Synthesis and Fluorescent Property Study of Novel 1,8-Naphthalimide-Based Chemosensors

Abstract

A series of novel mono- and di-substituted N-n-butyl-1,8-naphthalimide derivatives were synthesized simultaneously via a three-step reaction. The single crystal structure of N-n-butyl-4-[N',N'-bis(2',4'-dichlorobenzoyl)ethylamino]-1,8-naphthalimide (3f) was determined. The UV-vis and fluorescence properties of compound 3f were investigated. The 3f showed highly selective and sensitive fluorescence changes response towards Pb²⁺. A titration of monomer with Pb²⁺ ion was performed. When Pb²⁺ ion concentration increased from 0 to 10 eq., the fluorescent intensity of 3f decreased from 199.97 to 48.21. The pH effect on 3f showed that it is stable in a wide range of pH. The results indicated that 3f might be a probe molecule for Pb²⁺.

Keywords: N-n-Butyl-4-(N′,N′-dihydroxyethylamino)-1,8-naphthalimide; crystal structure; design; fluorescence; synthesis.

Scheme 1

Design of the novel 1,8-naphthalimide-based chemosensors.

Scheme 2

Synthetic route for the production of compounds 3 and 4.

Figure 1

Molecular structure of 3f.

Figure 2

Packing view of 3f.

Figure 3

π-π Stacking interactions between the core planes.

Figure 4

Various solvents’ influences on the fluorescence intensity.

Figure 5

Fluorescence intensity response of probe 3f to different metal cations.

Figure 6

Proposed structure of the 3f-Pb²⁺ complex.

Figure 7

UV–vis spectra of probe 3f under the same conditions except for the addition of different amount of Pb²⁺.

Figure 8

Fluorescence spectra of probe 3f under the same conditions except for the addition of different amount of Pb²⁺.

Figure 9

Effect of pH on the fluorescence intensity of 3f in the absence or presence of 3 eq. Pb²⁺.