Spectrophotometric studies of complexation of [60]fullerene with series of aromatic hydrocarbon molecules containing flexible phenyl substituents

The absorption spectra of the electron donor-acceptor complexes of 60]fullerene with five different aromatic hydrocarbon (AH) molecules containing flexible phenyl substituents have been investigated in toluene medium. An absorption band due to charge transfer (CT) transition is observed in each case in the visible region. The experimental CT transition energies are well correlated with the vertical ionization potentials of the AHs studied (through Mulliken's equation) from which we extract degrees of charge transfer, oscillator and transition dipole strengths of the CT complexes. The degrees of CT in the ground state of the complexes have been found to be very low (0.49-0.55%). The formation constants (K) for the complexes of 60]fullerene with the aromatic hydrocarbons have been determined by UV-vis spectroscopy. Both K values and PM3 calculations on 60]fullerene/AH complexes reveal that nature of substitution in the donor moiety as well as steric compatibility with the acceptor molecule govern the process of EDA complex formation.