From 1,4-Phenylenebis(phenylmaleate) to a Room-Temperature Liquid-Crystalline Benzo[ghi]perylene Diimide.

The photocyclization of tetraethyl 1,4-phenylenebis(phenylmaleate) in the presence of iodine and oxygen predominantly yields tetraethyl [5]helicene-5,6,9,10-tetracarboxylate, together with small amounts of tetraethyl dibenz[a,h]anthracene-5,6,12,13-tetracarboxylate and tetraethyl benzo[ghi]perylene-3,4,11,12-tetracarboxylate. The helicene tetraester is planarized to the benzoperylene tetraester by Scholl reaction with AlCl3 followed by reesterification of the partially hydrolyzed crude product. Subsequent treatment with a branched alkylamine yields a columnar liquid-crystalline benzoperylene diimide whose mesophase is stable at room temperature despite its limited and non-centrosymmetric alkyl periphery. Its absorption spectrum is markedly red-shifted compared to that of a similar benzoperylene triimide.