Synthesis and fluorescence property of some novel 1,8-naphthalimide derivatives containing a thiophene ring at the C-4 position

A series of novel 1,8-naphthlimide derivatives containing a thiophene ring at the C-4 position was synthesized through Pd-catalyzed direct C–H bond arylation and characterized by 1H NMR, 13C NMR, MALDI-HRMS and elemental analysis. The crystal structure of N-hexyl-4-(benzo[b]thiophen-2-yl)-1,8-naphthalimide was found to be a kite structure. The moderate π–π stacking interaction between the two core planes (naphthalimide ring) and the van der Waals' forces between the flexible hexyl groups constructed a 3D structure. The UV–vis and fluorescence property of synthesized compounds in chloroform were investigated. All compounds can emit blue, green or yellow emission except for N-hexyl-4-(5-nitrothiophene-2-yl)-1,8-naphthalimide. The results show that the 1,8-naphthalimide derivatives with an electron-donating group on the thiophene ring or larger conjugated structure have enhanced fluorescence properties.

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► Novel 1,8-napthalimide derivatives have been synthesized and characterized.
► X-ray crystal structure for one sample was determined.
► These dyes exhibit emission from blue to orange in CHCl3 solution.