The Role of Weak Bonding in Determining the Structure of Thiophene Oligomers inside Carbon Nanotubes

Abstract

The orientation preference of methyl-terminated thiophene oligomers inside an armchair nanotube was evaluated using density functional theory calculations with dispersion corrections (B97-D functional). According to the B97-D calculations, internal thiophene oligomers prefer to be located near the walls of the armchair nanotubes rather than at their center. The attractive π···π and CH···π interactions operating between the thiophene guest and nanotube host are sufficient within the nanotube to overcome the energy cost of deforming the thiophene oligomer from the more stable gas-phase conformation. As a result, thiophene oligomers inside the nanotube tend to form nearly planar structures, even though adjacent thiophene rings rotate around the connecting bond in the gas phase. These weak attractive interactions enhance the planarity of thiophene oligomers confined within larger-diameter nanotubes.