The Synthesis Of Crotonic Acid Cyanine Dye And Its Recognition Of Metal Ions

Croconaine is a kind of cyanine dye,it has attracted more and more researchers’attention due to its high molar absorption coefficient and good light stability.In this thesis,three different types of croconaine dyes were synthesized and characterized through dehydration and condensation reaction with croconic acid and nucleophiles such as aniline derivatives and indole derivatives as basic raw materials.A series of experiments were designed to study the recognition performance of different croconaine dyes to metal ions.Croconic acid and aniline derivatives with different substituents were used as substrates to synthesize two symmetric disubstituted aniline croconaines,2,5-bis[2-butylthioaniline]croconaine（BBAC）and2,5-bis[4-methylthioaniline]croconaine（BMAC）.The experimental results showed that this kind of croconaine dye molecule could be used as a colorimetric probe to specifically recognize Cu²⁺.Through metal ion selectivity experiments,it was found that this type of probe had obvious naked eye recognition effect and ultraviolet response to Cu²⁺.Through metal ion interference experiments,it was found that such probes had good anti-interference performance.Through kinetic experiments,it was found that both probes had good timeliness;According to the calculation of detection limit,it was found that the probes BBAC and BMAC had high sensitivity,and the lowest detection concentration could reach 5.76×10^-6 M and 7.04×10^-6 M respectively.In order to detect the trace amount of Fe³⁺in the environment and organisms,a nitrogen-containing heterocycle was introduced into the croconaine molecule to synthesize a monosubstituted benzoindole ccroconaine,1,1,2-trimethyl-1H-benzo[e]indole croconaine（TBIC）.The experimental results showed that the dye molecule TBIC could be used as a colorimetric and fluorescent probe that specifically recognizes Fe³⁺.Before and after adding Fe³⁺,it could be clearly observed that the TBIC solution had changed from dark purple to colorless,and both the UV absorption peak and the fluorescence peak were significantly weakened.By alternately adding Fe³⁺and EDTA,the fluorescence spectrum was alternately quenched and excited,indicating that the probe has good reversibility and has the value of repeated use.Therefore,Fe³⁺and EDTA were used as input signals to design molecular logic gates that can be stored and erased.The synthesized 1,1,2-trimethyl-1H-benzo[e]indole croconaine was further dehydrated and condensed with 2,3,3-trimethyl-3H-indole to form an asymmetric indole croconaine（IBC）.The experimental results showed that:IBC could be used as a colorimetric and fluorescent probe that specifically recognizes Ag⁺.According to the Job’s curve,the binding ratio of IBC and Ag⁺was analyzed,and the possible chelating mechanism was analyzed by comparing the FT-IR and ¹H NMR before and after chelation.By changing the pH of the solution,the tolerance of the probe IBC at different pH levels was explored.According to the color change before and after the formation of the metal complex IBC-Ag⁺,a colorimetric test paper that could be recognized by the naked eye was prepared.