Differentiating phosphates by an Mg²⁺ complex of the conjugate of Calix[4]arene via the formation of ternary species and causing changes in the aggregation: spectroscopy, microscopy, and computational modeling

Abstract

A phenylene diimine capped conjugate of 1,3-calix[4]arene (L) was synthesized and characterized, and its Mg²⁺ complex has been isolated and characterized. The chemo sensing ensemble of Mg²⁺ bound L provides distinguishable features of response toward phosphates, viz., HPO₄^2–, P₂O₇^4–, and AMP^2– (Set A) and H₂PO₄^–, ATP^2–, and ADP^2– (Set B). While the Set A shows the formation of ternary complex, the Set B does not exhibit any intermediate complex, but both show the release of Mg²⁺ and L at different equivalents. The structures of {L + Mg²⁺} and its phosphate bound ternary complexes have been established by computational calculations, and the corresponding results agree well with the experimental ones. The microscopy studies show an aggregation–disaggregation phenomenon in the presence of different equivalents of phosphates in both of the sets. Using the fluorescence data, an INHIBIT logic gate has been built.