A Series of Soluble Planar Oligorylenes up to Hexarylene†

Abstract

Preparation of large rylenes often needs the use of solubilizing groups along the rylene backbone, which results in the distortion of the skeleton and thus broadening of the absorption spectrum. In this work, we successfully synthesized 2,5,8,16,19,22-hexakis[2,6- bis(tri-fluoromethyl)phenyl]hexarylene (H) by using an oxidative fusion reaction of perylene trimer in 5% yield. The product is soluble in common organic solvents and could be purified with column chromatography. Single-crystal X-ray diffraction analysis revealed that the hexarylene core is not disturbed by the substituents very much and is almost planar. The longest absorption of H exhibits a sharp peak at 831 nm and an on-set at 875 nm in toluene with a small full-width-at-half-maximum (FWHM) of 660 cm-1. The molar extinction coefficient is as large as 131,000 M-1 cm-1. The substituents could not perturb the electronic properties of the hexarylene because aryl groups are perpendicular to the hexarylene core and the carbon atoms at 2,5,16,19-positions have negligible coefficients on its HOMO and LUMO, estimated by theoretical calculations. As a result, the hexarylene having less absorption at the visible light region was stable enough in solution under the LED room light for more than 1 week. This strategy gives a useful guideline to establish the near-infrared materials that exhibit stability under ambient conditions.