1,6-Naphthyridines are a class of compounds that exhibit second harmonic generation on excitation with a Nd–YAG laser (1064 nm). Solvatochromism has been used to estimate enhancement in the dipole moments on excitation and the values of first-order hyperpolarizability, β. Photophysical studies on the title compounds show that they have a fluorescence lifetime of about 10 ns and fluorescence quantum yield of ∼0.05–0.1 in different solvents. Kurtz powder method has been used to find the NLO efficiency of the compounds with reference to urea.