Synthesis and photoelectric properties of novel indeno[2,1-a]phenalene-based derivatives

A series of novel indeno[2,1-a]phenalene derivatives 4a–j including electron-donating or electron-withdrawing groups were prepared by Pd-catalyzed Sonogashira–Hagihara reaction of 7-iodo-12-phenylindeno[2,1-a]phenalene with various arylacetylene. Photoelectric properties of these compounds were investigated by UV–vis absorption and fluorescence. The fluorescent emission of 4d containing dimethyl amino group is correlated with solvent polarity and environmental acidity, which indicates that this kind of compound can be used as solvent polarity sensor and pH sensor. In addition, the band gaps of these indeno[2,1-a]phenalene derivatives can be tuned in the range 1.78–2.09 eV by using different substituted groups. These findings indicate that indeno[2,1-a]phenalene-based molecule can be developed as an excellent fluorophore for optoelectronic material applications.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis and characterization of novel indeno [2,1-a] phenalene derivatives. ► The emission spectra show solvent polarity and environmental acidity dependence. ► The band gaps of the new compounds are in the range of 1.78–2.09 eV.