Spectrophotometric studies of complexation of Safranine T and Safranine O with [60]- and [70]fullerenes and other electron acceptors

The electron donor-acceptor (EDA) interactions of the dye, namely, Safranine T (ST) and Safranine O (SO) with [60]- and [70]fullerenes and some other electron acceptors (e.g., 2,3-dichloro-5,6-dicyano-p-benzoquinone, o-chloranil, and p-chloranil) were studied in 1,4-dioxan medium using the absorption spectroscopic technique. An absorption band due to a charge transfer (CT) transition is observed in the visible region for all of the complexes studied. The experimental CT transition energies (hv(CT)'s) are well-correlated (through Mulliken's equation) with the vertical electron affinities of the acceptors. From an analysis of this correlation, vertical ionization potentials of ST and SO have been determined. The influences of ST and SO on the absorption spectrum of [60]- and [70]fullerenes are studied. The experimental results were explained using a theoretical model that takes into account the interaction between electronic subsystems of ST and SO with [60]- and [70]fullerenes. Oscillator strengths, transition dipole strengths, and resonance energies of the EDA complexes have been estimated. Formation constants of the complexes were determined in terms of the Benesi-Hildebrand equation. The magnitudes of the formation constants indicate that SO binds more strongly than ST with [60]and [70]fullerenes.