Construction And Performance Of Hydrazine Fluorescent Probes Based On 4-bromobutyrate Group Recognition Sites

Hydrazine（N₂H₄）is an important industrial chemical,which plays an important role in pharmaceutical intermediates,catalysis,chemical industry,textile dyes and agriculture.However,the leakage of N₂H₄ can lead to serious environmental problems.In addition,because of its known high toxicity,N₂H₄ can cause serious damage to human organs.Compared with other detection methods,fluorescent probe is easier to implement,fast response,non-destructive,high sensitivity,low detection limit and so on.Based on its advantages,the development of a fast and efficient fluorescent probe for identifying N₂H₄ is of great significance to the environment and biology.The important work of this thesis is to design and synthesize three new fluorescent probes by modifying the luminescent groups and introducing the recognition group 4-bromobutyric acid ester group,and study the optical properties.1.A new type of near-infrared fluorescence probe LN was designed and synthesized by modifying the fluorescent trianiline and introducing 4-bromobutyrate group,and its structure was characterized by NMR.The results show that the probe LN has good selectivity and anti-interference to hydrazine,the detection limit is 0.72μM and the Stoke shift is 130 nm.When N₂H₄ was added,the color of the solution changed from orange to purplish red,indicating that LN can be used for naked eye detection of N2H4.The fluorescence quantum yield changed from 0.0018 to 0.0124.It is speculated that the recognition mechanism of N₂H₄by LN belongs to ICT mechanism.2.Based on benzothiazole and introducing 4-bromobutyric acid ester group as recognition group,a new probe L-1 was designed and synthesized,and the structure and energy levels were calculated by DFT.The results of optical properties show that the probe L-l shows a"off-on"response to N₂H₄ in DMSO/deionized water（v:v=1:1）system.At p H=5-10:00,the fluorescence of N₂H₄ was enhanced.The probe Lmurl showed good selectivity and anti-interference to N₂H₄.The Stoke shift was 40nm and the detection limit was 0.49μM.The fluorescence quantum yield changed from 0.052 to 0.286.It is speculated that the recognition mechanism of N₂H₄ by L-1 belongs to ESIPT mechanism.3.Benzothiazole was modified again and a new fluorescent compound LZ with"D-π-A"structure was synthesized by Knoevenagel condensation reaction.Its structure was characterized by NMR,and its structure optimization and energy level analysis were carried out by DFT calculation.The results of optical properties show that in acetonitrile system,after the interaction of LZ with N₂H₄,the probe has strong fluorescence emission at 645nm,which is close to near-infrared light,and the Stoke shift reaches 269 nm,showing good selectivity,specificity and anti-interference.The fluorescence intensity of the probe LZ interacting with N2H4 is about 74 times of that of the probe interacting with other test substances.The detection limit is 0.65μM.It is speculated that the mechanism may belong to ESIPT mechanism.