Influence of the halogen atom on the solid-state fluorescence properties of 2-phenyl-benzoxazole derivatives

• Published in: Dyes and pigments 2015-02, Vol.113, p.219-226
• Main Authors: Ghodbane, Abdelhamid, Saffon, Nathalie, Blanc, Sylvie, Fery-Forgues, Suzanne
• Format: Article
• Language: English
• Subjects: 2-Phenyl-benzoxazole; Bromination; Chemical Sciences; Crystal structure; Derivatives; Elongation; Fluorescence; Fluorination; Halogens; Heavy atom effect; Microcrystals; Nanostructure; Photoluminescence; Reprecipitation; Solid-state fluorescence
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2014.08.011

Four halogenated derivatives of 2-phenyl-benzoxazole and the unsubstituted analog were studied in solution and as powders by absorption and steady-state fluorescence spectroscopy. In solution, the fluorescence quantum yield was progressively decreased with increasing the size of the halogen atom, as explained by heavy atom effect. In the solid state, an increase in photoluminescence efficiency was observed when passing from the fluorinated to chlorinated derivative, and then the fluorescence efficiency was decreased for the brominated and iodinated derivatives, the latter compound being virtually not emissive. To explain the solid-state behavior, the influence of molecular arrangement on the emission properties was discussed on the basis of X-ray data. Finally, microcrystals were generated using a solvent-exchange method. An evolution from elongated platelets to cubic particles was observed with increasing the size of the halogen atom, providing preliminary information for the use of these compounds as micro- and nano-materials. [Display omitted] •Both heavy atom effect and molecular arrangement contributed to photoluminescence properties.•The chlorinated derivative displayed the best photoluminescence properties.•The halogen atom also controlled the morphology of microparticles obtained by reprecipitation.