A thiacalix[4]crown based chemosensor for Zn2+ and H2PO4−: sequential logic operations at the molecular level

Abstract

A thiacalix[4]crown based di-topic receptor 3 possessing two types of binding sites viz. crown-5 ring and imino moieties has been synthesized which undergoes fluorescence enhancement in the presence of Zn²⁺ ions. The selective binding of Zn²⁺ to compound 3 does not allow the K⁺ ions to bind with the crown-5 ring and thus a negative allosteric behaviour has been observed between Zn²⁺/K⁺ ions. In addition, the 3-Zn²⁺ complex can be used for the detection of H₂PO₄⁻ ions with a fluorescence “turn-off” response. Furthermore, based on the fluorescence response, a two input and one output sequential logic circuit has been constructed.