Exploring the electronic and magnetic properties of C60 fullerene dimers with ladderane-like hexagonal bridges

A density functional study has been performed at B3LYP/6-31G(d) level of theory to investigate the electronic and magnetic properties of the dumbbell-like structures of fullerene dimers with boron-nitride hexagonal bridges C108(BN)3n+6, and their carbon counterparts C120+6n, n = 1–10. Interestingly enough, independent of the type and size of hexagonal bridge, the dumbbell-like structures of fullerene dimers represent a short range of negative NICS values (−11.4 to −13.8 ppm) calculated at the cage centers. Moreover, the computed variations of NICS values show that magnetic field decreases by going from the cage centers of fullerene dimers toward the ring centers of hexagonal bridge units. Magnetic field detects different behaviors inside the boron-nitride and carbon hexagonal bridges, an antiaromatic character in the C120+6n and almost non-aromatic character in the C108(BN)3n+6 compounds. The HOMO–LUMO gap as a function of the number of bridge hexagonal units follows a decreasing zigzag pattern in the C120+6n while in the C108(BN)3n+6 compounds it shows an upward trend up to C108(BN)12, and then remains constant until the formation of C108(BN)30. Moreover, binding energies for the C108(BN)3n+6 compounds are always lower than those of the C120+6n compounds and decrease linearly for both types of the fullerene dimers when the size of the hexagonal bridge increases.