| 摘要: | 我們設計並合成出具合作效應的螢光離子感應器 S1 及 S2，兩者皆主要以hydrazine-/hydrazone-與陰離子形成氫鍵作用力做為陰離子辨識單元，利用紫外光-可見光（UV-Vis）吸收光譜與螢光放射光譜的變化，可探討螢光離子感應器 S1 及 S2 與鹵素離子（F-, Cl-, Br-,I- )、氰離子(CN- )、醋酸根離子（CH3COO-）與磷酸氫根離子（H2PO4-）之感應機制。 由 UV-Vis 吸收變化以及螢光淬滅滴定實驗結果，得到感測器與不同陰離子之間的作用強度排序為 F- > CN- > OAc- > H2PO4- > Cl- > Br- ~ I- 。感測器 S1 因naphthyl上的氫氧根為拉電子基使其與陰離子形成氫鍵的作用力比感測器 S2 大，從Job Plot 得知感測器 S1 與 S2 與陰離子以等比例的方式作用，再從感測器 S1 對氟離子（F-）與氰根離子（CN-）螢光放射光譜上可清楚發現 excimer 的特徵鋒，由此可知感測器 S1 對氟離子（F-）與氰根離子（CN-）形成[2+2]的雙體結構， 另一方面 Hill Plot 與 Scatchard Plot 證實，感測器 S1 與氟離子（F-）與氰根離子（CN-）以正向的合作效應形成[2+2]雙體錯合物。 從實驗結果，我們可推論感測器 S1 與氟離子（F-）與氰根離子（CN-）之作用機制為經由陰離子作用使感測器 S1 與陰離子先形成[2+1]的錯合物，接著再形成形成[2+2]的雙體錯合物，此外在氟離子的例子中，過量的氟離子會將naphthyl官能基上的氫氧根作進行去質子化反應進而導致分子結構帶負電性，而[2+2]的雙體錯合物由於會因負電荷所造成的靜電斥力，使[2+2]的雙體錯合物不穩定而解離為帶電荷的單體分子。 We have designed and synthesized two chromogenic and fluorescent chemosensors S1 and S2, which provide hydrazine and hyrdazone groups to form hydrogen bonding interactions with various anions. Through the variations of UV-Vis absorption and fluorescent spectra, the sensing mechanism of compounds S1 and S2 with a variety of anion including F-, Cl- , Br- , I- , CN- , OAc- , and H2PO4- are systematically investigated. According to the results of UV-Vis absorption changes and fluorescence quenching, the binding strength of chemosensors S1 and S2 to different anions can be depicted in the following order: F- > CN- > OAc- > H2PO4- > Cl- > Br-~I-. Due to the electron-withdrawing nature of hydroxyl groups in S1, the hydrogen bonding between hydrazine/hydrazone and anions is stronger compared to S2. Furthermore, Job plots revealed that both sensors S1 and S2 react with anions in a 1:1 stoichiometry. On the other hand, the characteristic band for the excimer could be found from the fluorescent spectra of S1 titrated with F- or CN- . On the basis of these evidences We propose the formation of a [2+2] associated dimer complex via hydrazine/hydrazone-anion hydrogen bonding and ?-? stacking interaction. The Hill plots and Scatchard plots further confirmed that a [2+2] complex composed of sensor S1 and F- , or CN- formed under the positive coopreativity. In light of obtained information, we propose the stepwise formation mechanism for the interaction between sensor S1 and F- or CN-. Sensor S1 initially form a [2+1] complex with anion followed by a fast dimerization to form the [2+2] associated dimer complex. Moreover, in the case of F-, addition of excess F- could deprotonate the hydroxyl group and generate negative charged [2+2] dimer which disassemble into individual monomer due to the charge repulsion. |
