Synthesis of Zn (II)-Oxazoline/Pyridine Derivative Complex as a Molecular Sensing Ensemble for Aspartate and Histidine

Abstract

Synthetic receptors can readily be converted to optical chemosensors using a displacement assay and common fluorophores and/or chromophores. Most of them are designed with covalent attachment between a receptor and a reporter moiety. We now describe the design of spectroscopic chemosensors bearing Zn (II) chelates with oxazoline/pyridine sites. The current progress of our use of noncovalently attached indicators to signal binding of analytes are demonstrated. With these systems, analyte binding which we focus on the selected amino acids, aspartate and histidine, leads to indicator displacement from the binding cavity, which in turn yields a spectroscopic signal modulation. On the basis of ¹H NMR studies, and preliminary x-ray diffraction analysis, it is clear that Zn (II)-oxazoline/ pyridine derivative receptor cooperatively act to bind a carboxylate site of amino acids. Good agreement of the binding affinity revealed that our receptor can colorimetrically sense aspartate higher than histidine. In addition, it is demonstrated that careful choice of a chelating indicator with tuned affinity toward the receptor, lower than that of the envisaged analyte, higher than that of the interferent, can provide discrimination in sensing of a desired substrate.