Studies on the synthesis and spectral properties of novel 4-benzofuranyl-1,8-naphthalimide derivatives

A new series of 4-benzofuranyl-N-alkyl-1,8-naphthalimides was prepared from 4-ethynyl-N-alkyl-1,8-naphthalimides and substituted o-iodophenols catalyzed by a Pd(PPh3)2Cl2/CuI system under mild conditions. The starting materials, 4-ethynyl-N-alkyl-1,8-naphthalimides, were synthesized with trimethylsilylacetylene by Sonogashira coupling reaction. The absorption and fluorescence spectra of these benzofuran-1,8-naphthalimides were recorded and the quantum yields were measured using quinine sulfate as the standard. The UV/vis absorption spectra were in the range of 380-400 nm and the emission spectra were in the range of 500-520 nm.