in gas-phase and solvent using B3LYP and CAM-B3LYP methods with 6-311++G ** basis set. The agreement between calculated and experimental wavelengths was very good at CAM-B3LYP/6-311++G** level of theory.