Ratiometric fluorescent receptors for both Zn²⁺and H₂PO₄^–ions based on a pyrenyl-linked triazole-modified homooxacalix[3]arene: A potential molecular traffic signal with an R-S latch logic circuit

A ratiometric fluorescent receptor with a C3 symmetric structure based on a pyrene-linked triazole-modified homooxacalix[3]arene (L) was synthesized and characterized. This system exhibited an interesting ratiometric detection signal output for targeting cations and anions through switching the excimer emission of pyrene from the “on-off” to the “off-on” type in neutral solution. 1H NMR titration results suggested that the Zn2+ center of receptor L·Zn2+ provided an excellent pathway of organizing anion binding groups for optimal host–guest interactions. It is thus believed that this receptor has potential application in sensing, detection, and recognition of both Zn2+ and H2PO4– ions with different optical signals. In addition, the fluorescence emission changes by the inputs of Zn2+ and H2PO4– ions can be viewed as a combinational R-S latch logic circuit at the molecular level.