Synthesis and electronic properties of a linearly fused anthracene dimer

We describe the synthesis and electronic properties of the novel interrupted hexacene 5,16-diphenylcyclobuta[1,2-b:3,4-b′]dianthracene (1). The synthesis is rooted in a sequential twin Sonogashira coupling of 2,3-dibromo-9,10-dihydro-9,10-epoxyanthracene followed by a Vollhardt 2+2+2 cyclotrimerization to give o-bromoaryl(trimethylsilyl) 8, after selective bromination. A Diels-Alder cycloaddition of the aryne from 8 and 1,3-diphenylisobenzofuran gave 1 after deoxygenation. Photophysical studies suggest that the fused cyclobutane ring been the two anthracene rings allows through-conjugation, but does not allow 1 to behave as a conjugated acene. Attempts to synthesize the parent analogue, cyclobuta[1,2-b:3,4-b′]dianthracene (2) were not successful, but detailed calculations are reported for both 1 and 2.