Diameter-based separation of single-walled carbon nanotubes through selective extraction with dipyrene nanotweezers

We have been developing host-guest methodology for the separation of single-walled carbon nanotubes (SWNTs) according to handedness and diameter with gable-type chiral diporphyrins. The diporphyrins, designated as porphyrin nanotweezers, consist of two porphyrins and rigid spacer in between. As an extension of our strategy, novel nanotweezers having two pyrenes instead of porphyrins have been designed, because pyrene is known to have high affinity toward SWNT surface. The pyrene nanotweezers presented here consist of two 1- or 2-pyrenes and 3,6-carbazolylenes with various N-substituents. For the extraction of SWNTs, the 1- and 2-pyrene nanotweezers show a marked contrast: 1-pyrene nanotweezers selectively extract SWNTs with diameters ranging from 0.84 nm to 0.97 nm, while 2-pyrene nanotweezers are not able to extract SWNTs at all.