Interactions between tripodal porphyrin hosts and single walled carbon nanotubes: an experimental and theoretical (DFT) account

We describe a strategy for dispersing single walled nanotubes (SWNTs) in organic solvents using supramolecular coating with tailor-made, structurally adjustable tripodal porphyrin receptors. These have the ability to recognise SWNTs from DMF-toluene mixtures. HR TEM, TM AFM and SEM measurements showed that the hosts wrap around individual arc-made SWNTs, giving monodispersed composites in DMF which are stable for weeks. The dispersed composites were studied by Raman and fluorescence spectroscopies, including laser scanning confocal microscopy (for aggregates incorporated in cells). These porphyrin hosts encapsulate SWNTs based on pi-pi type interactions in an analogous manner to those observed by single crystal X-ray diffraction in their C(60) complexes. These interactions may be further reinforced by porphyrin-porphyrin stacking. Density functional theory (DFT) calculations predicted the structure of the SWNT : porphyrin host complex or composite formed and the binding energies of tripodal porphyrin hosts in composites with either C(60) or SWNT as guests.