Experimental and theoretical study of o-substituent effect on the fluorescence of 8-hydroxyquinoline

• Published in: International journal of molecular sciences Vol. 16; no. 2; pp. 3804 - 3819
• Main Authors: Zayed, Mohie E M, El-Shishtawy, Reda M, Elroby, Shaaban A, Obaid, Abdullah Y, Al-amshany, Zahra M
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10.02.2015; MDPI
• Subjects: 8-hydroxyquinoline (8-HQ); electronic absorption; ether and ester derivatives; Fluorescence; Ions; Models, Chemical; Models, Molecular; natural transition orbital (NTO); Oxyquinoline - chemistry; Protons; Quinolines - chemistry; Spectrometry, Fluorescence; Studies; TD-DFT calculations; UV-visible and fluorescence spectra
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms16023804

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.