Chemosensors For The Recognition Of Zinc Ion And Dihydrogen Phosphate

Ions are ubiquitous and play pivotal roles in many biological and environmental processes. Accordingly, the design of artificial chemosensors for biologically and environmentally important targets, including zinc ions and various phosphate anions, have attracted considerable attention over the last few decades.The Schiff base N-(2-hydroxy-l-naphthyl)methylidene-α-phenylethylamine (HNP) has been designed as a fluorescent chemosensor based on the photoinduced electron transfer (PET) and C=N isomerization mechanisms, which was prepared by the condensation reaction of2-hydroxy-l-naphthaldehyde with α-phenylethylamine. The receptor exhibited a switch-on fluorescence response toward Zn2+and especially avoided the interference of Cd2+when it was tested in unbuffered methanol solution. In contrast to what was seen with Zn2+, much smaller fluorescence increase was observed with other metal ions including Ag+, Mg2+, Cd2+, Ni2+, Cu2+, Mn2, Ca2+, Al3+and Fe3+. Furthermore, the in situ generated HNP-ZnⅡ complex could be employed for the specific detection of H2PO4-by fluorescence turn-off signaling through a ligand displacement process. Upon addition of NaH2PO4(0.15equiv) into the solution led to a dramatic decrease in fluorescence intensity due to the release of HNP, whereas other anions such as F-, Cl-, Br-, I-, NO2-, AcO-, SO42-, HPO42-, PO43-, or P2O74-(sodium salts) did not induce any significant variation in the emission spectrum. Thus, we have developed effective method that allow the sacecate recognition of Zn2+and H2PO4-ions in unbuffered methanol in an on-off mode using a simple Schiff base chemosensor.Based on the studies on HNP chemosensor, we designed and synthesized a new kind of main-chain chiral poly(triazole)s through metal-free click polymerization. The chiral polymer exhibited a moderate selective fluorescence response toward Zn2+and H2PO4-in DMSO. However, the zinc(II) detection was heavily interfered by certain metal ions such as Al3+, Cr3+, Cu2+or Fe3+due to the high affinity of1,2,3-triazole moieties to these cations. It should be noted that the polymer is useful as a highly sensitive chiroptical sensor for the recognition of zinc. Upon addition of Zn(II) to the polymer solution, a remarkable change in CD spectra was observed due to the formation of a supramolecular chiral structure. By contrast it displays no detectable affinity for other metal ions or a different response. The variation in molecular weight of the polymer seems to have little effect on its recognition ability. In addition, the in situ generated Zn(Ⅱ)-containing complex showed high selectivity towards H2PO4-with strong anti-interference ability. Thus, we have constructed a polymer based chemosensor for detecting Zn2+and H2PO4-using CD signal as the output.