Two reduced Schiff bases, namely 5-[(2-hydroxybenzyl)amino]isophthalic acid (1) and 5-[(pyridin-4-ylmethyl)amino]isophthalic acid (2), were synthesized in two-step method using 5-aminoisophthalic acid as the starting material, and were characterized by single-crystal X-ray diffraction, elemental analysis, infrared, 1H NMR, mass, absorption and fluorescence spectra. Both 1 and 2 crystallize in monoclinic system with space groups P21/c for 1 and P21/n for 2. Photophysical properties of both 1 and 2 are significantly different from those of raw material 5-aminoisophthalic acid due to stronger p → π conjugation when one amino hydrogen atom in 5-aminoisophthalic acid is substituted with electron-donor group. 1 displays a very strong narrow-band blue fluorescence with the maximum peak at 439 nm, a high quantum efficiency up to 64%, and a narrow full width at half maximum of 35 nm, while 2 has a broader and weaker fluorescence with the peak at 418 nm and FHWM of about 50 nm.
Two reduced Schiff bases with blue fluorescence were synthesized from 5-aminoisophthalic acid in two-step method including formation of the corresponding Schiff bases and further reduction by NaBH4.
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This work was supported by the National Natural Science Foundation of China (21561028), Science and Technology Program of Department of Education of Jiangxi Province (GJJ151064), and the National Natural Science Foundation of Jiangxi Province (2016BAB203071).
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