Density functional theory study on the [5,6]-diaryl-methano fulleroids of C70 with different functional groups

We investigated the functionalization of [5,6] bonds of a C70 fullerene by diphenyl-methano (DPM) derivatives using density functional theory calculations. It was found that the stability of [5,6]-DPM-fulleroids (products) displays the same trend (α > β > γ > δ) to that detected experimentally. The reaction energy is calculated to be in the range of −10.1 to −20.5 kcal/mol in the toluene solvent. We also investigated the effect of different para-substituent groups on the reaction and electronic properties. Amino group (especially N(CH2CH3)2) in the para position of the phenyl groups of the DMP (compared to the epoxy functionality used in the experiment) may make more easier the synthesis of the [5,6]- DMP [70] fluorides, releasing much more energy. Also, amino groups significantly increase the electrical conductivity and electron emission, and make the fullerene more suitable acceptor for solar cells. We found a linear relationship between the LUMO and reaction energy, and the para-Hammett constant of the substitutes. Theoretical orbital and NMR analyses explain the experimentally observed UV-visible spectrums and NMR data, confirming the [5,6]-fulleroids production rather than [6,6]-methanofullerenes.