The synthesis, crystal structure and photophysical properties of three novel naphthalimide dyes

Three new naphthalimide derivatives containing an electron-donor moiety (carbazole), 4-carbazolyl-N-methyl-1,8-naphthalimide, 4-carbazolyl-N-cyclohexyl-1,8-naphthalimide and 4-carbazolyl-N-phenyl-1,8-naphthalimide were synthesized and crystal structures confirmed. Crystallographic data revealed that the interplanar angles (θ) of the carbazole and naphthalimide moieties were, respectively, 70.7° and 66.5°. The UV–vis absorption and photoluminescent spectra of the systems in n-hexane, CHCl3, tetrahydrofuran and CH2Cl2 were investigated. The lowest absorption band of the naphthalimide molecular centered at 400–420 nm was assigned to charge-transfer transition with emission at ≈440 nm in n-hexane and at ≈560 nm in CH2Cl2.