DFT Study on Methanofullerene Derivative [6,6]-Phenyl-C₆₁ Butyric Acid Methyl Ester

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) with hybrid functional B3LYP were used to investigate several physical and chemical properties of [6,6]-phenyl-C61 butyric acid methyl ester (PCBM), including the geometry, electron structure, charge population, bond properties, as well as IR, Raman and electronic absorption spectra. The analysis of the natural bond orbital (NBO) suggested that there were about 0.11 electrons transferred from the moiety phenyl and butyric acid methyl ester group of PCBMto fullerene cage. The strongest IR and Raman peaks came from different modes with the frequencies of 1773 and 1492 cm-1, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant, and hyperpolarizability were 577.7, 96.9, and -22.8 a.u., respectively. Based on TDDFT, the electronic absorption spectra of PCBM were calculated and analyzed. The calculated absorption band near 349 nmagreed well with the experimental measurement.