Photochemical stitching of a tubularly assembled hexabenzocoronene amphiphile by dimerization of coumarin pendants.

A coumarin-appended amphiphilic hexa-peri-hexabenzocoronene (1) self-assembled to form graphitic nanotubes. Upon irradiation of lambda > 300 nm, the nanotubes in the solid state and suspension both underwent dimerization of the coumarin pendants, affording covalently stitched nanotubes, which were hardly soluble in CHCl3, a good solvent of 1. In contrast, a thin film cast from a homogeneous solution of 1 was intact to photoirradiation. Owing to the reversible nature of the photochemical stitching, both negative and positive patterns of the graphitic nanotubes were developed on a silicon substrate by a lithographic post processing.