Intermolecular photoinduced electron-transfer processes between C60 and aniline derivatives in benzonitrile

The quenching behavior of the triplets of C60 by various aniline derivatives (1a–d and 2a–e) was investigated by means of laser flash photolysis in benzonitrile at 293 K. Electron transfer process was proposed to be the main mechanism because of the direct detection of radical ions of aniline derivatives and C60 in time-resolved transient absorption spectra. The quenching rate constants (kq) of image by different substrates determined at 740 nm approach or reach the diffusion-controlled limit. DFT method was employed to calculate the unknown oxidation potentials of substrates in solution. With these Eox values, free energy changes (ΔG) were obtained through Rehm–Weller equation. Dependence of observed quenching rate constants on the free energy changes further indicates the photoinduced reactions between 3C60* and substrates proceed through an electron transfer mechanism. Obtained kq values for the aniline derivatives are impacted obviously by ground-state configurations and the kinds substituents quantified by Hammett σ constant. Good correlation between log kq and σ values conforms to the empirical Hammett equation. A more negative ρ value (−3.356) was gained for anilines (2a–e) than that of N,N-dimethylanilines (1a–d) (−1.382), which suggests a more susceptible reactivity for the former substrates. Charge density distribution of reaction center “N” originated from quantum calculation supports this suggestion. In addition, a relationship between quenching rate constants and solvent viscosity was gained from C60/dimethyl-p-toluidine system in altered mixtures of acetonitrile and toluene.