Two fluorophore compounds based on 1, 8-naphthalimide: Synthesis, crystal structure, and optical properties

Abstract

Two new 1, 8-naphthalimide-based fluorophore compounds, 4-piperazinyl-N-(4-Pyr-idinyl)-1, 8-naphthalimide (RB1) and 4-phenyl-N-(3-hydroxyphenyl)-1, 8-naphth- alimide (RB2) were synthesized via two-steps nucleophilic substitution reactions and Suzuki coupling reaction. The chemical structures of the title compounds were characterized by 1H NMR, 13C NMR, HRMS and FT-IR spectral analysis. Thermogravimetric analysis results show that the degradation temperatures of two compounds were about 300 °C. The single-crystal XRD analysis revealed that both RB1 and RB2 crystallize in the monoclinic P21/c (No. 14) space group, with lattice parameters of RB1a = 15.3016(10), b = 15.4468(9), c = 7.1919(4) Å, β = 95.384(2)°, V = 1692.38(18) Å3, Z = 4 and RB2a = 16.1990(3), b = 15.9460(3), c = 7.5870(15) Å, β = 98.718(5)°, V = 1937.2(7) Å3, Z = 4 respectively. Both crystals of two compounds have parallel offset stacking with extensive intermolecular interactions (hydrogen bond, C–H⋅⋅⋅π interaction), which are correspondence with the molecular packing of J-aggregation. The UV–vis and fluorescence properties of two compounds in different solvents were investigated, indicated that ICT characteristics of RB1 in organic solvents. Moreover, RB1 crystal can excite the strong green fluorescence with good thermal and optical stability qualifying it as a potential application in the fields of crystal luminescent functional materials.