Photoinduced energy–electron transfer studies with naphthalene diimides

Abstract

Seven derivatives of naphthalene diimides, synthesized, have shown similar photophysical properties. Low fluorescence quantum yields (0.002–0.006) and short fluorescence lifetimes (5–18 ps) have suggested rapid intersystem crossing processes from excited singlet state. Quenching of fluorescence emissions of aromatic donor molecules, i.e. naphthalene, phenanthrene and pyrene, at rates reaching to diffusion limits in acetonitrile (2–8×10 10 M −1 s −1), have proven the electron acceptor capacities of naphthalene diimides. Photooxydation of styrene to benzaldehyde, in presence of naphthalene diimide (NDI) molecule, is found to occur at similar rates with respect to perylene diimides. Addition of ferric and cupric ions to NDI, have enhanced the formation rate of benzaldehyde by about two-fold. Photooxidation of α-terpinene with naphthalene diimide, produced only p-cymene, no endoperoxide adduct was identified. Naphthalene diimides appear to produce no singlet oxygen, and photooxidation probably occurs on radical chain reactions of super oxide anion radical. But the electron transfer electron via excited triplet or singlet state, remains to be unclear.