Sapphyrin−Nanotube Assemblies

Single wall carbon nanotubes (SWNTs) bind strongly to sapphyrins, quintessential pentapyrrolic “expanded porphyrin” macrocycles, through donor−acceptor stacking interactions. The specific use of a functionalized sapphyrin diol yields stable water-suspendable nanotubes and also permits the formation of well-defined assemblies in ionic liquids. The absorption and steady-state fluorescence spectra of the resulting noncovalently functionalized nanotube complexes have been analyzed in aqueous media and ionic liquids, yielding a description of the photophysical properties of the nanotube−sapphyrin complexes as donor−acceptor species for light-harvesting.