Synthesis and Characterization of New Indeno[1,2-b]fluorene6,12-dione Derivatives

Indeno fluorene-6,12-dione derivatives 5 modified by different alkyl substitutions were designed and synthesized from 2,5-dibromo-p-xylene and phenylboronic acid derivatives through oxidation, esterification, Suzuki coupling, saponi-fication and cyclization reactions. Alkyl chains of different lengths were introduced into molecules to improve the solubility of the compounds and investigate the effects of systematic substitution variation on their properties. It was found that the solubility, thermal and optical stability of the new compounds were better than those of pentacene. Compounds 5 have increased electronegativities because of the low lowest unoccupied molecular orbital (LUMO) energies (=-3.4 eV). 2,8Diisopropylindeno[1,2-b]fluorene-6,12-dione (5b) and 2,8-dibutylindeno[1,2-b]fluorene-6,12-dione (5c) have rigid molecular frameworks and pack into slipped face-to-face p-stacks, the layer spacings are 0.3457 and 0.3423 nm, respectively. The molecular packing could facilitate carrier transport. The properties of these new materials indicate that they are good candidates for applications in organic optoelectronics.

Automated summary

Indeno fluorene-6,12-dione derivatives 5 were synthesized by modifying 2,5-dibromo-p-xylene and phenylboronic acid derivatives. The introduction of alkyl chains improved the solubility of the compounds and the effects of systematic substitution variation on their properties were investigated. The new compounds showed better solubility, thermal and optical stability than pentacene. The molecular packing of 2,8Diisopropylindeno[1,2-b]fluorene-6,12-dione (5b) and 2,8-dibutylindeno[1,2-b]fluorene-6,12-dione (5c) facilitated carrier transport.