Small molecule cyclopenta-fused polycyclic aromatic hydrocarbons (CP-PAHs) have been developed as electron accepting molecules that can be alternatives to fullerenes in organic solar cells. Previous work from our lab has shown the cyclopentannulated anthracene and pentacene chromophores result in electron accepting materials with low-energy lowest unoccupied molecular orbitals (LUMO) and small band-gaps. These systems are based on acenes, which are linearly fused six-membered rings. Traditionally, longer acenes are more reactive and relatively unstable compared to the shorter acenes and are highly sensitive to light and oxygen which results in their self-destruction. This work presents and intermediate case between the anthracene and pentacene chromophores with new CP-PAHs based on tetracenes being prepared. These molecules have been synthesized by a palladium-catalyzed cyclopentannulation reaction between 5,11-dibromotetracene and 1,2-bis(3-(dodecyloxy)phenyl)ethyne or 1,2-bis(5-methylthiophen-3-yl)ethyne, which was carried out in the presence of the catalyst system composed of Pd2dba3, P(O-Tol)3, LiCl, and KOAc in DMF at 130 oC. The new molecules were found to have LUMO energy levels, bandgaps, and photo-stabilities that were intermediate to previous chromophores, as expected for acene trends.

Electron acceptors based on cyclopentannulated tetracenes

2019 Spring National Meeting

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