Self-assembled columns of fullerene

Abstract

Columnar mesophases based on alternating triphenylene and hexaphenyltriphenylene moieties are exceptionally stable and able to accommodate bulky side-chain substituents within the alkyl chain continuum between the columns. This paper presents a system in which the triphenylene bears a fullerene on its side-chain and the hexaphenyltriphenylene equivalent is the aza-derivative hexakis(4-nonylphenyl)dipyrazino[2,3-f : 2′3′-h]quinoxalene, PDQ9. The mesophase formed was identified as hexagonal columnar (Col_h) by X-ray diffraction (a = 25.2 Å and c = 3.5 Å) but, in addition to the expected peaks, there is indication of a two-dimensional hexagonal superlattice with d-spacing 59 Å. This superlattice is believed to arise from ordering of the fullerenes within the liquid crystal matrix. It can be explained on the assumption that, to maximise fullerene–fullerene contact, the fullerenes form chains which wrap around the central column in every group of seven columns of the triphenylene : PDQ9 Col_h array.