Optoelectronic Properties of Cycloparaphenylene-Carbon Nanotube Based Molecular Architectures

Host-guest complexes comprising of cycloparaphenylene and carbon-based nanostructures have received enormous interest as a new class of materials in organic electronics. In the present study, the interactions of [10]cycloparaphenylene (CPP) and its derivatives with armchair carbon nanotube (CNT) are investigated by means of dispersion-corrected density functional theory. Different derivatives of cycloparaphenylene including nitrogen-doped, donor amino- and acceptor fluorine-substituted compounds viz., nN-[10]CPP, nNH(2)-[10]CPP and nF-[10]CPP, where n = 10, 20, and 40 are modeled. The values of stabilization energies reveal that the complexes of CPP with CNTs are energetically stable. Among the complexes of various CPP derivatives, only those with fluorine substitutions are found to be stable. The energy decomposition analysis suggests that the complexes are stabilized mainly by the dispersion interactions between constituent units. The optoelectronic properties of the complexes are investigated using the time-dependent density functional theoretical (TD-DFT) method and the results indicate that the complexes of bare CPP with CNT absorb in the near-ultraviolet and visible regions, whereas those of fluorine-substituted CPP with CNT absorb in wider range starting from near-ultraviolet to near-infrared region of the electromagnetic spectrum. The frontier molecular orbital analysis reveals photoinduced charge transfer in tetra-fluorinated complex. All complexes exhibit narrow energy gap between the highest occupied and the lowest unoccupied molecular orbitals. The high values of light-harvesting efficiency obtained for fluorine-substituted complexes suggest their use in photovoltaic devices. The studies also show that there is an energy barrier for the piston type movement of CNT in the complexes for the ground state, but not for the excited states. The barrier for rotation of bare and fluorinated CPP over CNT suggests the potential of these complexes as components in molecular wheels and shuttles.