Synthesis and spectral-luminescent characteristics of N-substituted 1,8-naphthalimides

A series of N-substituted 1,8-naphthalimides has been synthesized. The absorption and fluorescence spectra of the synthesized compounds show absorption in the 328–333 nm and 338–347 nm ranges and emission in the 358–391 nm range, depending on the solvent. The effect of substituents on the electronic spectra has been studied both experimentally and by electronic structure calculations. Introduction of the OH radical into the N-alkyl group does not increase the luminescence quantum yield, as may be expected based on the previous study with 2,5-diarylthiazoles [Tetrahedron Lett 2004;45:5291]. Only N-(1,1-dihydroxymethyl-2-hydroxy)ethyl 1,8-naphthalimide with three OH substituents shows an increased quantum yield, which is attributed to intramolecular H-bond.