A Novel Selective “Turn-On” Fluorescent Chemosensor Based on Thiophene Appended Cyclotriphosphazene Schiff Base for Detection of Ag+ Ions

摘要

The salicylaldehyde-functionalized cyclotriphosphazene (1) and thiophene appended cyclotriphosphazene based Schiff base (2) were designed and synthesized. The characterizations were carried out via MALDI-TOF, FTIR, 13 C, 31 P and 1 H NMR. The photophysical behavior of compound 2 was evaluated by UV- Vis absorption, time-resolved fluorescence, excitation-emission matrix (EEM) analysis, steady-state fluorescence, and 3D- fluorescence spectroscopies. Compound 2 demonstrated selec- tive fluorescence “turn-on” response at 427 nm towards to Ag+ ion when the tested competitive species did not affect fluorescence signal. The binding and sensing mechanisms were evaluated by DFT calculations which approved that the PET process between C=N and fluorophore groups was inhibited, and the fluorescence “turn-on” response was obtained with the contribution of CHEF after 1:1 coordination of compound 2 with Ag+ ion.