Synthesis, characterization, and photoluminescence properties of difluoroboron complexes with bis-β-diketone ligands

• Published in: Research on chemical intermediates 2016-04, Vol.42 (4), p.2857-2866
• Main Authors: Liu, Hua, Yang, Ji-Huan, Lin, Lu, Wang, Dun-Jia, Fan, Ling, Hu, Yan-Jun
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Physical Chemistry
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-015-2182-3

Some novel difluoroboron bis-β-diketonates containing a pyridyl moiety were synthesized from diethyl 2,6-pyridinedicarboxylate via Claisen condensation with the corresponding aryl methyl ketones and followed by complexation with boron trifluoride etherate. Their spectroscopic behaviors were studied by FTIR, 1 H NMR, UV–Vis, and fluorescence spectroscopic techniques. The results indicated that difluoroboron bis-β-diketonates exhibited violet or blue fluorescence emission at 428–454 nm under UV illumination in DMSO and possessed high extinction coefficients. It was found that the nature of the substituents at benzene ring in bis-β-diketone ligands had a significant impact on the photoluminescence behaviors of difluoroboron complexes. The complex 5b exhibited the strongest photoluminescence intensity and highest quantum yield ( Φ u  = 0.93), due to two strong electron-donating methoxyl moieties in molecule and the compound 4b displayed the lowest photoluminescence intensity and quantum yield, assigned to the heavy atom effect of the chlorine atom in its molecule. The photoluminescence intensity and quantum yield of these difluoroboron complexes decreased in the sequence, 5b  >  2b  >  1b  >  3b  >  4b .