The Synthesis And Properties Of Imidazole[2,1-b][1,3]benzothiazole-2-carbonhydrazide Derivatives

In this paper,three fluorescence probes were designed and synthesized based on imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide:N'-[?Z?-1H-indazol-3-ylmethylidene]imi dazo[2,1-b][1,3]benzothiazole-2-carbohydrazide?WS1?,N'-[?E?-?2-hydroxyphenyl?methylene]imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide?W1S?,N'-[?E?-3,5-di-tert-butyl-2-hydro xybenzylidene]imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide?W2S?.The chemical structure of WS1,W1S and W2S were confirmed by ¹H NMR,¹³C NMR,FT-IR and ESI-MS.And the results of three derivatives in UV-vis absorption spectrum experiment and fluorescence emission spectrum experiment indicated that all of them could act as fluorescence sensors for specific recognition toward metal ion.The Schiff base fluorescence probe WS1 was designed and synthesized based on imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide and 1H-indazole-3-carbaldehyde.The studies showed that WS1 exhibited high selectivity and sensitivity toward Cu²⁺in MeOH/H₂O?v/v=9/1?Tris buffer solution,and it could act as a dual-channel chemosensor for detect Cu²⁺via absorption colorimetry and fluorescence titration,respectively.Upon the addition of Cu²⁺,a new absorption band appeared at 390 nm and the solution changed from colorless to yellow.The detection limit of colorimetric for Cu²⁺was 4.63×10^-7 M.Meanwhile,the paramagnetic Cu²⁺complexed with WS1 caused the outstanding fluorescence quenching,and the detection limit for Cu²⁺was 4.32×10^-8 M.In addition,WS1 was a reversible fluorescent probe.When PPi?Na₄P₂O₇?was added,the fluorescence intensity of the complex[WS1+Cu²⁺]returned to a state similar to that of free WS1,and the detection limit for PPi was 5.34×10^-7 M.The Schiff base fluorescence probe W1S was designed and synthesized based on imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide and salicylaldehyde.The studies showed that W1S exhibited high selectivity and sensitivity toward Zn²⁺in MeOH/H₂O?v/v=9/1?Tris buffer solution.When Zn²⁺were added to the solution,the solution exhibited a strong fluorescence enhancement due to the formation of complex[W1S+Zn²⁺+Cl^-]inhibited the C=N isomerization.The detection limit for Zn²⁺was 2.08×10^-8 M.However,the presence of Cu²⁺,Co²⁺,Ni²⁺,Mn²⁺or Fe²⁺caused remarkable interference of the detection toward Zn²⁺.Moreover,the addition of PPi ions could recover the fluorescence enhancement caused by Zn²⁺.And W1S still displayed good detection effect for Zn²⁺and PPi ions after sequence added Zn²⁺and PPi,the detection limit for PPi was 3.42×10^-7 M.The Schiff base fluorescence probe W2S was designed and synthesized based on imidazo[2,1-b][1,3]benzothiazole-2-carbohydrazide and 3,5-di-tert-butyl-2-hydroxybenzaldehyde.Due to the introduction of the large steric hindrance tertiary butyl groups,W2S displayed more efficient anti-interference ability for the detection of Zn²⁺in the presence of other competitive ions.Just the addition of Cu²⁺,Co²⁺interfered with the detection toward Zn²⁺.The fluorescence enhancement phenomenon was also caused by the inhibition of C=N isomerization.The detection limit for Zn²⁺was 1.35×10^-8 M.Similarly,PPi could also recover the fluorescence intensity of W2S and the probe displayed good detection effect for Zn²⁺and PPi after 4 cycles.The detection limit for PPi was2.75×10^-7M.