荧光探针对识别金属离子具有检测快、 选择性好等特点, 设计合成了两个苯并噻唑类探针分子6-(3,5-二甲基苯氧基)-5-胺基-2-苯基苯并噻唑(L4)和6-(3,5-二甲基苯氧基)-5-苯甲酰胺基-2-苯基苯并噻唑(L5), 并通过探针分子的紫外可见光谱和荧光光谱的变化特征, 详细研究了探针L4和L5对溶液中三价金属离子Al³⁺, Fe³⁺, Cr³⁺和二价金属离子Cu²⁺的识别性能。 研究结果表明, 当L4分子中的识别基团胺基与苯甲酰基键合形成L5分子结构时, 会发生荧光猝灭, 同时获得了开启式荧光探针L4和关闭式荧光探针L5。 紫外可见光谱检测结果表明, 在有机溶液中, 探针L4选择性地识别出Al³⁺, Fe³⁺, Cu²⁺; 在含水乙腈溶液中, 探针L4高选择性地识别出Cu²⁺; 通过紫外光照射下的裸眼检测, 含探针L4的试纸有效地识别出纯水中的Cu²⁺; 在有机溶液中, 探针L5选择性地识别出Al³⁺和Fe³⁺。 荧光光谱检测结果表明, 当探针L4与Fe³⁺, Al³⁺, Cu²⁺存在于有机溶液中时, L4将发生荧光猝灭; 在含水乙腈溶液中, 探针L4对Cu²⁺具有高选择性识别作用; 当探针L5与Cr³⁺, Fe³⁺, Al³⁺, Cu²⁺存在于有机溶液中时, L5的荧光强度依次增强。 利用溶液浓度对吸收强度作图, 计算出了探针L4对Cu²⁺的检出限为4.51×10^-6 mol·L^-1, 络合常数 Kα为1.12×10³ M^-1; 探针L5对Al³⁺, Cr³⁺, Fe³⁺, Cu²⁺的检测限分别为2.85×10^-6, 4.79×10^-6, 5.95×10^-6和3.23×10^-6 mol·L^-1, 络合常数分别为: Kα(Al³⁺)=2.17×10³ M^-1, Kα(Cr³⁺)=2.06×10³ M^-1, Kα(Fe³⁺)=3.92×10³ M^-1, Kα(Cu²⁺)=4.43×10³ M^-1。 根据探针与识别金属离子的荧光滴定实验结果, 推测出探针分子与金属离子之间形成了1:1络合物。 抗金属离子干扰实验结果表明, 探针分子对特定金属离子的识别基本不受其他干扰金属离子的影响。¹H NMR滴定结果表明, 探针L4分子结构中胺基和二甲基苯氧基, 探针L5分子结构中的苯甲酰胺基和二甲基苯氧基取代基在识别金属离子过程中发挥了重要作用。 探针L4在识别Cu²⁺方面具有更广阔的应用前景。

For the characteristics of fast detection and good selectivity about fluorescence probe for recognition to metal ions, the synthesis of probes 6-(3,5-dimethyl phenoxy)-5-amine-2-phenylbenzothiazole (L4) and 6-(3,5-dimethyl phenoxy)-5-benzamide-2-benzothiazole (L5) was designed. The molecule structures of L4 and L5 were confirmed by spectroscopic characterization and single crystal diffraction analysis. The effects of probes L4 and L5 on recognizing to trivalent metal ions Al³⁺, Cr³⁺, Fe³⁺and divalent metal ion Cu²⁺ in the solution were investigated in detail by UV-Vis and fluorescence. The results showed when the molecule of probe L5 was formed by the benzoyl recognizing group bonding with the amine group of probe L4, the fluorescence of probe L4 was quenched, and the turn-on fluorescent probe L4 and the turn-off fluorescent probe L5 were simultaneously obtained. The UV-Vis results show that probe L4 could selectively identify to Al³⁺, Fe³⁺, Cu²⁺ in the organic solution and highly selectively identify to Cu²⁺ in the aqueous acetonitrile solution. A test paper of probe L4 could effectively identify to Cu²⁺ in pure water by the naked eye detection under UV irradiation. Probe L5 could selectively identify to Al³⁺ and Fe³⁺ in the organic solution. The fluorescence results show the fluorescence of probe L4 was quenched while probe L4 with Fe³⁺, Al³⁺, Cu²⁺ were coexisted in the organic solution, respectively. Probe L4 could highly selectively recognize to Cu²⁺ in the aqueous acetonitrile solution. The fluorescence intensity of probe L5 was successively increased while probe L5 with Cr³⁺, Fe³⁺, Al³⁺ and Cu²⁺ were coexisted in the organic solution, respectively. According to the L4 solution concentration to the absorption intensity was plotted, and the detection limit of probe L4 to Cu²⁺ is 4.51×10^-6 and the complex constant is 1.12×10³ M^-1. The detection limits of probe L5 to Al³⁺, Cr³⁺, Fe³⁺, Cu²⁺ are 2.85×10^-6, 4.79×10^-6, 5.95×10^-6 and 3.23×10^-6 mol·L^-1, respectively, and the complex constants of probe L5 to Al³⁺, Cr³⁺, Fe³⁺, Cu²⁺ are 2.17×10³, 2.06×10³, 3.92×10³, 4.43×10³ M^-1, respectively. It was inferred that 1:1 complex was formed by the linkage of probes with metal ions on the basis of the results of fluorescence titrations. The results of anti-interference to other metal ions display the identification to specific metal ions by probes is not affected by other interference metal ions.¹H NMR results show the amine group and dimethyl phenoxy group of probe L4 and the benzamide group and dimethyl phenoxy group of probe L5 play an important role in the identification of metal ions. Probe L4 has a positive application prospect on identifying to copper ions.