Heavy metal analysis using a Heck-catalyzed cyclization to create coumarin

This paper describes a new method for heavy metal analysis via catalytic signal amplification. This signal amplification protocol relies upon an exogenous inhibitor for deliberate deactivation of an organometallic reaction that catalytically creates a fluorophore. When the deactivation process is performed in the presence of the analyte, competitive binding of the inhibitor with the analyte and the catalyst occurs. A Heck reaction creating a coumarin fluorophore with a high quantum yield was studied. 1,4,7,10,13-Pentaaza-cyclopentadecane was chosen as the inhibiting ligand to selectively coordinate pre-catalyst Pd(II) and analytes Cd(II), Ni(II), Co(II). Monitoring product fluorescent intensity in real time revealed the concentration of analyte.