Optical sensing of inorganic anions employing a synthetic receptor and ionic colorimetric dyes

A novel optical sensing methodology for nitrate ions has been developed usi ng an ensemble of a: synthetic receptor and colorimetric dyes as indicators . Neutral receptor 1 forms one to one complexes with anionic dyes such as R esorufin or Methyl Red in organic solvents. The equilibrium between recepto r and dye is perturbed by added nitrate ion, resulting in a receptor-nitrat e complex. The displacement of the indicator by nitrate causes large absorb ance changes, because of alternation of the microenvironment of the chromop hore. The association constants between receptor 1 and various anions were determined by analyzing the intensity changes.