Scanning tunneling microscopy investigation of an inclusion complex between the β-cyclodextrin and the sodium salt of the trisulfonated triphenylphosphine

Scanning tunneling microscopy has been used to image on a highly orientated pyrolytic graphite substrate an inclusion complex between the sodium salt of the trisulfonated triphenylphosphine (TPPTS) and the β-cyclodextrin (CyD). The images were in very good agreement with the structure that has been reported for this inclusion complex and it is postulated that β-CyD/TPPTS inclusion complex lies on the apolar graphite substrate by its primary face. A correlation of image contrast with the frontier orbitals of the inclusion complex is also clearly established for the first time in the case of CyD-based supramolecular assemblies. The self-assembly of the inclusion complexes on the graphic surface is also discussed.