Luminescent properties and photo-induced electron transfer of naphthalimides with piperazine substituent

Abstract

Novel piperazine substituted naphthalimide model compounds 2-methyl-6-(4-methyl-piperazin-1-yl)-benzo[ de] isoquinoline-1,3-dione ( NA1), 2-methyl-6-(4,4-dimethyl-piperazin-1-yl)-benzo[ de] isoquinoline-1,3-dione iodide (NA2) and 2-methyl-6-(4-methyl-piperazin-1-yl)-benzo[ de] isoquinoline-1,3-dione hydrochloride ( NA3) were synthesized. Fluorescence spectra data of NA1 showed the fluorescence quantum yields plot of NA1 versus pH value is typically characteristic of pH probe. The approximate free energy of charge separation (Δ G cs) for the excited singlet state and the fluorescent lifetime data of NA1 showed that the fluorescence of 4-amino-1,8-naphthalimide fluorophore can be quenched by the PET process from the alkylated amine donor to the naphthalimide moiety. The PET path can be obviously switched off either by the protonation (as for NA3) or quarternization (as for NA2) of the alkylated amine donor.